EIS 1078 Vol 2
ABO1 9707
Sand extraction in Griffins Bay : environmental impact
statement ' flfl!•IIIflIJfl•&flfl SW DEPT PR1AR INDUSTRIES
AB01 9707
SOUTH COAST EQUIPMENT PTY LTD
SAND EXTRACTION I IN GRIFFINS BAY
VOLUME 2 I ENVIRONMENTAL IMPACT STATEMENT WORKING PAPERS SOUTH COASTEQUIPMENT PTY LTD
SAND EXTRACTION IN GRIFFINS BAY
VOLUME 2 ENVIRONMENTAL IMPACT STATEMENT WORKING PAPERS
April 1995 GUTTERIDGE HASKINS & DAVEY PlY LTD 39 Regent Street, RAILWAY SQUARE NSW 2000 Telephone: (02) 690 7070 Facsimile: (02) 698 1780
© Gutteridge Haskins & Davey Pty Ltd 1995 This document is and shall remain the property of Gutteridge Haskins & Davey Pty Ltd. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorised use of this document in any form whatsoever is prohibited.
217/027419/00 R4438 lJ:LT CONTENTS
Acoustical Impact Assessment Proposed Dredging of Griffins Bay, Lake illawarra, NSW
James Madden Cooper Atkins Pty Ltd, 1994
Soclo-Economic Impacts of the Proposal to Extract Sand from Griffins Bay, Lake Illawarra
Economic Planning Impact Consultants Pty Ltd, 1995
An Assessment of Impacts on Marine Flora, Fauna and Fisheries of a Proposal to Extract Sand from Griffins Bay, Lake Illawarra
The Ecology Lab Pty Limited, 1995.
Griffins Bay Sand Extraction EIS
Gutteridge Haskins & Davey Pty Ltd M114182 ACOUSTICAL IMPACT ASSESSMENT
PROPOSED DREDGING OF GRIFFINS BAY,
LAKE ILLAWARRA NSW
JAMES MADDEN COOPER ATKINS PTY LTD, 1994
Griffins Bay Sand Extraction EIS
Gutteridge Haskins & Davey Pty Ud M114182 JAMES MADDEN COOPER ATKINS PlY LIMITED. CONSULTING ACOUSTICAL & VIBRATION ENGINEERS
ACOUSTICAL IMPACT ASSESSMENT PROPOSED DREDGIIG OF GR1FFIT' BAY LAKE ILLAWARRA NSW 24.2467.R2:GA37
Prepared for: Gutteridge Haskins & Davey Pty Limited 39 Regent Street RAILWAY SQUARE. NSW 2000
May 1994 8-10 Wharf Road, Gladesville, N.S.W. 2111 AUSTRALIA Telephone: 879.6844 Fax: 879.6622 Principals Member Firm of the Association Steven E. Cooper Graham F. Atkins A.C.N. of Australian Acoustical Oonsultants. BSc (Eng), MSc (Arch M I.E. (AUST BE (Mech.), M.A AS.. M.I.E. (AUST.) 002 353 497 A.A.A.C. CONTENTS
1.0 INTRODUCTION
2.0 GENERAL DESCRIPTION OF SITE AND PROPOSAL 2 2.1 Plant and Equipment 2 2.1.1 Main Dredge Plant 2 2.1.2 Screen and Booster Pump 3 2.1.3 Processing Plant 3 2.1.4 Road Transport 3
3.0 PROCEDURES 4 3.1 Instrumentation 4 3.2 Methodology 4 3.2.1 Noise Level Descriptors 4
4.0 CRITERIA FOR NOISE ASSESSMENT 5
5.0 AMBIENT BACKGROUND NOISE SURVEYS 6 5.1 Methodology 6 5.2 Measurement Locations 6 5.3 Survey Dates 6 5.4 Weather Conditions 7 5.5 Results 7
6.0 PREDICTION OF NOISE EMISSIONS FROM PROPOSED EQUIPMENT AND SITE OPERATIONS 8 6.1 Main Dredge 8 6.2 Booster Pump 8
7.0 NOISE ASSESSMENT 9 7.1 Continuous Noise 9
8.0 NOISE CONTROLS AND PLANNING 10
9.0 CONCLUSION 11
APPENDICES
APPENDIX A: SITE LOCATION AND ASSESSMENT LOCATIONS APPENDIX B: SITE LAYOUT APPENDIX C: CALCULATION OF PLANT SOUND PRESSURE LEVELS Gutteridge Haskins & Davey Pty Limited. Page 1 Rev 02 Dxdging of Griffin Bay. Lake Illawarra.
i 1NTROD]JCTION
This Report presents the results and findings of an assessment of the likely noise impact associated with the proposed sand dredging operations on (iriffins Bay, Lake Illawarra (Appendix A).
The assessment is based on:
an inspection and evaluation of the proposed dredging site and nearby residential areas,
the measurement of ambient background noise levels in nearby residential areas, the measurement of noise emissions from similar plant and equipment, and
the assessment of the likely noise emissions from the proposed dredging operations and their impact on the existing acoustic amenity of the area.
The Report has been prepared for the particular investigation described herein, and no part of it should be used in any other context or for any other purposes. Gutteridge Haskins & Davey Pty Limited. Page 2 RevO2 Dredging of Griffin Bay. Lake Illawarra. I
2.0 GENERAL DESCRIPTION OF SITE AND PROPOSAL
The overall strategy of the proposed dredging programme is detailed in the Environmental Impact Study prepared by Gutterridge Haskings & Davey Pty Limited.
The plan is to electrify the dredge and install a floating screen. The dredge will pump the sands and residues from the lake bed and pump it to the screen. The screen will have the ability to be floated or be based on skids, which will allow it to be moved easily and rapidly to other locations.
The screen will scalp the material and only allow material below 5mm pass onto the rest of the process. The oversize material which will consist of rocks, shells and other materials of an oversize nature, will be deposited on the island site (if recommended) initially. Once the island is formed the screen will be floated to area A and start filling the area.
A booster pump installed with the screen, will pump the sand from the lake direct to the Korrungulla processing area. This will eliminate the requirement for a booster station in Nicolle Avenue.
2.1 Plant and Equipment
2.1.1 Main Dredge
The major noise source associated with the proposal is associated with the electrified dredge. The dredge will be a cutter suction type with a motor capacity of approximately 300Kw.
It is proposed that dredging will commence on the north section of the dredge area and proceed in a southerly direction. The dredging programme will be undertaken in four (4) stages (Appendix B). The envisaged time frame for completion of each stage is dependent upon demand requirements. Under the present requirements (20,000 tonne per month) it is envisaged that stage 1 will be completed in three (3) years, stage 2 four (4) years, stage 3 four (4) years and stage 4 three (3) years.
2.1.2 Screen and Booster Pump
Due to the distances involved in pumping the sand slurry from the dredging areas it will be necessary to install and use a booster pump. The pump will be powered by an electric motor with a capacity of 200Kw.
The booster pump which will be housed in an acoustic enclosure will be located on the floating screen, (Appendix B). Gutteridge Haskins & Davey Pty Limited. Page 3 Rev 02 Dredging of Griffin Bay. Lake Illawarra.
2.1.3 Processing Plant
It is proposed to process the sand through the existing land facility (Appendix B) at Korrongulla, hence noise emission from this established site has not been considered as an acoustic issue in this assessment.
2.1.4 Road Transport
As there will be no increase in truck movements at the existing K000ngulla land base site. It is not envisaged that there will be a change to the existing traffic noise in the area as a result of this development. Guttcndgc Haskins & Davey Pty Limited. Page 4 Rev 02 Ddging of Gnffin Bay. Lake Illawarra.
3.0 PROCEDIJRES
This assessment has been undertaken generally in accordance within the recommendations of the N.S.W, Environmental Protection Authority (EPA), "Environmental Noise Control Manual (1985)" and the Australian Standard AS 1055 - 1984 "Acoustics - Description and Measurement of Environmental Noise".
3.1 Instrumentation.
For the purpose of our measurements the instrumentation selected consisted of, a;
Bruel & Kjaer Statistical Noise Level Analyser Type 4426, fitted with a 12mm Microphone Type 4165, and a
Bruel & Kjaer Precision Sound Level Meter Type 2203, fitted with a 12mm Microphone Type 4165.
The reference levels of the instruments were checked prior to and after measurements with a Bruel & Kjaer Sound Level Calibrator Type 4230.
3.2 Methodology
The methodology adopted for the assessment was based on the percentile exceedance sound pressure levels (LAN) measured at selected reference locations. In accordance with the EPA recommendations the measurements were recorded over fifteen minute sample periods..
3.2.1 Noise Level Descriptions
Fluctuating environmental noise is normally described by reference to the percentile noise levels or noise exceedance levels.
The most common percentile levels commonly referenced, and normally determined by statistical sound level measurement equipment, are the statistical values designated as "LAN" The parameters regarded as being the most significant amongst these are:
"LAI", the A-weighted sound level exceeded for 1% of the sample period.
"LAb ", the A-weighted sound level exceeded for 10% of the sample period, which is commonly termed the "average maximum noise level";
"LA901', the A-weighted sound level exceeded for 90% of the sample period and which is commonly termed the "average minimum noise level' or the background level";
"LAeq", is the energy equivalent sound level or what is described as the average energy level for the sample period. Guttcridgc Haskins & Davcy Pty Limited. Page 5 Rev 02 Dredging of Griffin Bay. Lake Illawarra.
4.0 CRITERIA FOR NOISE ASSESSMENT
The noise criterion normally recommended for the assessment of noise emissions from new development, are those recommended in the Environmental Protection Authority (EPA), Environmental Noise Control Manual. The EPA Manual states that noise emissions from a development should not increase the background (LA90) noise level at any affected residential premises by more than SdB(A). For assessment purposes, the noise is assessed as a contribution and in terms of a LA10 noise level. This criteria and procedure has been adopted for this assessment. Gutteridge Haskins & Davey Pty Limited. Page 6 RevO2 Dredging of Griffin Bay. Lake Illawarra. I
5.0 AMBIIENT BACKGROUND NOISE SURVEYS
5.1 Methodology
For our assessment of the ambient background noise levels, statistical noise level measurements were conducted during the month of August '91. From more recent inspections of the area, in our opinion the ambient noise levels measured in '91 would not have changed significantly, and are representative of the existing noise levels in the area.
5.2 Measurement Locations
Measurements were conducted at five (5) reference locations.
Location 1 - This location represents the rear boundary of residential properties in Northcliffe Drive west of the Illawarra Yatch Club. It was approximately 200 metres north of the northern extremity of the main dredge area and will have a direct line of sight to the dredge. The noise levels in this area are controlled by local traffic and the local natural habitat of boats, birds, wind, etc.
Location 2 - Location 2, was located on the eastern side of the Illawarra Yatch Club on the corner of Jackson Avenue and Northcliffe Drive. The measurement location was approximately 500 metres north of the main dredge area. The residents in this area will be partly shielded from the dredge when it is working on the northern foreshore of the bay. The prevailing noise climate of this area is controlled by road traffic and the local activities of the residents.
Location 3 - This location was located on Lakesview Drive on the south side of the bay. The measurement location was selected to represent residential properties approximately 500 metres south of the southern extremity of the main dredge area and 30 metres from the likely trimming activities along the edge of the dredging area. The residents in this area will have a direct line of sight to both dredging areas. The prevailing noise climate of this area was controlled by distant road traffic, industrial noise from Port Kembla, local road traffic and the natural habitat of people, birds, breezes, etc.
Location 4 - This location was similar to location 3 on the south side of the bay. The location was approximately 250 metres south of the main dredging area.
Location 5 - This location is also on the south side of the bay, and is similar to locations 3 and 4. The location was also approximately 250 metres south of the main dredging area.
5.3 Survey Dates
The ambient noise level surveys were undertaken on the mornings of Tuesday 27th August, Wednesday 28th August 1991. Gutteridge Haskins & Davey Pty Limited. Page 7 Rev 02 Dredging of Griffin Bay. Lake Illawarra.
5.4 Weather Conditions
The weather conditions throughout the surveys were fine with negligible wind. On Tuesday 27th August, the sky was clear there was no wind and the temperature ranged between 12'C - 16'C. While during Wednesday 28th August, the sky was overcast there was a slight breeze and the temperature ranged between 14'C - 16'C.
5.5 Results
The results of our field measurements are presented as percentile exceedance noise levels in Table 1.
Table I: Statistical Ambient Noise Levels Sound Pressure Level dB(A) re: 20 x 106 Pa Location Date Time LAeg LAI L LAl Location 1. Northcliffe Drive
27 Aug 0615 60.5 58.5 56.5 63.0 27 Aug 1305 59.1 59.0 56.8 62.0 28 Aug 0645 51.1 56.0 47.3 53.5 28 Aug 1011 55.8 60.0 54.0 57.5 Location 2. Northeliffe Drive
27 Aug 0638 70.6 78,5 59.0 74.0 27 Aug 1245 67.3 76.0 51.0 71.5 28 Aug 0625 67.2 75.8 53.0 72.0 28 Aug 1030 59.1 77.8 53.5 73.0 Location 3. Lakeview Drive
27 Aug 0703 54.1 66.3 49.0 55.5 27 Aug 1218 45.8 52.0 44.0 48.8 28 Aug 0712 49.7 53.8 46.5 51.5 28 Aug 1115 56.2 63.3 45.0 51.0 Location 4. Lakeview Drive
27 Aug 0720 51.5 53.5 51.0 52.5 27 Aug 1154 48.9 51.0 48.5 50.0 28 Aug 0755 48.5 54.3 45.5 51.5 28 Aug 1134 49.1 57.3 45.0 48.5 Location 5. Lakeview Drive
27Aug 1412 45.1 53.0 41.5 48.3 28Aug 0815 53.5 62.3 44.5 57.5 28 Aug 1155 49.1 57.3 45.0 48.5 Gutteridge Haskins & Davey Pty Limited. Page 8 RevO2 Dredging of Griffin Bay. Lake Illawarra.
6.0 PREDICTION OF NOISE EMISSIONS FROM PROPOSED EqUIPMENT AND SITE OPERATIONS
For the purpose of assessing the noise emissions from the proposed dredging operation, the noise level predictions have been based on the attenuation of sound as a result of hemispherical dispersion. For the purpose of establishing sound power levels for the plant, noise levels from previous measurements on similar equipment have been used.
The main plant evaluated in terms of predicting the operational noise, include the main dredge and the booster pump.
6.1 Main Dredg
The electric drive motor and hydraulic pumps are the main noise sources associated with the dredge. To reduce noise emissions from these sources, they will be housed in a plant room enclosure on the dredge.
The calculated sound power level of the dredge motor and pumps is 98dB(A) re: 1 (112 Watts. The likely noise spectrum for this source is:
dB(A) 63 125 250 500 1K 2K 4K 8K 98 97 104 96 97 93 90 82 78
6.2 Booster Pump
The booster pump will be powered by an electric motor, it also will be housed in an enclosure mounted on the floating screens. The sound power determined for the booster pump installation is 85dB(A) re: 102 Watts. The sound spectrum from this source will be generally broadband. Gutteridge Haskins & Davey Pty Limited. Page 9 Rev 02 I Dredging of Griffin Bay. Lake illawarra.
7.0 NOISE ASSESSMENT
7.1 Continuous Noise
Appendix C, presents the calculations for the noise emissions from the plant referenced to the referenced assessment locations, the results of these calculations are summarised in Table II.
Table H. Calculated Noise Level Contributions.
Sound Pressure Levels dB(A) re: 20 x 10 Pa
Location Stage 1 Stage 2 Stage 2A Stage 3 Stage 4 Measured I Background LA10 LA10 LA10 LAID LAD0 L Northcliffe Drive 24/26 19/24 28/37 26/32 23/28 56 I Northeliffe Drive 23/26 20/25 23/28 19/27 17/23 51 Lakeview Drive 24/27 25/5 1 19/23 19/24 17/25 44 Lakeview Drive 28/32 23/5 1 23/24 I 22/28 2 1/23 41 Lake view Drive 25/28 7/19 2 1/23 22/25 2 1/28 43
I In summary the range of noise levels have been calculated to give the resultant noise levels for each stage of the dredging programme. For the most exposed residences on Lakeview I Drive (Location 3 and 4), the resultant noise level is LA10 5ldB(A). This level represents the worst situation when the dredge is working in close proximity to the foreshore, and at its closest distance to the residences, as the dredge moves away from this exposed location the I noise levels will decrease (Appendix C).
Our assessment has shown that the predicted noise levels generally satisfy the recommended EPA goals and are generally less than the measured background LA90 noise levels. The only exceptions being for Locations 3 and 4 (Lakeview Drive) where the LA10 noise level exceeds the measured background noise by up to lOdB(A). At this time, it is envisaged that the dredge could be working in close proximity to the foreshore for periods of less than a week. It is therefore considered that the exceedances would not normally be considered to be significant in terms of being offensive. If required a time restriction could be placed on the dredging activities, whilst the dredge is in close proximity to the foreshore, i.e., within a distance of approximately sixty (60) metres from any residential boundary.' Gutteridge Haskins & Davey Pty Limited. Page 10 Rev 02 Dredging of Griffin Bay. Lake Illawarra.
&O NOISE CONTROLS AND PLANNThG
Listed below are the noise controls and planning recommendations that have been incorporated into our assessment.
8.1 Main Dredge
The overall sound power specified for the acoustically modified dredge plant is 85dB(A) re: 10 12 Watts.
8.2 Booster Pump
The pump will be enclosed in a pump house with acoustic air intake. The maximum sound power rating for the booster pump installation is 90dB(A) re: 1 012 Watts. 8.3 Operating Hours
Operations of the dredge and the pump shall be restricted to 7am to 5pm from Monday to Friday, with no operations on Saturdays, Sundays or Public Holidays. Gutteridge Haskins & Davey Pty Limited. Page 11 Rev 02 I Dredging of Griffin Bay. Lake Illawarra. I I 9.0 CONCLUSION This report presents the results, findings and recommendations from our assessment of the likely noise impact associated with the proposed dredging operations at Griffins Bay, Lake I Illawarra. This assessment has been based on ambient noise levels measured in August '91. From I recent inspections of the area, it is our opinion the ambient noise levels measured in '91 have not changed significantly, and are representative of the existing noise levels in the area.
I Our assessment has confirmed that with the selection of plant detailed in this report, the predicted noise levels contributions at the reference residential locations will generally satisfy the reconmended EPA goals, and will be generally less than the measured background LA90 I noise levels. The only exception being for Locations 3 and 4 (Lakeview Drive) where the LA10 noise level exceeds the measured background noise by up to lOdB(A), when the dredge is working in close proximity to the foreshore. These likely exceedances would not normally I be considered to be significant due to the activities being restricted to less than a period of two (2) to three (3) weeks. If required, during these operations a time restriction could be placed on the dredging activities, whilst the dredge is in close proximity to the foreshore, i.e., I within a distance of approximately sixty (60) metres from any residential boundary.
As it is proposed to process the dredged sand through the existing land facility, the proposal I will not add to the existing traffic volumes in the area. Hence, noise emission from the existing sand processing area and its associated traffic, are not considered to be an acoustic I issue in this assessment. Our assessment of the activities associated with the proposed dredging operations at Griffins Bay, Lake Illawarra, has shown that the likely resultant noise levels can be controlled, and I would not normally be considered to result in a significant loss of acoustic amenity in the I area. I I I I APPENDIX A: SITE LOCATION AND ASSESSMENT LOCATIONS.
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Reference Loctj0 1: li APPENDIX B: SITE LAYOUT
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CHANNEL STAGE PRIMBEE BAY
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SITE LAYOUT AND STAGING
ommo H4.lJr.. Dsqy Py Ud U 2I• *1 )H 5•4 to tJII It P%f . AWNDLX : CALCULATION OF PLANT SOUND PRESSURE LEVEL Reference Location 1: Northcliffe Drive
Noise Sources A-weighted Distance Distance Excess Noise Resultant Sound Attenuation Attenuation Control Level Power Level dB(A) In dB dB dB dB STAQJ Dredge 98 500/650 62/64 - 10 26/24 Booster Pump 90 500/650 62/64 - 10 18/16 STAQ Dredge 98 650/1100 64/69 - 10 24/19 Booster Pump 90 650/1100 64/69 - 10 16/11 STAGE 28 Dredge 98 150/420 51/60 - 10 37/28 Booster Pump 90 150/420 51/60 - 10 29/20 STAGE 3 Dredge 98 250/500 56/62 - 10 32/26 Booster Pump 90 250/500 56/62 - 10 24/18 STAA
Dredge 98 420/800 60/66 - 10 28/22 Booster Pump 90 420/800 60/66 - 10 20/14 I I I APPENDIX C: CALCULATION OF PLANT SOUND PRESSURE LEVEL I Reference Location 2: Northcliffe Drive
Noise Sources A-weighted I Distance Distance Excess Noise Resultant Sound Attenuation Attenuation Control Level Power Level dB(A) In dB dB dB dB I STAGE 1 Dredge 98 500/700 62/65 - 10 26/23 Booster Pump 90 I 500/700 62/65 - 10 18/15 STAGE 2 Dredge 98 550/1000 63/68 - 10 25/20 Booster Pump 90 550/1000 63/68 - 10 17/12 STAGE 2B Dredge 98 1 400/750 60/65 - 10 28/23 Booster Pump 90 400/750 60/65 - 10 20/15 I STAGE 3 Dredge 98 450/1100 61/69 - 10 27/19 Booster Pump 90 450/1100 61/69 - 10 19/11 1 STAGE 4 Dredge 98 700/1500 65/71 - 10 23/17 Booster Pump 90 I 700/1500 65/71 - 10 15/9 I I I I I U I I I APPENDIX C: CALCULATION OF PLANT SOUND PRESSURE LEVEL Reference Location 3: Lakeview Drive
Noise Sources A-weighted Distance Distance Excess Noise Resultant Sound Attenuation Attenuation Control Level Power Level dB(A) In dB dB dB dB STAGE 1 Dredge 98 475/625 61/64 - 10 27/24 Booster Pump 90 475/626 61/64 - 10 19/16 STAGE 2 Dredge 98 30/550 37/63 - 10 5 1/25 Booster Pump 90 30/550 37/63 - 10 42/15 STAGE 2 B Dredge 98 750/1100 65/69 - 10 23/19 Booster Pump 90 750/1100 65/69 - 10 15/11 STAGE 3 Dredge 98 650/1150 64/69 - 10 24/19 Booster Pump 90 650/1150 64/69 - 10 16/11 STAGE 4 Dredge 98 600/1400 63/71 - 10 25/17 Booster Pump 90 600/1400 63/71 - 10 17/9 1 I 1 APPENDIX C: CALCULATION OF PLANT SOUND PRESS1JRE LEVEL I Reference Location 4: Lakeview Drive
Noise Sources A-weighted Distance Distance Excess Noise Resultant I Sound Attenuation Attenuation Control Level Power Level I dB(A) In dB dB dB dB STAGE 1 Dredge 98 250/400 56/60 - 10 32/28 I Booster Pump 90 250/400 56/60 - 10 24/20 STAGE 2 I Dredge 98 30/700 37/65 - 10 5 1/23 Booster Pump 90 30/700 37/65 - 10 43/15 STAGE 2 B I Dredge 98 650/750 64/65 - 10 24/23 Booster Pump 90 650/750 64/65 - 10 16/15 I STAGE 3 Dredge 98 400/850 60/66 - 10 28/22 Booster Pump 90 400/850 60/66 - 10 20/14 1 STAGE 4 Dredge 98 250/900 56/67 - 10 32/21 I Booster Pump 90 250/900 56/67 - 10 24/13 I I 1 I 1 I I I I APPENDIX C: CALCULATION OF PLANT SOUND PRESSU E LEVEL Reference Location 5: Lakeview Drive
Noise Sources A-weighted Distance Distance Excess Noise Resultant Sound Attenuation Attenuation Control Level Power Level dB(A) In dB dB dB dB STAGE 1 Dredge 98 400/600 60/63 - 10 28/25 Booster Pump 90 400/600 60/63 10 10 10/7 STAGE 2 Dredge 98 200/800 54/66 15 10 19/7 Booster Pump 90 200/800 54/66 15 10 11/- STAGE 2 B Dredge 98 700/900 65/67 - 10 23/21 Booster Pump 90 700/900 65/67 - 10 15/13 STAGE 3 Dredge 98 600/850 63/66 - 10 25/22 Booster Pump 90 600/850 63/66 - 10 17/14 STAGE 4 Dredge 98 400/900 60/67 - 10 28/2 1 Booster Pump 90 400/900 60/67 - 10 20/13 SOCIO-ECONOMIC IMPACT OF THE
PROPOSAL TO EXTRACT SAND FROM
GRIFFINS BAY, LAKE ILLAWARRA
ECONOMIC PLANNING IMPACT CONSULTANTS PTY LTD, 1995
Griffins Bay Sand Extraction EIS
Gutteridge Haskins & Davey Pty Ltd Ml14182 SOCIO-ECONOMIC IMPACTS OF THE PROPOSAL TO EXTRACT SAND FROM GRIFFINS BAY, LAKE ILLAWARRA
EPIC Pty Ltd
March 1995 SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 1
SOCIO-ECONOMICS
THE EXISTING ENVIRONMENT The estimated resident population of the Illawarra Statistical Division for June 30th 1993 was 359,600. It is forecast that the region will grow to between 401,300 and 452,100 persons by the year 2006 (DOP, 1990). The region's economic base has traditionally been in the heavy manufacturing sector. However, in recent years there has been significant reductions in the manufacturing workforce, and Councils and other regional development authorities have attempted to diversify the local economies, highlighting in particular its potential as a recreation and tourism destination.
DESCRIPTION OF RELEVANT INDUSTRIES The construction industry The construction industry is an important industry in the Illawarra region. In the year ending October, 1994 the value of building approvals in the region was over $539,545,000. About 25 percent of the total value of approvals is for non-residential construction. The construction industry is a large consumer of sand, mainly as a raw material for concrete, although general construction, fill and mortar uses are also important.
The fishing industry. Commercial fishing The Illawarra region is an important centre for the NSW commercial fishing industry. Fishing occurs in both the lakes and estuaries of the region and also in the ocean. Fishing is largely regulated in New South Wales by the NSW Fisheries and Oyster Farms Act and its associated regulations. Commercial fishermen are required to hold a licence and to provide details of their catch. Fishing activities are often subject to closures in various areas and at different times of the year. It may also be subject to restrictions on the types of gear that can be used.
At present, of the 100 licensed fishers in the Lake Illawarra area, approximately 50 use Lake Illawarra at some time during the year. The following description of the commercial fishing activities in Lake Illawarra was summarised from discussions with several local fishers, representatives of the CFAC and the local NSW Fisheries inspector and reported in TEL (1995).
This section is based on the report of The Ecology Lab (TEL, 1995) SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 2
Prawning:The prawn season is generally from September through to May or June. Approximately 18 crews of 2 people each deploy nets for prawns in Lake Illawarra. There are several methods used to catch prawns. These include pocket set nets, snigging nets and running nets. No prawning takes place within the area which is planned to be dredged, although it is undertaken near the dredged areas. Meshing for fish and crabs: Meshing for fish and crabs occurs lake-wide, including the area proposed for dredging. Hauling for fish: Hauling for fish also occurs lake wide but requires shallow areas to haul the net onto and a lack of any obstructions on the hauling ground. The area proposed for dredging is one of a large number of recognised hauling grounds. Cockles: Cockles are collected by hand within seagrass beds on the eastern shore of the lake up to the entrance into Griff ins Bay, on the western side near Purrah Bay and to the west of Bevans island. There are up to 4 harvesters and the amount harvested is variable depending on price.
Figure 1 shows the weight of a variety of commercial species caught by fishers between the years 1985 to 1992. Whilst for most species there is a significant variation in the amount caught from year to year, there is no indication that there have been substantial changes overall in the amount of fish caught between 1985 and 1992. The exceptions to this are cockles, blue swimmer crabs and mudcrabs which were harvested in increasing quantities in the 1990s.
In comparison with other similar fishing areas, Lake Illawarra is ranked 11th out of 41 major estuaries in NSW in terms of production (kg) of 37 major species of commercial fish during 1990/91 (NSW Fisheries statistics). Lake Illawarra is a regionally significant commercial fishery, particularly for prawns and cockles. No data are available on the relative significance of the commercial catch from Griff ins Bays since only lake-wide data are available.
Recreational fishing Information on recreational fishing was obtained by the Ecology Lab from the NSW Fisheries Inspector, members of the Windang Hotel Fishing club and observations made by the Ecology Lab staff, during field sampling. On the basis of these discussions and observations it is considered that most recreational fishing in Lake Illawarra is in the entrance channel, and that Griffin Bay is only of limited significance to recreational fishing. This may change as a result of foreshore improvements, which may increase access to the water. I SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 3
Figure 1 The total weight per year (in 1000 kilograms) of 6 selected species caught by commercial fishers in Lake Illawarra from 1985 to 1992.
h)
3i
2
1985 1986 1987 1988 1989 1990 1991 1992
i) eastern king prawn j)
15 ,
10
5
1985 1986 1987 1988 1989 1990 1991 1992
k) blue swimmer crab 1) cockies
60
50 ii 2 40 1 30 Hi I :120
1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992
Source: TEL (1995)- Table 14
SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 4
Figure 1. The total weight per year (in 1000 kilograms) of all commercial species, all finfish and 4 selected species caught by commercial fishers in Lake Illawarra from 1985 to 1992.
a) All species b) All finfish
300 200
250 150 200
150 100
100 50 50
1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992
0 0 0 c) river garfish d) yellowfln bream -4
12 40
10 30 8
20
10
1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992
0
e) luderick f) flathead
35 25
30 20 25 15 20
15 10 10 5 5
1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992
Source: TEL (1995)- Table 14 SAND EXTRACTION IN GRIFFINS BAY - 50Gb-ECONOMICS -Page 5
OTHER IMPORTANT GROUPS AND ORGANISATIONS
The Lake Illawarra Authority The Lake Illawarra Authority commenced operation in 1987 after gazettal of the Lake Illawarra Authority Act. A central aim of the Act was "to constitute the Lake Illawarra Authority (LIA) for the purpose of improving the environment of Lake Illawarra, its foreshores and environment; and for related purposes". The LIA is the determining authority for all development within the lake below the mean high water mark. The LIA in their Draft Strategy Plan for Improvements to Lake Illawarra have identified the dredging of Griff ins and other bays as a priority.
Recreational Boating A previous demand assessment for boating facilities in Griff ins Bay, undertaken by Hassell Planning Consultants (1992) for the Public Works Department, indicated that demand over existing levels of use in Lake Illawarra are expected to increase by 70% over the next 5 years, 92% over the next 10 years and 115% over the next 15 years if appropriate improvements are undertaken. By 2001 they estimate that demand relating to boating activities could reach about 28,000 in the Illawarra. The study made the point that Griff ins Bay is excellently located being easy to access, close to amenities and conspicuous, and that over 2 million people live within a reasonable driving distance of the lake. The study also made the point that the use of the Lake for recreational boating is inhibited by the common perception that the water is unclean and by the smell from decomposing weed. The Illawarra Yacht Club is located adjacent to Griff ins Bay. The Yacht club is a major Illawarra Region recreation facility, with a large licensed club. It offers sailing in a number of classes for both dinghies and yacht sailing. Its current membership is 5100 of which 400 are sailing members, and 130 junior sailors. The club hosted two international events in 1994, namely the Windsurfer World Championships and the World University Windsurfing Championships. The club hopes to attract some major events as "warm-up" events for the Sydney 2000 Olympics. Officials of the club consider that the present state of Griff ins Bay is not conducive to boating activities. In particular they are concerned with the shallowness of the water and the water quality. Their use of Griff ins Bay is restricted to the deeper water at the entrance to the bay.
Local Residents Residents, especially those who have visual views of Griff ins Bay have expressed concerns at the current state of the bay, and are keen to see improvements undertaken. In particular, they have expressed concerns about the water quality in the Lake and the offensive odours which occur when algal blooms decompose. They have expressed support at public meetings for improvement works undertaken in recent years. SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 6
IMPACTS OF THE PROPOSED DEVELOPMENT
The operation of the dredging and cleaning operations will involve the employment of 5 people directly. The construction will provide 9 jobs for two years. It is estimated that through the multiplier effect, about another 5 jobs will be generated. I When the project is fully operational, royalty payments of about $500,000 per annum will be made to the Lake lllawarra Authority. In addition, the proposal will have an impact on a number of other industries, I especially the construction industry and the fishing industry.
The construction industry The proposed development will be to generate an important source of local sand for the construction industry. Section 4.1 has highlighted the relative shortage of sand. At the end of 1994, construction sand reserves within the Wollongong Statistical District are dwindling. Sand is available from Dunmore Sand and Soil at Dunmore, but this must be mixed with coarser sand for concrete manufacture. Some sand is also available from the Shoalhaven LGA (from Cleary Brothers at Seven Mile Beach), but it is estimated that this will be exhausted by 1998. Sand is available from several sites in the Southern Highlands, but the use of this sand has a number of disadvantages: The sand has to be carted a considerable distance: this additional cartage adds to the production costs of the Illawarra Construction Sector. The cost disadvantage, compared to local sand, is about $7.50 per tonne; The cartage of the sand from the Southern Highlands adds considerably to truck traffic (about 30 movements per day). Much of this cartage takes place on roads which are not suited to heavy vehicle movements, such as the Macquarie Pass.;
The use of sand from Gruff ins Bay would overcome these problems.
The fishing industry Table 1, which is reproduced from Table 15 of the TEL summarises the likely impact of the project on the commercial fishing industry. During dredging commercial fishing would be impacted through the loss of recognised fishing grounds where dredging is occurring. TEL estimate the impact of the proposal on prawning in the following terms: ° Changes in the circulation of water along the northern foreshore are predicted to be minimal (GHD, 1994). On this basis it would be expected that prawning in this area would be viable and similar to pre-dredging operations. The extension TABLE 1: LIKELY IMPACT OF THE PROPOSAL ON THE FISHING INDUSTRY
N- Undertaken Undertaken Likely tobe - Why? - Fishing Method within near impacted by dredged areas dredged area project (,) 0 z0 COMMERCIAL 0 0 Prawning: w a Pocket set nets No No No Only undertaken in entrance channel 0 Yes Possible Undertaken lakewide, but disturbance to area may alter 0 Snigging nets No Cl) prawn behaviour and movement >- Running nets No Yes Possible Undertaken lakewide, but disturbance to area may alter ca prawn behaviour and movement zC,) LL Meshing for Fish and Crabs LI- Splash method Yes Yes Yes Loss of fishing ground, during and after dredging (!3 z Set net Yes Yes Yes Loss of fishing ground, during and after dredging z0 Hauling for Fish Yes Yes Yes Loss of fishing ground, during and after dredging I- 0 Hand-collecting of Cockles No Yes Unlikely Only if smothering by settling of fines over seagrass on cr eastern foreshore I- x w z0 C')
Source: Table 15, TEL (1995)
— — — — — — — — — — — — — — — — — — — — — I SAND EXTRACTION IN GAl FFINS BAY - SOCIO-ECONOMICS -Page 8 of the channel in the southern part of Griffins Bay may provide another area available for prawning. If, however, the movement and behaviour of prawns has I been altered by the dredging works, this may not be the case" (TEL, 1995;p42)
In regard to other forms of fishing, in the short term, TEL indicate "that there will be a decrease in the productivity of the area where dredging takes place near Gruff ins Bay" (TEL, 1995;p39). 1 However, it should be stressed that fishers use a variety of sites in the Lake not just Gruff ins Bay. If they can increase their catches in other parts of the Lake in order to I compensate for any losses in the areas subject to dredging then the net impact on the fishing industry will be negligible. However, it is possible that there might be a loss in the productivity of the whole lake as a result of the loss of the seagrass I habitat. However, since its estimated that only 2.4 to 5 percent of the lakes total seagrass bed will be affected in the short term, it is considered that any loss on overall productivity is likely to be small. There is evidence that seagrass has I recolonised other dredged areas of the lake, so it is considered that in the long term the loss of seagrass will be much smaller than in the short term. It is not considered likely that cockles will be impacted by the proposal. Any loss of production will affect the income of fishers who use the Lake, but in many cases they will be able to reduce the impact of any loss by increasing their I activity in other fishing grounds.
It is considered that there will no adverse impacts on the recreational fishing industry. There will be a minor impact on bait collection since this is currently undertaken near the dredged areas. However, other areas where bait could be collected away from dredging operations are available.
The Lake Illawarra Authority The proposal will have a number of positive impacts for the Lake Illawarra Authority. Firstly, it will allow for the completion of part of the Authority's Lake Improvement program by dredging a shallow section of the Lake. Second, envisaged project sand sales will have the added benefit of providing royalty payments of about $500,000 per annum. These payments will allow for the completion of other improvement works by the authority.
Recreational Boating Improving water quality, deepening shallow water areas at the mouth of the bay and removing silt along the Primbee foreshore will have a positive impact on the recreational potential of the Bay. Organised events conducted by the Illawarra Yacht Club and the Illawarra Sailing and Rowing Club will benefit directly from the proposed development. In particular, the proposal will assist the Lake Illawarra Yacht Club in a number of ways:- SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 9
Increase in depth of the Griff ins Bay will provide the potential for the club to hold races in water closer to the club and in a sheltered location. This will be of particular assistance for the safety of junior sailors; The increase in the depth will help alleviate congestion - boats currently have to leave and return to the club in a narrow channel; The increase in amenity will assist the club with their efforts to establish themselves as a venue for pre-Olympic regattas.
Local Residents For similar reasons, nearby residential properties will be enjoy improvements in amenity after the completion of the project. However, they will experience other short term negative impacts from the operation of the project, including access to areas being dredged and reclaimed as well as minor visual impacts. It is considered that the residents will regard them only as minor annoyances, given the improvements in amenity that they will enjoy at the completion of the project. I- SAND EXTRACTION IN GRIFFINS BAY - SOCIO-ECONOMICS -Page 10 I REFERENCES I Australian Bureau of Statistics, Building Approvals, NSW - various 1993 and 1994 I issues, Cat No 8731.1. Australian Bureau of Statistics (1994), Regional Population Growth, Australia, Cat No 3218.0. Hassell Planning Consultants (1992) "Boating Facilities - Griff ins Bay Warrawong -, Demand Assessment", Report prepared for the NSW Department of Public Works I The Ecology Lab (1995) "An Assessment of Impacts on Marine Flora, Fauna and Fisheries of a Proposal to Extract Sand from Gruff ins Bay, Lake lilawarra". AN ASSESSMENT OF IMPACTS ON
MARINE FLORA, FAUNA AND FISHERIES
OF A PROPOSAL TO EXTRACT SAND
FROM GRIFFINS BAY, LAKE ILLAWARRA
THE ECOLOGY LAB PTY LIMITED, 1995
Griffins Bay Sand Extraction EIS
Gutteridge Haskins & Davey Pty Ud M114182 I I I I An Assessment of Impacts on Marine Flora, Fauna and Fisheries of a Proposal to Extract Sand from I Griffins Bay, Lake Illawarra I I April, 1995 I I FINAL REPORT I I I
I Report prepared for: Gutteridge Haskins and Davey I 39 Regent Street I Railway Square, Sydney, 2000 Report Prepared by: I The Ecology Lab Pty Limited I 14/28-34 Roseberry Street Balgowlah, NSW, 2093 I I I I TABLE OF CONTENTS Summary...... 1.0 Introduction ...... 1 1.1 Background and Aims ...... I 1.2 Existing Information ...... 2 1.2.1 Physical and Chemical Conditions ...... 2 1.2.1.1 Lake Illawarra ...... 2 1.2.1.2 Griffins Bay ...... 4 1.2.2 Seagrass Beds ...... 6 1.2.3 Saitmarshes and Mangroves ...... 8 1.2.4 Benthic Macrofauna ...... 8 1.2.5 Fish and Mobile Invertebrates ...... 8 1.2.6 Commercial and Recreational Fishing Activities ...... 9 1.3 Matters Arising from Previous EIS ...... 9
2.0 Study Methods ...... 11 2.1 Benthic Macrofauna ...... 11 2.1.1 Survey Procedures ...... 11 2.1.2 Statistical Analyses ...... 12 2.1.2.1 Multivariate Analyses ...... 12 2.1.2.2 Univariate Analyses ...... 13 2.2 Fish and Mobile Invertebrates ...... 13 2.2.1 Survey Procedures ...... 13 2.2.1.1 Beam Trawling ...... 14 2.2.1.2 Beach Seining ...... 14 2.2.2 Statistical Analyses ...... 14 2.2.3 Sizes of Fish ...... 15 2.3 Commercial Fishing ...... 15 2.3.1 Description of Commercial Fishing Activities ...... 15 2.3.2 Commercial Fisheries Statistics for Lake Illawarra ...... 15 2.4 Recreational Fishing ...... 16 2.4.1 Description of Recreational Fishing Activities ...... 16
3.0 Study Results ...... 16 3.1 Benthic Macrofauna ...... 17 3.1.1 Analysis of Assemblages ...... 17 3.1.2 Analyses of Populations ...... 18 3.2 Fish and Mobile Invertebrates ...... 19
I 3.2.1 Beam Trawis . 19 I 3.2.1.1 Analysis of Assemblages ...... 20 3.2.1.2 Analyses of Populations ...... 21 3.2.1.2.1 Spatial Comparisons ...... 21 1 3.2.1.2.2 Sizes of Fish ...... 22 3.2.2 Beach Seines ...... 22 I 3.2.2.1 Analysis of Assemblages ...... 23 3.2.2.2 Analyses of Populations ...... 23 I 3.2.2.2.1 Spatial Comparisons ...... 23 3.2.2.2.2 Sizes of Fish ...... 24 I 3.3 Commercial Fishing ...... 25 3.3.1 Description of Commercial Fishing Activities ...... 25 3.3.2 Commercial Fisheries Statistics for Lake Illawarra ...... 27 1 3.3.2.1 Temporal Comparisons ...... 27 3.3.2.2 Comparisons with other NSW lakes ...... 28 I 3.4 Recreational Fishing ...... 28 3.4.1 Description of Recreational Fishing Activities ...... 28 I 3.5 Conclusions from Field Studies ...... 29 3.5.1 Benthic Macrofauna ...... 29 I 3.5.2 Fish and Mobile Invertebrates ...... 30 3.5.3 Commercial and Recreational Fisheries ...... 31
4.0 Assessment of Impacts ...... 31 4.1 Brief Description of the Pmposal ...... 31 I 4.2 Dredging Areas A to D and the Channel Extension ...... 33 4.2.1 Impacts during Dredging ...... 33 I 4.2.1.1 Seagrass Beds ...... 35 4.2.1.2 Benthic Macrofauna ...... 36 I 4.2.1.3 Fish and Mobile Invertebrates ...... 39 4.2.1.4 Commercial Fisheries ...... 41 4.2.1.5 Recreational Fisheries ...... 42 I 4.2.2 Impacts after Dredging ...... 42 4.2.2.1 Seagrass Beds ...... 43 I 4.2.2.2 Benthic Macrofauna ...... 44 4.2.2.3 Fish and Mobile Invertebrates ...... 45 I 4.2.2.4 Commercial Fisheries ...... 45 4.2.2.5 Recreational Fisheries ...... 45 I 4.3 Creation of Deep Hole ...... 45 4.4 Creation of Channel ...... 47 4.5 Creation of Island . 48 4.6 Interactions with Other Proposals for Lake Illawarra ...... 48 4.7 Recommendations ...... 50 4.7.1 Mitigation of Impacts ...... 50 4.7.2 Rehabilitation of Seagrass ...... 51 4.7.3 Environmental Monitoring Programme ...... 53 4.7.3.1 General Considerations ...... 53 4.7.3.2 Seagrasses ...... 55 4.7.3.2.1 Natural Colonisation of Dredged Areas ...... 56 4.7.3.2.2 Indirect Loss or Damage ...... 58 4.7.3.3 Benthic Macrofauna ...... 58 4.7.3.4 Fish and Mobile Invertebrates ...... 59 4.7.3.5 Commercial Fisheries ...... 59 Acknowledgments ...... 60 References ...... 61 Tables Figures Appendices
LIST OF TABLES Table 1: Concentration of heavy metals and their detection limits in sediment samples from different locations in and around Griffins Bay. Table 2: Results of SIMPER analyses listing the 10 species of benthic macrofauna contributing most to the dissimilarity between groups identified in the MDS and tested using ANOSIM. Table 3: Summary of ANOVAs comparing mean values of benthic macrofauna at three spatial scales; between Griffins Bay and a reference area, locations and sites. Table 4: Results of pairwise comparisons of locations sampled for fish and mobile invertebrates collected by beam trawling using ANOSIM. Table 5: Results of SIMPER analyses listing the species of fish and mobile invertebrates collected in beam trawls contributing most to the dissimilarity between groups identified in the MDS and tested using ANOSIM. Table 6: Summary of ANOVAs comparing mean values of fish and mobile invertebrates collected in beam trawls at 5 locations and 2 sites per location in Lake Illawarra. Table 7: Summary of sizes of fish of commercial importance caught by beam trawling. Table 8: Results of pairwise comparisons of locations sampled for fish and mobile invertebrates collected by beach seining using ANOSIM. Table 9: Results of SIMPER analyses listing the species of fish and mobile invertebrates collected in beach seines contributing most to the dissimilarity between groups identified in the MDS and I tested using ANOSIM. I Table Summary of ANOVAs comparing mean values of fish and mobile invertebrates collected in beach seine nets at 5 locations and 2 sites per location in Lake Illawarra. Table Summary of sizes of fish of commercial importance caught by beach seining. I Table 12: Summary of ANOVAs comparing the annual catch by commercial fishers between 1985 and 1992. I Table 13: Comparison of the production (catch by fishers) in Lake illawarra with other lakes in NSW in 1991. I Table 14: Summary of details of the dredging proposal most relevant to aquatic ecological impacts. Table 15: Summary of impacts on different methods of fishing.
I LIST OF FIGURES Figure Si: Map of Griffins Bay indicating stages and areas to be dredged for proposal to extract sand. Figure 1: Comparison of distribution of seagrasses in Lake Illawarra as mapped by West et al. (1985) and King et al. (1991). I Figure 2: Comparison of distribution of seagrasses in Griffins Bay as mapped by West et al., 1985 and WBM Oceanics (1993). I Figure 3: Location of sampling sites for benthic macrofauna collected by cores. Figure 4: Location of sampling sites for fish and mobile invertebrates collected by beam trawl. Figure 5: Location of sampling sites for fish and mobile invertebrates collected by beach seines. I Figure 6: Two dimensional MIDS plot of benthic macrofauna assemblages at Griffins Bay, the reference area along the eastern shore and muddy areas. I Figure 7: Mean (+1 SE) abundance of selected species, total number of taxa and number of individuals of benthic macrofauna at all sampling sites. I Figure 8: Two dimensional MDS plot of fish and mobile invertebrate assemblages collected by beam trawls at two locations in Griffins Bay and three other locations in Lake Illawarra. I Figure 9: Mean (+1 SE) abundance of selected species, total number of taxa, total number of individuals and total number of commercial species of fish and mobile invertebrates collected by beam trawls at all sampling sites. Figure 10: Two dimensional MDS plot of fish and mobile invertebrate assemblages collected by beach seines at two locations in Griffins Bay and three other locations in Lake Illawarra. I Figure 11: Mean (+1 SE) abundance of selected species, total number of taxa, total number of individuals and total number of commercial species of fish and mobile invertebrates collected by I beach seines at all sampling sites. Figure 12: Length frequency distributions of sand mullet collected by beach seining at 5 locations. I Figure 13: Map of locations used by commercial fishers for setting prawn running nets. Figure 14: Total weight of commercial species harvested by fishers in Lake Illawarra from 1985 to 1992. Figure 15: Map of Griffins Bay indicating stages and areas to be dredged for proposal to extract sand. I
LIST OF APPENDICES I Appendix A: Mean and standard error of each species of benthic macrofauna per site collected by cores. Appendix B: Mean and standard error of each species of fish and mobile invertebrate per site collected by beam trawis. Appendix C: Mean and standard error of each species of fish and mobile invertebrate per site collected by beach seines. Appendix D: Data summarised from NSW Fisheries database on the species caught by commercial I fishers in Lake Illawarra from 1985 to 1992.
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I The Ecology Lb Pty. Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
SUMMARY
I Introduction The Ecology Lab Pty Ltd was commissioned by Gutteridge Haskins and Davey (GHD) to describe I the existing estuarine environment of Lake Illawarra and to assess potential impacts of a proposal by South Coast Equipment Pty Ltd (SCE) to extract sand near the entrance to Griffins Bay. The L proposal to dredge the entrance to Griffins Bay has been the subject of a previous environmental impact statement (EIS). Reviews of that EIS indicated that some issues associated with the proposed development required further work and those issues related to aquatic ecology have been incorporated into the present study, which in turn have been incorporated in the new EIS. I prepared by GHD.
II Description of the Existing Environment
Lake Illawarra is a barrier estuary and is separated from the ocean by a long, shallow channel. The lake covers an area of about 35 km2 and has a catchment of about 270 km2. Tidal range within the lake is 3-5 cm and is 10-25 cm within the entrance channel. Residence time of water in the lake has been estimated as 26 to 39 weeks. Several studies have been done on the levels of contaminants in the sediments of Lake Illawarra. Sources of heavy metals in sediments are believed to be the Port I Kembla industrial complex, the Dapto smelting works (closed in 1906) and Tallawarra Power Station (decommissioned in 1989). Urban run-off also contributes to the load of contaminants. The I lake is surrounded almost entirely by urban and industrial development.
I Griffins Bay is in the north-east of Lake Illawarra. GHD studied water circulation, water chemistry and sediment chemistry in Griffins Bay as part of the EIS. A hydrological model used by GHD indicated that currents (which were in a southerly direction) in Griffins Bay were wind-induced and that there was little or no tidal influence. Water temperature in Griffins Bay was found to vary little with depth or location within Griffins Bay, but concentrations of dissolved oxygen were low near the bay floor. Sediment samples collected by GHD in Griffins Bay were analysed for six heavy metals. Of these, mercury was not detected, cadmium, lead and copper were detected in some samples and chromium and zinc were detected in all samples. The concentration of chromium was greater in sediments collected from Primbee Bay than elsewhere in Griffins Bay The Ecology Lab Pty. LtiL Griffins Bay sand extraction - Marine Ecology - Final Report, April1995 and the concentration of zinc was greater in Primbee Bay and north of Puny Burry Point than all other locations sampled. The concentrations of chromium and zinc in the sediments were probably large enough to have the potential to affect organisms living in the substratum.
Preliminary tests done by GI-ID (1995) on the sediments in Griffins Bay indicated that there was the potential for acid sulphate soils to occur in Griffins Bay. GI-ID (1995) recommended that a more comprehensive survey be undertaken prior to dredging. An assessment of the effects of acid sulphate soils on aquatic biota cannot be made using the data collected to date. Therefore, the potential for acid sulphate soils needs to be quantified and investigated further. Acid sulphate soils (ASS) are found in many places along the Australian coast. They contain iron pyrite, a naturally occurring mineral in estuarine sediments. Iron pyrite is stable under waterlogged (reducing) conditions where it is no threat to the environment. When exposed to air, however, it reacts rapidly with oxygen to produce sulphuric acid and iron. Exposure to air can happen naturally (e.g. during drought) or through a human activity such as dredging and some agricultural practices. The oxidation of pyrite to sulphuric acid and iron decreases the pH of the sediment making it acidic. The lowered pH levels may affect groundwater as well as surface water bodies. Elements such as aluminium and iron can dissolve and reach concentrations high enough to be detrimental to aquatic biota. The influx of acidic water high in aluminium and iron clogs the gills of fish, crustaceans and oysters causing 'fish kills'.
Apart from phytoplankton and algae, three types of aquatic vegetation are significant in NSW, saltmarshes, mangroves and seagrasses. This vegetation may be ecologically important as it contributes to the productivity of the estuary, and provides food and shelter for many aquatic animals, some of which are economically valuable. Significant saltmarshes are limited to one small area in Koona Bay and there are no mangrove forests reported in Lake Illawarra. Seagrasses, however, are very common in the lake, where at least four species occur, Zostera capricorni, Ruppia megacarpa, Halophila oval is and Halophila decipiens. Large beds of seagrass occur in the shallows off the shoreline and are mainly formed by Zostera. In Lake Illawarra, seagrasses appear to be limited in depth between the intertidal zone and -2 m Australian Height Datum (AHD). Since 1976, estimates of the total area of seagrasses in Lake Illawarra have ranged from 5. 12-10.9 km2. In a recent study of seagrasses in the lake, it was found that, following dredging, Zostera successfully recolonised in one area - Koonawarra Bay - but that in another area - Griffins Bay - recolonisation was minor. It was concluded that the extent and rate of recolonisation were probably related to the final depth of the substratum and possibly the type of dredging.
Prior to the present study, there was little information on the animals inhabiting the sediments of
11 The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Griffins Bay. One group of these animals is known as benthic macrofauna and consists mostly of invertebrates which are retained on a 1 mm sieve. Examples include marine worms (po!ychaetes), snails (gastropods) and crustaceans (e.g. amphipods). They are important because they are eaten by a variety of predators (e.g. birds and fish), they play an important role in pathways of detrital and nutrient recycling and they are good indicators of environmental disturbance (e.g. pollution). Like the benthic macrofauna, there is little information on the fish and mobile invertebrates (e.g. prawns) occurring in Lake Illawarra. Some studies have been commissioned along the western shores of the take, but there is vety little information on the fishes of Griffins Bay.
During field studies for the EIS, The Ecology Lab made several qualitative observations of the biota of Lake Illawarra. First, some isolated saltmarsh (Sarcocornia quinqueflora) was observed at Purry Burry Point and rushes grew along parts of the shoreline of the Point. Second, just offshore from Purry Burry Point along the entire eastern shore of lake there were masses of filamentous algae. The occurrence of this algae is probably seasonal. Numerous observations were made of water birds during the field studies, including pelicans, silver gulls, black cormorants, pied cormorants and black swans. The black swans formed large flocks off the eastern shore of the lake, well to the south of Griffins Bay. The other birds showed no obvious patterns in their distribution.
Quantitative field studies done by The Ecology Lab for the supplementary EIS focused on benthic macrofauna, fish and mobile invertebrates and commercial and recreational fisheries. Benthic macrofauna were collected at two sites within each of eight locations in Lake Illawarra in November 1993. Three locations were on the sand body proposed for dredging at the entrance to Griffins Bay, one location was on muddy substratum within Griffins Bay, three locations were on sand along the eastern shore of Lake Illawarra and were sampled as reference locations to compare with the locations on sand at Griffins Bay. A final location was on muddy substratum at the southern end of Lake Illawarra. At each site, five samples of sediment were collected by a diver using a corer and sieved through a 1 mm mesh. Fish and mobile invertebrates were sampled in seagrass beds using a beam trawl and a beach seine in November 1993. Collections were made at two sites within five locations, two at Griffins Bay and three at reference locations around Lake Illawarra. At each site, four replicate samples were obtained.
The use of reference locations was crucial to the study because they provided a geographical context against which the findings for Griffins Bay could be compared.
The study of benthic macrofauna yielded a total of 8 235 individuals, representing 47 taxa. Most of the species are common in estuaries in New South Wales. Statistical analysis of the assemblage of
111 The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
macrofauna indicated two major trends: 1) there were differences in the assemblages of benthic macrofauna between sandy and muddy substrata, while the assemblages of the muddy substratum were very similar, despite being collected from opposite ends of Lake Illawarra. 2) The samples taken from the proposed dredge area were relatively distinct from those taken from the reference locations along the eastern shore of the lake. Statistical analysis of biodiversity, total abundance and populations of macrofauna yielded a variety of trends. The mean number of taxa did not vary significantly at any of the spatial scales examined, indicating that the biodiversity of benthic macrofauna in Griffins Bay was, at the time of sampling, similar to other parts of Lake Illawarra. Some of the samples taken from Griffins Bay were taken near to, or within, areas that had been previously dredged. Variability in total abundance was large among locations in the proposed dredge area in Griffins Bay compared to the eastern shore, despite the fact that locations were much further apart on the eastern shore. In terms of individual species that were numerically abundant, there was no statistical distinction between Griffins Bay and the Eastern shore and variability often occurred at small spatial scales.
The beam trawl samples yielded at total of 42 967 fish and mobile invertebrates, representing 30, 7 and 1 species of fish, crustaceans and cephalopods, respectively. The most abundant species of fish were two gobies and a pipefish, representing 65% of the total catch. Species of economic value represented only 0.5% of the catch, the most abundant of which were the six-spined leatherjacket, blue groper and luderick (79% of the catch of economically valuable fishes). King prawns and blue swimmer crabs were also collected. Statistical analysis of the assemblage sampled with the beam trawl indicated that samples from the two locations within Griffins Bay (one of which appears to have been in a previously dredged area) were similar to most of the other locations sampled within Lake Illawarra. The exception was the southern side of Windang Channel, which was distinctive compared to all other locations, due primarily to very large numbers of the non- commercial shrimp, Macrobrachium intermedium. The diversity of biota sampled by beam trawl in locations in Griffins Bay was within the range found at the other locations within Lake Illawarra. None of the species collected was considered to be rare or endangered. On average, there were 5 - 10 individuals of commercially important fish caught per trawl at all locations except the eastern shore, where the average was slightly less. No significant difference between sampling locations or sites was found for the abundance of king prawns or blue groper, leatherjackets did vary among locations, but mean abundance in Griffins Bay was within the range observed elsewhere. The total abundance of individuals sampled by beam trawl was significantly larger at one location in the Windang Channel, due to the very large abundance of Macrobrachium. Other species examined varied in abundance at the scales of locations or sites and in general Griffins Bay was within the range observed at other locations. Measurements of the sizes of fish collected by beam trawl
lv The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
revealed that all species of economic value were juveniles, many of which had probably settled from the plankton shortly before capture.
Sampling with the beach seine yielded a total of 38 275 fish and mobile invertebrates, representing 43, 6 and I species of fish, crustaceans and cephalopods, respectively. The most abundant species of fish were the Port Jackson perchlet, transparent goby and smalimouth hardyhead, representing 62% of the total catch. Species of economic value represented 10.3% of the catch, the most abundant of which were sand mullet, luderick and tarwhine (55% of the catch of economically valuable fishes). King prawns represented 99.5% of the catch of commercially important crustaceans, with a few blue swimmer crabs making-up the remainder. Statistical analysis of assemblages suggested that each location had a distinct assemblage of fish and mobile invertebrates. The location in Windang Channel was distinguished by the presence of large numbers of Macrobruchium, as was found with the beam trawis. The location at Furry Burry Point (Griffins Bay) was distinctive, due to the presence of smallmouth hardyheads and the absence of tarwhine, sand mullet and luderick. These species are relatively mobile and were probably under- sampled by the beam trawl, hence the different findings for the seine netting (it may also be due to the positions of sampling, as the beam trawls were done further offshore). The biodiversity of fish and mobile invertebrates at one location in Griffins Bay (on the northern shore of the bay, east of the yacht club) was within the range recorded at the reference locations, but biodiversity off Purry Burry Point tended to be less than elsewhere. The total abundance of species of economic value was significantly greater on the northern shore of Griffins Bay compared to all other locations. The total abundance of all species caught in the beach seines was highly variable among locations and within sites, but variability in Griffins Bay was similar to the reference locations. All the fish caught by beach seine were juveniles (many recently settled) except for a few adults of three species of mullet.
The following conclusions can be drawn from the field studies described above. First, assemblages of benthic macrofauna in the proposed dredge area were distinctive compared with similar sandy habitats along the eastern shore of Lake Illawarra. The assemblages of muddy habitats within Griffins Bay were very distinctive compared to sandy habitats, but were very similar to muddy habitats sampled at the southern end of lake Illawarra. The biodiversity of benthic macrofauna and abundance of the species examined varied at several spatial scales. None of the data suggest that the proposed dredge area is particularly rich in benthic macrofauna, nor that the sediments within Griffins Bay are poor in macrofauna. Note, however, that this conclusion is based on one survey and no measure of temporal variability was made. GElD found that oxygen levels in bottom waters of Griffins Bay can be low, hence there may be times when the benthic macrofauna is
V The Ecology l.ah Pt y. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 2995
affected by poor water quality within the bay.
Second, assemblages of fish and mobile invertebrates showed similarities and differences when sampled by beam trawl and beach seine. The most notable similarity was the distinctive nature of one location in Windang Channel, which was numerically dominated by Macrobrachium. The most notable difference was the distinctive nature of the assemblage at Puny Buny Point sampled by beach seine - here attributed to the collection of very mobile fish in the seine net that could probably avoid the beam trawl. Another notable finding from the beach seining was the presence of relatively large numbers of fish of commercial value in the seagrass bed on the northern shore of Griffins Bay. These fish were all juveniles, suggesting that particular bed may be a relatively important nursery area. Studies by other workers in NSW have found that some beds consistently rate highly in terms of their value as nursery habitat and this may be due to a number of factors, such as aspects of the beds or the nature of currents transporting larval fish to the bed. This site in Griffins Bay was in the vicinity of previous dredging works which were completed in September 1991. This provides anecdotal evidence that seagrass beds which have been exposed to dredging close by function as nursery habitat several years after dredging was completed. The findings for Griffins Bay must be considered cautiously as only one survey was done, but they do have important consequences for the present proposal. The seagrass beds on the northern shore of the bay are not within the proposed dredge area, but the dredging operation can and would need to be managed so that a) current patterns are not significantly altered by the dredging and b) indirect effects, such as plumes, are mininiised. The hydrological model (GI-ID, 1995) predicts negligible changes in current speed (maximum change of 0.05 rn/sec in the northern channel) and no change in the direction of currents from present conditions.
Commercial and Recreational Fishing
Approximately 50 licensed fishers use Lake Illawarra at some time of the year. Four major types of fishery were identified in the lake. First, prawns (mostly king prawns) are caught using pocket set nets in Windang Channel and snigging nets and running nets in other parts of the lake. Snigging may be done virtually anywhere in the lake outside the channel (where it is prohibited), running nets are laid shore-normal and rely on currents running longshore to transport prawns to the nets. Running nets are prohibited in Windang Channel, but are set in several parts of the lake, including the shore to the north of Griffins Bay and, at times, in Griffins Bay itself. Second, fish and crabs are taken by mesh-netting throughout the lake, including the area proposed for dredging. Third, beach hauling occurs lake-wide for fish and crabs. This method requires the presence of a gently-
VI The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
I sloping shore without obstructions. One area hauled is off the western part of the proposed dredge area. Fourth, cockles are collected by hand within seagrass beds along the eastern shore up to the I entrance of Griffins Bay.
Data compiled by NSW Fisheries were examined to determine variation in the commercial catch over about the last 8 years. For most of the species examined, and for the total commercial catch, there was significant variation from year to year, but, with two exceptions, there were no long I term trends apparent. The exceptions were cockles and crabs (blue swimmer and mud crabs), I which have been caught in increasing numbers during the early 1990's. Ina regional context, Lake Illawarra ranked 11th of 41 major estuaries in NSW in terms of production (kg) of 37 major species of commercial fish during 1990/91. Comparing the lake to six other, similar lakes in NSW, Lake Illawarra produced the largest catch of cockles and king prawns and substantial catches of garfish, bream, luderick, sea mullet and school prawns. On this basis, it is concluded that Lake Illawarra has a regionally significant commercial fishery. Note that the data do not allow a comparison of different areas within Lake Illawarra.
' It is estimated that some 90% of recreational fishing for finfish occurs within Windang Channel and therefore well to the south of Griffins Bay. It appears that very little recreational fishing is done in Griffins Bay. Recreational prawning is done in Windang Channel and along the eastern I shore of Lake Illawarra, with little done in Griffins Bay. Bait is also collected in the lake. Blackfish- weed is collected along the shallows as far north as the entrance to Griffins Bay and worms and I flippers are collected in Windang Channel and along the eastern shore.
Assessment of Impacts
The main parts of the proposal that need to be considered in assessing the impacts on the aquatic environment are: 1) direct removal of habitat such as seagrass and unvegetated substratum by dredging, 2) indirect effects of dredging on surrounding habitats; 3) direct creation of new habitats, including an island off Purry Burry Point, extension of a channel out of Griffins Bay and if the embankments were removed, creation of a hole to 14 m depth; and 4) indirect effects of the newly created habitats.
vii The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 7995
Impacts Associated with Dredging
Seagrasses. The proposed dredging, including the channel extension, would cause the direct removal of seagrasses from the entrance to Griffins Bay. The estimated loss is between 25 and 26.4 ha, or in the range of 2.4 - 5% of the total area of seagrass in Lake Illawarra depending on which estimate of total area of seagrass is used. The loss of seagrass would be progressive through the life of the project and the rate of removal of seagrass would depend on the progress of the dredging operations. Thus, the 2.4 - 5% loss represents the maximum removed over a period of 10- 13 years. Once one area of the seabed had been dredged, it may be possible for seagrasses to recolonise that area, which would reduce the overall loss. The success of recolonisation would depend, however, on the conditions in the dredged areas, particularly depth, which would need to be less than 2 m (ideally less than 1.5 m) to allow seagrasses to grow. Two of the designated dredge areas (part of Area A and all of Area B - see Figure Si) would be at a suitable depth, although other areas would either be too deep (unless backfilled) or form part of an island proposed as part of the project. If recolonisation by seagrasses of Areas A (excluding the island) and B occurred, the overall loss of seagrasses at the end of the project would be 80.2% of the estimated total removed by the proposal. If Areas C and D were also backfilled to a suitable depth for seagrass to grow, then the overall loss of seagrasses, following recolonisation, would be negligible. The water quality of Griffins Bay would probably need to improve from its present condition, however, to allow seagrasses to grow at a depth of 1.5 m or more.
Potentially, seagrasses could also be lost due to indirect effects, such as smothering of beds by sediment plumes, changes in water quality and physical damage due to anchoring and other dredging activities. The extent of these effects can and would be ininimised by anticipating them and adopting mitigative measures and by compliance monitoring. Mitigative measures include the use of silt curtains and design of work practices to minimise or avoid damage to seagrasses.
Benthic macrofauna. Dredging would cause the removal of benthic macrofauna associated with seagrass beds and unvegetated sandy substrata. Following the completion of dredging, macrofauna would recolonise the disturbed areas, particularly in Areas A and B. It is impossible to predict accurately the rate of recolonisation or the structure of the assemblage occurring after dredging. It is expected, however, that initial colonisation would be relatively rapid (i.e. over periods of months), but that the structure of the assemblage would be highly variable through time and space, depending on the staging of other parts of the dredging, the possibility of using some areas
for fill from other dredging works (which is not part of the present proposal), the availability of colonising organisms in the area, water quality and the nature of the changes to the substratum The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
through time (e.g. due to possible colonisation by seagrasses). It seems likely that Area B, which would be similar in depth and sediment type to the pre-dredging condition, potentially could be recolonised by an assemblage of benthic macrofauna similar to that found prior to dredging. For the other dredged areas it is difficult to predict what animals could recolonise because the substratum would be at different depths and have different sediment characteristics to the pre- dredged condition.
As with the seagrasses, benthic macrofauna may be affected by indirect effects of the proposal, particularly the settlement of sediment plumes. Associated with this is the potential effect of smothering and the release of toxic contaminants (e.g. chromium and zinc). A preliminary test indicated that heavy metals would remain bound to the fine sediments rather than be released into the water column after being washed and returned to the lake as backfill for the island and Area A (Cl-ID, 1995). The use of a silt curtain around all dredging operations should minimise the potential for indirect effects on benthic macrofauna.
Fish and mobile invertebrates. During the dredging, many fish and mobile invertebrates would be able to avoid being sucked into the head of the dredger, but there are two exceptions to this. First, small fish and mobile invertebrates associated with seagrasses that would be removed when the dredging first began would also be lost. This loss would include fish and prawns of economic value utilising the seagrasses as nursery habitat. It may be possible to minimise the loss of economically valuable species utilising the seagrass beds by removing seagrass at times of the year when significant settlement is not expected. Second, some relatively sedentary fish (e.g. flathead, leatherjackets) may be trapped occasionally by the dredger, but such losses would be expected to be relatively small.
Once the seagrasses had been removed from the proposed dredge areas, the potential of these areas to act as nursery habitat in subsequent years would be reduced, pending the recolonisation of seagrasses. There are three possible consequences for fish and mobile invertebrates that could have utilised these beds: 1) that they will simply redistribute to other beds in the lake and their development will be unaffected; 2) that they will redistribute to other beds in the lake and their development will be affected due to increased competition from animals using these beds; 3) that they will not be transported to any other beds, or transport will take much longer, thus extending the planktonic period and an increase in the risk of lack of food or predation in the planktonic phase. The scientific understanding of such mechanisms is not well understood, but there are studies which suggest that particular seagrass beds in NSW can support relatively large numbers of fish and mobile invertebrates. It is therefore predicted that there is likely to be a loss in the The Ecology Lab Ply. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
productivity of fish and mobile invertebrates associated with the loss of seagrasses from the dredging operation, but that this loss would be less than that directly proportional to the area of seagrass lost.
As with the benthic macrofauna, indirect effects of the proposal have the potential to affect fish and mobile invertebrates beyond the actual dredging areas. In particular, any effects on the seagrass bed on the northern shore of Griffins Bay could be significant due to the large numbers of species of commercial value found there during the field studies. According to GI-ID, the proposal would increase water movement into Griffins Bay, so presumably larval transport to the bed would be maintained. Other possible effects, such as movement of turbid water, could be controlled using silt curtains during dredging.
Fishing. Commercial fishing could be affected by: 1) loss of fishing grounds; 2) interference with currents affecting the movement of harvested species, particularly prawns; and 3) reduction in productivity. There would be a loss of hauling grounds and splash meshing grounds at the entrance to Griffins Bay. According to GHD, currents would not be affected by more than 0.05 m/s (increase or decrease in flow velocity depends on the prevailing winds) in areas where prawn running nets are deployed, near the northern shore of Griffins Bay close to dredging areas. The extension of the channel in Griffins Bay on the southern shore may provide a new area where running nets could be deployed. As discussed above, there is likely to be some loss in the productivity of the lake due to the loss of habitat. In the long term, recolonisation of the dredged areas by species of commercial value may restore productivity. Improvements to the water quality of Griffins Bay, as predicted by Gl-[D, may also lead to an increase in fisheries productivity within Griffins Bay, after completion of dredging. Recreational fishing is unlikely to be affected negatively by the dredging proposal, although construction of the channel may improve access to Griffins Bay for anglers, which would be a positive benefit.
Creation of New Habitats
Deep Hole. GI-ID have predicted that water quality and circulation in the dredged hole (Areas C and D, Fig. Si) would be different to other parts of Lake Illawarra. Water temperature could be less and oxygen levels depleted. Under these conditions, the hole would provide poor habitat and, if poor quality water were transported out of the hole, may have detrimental effects on biota elsewhere in Lake Illawarra. However, under the proposal, this problem would be mitigated by the isolation of the hole from the lake by an embankment and the use of an aeration system to mix
x The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
the waters of the hole to avoid stratification. Compliance monitoring would be essential to ensure
that adequate conditions of water quality were maintained in the hole at all times in case of escape
of this water to the rest of the lake. The ELS includes plans to monitor the dissolved oxygen and
temperature at several depths within the deep hole so that adjustments can be made, if necessary,
to the aeration system. The bunding of the hole would also prevent this area from being a sink for
debris such as seagrass, algae and gross pollutants. The hole would be bunded for the duration of
the dredging project. According to the EIS, after the dredging contract is completed, the Lake
Illawarra Authority would be responsible for the maintenance of the embankments around the
deep hole. I
If the embankments around the deep hole were removed before backfllling, the hole would
provide a new habitat in Lake Illawarra and it is impossible to predict accurately the biota that
would occupy them. It is clear, however, that no seagrasses would colonise the hole beyond about
2 m depth. Some species of benthic macrofauna recorded in Lake Illawarra have been recorded to
depths of 20 m in other estuaries. It is therefore expected that, provided dissolved oxygen levels
are maintained, there would be colonisation of the substratum of the hole. Studies of the use by
fish and prawns of deep holes in Botany Bay indicated the presence of a wide variety of species,
and it was concluded that the deeper habitats there provided feeding areas for some commercially
valuable fish in winter. Extrapolation of these results to Lake Illawarra is questionable, however,
for two reasons. First, the holes were relatively close to the entrance to Botany Bay and colonisers
included species of fish from adjacent coastal waters. The hole in Lake Illawarra would be
relatively remote from the sea. Second, the hole would be isolated from Lake Illawarra by bunds
and it is not clear if any fish would be able to gain access to the hole (e.g. as larvae or small
juveniles transported in slurry water). Therefore, it is predicted that, provided adequate water
quality were maintained, the deep hole may be utilised by some fish, but it is not possible to
predict the structure of assemblages or occurrence and abundance of particular species.
Creation of Channel. Increased water circulation as a result of the channel would improve water
quality within Griffins Bay and should therefore reduce the risk of deoxygenated bottom waters in
Griffins Bay. There are two potentially adverse effects, however, that need to be considered. First,
there may be transport of silt out of Griffins Bay into the lake in the first six months or so
following dredging. Thus, there may be short-term smothering of benthic macrofauna in areas
where the silt settles. There may also be transport of contaminated sediments (e.g. with chromium
and zinc) out of the bay which may have direct toxic effects or bioaccumulate. Removing the silt
prior to dredging the channel would substantially reduce the risk of adverse effects on the benthic
macrofauna at the western end of the channel extension. Compliance monitoring is recommended
xi The Ecology Lab Ply. Ltd. Griffins Bay sand extraction - Marine Ecology Final Report, April 1995
to evaluate the success of this. Second, maintenance dredging may be required to maintain the channel at a navigable depth. Where such dredging is required, use of a silt curtain should be considered and dredging should be programmed to avoid damage to seagrass beds within the bay
Creation of island. The location of the island in the more south westerly position would allow increased water flow into Griffins Bay. The island would provide a habitat for bird life. To prevent erosion of the island from wind-waves, reinforcement may be required around the island's perimeter. This reinforcement would provide a habitat for aquatic biota.
Cumulative Effects
The proposal to dredge Griffins Bay was considered in relation to a proposal for dredging the channel at the entrance to Lake Illawarra. On the basis of a review of this EIS, it is concluded that the cumulative effects (apart from effects already discussed with regard to the Griffins Bay proposal) would be negligible.
It is possible that the deep hole in Areas C and D may be used for placement of spoil obtained from other works in Lake Illawarra. Subject to assessing the effects of the dredging and disposal operations for these other works, the filling of the dredge hole could, ultimately, return the area to a state similar to its pre-dredged condition, which may allow for the recolonisation of seagrasses, restoration of estuarine productivity and return of fishing grounds. It would also obviate the need to find disposal sites for spoil from the other works. In this case, cumulative effects would be beneficial, provided that the subsequent dredging and disposal operations were environmentally sound.
Mitigation of Impacts
Mitigation of impacts has been discussed in relation to specific aspects of the proposal. The following measures are recommended: 1) minimising overall loss of seagrass; 2) preventing the escape and spread of fine sediments; 3) minimising the frequency and extent that bottom sediments are disturbed; 4) bunding of the deep hole; 5) aerating the deep hole to prevent stratification; and 6) allowing fishers access to areas not being dredged at any one time.
xii The Ecology Lab Pty. Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
It is also recommended that a programme be initiated to restore seagrasses as quickly as possible by: 1) contouring as much of the dredged areas as possible to the appropriate depth (say 0.5-1.5 m below AHD) to promote the growth of seagrasses; and 2) if necessary, considering transplanting of seagrasses - particularly Zostera - to enhance restoration.
I Monitoring
The Director of the Department of Planning requires that a monitoring plan be formulated for the proposal. The aims of the plan should be to: 1) distinguish impacts associated with the dredging proposal from natural variation or other human induced impacts; 2) test predictions made in the EIS; and 3) assist in formulating strategies to mitigate any unforeseen impacts after dredging has commenced. It is recommended that seagrasses, benthic macrofauna, fish and mobile invertebrates be monitored for the current proposal, in addition to any monitoring of water quality, water circulation and sediments that may be recommended by GELD. Also, consideration should be given to monitoring the potential effects of the proposal on fishing in Lake Illawarra.
The essential elements of monitoring are the use of adequate temporal and spatial controls, which 1 means sampling on several occasions before, during and after the project and at appropriate reference areas. In addition, prior to initiating monitoring, it is recommended that the dredging I operator, the Lake Illawarra Authority, other regulatory authorities and interest groups determine the limits of change in biota, water quality, etc, that can occur before alternative management I strategies are initiated. Once these limits are set, the most sensitive and cost effective monitoring programme can be designed.
I Given the ecological significance of seagrasses and the large size of the area of seagrasses that ' would be directly lost or disturbed by the proposal, it is recommended that a plan of management be formulated to be initiated if recolonisation of seagrass beds does not occur or is unacceptably slow. The recommended plan of management is outlined as follows:
Step 1. Areas where seagrass had been removed and where dredging and backfilling is completed should be inspected for; i) the presence of seagrass and ii) the growth of seagrass from adjacent undredged areas, at regular intervals (e.g. 3 monthly) over two years to observe if and how seagrass is colonising the dredged area.
Step 2. If seagrasses are detected during the inspection period, patches of seagrass should
xiii
I The Ecology Lab Ply, Ltd. Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995 be mapped accurately and their area determined. In addition, measurements of the density and length of leaves of seagrass should be obtained in the colonised patches and compared to measurements obtained in reference (i.e. undisturbed) beds. Inspections of the dredged area should continue regularly to identify any new patches.
Step 2a. The growth of colonising patches should be monitored through time, so that the rate of patch growth (i.e. increase in area) and the proportion of the dredged area covered by seagrasses may be determined. There is no information available to suggest how quickly patches of seagrass should grow, or what the rate of development of new patches should be, so it is difficult to assign a period of time for complete recolonisation (defined here as the areal coverage of seagrass equivalent to the amount removed). At this stage, it is suggested that an arbitrary criterion of 10% of the dredged area be recolonised per year, after a 1 year period of stabilisation following dredging and backfilling. At this rate, complete recolonisation would be expected to take 11 years after dredging of a particular area was completed. For example, dredged Area B would be the first area available for colonisation of seagrass approximately 3 years after the dredging proposal commenced. Area B is 2.4 ha., thus, the criteria for growth of seagrass would be 0.24 ha. per year. If seagrasses are present but the 10% rate of growth is not being achieved after five years, transplantation of seagrasses should be considered to assist with seagrass growth and to help meet the objective of complete recolonisation.
Step 3. If seagrasses are not detected during the inspection period of two years, two options should be considered. First, if the area is at the lower depth limit for growth of seagrass in Lake Illawarra (i.e. 1.5 - 2.0 m below Al-ID), consideration should be given to further backfilling with sand to make the substratum shallower either over the whole of that particular dredged area, or within a portion of it, as an experiment. If backfilling is done, a further period of inspection should be initiated and Step 2a followed. Second, if the area is already suitably shallow (i.e. <-1.5 m AHD), transplantation of seagrass should be initiated.
Step 4. If seagrass recolonisation does not occur following Step 3 - which is considered most unlikely, given that seagrasses have already recolonised other dredged areas in Lake Illawarra - further research and remediation works should be considered to facilitate the growth of seagrasses (e.g. further backfilling).
One further advantage of the above plan of management is that monitoring of colonisation of Area B would take place after 3 years from the start of the dredging programme and run for 7 to 10 years before any of the other dredged areas were ready for seagrass to colonise. In other words,
WA The Ecology Lab Ply. Ltd. Gr[fins Bay sand extraction - Marine Ecology - Final Report, April 1995 the plan of management for Areas A and possibly Areas C and D can be modified, if necessary, to incorporate the information collected from Area B. Thus, the monitoring of Area B would provide a good test case of the management plan.
Clearly, there are a number of possible approaches that could be adopted for a plan of management for seagrasses in the proposed dredge areas. The final approach should be determined in consultation between SCE, the Lake Illawarra Authority and other relevant organisations, such as the NSW Environment Protection Authority (EPA), NSW Fisheries and the Commercial Fisherman's Advisory Council (CFAC).
N
-. =---
(XIS-T WO 0 ,• — - ____ - A4O CAHNEL - - AzaB ••Th . GRIFflNS Phase I
Stage 4 AreaA / / •1 \. -... - 2 / /7/ Stage 1 , 2200 - -.1 AreaD 'S ( i - z- ui ,e 2
ii r — --- —fl--- — Stage2-channel extension . PRM Poon-
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/ .
EXSTING CONTOURS 1 / 1 I CONTOUR ARE ON STRLIN / hOGHT OTUM (r ftD.) fi /
Figure SI: Map of Griffins Bay indicating the stages and areas to be dredged for sand extraction in Griffins Bay. The Ecology Lab Pty Lid Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
1.0 INTRODUCTION I 1.1 Background and Aims
I The Ecology Lab Pty Ltd was commissioned by Gutteridge Haskins & Davey (GHD) to describe the existing estuarine environment of Lake Illawarra and to assess potential impacts of a proposal to dredge and extract sand near the entrance to Griffins Bay by South Coast Equipment Pty Ltd (SCE). Specifically, The Ecology Lab was contracted to do field studies on the estuarine fauna of I Lake Illawarra, with emphasis on Griffins Bay, and to use existing information to describe the environment of Lake Illawarra. A thorough description of the commercial and recreational fishing I activities of Lake Illawarra was also required. Using these descriptions as background information, in addition to information provided by GHD on the nature of the proposal and on predicted physical and chemical effects, impacts were assessed, suggestions to mitigate impacts I made and a preliminary monitoring programme formulated.
The proposal to dredge the entrance to Griffins Bay by South Coast Equipment Pty Ltd has been the subject of a previous environmental impact statement, or EIS (KayBond, 1993). Reviews of the I previous EIS by some government departments and interest groups identified some issues which required further work. Issues relating to marine ecology were incorporated into the present study. The specific aspects of the existing environment that required field sampling were the benthic macrofauna within seagrass beds and the fish and mobile invertebrates within seagrass beds. These aspects plus descriptions of fishing activities, were identified by NSW Fisheries, the I Australian Museum, Commercial Fisheries Advisory Council (CFAC), Ocean Watch Environmental Protection Authority and others as requiring further information to supplement the I previous EIS.
To assess the significance of the assemblages of benthic macrofauna, fish and mobile invertebrates in Griffins Bay, it was important to compare the bay with other areas in Lake Illawarra. Thus, the field sampling design included; i) several areas within and near the proposed area of dredging in Griffins Bay and ii) several areas within reference locations in similar habitats situated away from the proposed dredge area. Comparisons of abundance and species composition can then be made within and among locations (Andrew and Mapstone, 1987). The value of this sampling design is twofold. First, the relative importance of the proposed dredge area can be assessed and second, I the range of natural variation in the abundance and distribution of assemblages prior to dredging can be used to measure the impacts of that activity.
I The Ecology Lab Pty Ud Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
The aims of the study were:
to describe the estuarine environment of Lake Illawarra with specific reference to Griffins Bay using field sampling of benthic macrofauna, fish and mobile invertebrates and existing information,
to describe the commercial and recreational fishing activities on Lake Illawarra by interviewing local fishers and NSW Fisheries Inspectors and using existing information,
to assess the impacts of the dredging proposal on the estuarine environment and fishing activities of Lake Illawarra,
to suggest any measures that would assist in minimising the predicted effects of the proposal so that they could be incorporated into the final design of the project and
to outline a monitoring strategy should the proposal to dredge proceed.
1.2 Existing Information
1.2.1 Physical and Chemical Conditions
1.2.1.1 Lake Illawarra
Lake Illawarra is a barrier estuary (Adam et al., 1985) and is separated from the ocean by a long, shallow channel (2.4 km long, 600 m wide and maximum depth of 2 m). The position of the mouth of the channel varies depending on rainfall, wave action and sediment redistribution and on several occasions in the last 50 years, heavy shoaling at the mouth has resulted in the complete closure of the lake from the ocean (Ellis et al., 1977). This occurred most recently occurred in 1971. The lake's water level is about 25-30 cm above mean sea level (Clarke and Eliot, 1984 in Yassini and Jones 1987). The maximum depth of the lake is 3 m
Lake Illawarra covers an area of 35 km2 and its catchment area is about 270 km2. The tidal range is 3-5 cm in the body of the lake and 10-25 cm in the entrance channel (Clarke and Eliot, 1984 in Yassini and Jones, 1987). Tidal currents are mainly limited to the entrance channel (36 cm s') whereas currents within the lake are generated by wind action (Clarke and Eliot, 1984 in Yassini and Jones, 1987). Residence time of the water in the lake varies between approximately 26 and 39
weeks (Ellis et al., 1977). The Ecology Lab Ply Ud Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
The long-term average salinity for the lake is 28.50 / but extremes of 8.7°/ during flood and I 42.5 0/ during drought have been recorded (Elcom, 1987). The difference in salinity between the bottom and surface waters ranges from 0.4 to 2.9 O/ and no difference between the eastern and I western sides of the lake has been reported.
Variations in the temperature of water in Lake Illawarra were measured by Elcom from 1981 - I 1983, Ellis and Kanamori (1977a) from 1973 -1974 and CSIRO from 1976 - 1978 (in Yassini and Jones, 1987). Ellis and Kanamori (1977a) reported a range of water temperatures of 11.6 - 25.6°C I for Lake Illawarra. Comparison of the surface water of the lake to the nearby ocean showed that the lake experiences greater temperature extremes and the timing of maximum and minimum I temperatures is one month earlier than in the adjacent ocean.
The concentration of dissolved oxygen in the surface waters of Lake Illawarra during the day varies between 4 - 11 mg 1.1 (Ellis and Kanamori, 1977b). Yassini and Jones (1987), in October 1984, measured dissolved oxygen concentrations in areas of Lake Illawarra affected by macroalgal I blooms, such as the eastern side of the lake and Griffins Bay. They found that the dissolved oxygen levels were very small at night (0.5 mg 1.1) and this could enhance denitrification and the I release of phosphorous into the water column.
The quality of sediment and water of Lake Illawarra has been assessed previously in several ways. Ellis and Kanamori (1977b) measured the concentration of heavy metals in several areas within Lake Illawarra and found greater concentrations of metals (copper, lead, zinc and cadmium) in the I top 10 cm of sediment in Griffins Bay and Koona Bay. They concluded that the main source of these metals was the Port Kembla industrial complex, the Dapto smelting works (closed in 1906) I and Tallawarra Power Station (decommissioned in 1989). Urban run-off is also a source as Lake Illawarra is almost entirely surrounded by residential development. Yassini (1992) attributed the I presence of heavy metal contaminants to both industrial activities and urban run-off. He found concentrations of metals such as zinc and cadmium in molluscs and plant tissue exceeded the sediment background levels. Algal species had greater concentrations of sulphur and seagrasses had greater concentrations of phosphorous. Yassini and Clarke (1986) reported a fourfold increase in the mean levels of phosphate and nitrate in the lake over the period from 1974 to 1986. Sources of nutrients included rural and urban runoff, sediments, sewage overflows, coastal waters and precipitation. The Electricity Commission (now Pacific Power) have monitored the nutrient status of the lake since 1981 and reported an increase in the level of phosphorous and nitrogen (Dames and Moore, 1993). These levels exceed the guidelines recommended by ANZECC (1992) and indicate that phosphorous and nitrogen in these concentrations are likely (according to Dames and
3 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Moore, 1993) to be causing some eutrophication.
1.2.1.2 Griffins Bay
Griffins Bay is located in the north-east of Lake Illawarra. As part of the preparation of the EIS for sand extraction in Griffins Bay, GI-ID (1995) collected data on water quality, water circulation and heavy metal content of the sediment within the vicinity of Griffins Bay. This was required as background information so that predictions about changes in these physical conditions due to the proposal could be made. These results are discussed in the ETS but have been summarised here because reference will be made to these results in later sections of this report.
Patterns of water circulation in and around Griffins Bay were determined by drogue and dye tracking on one day in April 1994 when the wind was calm in the morning but increased to 6 m/s from the north east in the afternoon. These measurements were taken to calibrate the hydrological model (GHD, 1995). Results indicated that the southerly movement of drogues and dye plumes was wind induced, with velocity increasing in the surface current with increasing wind speed. The lake level did not change throughout the day, indicating either closure at the entrance to Lake Illawarra or negligible tidal influence in Griffins Bay. There was little evidence for transport of material in an east-west or west-east direction suggesting little current flow in the bay. The maximum current in Griffins Bay was predicted to be 0.1 m/s occurring in the northern channel for a 10 knot westerly wind. The maximum current along the southern shore was 0.05 m/s (GI-ID, 1995).
Salinity, water temperature and dissolved oxygen concentration were examined through the water column at eight locations in and around Griffins Bay on one day in January 1994. Water temperature varied little with depth or location around Griffins Bay. Salinity did not vary with depth but the two locations along the southern shoreline of Griffins Bay (in Primbee Bay and Joes Bay) had lower salinities than the other locations. Dissolved oxygen concentration at approximately 30 cm below the surface did vary among locations around Griffins Bay (range: 7.5 - 10.3 mg/L) and with depth such that surface waters ranged from 8.5 to 10.5 mg/L whilst at the bed of the lake concentrations ranged from 3.4 to 4.7 mg/L. These values are within the range recorded previously from Lake Illawarra (Section 1.2.1.1). Levels below 6 mg/L are deemed unsatisfactory by the water quality standards of ANZECC (1992).
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Heavy Metals A previous study of sediments in Lake Illawarra recorded concentrations of heavy metals (copper, zinc, lead and cadmium) in Griffins Bay up to 10 times that of locally-defined background levels (Chenhall et al., 1994). The other sites studied exhibited only slightly greater concentrations than background in nearsurface sediments.
For this proposal, sediment samples were collected from 8 locations in and around Griffins Bay and analysed for 6 heavy metals (GI-ID, 1995). Of these metals, cadmium and mercury were not I detected in any of the samples, lead and copper were detected in some of the samples (20% and 47% respectively) and chromium and zinc were detected in all samples. Only chromium and zinc I occurred in enough samples to address statistically if any differences occurred among the locations within Griffins Bay. The concentration of chromium was greater in the location in Primbee Bay compared to all other locations and the concentration of zinc was greater in the locations in I Primbee Bay and North of Purry Burry Point compared to all other locations. The range of concentrations in samples for all metals is given in Table 1A. Because the detection limits were U high for these samples, additional samples were taken from 2 locations in Griffins Bay where the proposed dredging would occur and were analysed at lower detection limits (Table 1B). With the I lower detection limit, Cadmium was also detected in the samples.
Table I also contains guidelines for assessing whether the concentrations of metals are likely to affect organisms in contact with the sediment. The criteria for the quality of sediment are those compiled by MacDonald (1992) and are based on data from the US EPA's National Status and I Trends estuarine sediment quality monitoring program. The use of these criteria is necessitated by the lack of suitable data from Australia. These criteria are expressed in dry weight, which I necessitated the conversion of the Griffins Bay data from wet weight to dry weight using the percentage of moisture given per sample. The criteria reflect the minimum concentration at which I effects on organisms can be detected. Concentrations less than the screening level (SL) are unlikely to affect even the most sensitive organisms in contact with the sediment. Concentrations between the SL and probable effects level (PEL) may have effects on sensitive organisms whilst I concentrations larger than PEL are likely to adversely affect sensitive organisms. Applying these criteria to the samples collected around Griffins Bay, the concentration of chromium, copper and I zinc may be having adverse effects on some organisms because some samples exceeded the SL and several samples had chromium levels exceeding the PEL. The samples that exceeded these limits I for chromium, copper and zinc were taken from Primbee Bay and north-east of Purry Burry Point. For chromium, samples taken from a location outside but near Griffins Bay also exceeded the SL. I The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Samples taken from the proposed dredge areas and analysed at lower detection limits had no metals exceeding the SL and PEL.
Acid Sulphate Soils Samples of sediment were taken from the proposed dredged areas in Griffins Bay and analysed for their potential as acid sulphate soils (GHD, 1995). The tests indicated that the sediments in Griffins Bay have the potential to become acid sulphate. The intensity of the chemical reaction that was used as a test varied considerably among sites and between depths of sediment (GI-ID, 1995). The preliminary tests, however, did not quantify this potential. GI-ID (1995) recommend a more comprehensive survey be undertaken prior to dredging.
1.2.2 Seagrass Beds
Four species of seagrass occur in Lake Illawarra; Zostera capricorni, Ruppia megacarpa, Halophila ovciiis and Halophila decipiens. Large beds of seagrass grow in the shallows off the shoreline and are mainly formed by Zostera but there are stands consisting of predominantly Ruppia and mixed stands of Zostera and Ruppia. The densest seagrass beds in the lake are located along the Windang Peninsula, on medium-grained sand and extend out to a maximum depth of 2 metres. In other parts of the lake, seagrass beds are also limited to a depth of 2 metres and occur on sandy and muddy substrate (Yassini, 1993). In Lake Illawarra, Ruppia grows in a maximum depth of 40 cm whereas Zostera grows in a maximum depth of 2 m (Yassini, 1993). Factors that may influence the growth and extension of seagrass beds include; water depth, turbidity, temperature, salinity, nutrient supply and the nature of the substratum (Larkum et cii., 1989).
Since 1976, estimates of the total area of seagrass in Lake Illawarra have ranged from 5.12 km2 to 10.9 km2 (see Harris, 1977; Evans and Gibbs, 1981 in WBM Oceanics, 1993; West et cii., 1985; King, 1988; King et cii., 1991). Some of the differences are inevitably related to the technique used to estimate cover but most of the variation probably represents real changes in the area of Lake Illawarra covered by seagrass beds. Changes in the cover of seagrass have not been strongly linked to seasonal or environmental changes (King, 1988). The area of seagrass mapped by West et cii. (1985) (a total of 5.12 km2) and the area of seagrass mapped by King (1991) (a total of 10.9 km2) is presented in Figure 1.
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The most recent survey of the seagrasses of Lake Illawarra did not estimate the entire area of seagrass within the lake but examined in detail five smaller areas within the lake using aerial photography (1:6 800) and field surveys (WBM Oceanics, 1993). The present cover and characteristics of seagrass in two areas that had a history of dredging (Koonawarra Bay and Griffins Bay) and in three areas that had no history of dredging (Purry Burry Point, Duck Creek and Mullet Creek) were compared to the cover estimated in 1988 using aerial photography (1:16 300) and maps in King (1988) from a survey in March 1987. Seagrass beds at Mullet Creek, Koonawarra Bay and Duck Creek have expanded in area indicating that Zostera can extensively I and rapidly recolonise some dredged areas such as Koonawarra Bay. In Griffins Bay, however, there has only been minor recolonisation of Zostera in the dredged area since 1991. Figure 2 I illustrates the decrease in the area of seagrass in Griffins Bay from 1988 to August 1993 using maps drawn by WBM Oceanics (1993). Dredging in Griffins Bay was done to construct a navigation channel at approximately - 1.5 m AHD along the northern and eastern perimeter of the I bay. This depth is greater than the range of depths examined by WBM Oceanics (1993) but is within the depth range of Zostera reported in other studies (Yassini, 1993). WBM Oceanics I concluded that the extent and rate of recovery are related to the final depth and turbidity after dredging. Thus, it may be possible that if dredging works improve circulation and turbidity is I reduced, the depth distribution of seagrass may be extended (WBM Oceanics, 1993). I WBM Oceanics (1993) found that the structural characteristics of Zostera, such as the density of shoots, number of leaves per shoot and length of leaves varied among depths and among the 5 locations sampled in the lake. There tended to be a greater density of shoots with decreasing I water depth. The density of shoots within Griffins Bay was also greater compared to the other locations for 3 depth ranges. The overall mean density of shoots among locations ranged from I 1025 to 3336 shoots per m2. There was no relationship between the number of leaves per shoot or the length of leaves with water depth. The overall mean length of leaves ranged from 24.7 to 31.7 I cm and there were, on average, 4 leaves per shoot. Variability in structural characteristics of Zostera is not unusual, for example, Larkum et al. (1984) reported that Zostera in Botany Bay had I smaller densities of shoots and longer leaves with increasing depth and reduced exposure to waves. Furthermore, the structural characteristics of Zostera in Lake Illawarra are within the range I found for other places on the NSW coast (WBM Oceanics, 1993; The Ecology Lab Pty Ltd, 1994).
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1.2.3 Saitmarshes and Mangroves
According to West et al. (1985) there is only one small area (0.203 km2) in Koona Bay, in the south of Lake Illawarra, that has saltmarsh habitat (see Figure 1). There are no stands of mangroves on any of the shores of the lake.
1.2.4 Benthic Macrofauna
Benthic macrofauna typically comprise invertebrate animals such as marine worms (polychaetes), shells (bivalves and gastropods) and crustaceans which live on or in the seafloor (often termed the 'substratum'). Benthic invertebrates exhibit a wide range of sizes and 'macrofauna' are defined conveniently as those invertebrates which are retained by a 1 mm sieve.
Very little information exists on the assemblages of benthic macrofauna in Lake Illawarra. Garcia (1986) compared the abundance of macrofauna at seven sites around the lake, sampling once each in summer and winter. Differences were found among locations and related to differences in the grain size of sediment and the presence and type of vegetation. Yassini and Jones (1987) sampled the sediments for ostracods and found more species at the entrance channel than inside the lake. Within the lake, the diversity of ostracods was related to the presence of benthic flora with the most diverse assemblages occurring in areas covered by seagrasses. The deeper areas of the lake where the sediment is predominantly muddy had a different assemblage of ostracods compared to shallow, vegetated, sandy areas.
1.2.5 Fish and Mobile Invertebrates
Few studies have examined the distribution and abundance of fishes in Lake Illawarra. Of these, Jordan (1986) concluded that Lake Illawarra supported a rich and diverse fish fauna comparable to other similar lakes in N.S.W. In his study, the greatest diversity of fish occurred at a site near the entrance to Mullet Creek in a bed of Zostera capricorni. The diversity of fishes within the lake did not change seasonally except at a site on the eastern shore in the Ruppia megacarpa bed and a site at the entrance to Griffins Bay in the Zostera capricorni bed. At these sites, diversity was greatest in February and April mainly due to the abundance of silver biddy (Gerres subfasciatus), tarwhine (Rhcthdosargus sarba) and flat-tail mullet (Liza cirgentea). The abundance and biomass of commercial and recreational species of fish, however, were significantly greater in summer and autumn, largely due to the significant increase in abundance of luderick (Girelici tricuspidata), tarwhine
8 The Ecology Lab Ply Ltd Griffins Bay sand extraction - Marine Ecology - Final Repert, April 1995
(PJzabdosargus sarba) and bream (Acanthopagrus australis) in October at most sites sampled in Lake Illawarra. Also, in spring many species of fish settle from the plankton into seagrass beds. For I example, McNeill et al. (1992) reported consistently large abundances of Acanthopagrus austraiis, Rhabdosargus sarba, Girella tricuspidata, Achoerodus viridis and Meuschenia trachylepis between June I and March compared to other times of the year in a seagrass bed in Botany Bay. Non-commercial species that were caught in large numbers included perchlet (Ambassis jacksoniensis), hardy-head I (Atherinosoma microstoma) and gobies (Pseudogobius olorum and Favonigobius tainarensis). 1 The abundance of commercially and recreationally important species of fish and mobile invertebrates have been compared among different locations along the western shores of the lake with locations near Tallawarra Power Station (Scanes et al., 1991). No differences among locations I was detected statistically but differences occurred at different times of the year. More species of fish were found in autumn than in summer and less were found in spring and winter. The total k number of fish was greater in summer, autumn and spring compared to winter.
I 1.2.6 Commercial and Recreational Fishing Activities I Studies on the fisheries of Lake Illawarra are few. The Fisheries Research Institute studied the impact of the Tallawarra Power Station on the fish and fisheries of Lake Illawarra in 1990 and found that the assemblages of fish at Tallawarra power station were not significantly different from the other areas sampled (Scanes et al., 1991). Sampling effort for this study was concentrated in the area of the power station and along the western shore of the lake and as such does not I contain information directly relevant to the present study. Scanes et al. (1991) also suggested that the size of the commercial catch, although variable, is decreasing from a peak in the late 1960's and early 1970's but commercial catch per person is similar to that for Lake Macquarie. The commercial catch from Lake Illawarra is supposedly more seasonal than other lakes with a definite I low point in winter (Scanes et al., 1991).
1.3 Matters Arising from Previous EIS
The review of existing information in Section 1.2 has highlighted the need for further work because of insufficient data to adequately assess the likely impacts of sand extraction in Griffins Bay on the marine ecology of Lake Illawarra. Data on the relative abundance and distribution of benthic macrofauna, fish and mobile invertebrates in Griffins Bay compared to other areas within the lake are needed. Likewise, a thorough description of the commercial and recreational fishing
9 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
activities carried out in Lake Illawarra is also required. Information on production of fish and prawns for Lake Illawarra needs also to be placed in a regional context.
There is insufficient information on the spatial patterns of distribution and abundance of benthic macrofauna in the lake. These animals are important in estuarine ecosystems for several reasons; they are a source of food for fish, mobile invertebrates and birds, they play an important role in pathways of detrital and nutrient recycling and they are good indicators of environmental distuthance (e.g. Warwick1 1993). The proposal to dredge in Griffins Bay may affect this group of animals, which may in turn affect the abundance and diversity of fish and other biota. Therefore, it is necessary to obtain data on the relative importance of Griffins Bay compared to other areas in the lake.
There are no data on the relative significance of different areas of seagrass as habitat for fish and mobile invertebrates in Lake Illawarra. Bell and Pollard (1989) provide a very comprehensive analysis of the value of seagrass habitats to fish and fisheries in Australia. There are two aspects of seagrasses that make them important as habitat for fish and mobile invertebrates. First, they typically support a greater diversity and abundance of fishes and invertebrates than nearby unvegetated substrata. Second, many fish and invertebrates spawn their eggs into the water column, or on to the seabed, from which the hatchlings ('larvae') disperse via the water column. When they return to the seabed, many of these larvae use seagrass beds as 'nursery' areas, because of the food and shelter supplied there. Therefore, seagrass beds play a very important role as nursery habitat in NSW estuaries. Research has shown that the locations of seagrass beds within an estuary can be important in determining the relative abundance of fish and mobile invertebrates (McNeill et al., 1992). Characteristics of seagrasses such as the density of shoots and length of leaves may also influence the abundance and species composition of fish and mobile invertebrates (Bell and Westoby, 1986a; Bell and Westoby, 1986b). In addition, successful recruitment from planktonic to juvenile and sub-adult stages is dependent on the availability of suitable benthic habitat at the time when larvae are competent to settle from the plankton (Bell and Westoby 1986c; Bell et al., 1987). There is a need, therefore, to assess the relative value of the seagrass beds of Griffins Bay in relation to other beds in the estuary
No field studies were required by The Ecology Lab to describe the seagrass beds themselves because a recently published description of the seagrass beds in Griffins Bay and other areas within Lake Illawarra (VVBM Oceanics, 1993) was considered by GHID to be adequate for this study. Information on seagrass beds is necessary because recent research has emphasised the
10 The Ecology Lab Pty Ud Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
importance of seagrasses in the ecology of shallow estuarine environments (reviewed by Larkum et al., 1989). Seagrasses stabilise sediments (Fonseca et al., 1982), provide an important habitat for juvenile fishes and mobile invertebrates, many of which are of commercial or recreational importance (Bell and Pollard, 1989) and are significant components in the cycling of nutrients in I estuaries (Kenworthy et al., 1982). 1 I 2.0 STUDY METHODS 2.1 Benthic Macrofauna I 2.1.1 Survey Procedures I Benthic macrofauna were collected from 8 locations (100's metres to kilometres apart) in Lake Illawarra on the 8-9 November 1993 (Figure 3). At each location, 2 sites (10's metres apart) were sampled. The design of the sampling programme enabled a comparison to be made of the assemblages of macrofauna at 3 locations (Sites 1-6) at or near the proposed dredging area (entrance to Griffins Bay) with 3 reference locations (Sites 13-16) away from the proposed dredging area (along the eastern shore of Lake Illawarra). At all these locations the sediment was sandy (The Ecology Lab (TEL), observation). Additional samples were taken from 2 other locations, one in Kully Bay within Griffins Bay (Sites 7 and 8) and the other in Burroo Bay (Sites 9 and 10) (Figure 3). At these locations the sediment was muddy (TEL observation).
Five samples were taken at each site by a scuba diver using a hand-held corer (19 cm diameter, surface area of 0.028 m2) that penetrated approximately 10 cm into the sediment. A total of 80 samples was collected. All samples were taken from bare substratum located within the seagrass I bed rather than directly through the seagrass itself, as sorting of these samples would have taken I too long due to the presence of the seagrass root mat. Samples of benthic macrofauna were sieved through a 1 mm mesh screen and the animals and other material retained on the sieve were preserved in 10% formalin. The samples were stained with Rose Bengal in the laboratory and all animals sorted with the aid of magnifying lamps (approximately 2X). Crustaceans and molluscs were sorted into species groups and a representative selection was identified to species by the staff at the Australian Museum. Most polychaetes were identified to species except for a few family groups that were not very abundant.
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Some rare groups (oligochaetes, nemerteans, hydroids and holothurians) were counted but not identified further due to a lack of taxonomic information.
2.1.2 Statistical Analyses
2.1.2.1 Multivariate Analyses
Variation in the assemblages of benthic macrofauna among all 16 sites (8 locations) was examined using the multivariate procedures proposed by Clarke (1993). These analyses use a measure of similarity between samples to map the relationships among samples in an ordination using non- metric Multi-Dimensional Scaling (MDS). They produce a graphical representation of the similarity (and dissimilarity) of the samples from all sites sampled.
The data matrix (species by samples) was double square-root transformed to reduce the weighting given to abundant taxa and increase the weighting given to rarer species. Similarities among samples were calculated using the Bray-Curtis Similarity measure and used to construct the two- dimensional MDS plots. The adequacy of the two dimensional representations of the similarities among samples is assessed by examining the stress value. Stress values of < 0.1 indicate a good representation which may be easily interpreted and plots with stress < 0.2 provide a reasonable representation of the data. Plots where the stress value exceeds 0.2 indicate a poor representation of the relationship among samples in 2 dimensions and are of little value. For this reason, the plots are not presented when stress exceeds 0.2.
The significance of any apparent differences among areas was determined using the ANOSIM randomisation test (Clarke, 1993). The null hypothesis being tested is one of no difference among areas in the structure of benthic assemblages. The significance levels in pairwise tests were adjusted to allow for multiple comparisons using the Bonferroni Correction formula (Winer, 1971).
Similarity analyses (SIMPER) were used to determine the relative contribution that particular species or taxa make to the dissimilarity of groupings and are based on the Bray-Curtis similarity measures among all samples (Clarke, 1993). SIMPER identifies which species or taxa are good discriminators between areas. All species can potentially contribute to the dissimilarity among areas but for reasons of brevity, only the first few species that contribute the most to the dissimilarity among areas are presented and discussed.
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2.1.2.2 Univariate Analyses
Analysis of variance (ANOVA) was used to compare the abundance of common taxa, the total I number of individuals and the number of taxa per sample at three spatial scales; between Areas (Griffins Bay versus Eastern Shore), among Locations (within Areas) and among Sites (within Locations and Areas). The analytical design was a three factor ANOVA, in which Griffins Bay I versus Eastern Shore was a fixed factor, Locations was a random factor and nested within Areas and Sites was a random factor and nested within Locations and Areas. Post-hoc pooling I procedures were used if higher-order interaction were non-significant at P >0.25 to provide a more powerful test (Winer, 1971; Underwood, 1981).
Cochran's C statistic was used to test the assumption of homogeneous error variances (Winer, 1 1971; Underwood, 1981). Data were transformed using ln(x+1) only when Cochran's C was significant at P < 0.05. If, after transformation, Cochran's C was still significant, the ANOVA on the untransformed data was used and statistical significance determined with a = 0.01 instead of a = 0.05 (a reduced probability of making a Type I error (Underwood, 1981)). Post-hoc comparisons among means were done using Student-Newman-Keuls (SNK) procedures when the I ANOVA produced a significant effect.
I 2.2 FIsh and Mobile Invertebrates 1 2.2.1 Survey Procedures
Fish and mobile invertebrates were sampled using two methods; beam trawling and beach seining. Each method has various advantages and disadvantages. The beach seining technique is better at catching very mobile fish such as mullet, bream and tailor but it cannot be readily used to sample in areas away from the shoreline. Beam trawling was necessary to sample in areas offshore, such as, the area proposed for dredging at the entrance to Griffins Bay.
For each method, 5 locations were sampled in the lake, two of these in or near Griffins Bay. At each location, 2 sites were sampled and four replicate beam trawis or beach seines were taken in each site. Each sample was preserved in 10% formalin and sorted back in the lab. All fish and mobile invertebrates (crustaceans and molluscs) were identified to species and counted. Species of 1 commercial importance were measured to fork length (LCF). The number of Mucrobrachium a small and sometimes very abundant carid shrimp, was estimated by weight. The I intcrmecJium, 13 1 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
average weight of 5 replicate batches of 50 shrimp was used to calculate the number of shrimp from the total weight of the sample.
2.2.1.1 Beam Trawling
Beam trawl samples were collected in 5 locations; 2 near Griffins Bay, 2 in Windang Channel and 1 on the eastern shore of Lake Illawarra (Figure 4). The beam trawl was 1 m wide and 0.5 m high. The net was 2.5 m long with 5 mm mesh around the frame and 2.5 mm mesh in the bag. The beam trawl was towed behind a small, outboard-powered punt. Each replicate tow, of 4 minutes duration, was in a straight line through seagrass.
Some samples were very large and full of algae and seagrass making it necessary to subsample because of the large amount of time involved in sorting them. A small pilot study indicated that sorting 3/ 5 of the sample was adequate, in terms of precision, to estimate the abundance in the whole sample. Samples were divided into fifths by weight and 3 randomly chosen to sort.
2.2.1.2 Beach Seining
Beach seine samples were collected at 5 locations; 2 near Griffins Bay, I in Windang Channel, 1 in Boat Harbour and 1 in Hennegar Bay (Figure 5).
The seine net was 25 m long and approximately 3 m deep with 8 mm mesh size. The net was hauled through seagrass and over sand onto the shore.
2.2.2 Statistical Analyses
Multivariate analyses were done on each data set as described in Section 2.1.2.1 except that locations rather than areas are the spatial scale of interest. For the ANOSIM randomisation test, the null hypothesis of no difference among locations in the structure of fish and mobile invertebrate assemblages was examined. Similarly, SIIvIPER was used to determine the relative contribution that particular species or taxa made to the dissimilarity of groupings, which for sampling fish and mobile invertebrates are the locations.
Data from the beam trawls and beach seines were also analysed using analysis of variance (ANOVA) to compare the abundance of the more common taxa, the total number of individuals,
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the number of individuals of commercially important species and the total number of taxa per sample among the locations and sites sampled. The analytical design was the same for the beam I trawls and beach seines and consisted of two factors, locations (random factor) and sites, nested within location (random factor). Cochran's C statistic and SNK procedures were used as described I in Section 2.1.2.2.
2.2.3 Sizes of Fish
The length of all species of fish of commercial importance caught either by beam trawling or beach seining were measured to the caudal fork (LCF). The range, mean and standard error for each species was calculated and life history stage was determined from published data on length at maturity for fish in Botany Bay by SPCC (1981). If species were very abundant, length-frequency distributions for each location (sites pooled) were plotted and interpreted graphically. The length frequency distributions for some less abundant species were examined by pooling data from all I locations. 2.3 Commercial Fishing
2.3.1 Description of Commercial Fishing Activities
Discussions were held with several local commercial fishers to ascertain what areas of Lake Illawarra they fished in, what methods they used and what species were targeted. The local NSW Fisheries Inspector was also interviewed. This information was used to describe the commercial fishing operations in Lake Illawarra.
2.3.2 Commercial Fisheries Statistics for Lake Illawarra
The NSW Fisheries database was used to examine the commercial fishing activities of Lake Illawarra. The data available covers the financial years from July 1984 to June 1992. For example, 1985 covers the period from July 1984 to June 1985. The database contains information on the catch (weight of each species), effort and methods used per month during this time around Lake Illawarra.
One factor ANOVAs were used to compare years in the catch of individual species of fish, crustaceans and molluscs and the total of all species caught using the NSW Fisheries database.
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The catches per month were used as replicates for each year. Many species were caught in abundance all year so the catch for all 12 months was used. For species that were seasonally caught, however, only the months that had an average catch (over 8 years) of greater than 100 kg were used to reduce within-year variability (which would have made the test much less sensitive to among-year variability). Therefore, the number of replicate months used in the analyses varied according to the species analysed.
Commercial fisheries statistics for NSW for 1991 (July 1990 to June 1991) were available for all estuaries in NSW and these data were used to compare Lake Illawarra with other estuarine lakes in NSW.
2.4 Recreational Fishing
2.4.1 Description of Recreational Fishing Activities
Discussions were held with several local recreational fishers from the Windang Hotel Fishing Club to ascertain what areas of Lake Illawarra they fished in, what methods they used and what species were targeted. The local NSW Fisheries Inspector was also consulted regarding recreational fishing activities. This information and observations made by TEL of recreational fishing activities during the field studies, were used to describe recreational fishing on Lake Illawarra.
3.0 STUDY RESULTS
Although West et al. (1985) identified only one saltmarsh - in the southern portion of Lake Illawarra - a few saltmarsh plants were observed at Purry Burxy Point. These included a few isolated Sarcocornia quinqueflora and a band of unidentified rushes growing along the water's edge close to the shore. There were also masses of filamentous algae. Studies done in the Shoalhaven Estuary suggest that the occurrence of this algae may be seasonal (The Ecology Lab Pty Ltd, unpublished data).
During the field studies in November 1993, numerous waterbirds were observed, including pelicans, silver gulls, black cormorants, pied cormorants and black swans. The black swans formed large flocks off the eastern shore of the lake, well to the south of Griffins Bay. The other birds showed no obvious pattens in their distribution during the field studies.
16 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Reix,rt, April 1995
The remainder of this section discusses the findings of quantitative surveys of benthic macrofauna, fish and mobile invertebrates, and describes fishing activities.
3.1 Benthic Macrofauna
A total of 8 235 individuals of benthic macrofauna were collected, representing 47 taxa. Most of I these were identified to species. Polychaetes and molluscs were the numerically dominant groups. Appendix A lists the species collected and the mean abundance and standard error per species per I site. I 3.1.1 Analysis of assemblages
The two-dimensional plot derived from the ML'S ordination indicated two major trends (Figure 6). First, there were differences in the assemblages of benthic macrofauna between samples from sandy and muddy substratum. Second, the samples taken from the proposed dredge area did not I overlap (except for two samples) with those taken from the reference locations on the eastern shore of Lake Illawarra. Thus, although these locations were all from the sandy substratum within a I seagrass bed, the assemblages were distinct at the time of sampling. The MDS plot suggested that the sites and locations sampled fell into three groupings; i) the proposed dredge area locations on I sandy sediment, ii) the reference locations on sandy sediment and iii) the locations on muddy sediment (Figure 6). The stress value of 0.191 indicated that the 2-D plot gives an acceptable presentation of the (dis)similarities in faunal composition among locations and sites. The ANOSIM I randomisation test showed that this grouping was a significant factor at p < 0.01 (ANOSIM, R=0.648) and that all pairwise comparisons between each group were significantly different at p < I 0.02 (probability level corrected for multiple comparisons).
SIMPER analyses were used to identify which species made the greatest contribution to the dissimilarity between groups. Table 2 lists the 10 principal taxa ranked in descending order of their individual magnitude of contribution to the overall average dissimilarity. Generally, the principal contributors are species that are abundant in one group and not very abundant in the other. The bivalve, So1eellinu alba, was very abundant in the sandy sediment of Griffins Bay (Sites 1-6, Figure 3) but absent from the muddy sediment grouping (Sites 7 & 8, Figure 3) (Table 2a). an amphipod, contributed most to the dissimilarity between Griffins Bay andLirohaustorius the Eastern metungi, Shore (Sites 11-16, Figure 3) and to the dissimilarity between the muddy sediments
17 The Ecology Lab Ply Ud Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
and the Eastern Shore as it was largely absent from Griffins Bay and muddy sediments and vety abundant on the Eastern Shore (Table 2b,c).
SIMPER analyses were also used to identify which species were good discriminators between groups. These species have a large ratio of average dissimilarity to standard deviation, i.e. their abundance is spatially consistent and not very variable. Species that were good discriminators
between the groups differ according to the comparison being made. The bivalve, Theorafragilis, discriminated well between Griffins Bay sandy sediments and muddy sediments and also between the sandy sediments on the Reference area and muddy sediments because it consistently occurred in large numbers in the muddy sediments and was largely absent from sandy sediments (Table 2a,c). Another bivalve, Tellina deltoidalis, was a good discriminator between the sandy sediment areas, being consistently more abundant in Griffins Bay than the Eastern Shore (Table 2b).
3.1.2 Analyses of Populations
The mean number of taxa did not vary among any of the spatial scales examined (Table 3, Figure 7a). Thus, the biodiversity of benthic macrofauna in Griffins Bay was, at the time of sampling, similar to other parts of Lake Illawarra. The overall abundance of individuals of benthic macrofauna, however, differed among locations nested within areas (Table 3, Figure 7b). The locations in Griffins Bay were significantly different from each other whereas the locations on the Eastern Shore were not different from each other (Table 3, Figure Th). Location A in Griffins Bay had the largest mean number of benthic macrofauna (Figure 7b). Thus, variability in the abundance of macrofauna was large among locations in the proposed dredge area in Griffins Bay compared to the abundance along the eastern shore. This is despite the fact that locations were much further apart on the eastern shore (Figure 3).
There were no individual species that differed in abundance at the largest spatial scale examined, that is, between Griffins Bay and the Eastern Shore (Table 3). Variation in abundance occurred only at the smaller spatial scales of locations and sites. Therefore, in terms of the abundance of individual species that were numerically dominant, there was no statistical distinction between Griffins Bay and the Eastern Shore.
The abundance of several species varied significantly among Locations i.e. at a spatial scale of 100's of metres (Table 3). These species can be divided into those that were variable among locations in: Griffins Bay only (Tellina deltoidalis, Rarantolla lepte and Gweniafusiformis) (Figure 7c,d,e);
18 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
the Eastern Shore only (Mysella sp., Urohaustorius metungi and Corophium volutator) (Figure 7f,g,h); and both areas (Spisula trigonella) (Figure 7i).
Location A (Sites I & 2) in Griffins Bay had more individuals of benthic macrofauna and more I individuals of the species T. deltoidalis, B. lepte, 0. fusiformis and S. alba than the other locations in Griffins Bay (Figure 7b,c,d,e,j). For the Reference locations, there appeared to be no consistent I differences among locations in their abundance of different species. I Although they were highly variable in abundance, there tended to be more T. deltoidalis in locations at Griffins Bay compared to locations on the Eastern Shore (Figure 7c). The abundance of T. deltoidalis was greatest, however, at the location in Griffins Bay on muddy sediment (Figure 7c, Appendix A). The amphipod, U. metungi, was very abundant at two of the Eastern Shore locations (eastern shore mid and eastern shore south) but occurred only in very small numbers at all the I locations in Griffins Bay (Figure 7g).
Several taxa differed significantly between sites situated only 10's metres apart (Table 3). These species were C. vol utator, Soletellina alba, Australonereis ehiersi and Cirrformia filigera (Figure 7h,j,k,l).
The spatial pattern in the abundance of A. ehlersi (commonly known as squirt worm) illustrates the magnitude of differences in abundance of some species of benthic macrofauna that can occur within the same habitat (in this case, sandy sediment within a seagrass bed) at only small distances apart (see also Morrisey et al., 1993). Processes that affect the abundance and distribution of benthic macrofauna at these small spatial scales may be abiotic, biotic or a combination of both (Thrush et al., 1991).
3.2 Fish and Mobile Invertebrates
3.2.1 Beam Trawis
An estimated abundance of 42 967 individual fish and mobile invertebrates were sampled using the beam trawL All these animals were identified to species. There were 30 species of fish, 7 species of crustaceans and I species of cephalopod mollusc. The most abundant species of fish
were two gobics (Pscudogobius olorum and Gobiopterus semivestitus) and a pipefish (Stigmatopora
nigra) representing 301/o, 25% and 101/c, respectively, of the total catch. Species of economic value comprised 0.5% of the total catch. The most abundant species of fish of economic value were six-
19 The Ecology Lab Pty Ltd Griffins Bay sand extraclion - Marine Ecology - Final Repoit, April 7995 spined leatherjacket (Meuschenia freycineti), blue groper (Achoerodus viridis) and luderick (Gircila tricuspidata) representing 39%, 26% and 14%, respectively, of the economically valuable fish catch. Eastern king prawns (Penaeus plebejus) and blue swimmer crabs (Portunus pelagicus) were the only economically important crustaceans caught in the beam trawls (95% and 5% of the catch respectively). Appendix B lists all the species collected and their mean abundance and standard error per site.
3.2.1.1 Analysis of Assemblages
The two-dimensional plot derived from the MDS ordination does indicate some differences in the assemblages of fish and mobile invertebrates sampled by beam trawling at five locations in Lake Illawarra (Figure 8). Samples from the two locations at Griffins Bay overlap and indicate that the assemblages at these locations are not distinct from each other. Samples from the Eastern Shore do not form a cohesive group and overlap with samples from Windang Channel North and Griffins Bay A. The samples from Windang Channel South, however, form a tight group with no overlap with samples from other locations indicating that the assemblage at this location is quite distinct from those at the other 4 locations. The ANOSIM randomisation test indicated that locations were significantly different at p < 0.01 (ANOSIM, R=0.528). Pairwise comparisons of locations, however, indicated that only half of the comparisons were significantly different (Table 4).
Table 5 summarises the results of SIMPER analyses for those comparisons between locations that were significant in the ANOSIM test. In 3 of the 5 comparisons, the shrimp Macrobrachium intermedium contributed the most to the overall dissimilarity between locations (range from 15.41% to 22.949,,) (Table 5). In all comparisons with Windang Channel South, Macrobrachium contributed most to the dissimilarity because there was an order of magnitude greater abundance there than other locations. Pseudogobius olorum contributed most to the dissimilarity between Griffins Bay B and Windang Channel North and Griffins Bay B and Eastern Shore because of the large abundance of this species at Griffins Bay B. Good discriminating species between location groups that were identified as different in the SIMPER analyses were Macrobrachium and the gobies Favonogobius tamarensis, Pseudogobius olorum, Redigobius macros toma and Arenigobius bifrenatus which all had ratios (average contribution to dissimilarity/standard deviation) of greater than 2.
20 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
3.2.1.2 Analyses of Populations
3.2.1.2.1 Spatial Comparisons
The number of taxa of fish and mobile invertebrates sampled by beam trawling varied among locations in Lake Illawarra but was statistically consistent at the smaller spatial scale of sites (Table 6). Both locations in Windang Channel appeared to support slightly more taxa than both locations in Griffins Bay, although these differences could not be resolved by the SNK tests (Table 6, Figure 9a). In summary, the biodiversity of biota sampled by beam trawling in locations in Griffins Bay was within the range found at the other locations in Lake Illawarra.
The abundance of individuals of commercial species caught using beam trawls did vary significantly among locations and sites sampled but SNK tests could not resolve these differences (Table 6). Although variable, on average there were between 5 and 10 individuals of commercially important fish caught per trawl per site except at the locations on the eastern shore where the average was slightly less (Figure 9c). There were 10 species of fish and 2 species of crustaceans that were of commercial importance that were caught in the beam trawls (see Appendix B). Of these species, the only ones abundant enough to analyse formally were the blue groper (Achoerodus
viridis), leatherjackets (Meuschenia spp.) and eastern king prawn (Penueus plebejus). There were no differences among locations and sites in the abundance of either blue groper or the eastern king prawns (Table 6, Figure 9d,j) although variability among trawls within sites was very large (as shown by the large standard errors in Figure 9d,j) which may have masked potential differences among locations. The abundance of leatheijackets varied significantly among locations but these differences were not resolved in the SNK tests (Table 6; Figure 9e). The abundance of leatheriackets in the locations in Griffins Bay did, however, fall within the range of abundance of the other locations in Lake Illawarra.
The total abundance of individuals caught in beam trawls was significantly greater at Windang Channel South (Table 6, Figure 9b). This difference was due to the large numbers of a non- commercial shrimp, Macrobrachium inlermedium, at Windang Channel South (Figure 9k). There were also significant differences in total abundance between sites within each location except on the Eastern Shore. All abundant non-commercial species analysed showed differences predominantly at the spatial scale of locations but also among sites. The exception was the eastern I fortesque (Centropogon australis), which did not vary in abundance among locations or sites (Table 6, Figure 9g). Two species of gobies, I' seudogobi us olorum and Cobiopterus semivest it us, were
21
i The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995 significantly more abundant at location B in Griffins Bay (Table 6, Figure 9f,i). The bridled goby, Arenigobius bfrenatus, and the snub-nosed pipefish, Lirocam pus carinirostris, were also most abundant at location B in Griffins Bay, although SNK tests could not detect differences among the locations (Table 6, Figure 9h). The abundance of the remaining species of non-commercial fish analysed (the porcupine fish, Dicotolichthys punctulatus, the large-mouth goby, Redigobius macrostoma, and the wide-bodied pipefish, Stiginatopora nigra) varied significantly among locations, such that, the locations at Griffins Bay fell within the range of the other locations. The squid, idiosepius notoides, varied significantly between sites at location A in Griffins Bay, Windang Channel North and the Eastern Shore (Table 6, Figure 91).
3.2.1.2.2 Sizes of Fish
The size ranges and numbers of individuals of fish of commercial importance collected by beam trawling are summarised in Table 7. All individuals were within the size range for juveniles of each species. For most species the size range was relatively small and Meuschenia trachylepis had the broadest size range.
3.2.2 Beach Seines
A total of 38 275 individual fish and mobile invertebrates were sampled using beach seining. All of these were identified to species. There were 43 species of fish, 6 species of crustaceans and 1 species of cephalopod mollusc. Species of economic value comprised 10.390' of the total catch. In the seine nets, twenty-one species of fish and 2 species of crustaceans of commercial importance were collected (see Appendix C). The most abundant species of fish were perchlet (Ambassis jacksoniensis), transparent goby (Gobiopterus setnivestitus) and hardyhead (Atherinosoma microstorna) representing 249o, 2017o and 189o' respectively of the total catch. The most abundant commercial species of fish were sand mullet (Myxus elorzgatus), luderick (Girella tricuspidata) and tarwhine (Rhabdosargus sarba) representing 25%, 17% and 13% of the commercial fish catch. Eastern king prawns (Penaeus plebejus) represented 99.5% of the commercially important crustacean catch with blue swimmer crabs (Portunus pelagicus) making up the remaining 0.59o. Appendix C lists the species collected and the mean abundance and standard error per site.
22 The Ecology Lab Pty Ltd Griffins Bay sand extradion - Marine Ecology - Final Report, April 1995
3.2.2.1 Analysis of Assemblages
There was little overlap in the position of samples from different locations on the MDS ordination plot which suggested that each location had a distinct assemblage of fish and mobile invertebrates (Figure 10). Furthermore, samples from Griffins Bay A were positioned closely together but at a distance away from the other four locations (Figure 10). This result should be interpreted with caution; however, as the two-dimensional plot derived from the NMS ordination had a stress value of 0.197, which is borderline for a reasonable interpretation of the plot. The MDS plot was still presented but caution should be used when interpreting the plot because the relationship among the samples in two dimensions may not reflect adequately their true relationship. The ANOSIM randomisation test indicated that locations were significantly different at p < 0.01 (ANOSIM, R=0.799). Pairwise comparisons of locations indicated that all locations were significantly different at p < 0.005 except for the comparison between Griffins Bay B and Boat Harbour (Table 8).
Table 9 summarises the results of SIMPER analyses for those comparisons between locations that I were significant in the ANOSIM test. As with the beam trawling, Macrobrachium intermedium contributed most to the dissimilarity between Windang Channel and all other locations. At I Windang Channel an order of magnitude more Macrobrachium were caught than at any other location. Griffins Bay A was distinguishable from the other locations largely due to a greater I abundance of /ktherinosoma microstoma and an absence of fish such as Rhabdosargus sarba, Liza argen tea, Ambassis jacksoniensis and Girella tricuspidata.
3.2.2.2 Analyses of Populations
3.2.2.2.1 Spatial Comparisons
The number of taxa of fish and mobile invertebrates collected using seine nets varied significantly at the spatial scales of location and sites but significant differences among locations were not I resolved by the SNK tests (Table 10). The locations at Griffins Bay B was within the range of the other locations but biodiversity at Griffins Bay A was relatively small compared to the other I locations (Figure ha). The numbers of taxa at sites within locations were similar at all locations except Windang Channel (Table 10, Figure ha).
The total abundance of the commercial species was significantly greater at location B in Griffins Bay compared to all other locations (Table 10, Figure lIc). The individual species of commercial
23 i I The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995 importance that were relatively more abundant at location B in Griffins Bay were; sand whiting (Sillago ciliata), river garfish (Hyprohainphus regularis) and tarwhine (Rhabdosargus sarba) (Table 10, Figure lld,j). A further 7 species of commercial importance were analysed and 3 of these, yellowfin bream (Acanthopagrus australis), sand mullet (Myxus elongatus) and sea mullet (Mugil cephalus), did not differ in abundance among locations or sites (Table 10, Figure lle,f). The abundance of flat-tail mullet (Liza argentea) was largest at Hennegar Bay compared to all the other locations (Table 10). Significant differences in abundance between sites within locations were evident for the blue groper (Achoerodus viridis), luderick (Girella tricuspidata) and eastern king prawn (Penaeus plebejus) with sites at the locations in Griffins Bay just as variable as sites within other locations (Table 10, Figure llg,h,i).
The total abundance of all species caught in beach seines was highly variable among locations and between sites within locations (Table 10). The locations at Griffins Bay fell within the range of abundance of the other locations although differences among the locations could not be detected by the SNK tests (Table 10, Figure lib). The abundance of the carid shrimp, Macrobrachium intermediurn, was significantly larger at Windang Channel than other locations (Table 10, Figure Ilk). This is similar to the result from beam trawling. The abundance of the non-commercial fish species, perchiet (Ambassis jacksoniensis), was significantly greater at location B in Griffins Bay than elsewhere (Table 10, Figure 111). The abundance of the goby, Pseudogobius olorum, also differed significantly among locations with greater abundances occurring at both locations in Griffins Bay and Boat Harbour than elsewhere (Table 10). The abundance of transparent gobies, Gobiopterus seniivestitus, and hardyheads, Atherinosoina microstoina, varied between sites at most locations (Table 10).
3.2.2.2.2 Sizes of Fish
All the fish caught by beach seining were juveniles except for some species of mullet (Liza argentea, Mugil cephalus and Myxus elongatus), where a few individuals caught were of adult size (Table 11). Sand mullet, Myxus elongatus, were abundant enough to compare their size distributions among locations (Figure 12). The locations at Griffins Bay show similar distributions in their lengths to the other locations. A few larger individuals were caught at location B in Griffins Bay, Windang Channel and Hennegar Bay.
24 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
3.3 Commercial Fishing
Fishing is largely regulated in New South Wales by the Fisheries and Oyster Farms Act and its associated regulations. Fishing activities are often subject to closures in various areas and at different times of the year. It may also be subject to restrictions on the types of gear that can be used. In Lake Illawarra, there are restrictions on the places and times that commercial fishing may take place. In particular, the entrance channel to the lake is closed to most forms of commercial fishing. Also, there are restrictions on the timing of some activities, such as mesh netting.
Under the Fisheries and Oyster Farms Act, it is an offence to obstruct recognised fishing grounds. For example, emplacement of objects in areas where beach hauling takes place would be in breach of the Act if fishing is significantly affected. Clearly, the present proposal has the potential to affect some fishing activities in Lake Illawarra. The following sections describe fishing practices in the lake, including the types of fishing and all the areas in which each activity is done, with emphasis on the waters around Griffins Bay. Trends in fishing in recent years are also described.
3.3.1 Description of Commercial Fishing Activities
At present, of the 100 licensed fishers in the Lake Illawarra area, approximately 50 use Lake Illawarra at some time during the year (W. Winter, NSW Fisheries Inspector, pers. comm.). The following description of the commercial fishing activities in Lake Illawarra was summarised from discussions with several local fishers, representatives of CFAC and the local NSW Fisheries Inspector.
I Prawning There are no seasonal closures on prawning in Lake Illawarra but the prawn season is generally from September through to May or June. Approximately 18 crews of 2 people each, deploy nets for prawns in Lake Illawarra (W. Winter, NSW Fisheries Inspector). There are several methods used to catch prawns. These include pocket set nets, snigging nets and running nets. The pocket set net method is used only in the entrance channel where fishing is restricted and places where nets may be deployed are allocated by ballot (18 crews). Pocket set nets are 5 m long with a mesh of 30-36 mm.
The snigging net method is used lake-wide outside of the entrance channel to the lake. Nets are generally 140 metres long with 220 metre hauling lines on each side and with a mesh size of 30 -
25 The Ecology Lab Pty Ltd Griffins Bay sand ext raclion - Marine Ecology Final Reprrt, April 1995
36 mm. By-catch from this method includes small fish and blue-swimmer crabs. This method is prohibited on weekends and public holidays and requires I licensed fisher.
Prawn running nets are used lake-wide but predominantly on the eastern and northern shores of the lake (see Figure 13). With respect to Griffins Bay, they are used on the northern shore near and within Griffins Bay and along the south-eastern shore between Joes Bay and Primbee Bay. Prawn running nets rely on the presence of currents and the movement of prawns for a successful catch. The net is set in shallow water and is shot out into deeper water, sometimes into deeper channels. This method requires 2 licensed crew and the net can only be shot for 1 hour at a time. The net dimensions are 140 m long and approximately 3 m deep with a mesh size between 25 - 36 mm. The season is from September through to May/June and there is no temporal closure imposed.
Meshing for fish and crabs Meshing for fish and crabs occurs lake-wide, including the area proposed for dredging. The splash method is done all year-round whereas the set net method is allowed only in winter. Nets may not be left unattended. The size of the mesh depends on the species targeted e.g. bream - 100 mm, mullet - 80 mm, flathead - 70 mm.
Hauling for fish Hauling for fish also occurs lake-wide but requires shallow areas to haul the net onto and a lack of any obstructions on the hauling ground. Hauling in Lake Illawarra is done from autumn through to spring as there is a closure on hauling from the end of November until March throughout the lake. The hauling nets are generally 725 m long with 750 m hauling lines and the mesh is from 80 mm to 30 mm in the smallest part of the bunt. Hauling is done in many locations along the eastern and western shores. The area proposed for dredging appears to be one of a relatively large number of recognised hauling grounds.
Cockles Cockles are collected by hand within seagrass beds on the eastern shore of the lake up to the entrance into Griffins Bay, on the western side near Purrah Bay and to the west of Bevans Island. There are up to 4 harvesters and the amount harvested is variable depending on price.
26 The Ecology Lab Pty LId Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
3.3.2 Commercial Fisheries Statistics for Lake Jilawarra
3.3.2.1 Temporal Comparisons
Table 9 summarises the results of analyses comparing the weight of commercial species caught by fishers among years from 1985 to 1992. Graphical presentations of the total amount caught annually for some of these species appear in Figure 9. For most species, significant variation occurs in the amount caught from year to year (Table 12). The total catch of commercial species also varies from year to year, with 1985 being the least productive year and 1987 the most productive and other years were not significantly different from each other. Although years were significantly different in the total amount of finfish caught (excludes crustaceans and molluscs), these differences were not resolved by the SNK test (Table 12).
For most species of finfish, there were significant differences in the amount caught from year to year. The exceptions were; river garfish (Table 12, Figure 14c) and silver biddys (Table 12) which showed no changes in the amount caught among years. Peaks in the amount caught per year differ for some species. For instance, yellowfin bream and luderick were caught in their greatest numbers in 1987; flathead, mullet and whiting peaked in 1989 and leatheijackets peaked in 1988 (Table 12, Figure 14d,e,f,g,h).
Eastern king prawns were variable in the amount caught per year, the catch being greatest in 1985 and least in 1992 (Table 12, Figure 14i). The catch of school prawns, however, was not significantly different among years, largely because of the huge variability within individual years (Table 12). The amount of school prawns caught peaked in 1990 and 1991 (Figure 14j). Mudcrabs and blue-swimmer crabs were caught in variable amounts from year to year although both species were collected in significantly greater amounts in 1992 (for blue-swimmers) and in 1991 and 1992 (for niudcrabs) (Table 12, Figure 14k).
Cockles were harvested in significantly different amounts during the years 1985 to 1992 (Table 12). Negligible amounts were collected in 1985, 1986, 1987, 1989 and 1990. In 1992, twice as many cockles were harvested compared to any previous year (Figure 141).
In summary, there were differences in the catch among years for some species, but there is no indication that there have been substantial changes overall in the amount of fish caught between
27 The Ecology Lab Pty Ud Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
1985 and 1992. The exceptions to this are cockles, blue-swimmer crabs and mudcrabs which were
harvested in increasing amounts in the 1990's. I
3.3.2.2 Comparisons with other NSW lakes
Lake Illawarra is ranked 11th out of 41 major estuaries in NSW in terms of its production (kg) of 37 major species of commercial fish during 1990/91 (NSW Fisheries Statistics). Table 13 summarises some of these data by examining 15 species caught in Lake Illawarra compared to that of 6 other similar lakes in NSW. In this comparison, Lake Illawarra produced the biggest catch of cockles and eastern king prawns and a substantial catch of garfish, bream, flathead, luderick, sea mullet and school prawns. On this basis, it is concluded that Lake Illawarra has a regionally significant commercial fishety, particularly for prawns and cockles.
3.4 Recreational Fishing
3.4.1 Description of Recreational Fishing Activities
The local NSW Fisheries Inspector estimates that some 90% of recreational fishing for finfish occurs in the channel entering Lake Illawarra. The popularity of the channel was confirmed in discussions with some members of the Windang Hotel Fishing Club and observations made by TEL during field sampling. Members of the Windang Hotel Fishing Club maintained that very little recreational fishing is done in or near Griffins Bay and that most occurs off Bevans Island where bream and luderick are caught. There are, however, a few reefs near the entrance to Griffins Bay that are used by recreational fishers for catching bream. New jetties built around Griffins Bay may allow more people to fish from them.
Recreational prawning may occur in many areas of shallow, suitable water in the lake. The majority of recreational fishers, however, use the entrance channel to the lake and to a lesser extent, the eastern shore, for prawning. Recreational fishers are allowed to use scoop nets in these closure areas. There are no seasonal closures but recreational prawning mainly occurs in summer. In the past, prawns were collected in the back of Griffins Bay using 20 foot dragnets (W. Winter, pers. com.).
The 'squirt' worm (Australonereis ehiersi) and 'flippers' (Cullianassu spp.) are used for bait and are collected using a suction core in shallow areas in many places within the lake such as the entrance
28 I
The Ecology Lab Pty Ud Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
channel and the eastern shore entering Griffins Bay. 'Blackfish weed' (probably Enteromorpha sp.) is also used as bait and is often collected in the shallows on the eastern shore of the lake as far north as the entrance into Griffins Bay, near the Oasis Motel and at the mouths of several small creeks that run into the lake.
On the basis of our discussions, we conclude that most recreational fishing in Lake Illawarra is in I the entrance channel, and that Griffins Bay is of limited significance to recreational fishing. This may change as a result of foreshore improvements, which may increase access to the water.
3.5 Conclusions from Field Studies I 3.5.1 Benthic Macrofauna I The assemblages of benthic macrofauna in Griffins Bay were distinctive when compared to those from similar sandy sediments nearby along the eastern foreshore and from muddy sediments at I two locations within Lake Illawarra. The benthic macrofauna appear to vary with the type of sediment (i.e. sandy versus muddy) and the location within the sandy sediment habitat. This is an I important result because the dredging associated with this proposal would directly remove an area of sandy-sediment habitat and, indirectly, it may change the type of sediment found around the I dredged area through the dispersal of fine sediments.
The abundance of individual species of benthic macrofauna did not differ between Griffins Bay and the reference area - differences were generally greater among the smaller spatial scales of locations and sites within each area. Although locations in Griffins Bay were only 100's metres I apart, the abundance of macrofauna was highly variable in Griffins Bay and, to a lesser extent, the reference area. Thus, Griffins Bay is not unique in the abundance of numerically dominant taxa or I the total number of taxa. Provision for the large variability in the abundance of benthic macrofauna would by necessary if monitoring is required in the future, by sampling at several spatial scales and at several reference locations for an informative comparison. Sampling once has provided a 'snapshot' view of the distribution and abundance of benthic macrofauna in the lake but it has not provided a measure of temporal variability, which would also be necessary should I monitoring be required. I I 29 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
3.5.2 Fish and Mobile Invertebrates
The methods of beam trawling and beach seining used to sample fish and mobile invertebrates, were deployed in different sampling locations and collected a different range of species. Most fish caught by these methods were smaller-sized fish and juveniles, with the exception of a few adult mullet caught in the beach seines. Slightly more fish and mobile invertebrates were caught by beam trawling than beach seining whereas more species were caught using beach seines (50 species compared to 38 species). Both methods were used so that a broader range of species were sampled overall.
The number of species and the number of individuals sampled using both methods varied among locations and sites. Generally, the locations at Griffins Bay were within the range of variation for all the sites sampled. There was a noteworthy exception, however. The abundance of juveniles of commercially important species caught by beach seining was greater at the location along the northern shore of Griffins Bay compared to the other locations. Species contributing most to this result were river garfish, sand whiting and tarwhine. On this basis we conclude that this area of Griffins Bay appears to be a relatively important habitat for juvenile fish. It should be noted that this site was located within approximately 100 m of previously dredged areas completed in 1991.
Each location sampled was fairly distinctive in the structure of the assemblages of fish and mobile invertebrates. Locations differed in the presence and relative abundance of species. In some cases, the locations at Griffins Bay differed just as much from each other as they did from the other locations in the lake. Notably, the assemblage sampled by beam trawls at the back of Griffins Bay had large numbers of a goby, Pseudogobius olorum, compared to other places. The assemblages sampled by beach seining were even more distinctive between locations. Most notably, the entrance to Griffins Bay was characterised by the greater abundance of hardy-heads, Atherinsoma microstoma and the absence of juveniles of yellowfin bream, blue groper, tarwhine, flat-tail mullet, perchlets and luderick
These results indicate that areas within Griffins Bay support a diverse fauna of fish and mobile invertebrates that falls generally within the range of abundance and diversity of other locations examined in the lake and should not, on this basis, be regarded as depauperate or degraded. Again, sampling more than once is necessary to determine if these patterns are consistent through time.
30 The Ecology Lab Pty Ud Griffins Bay sand extradion - Marine Ecology - Final Report, April 1995
3.5.3 Commercial and Recreational Fisheries I Information on the commercial catch from different areas within Lake Illawarra is not available so that an assessment of the relative catch from areas in and around Griffins Bay compared to other places in Lake Illawarra is not possible. Griffins Bay and its surrounds are, however, recognised as areas for haul and mesh fishing and places where prawn running nets and snigging nets are set. I These types of fishing activities also happen at other places within Lake Illawarra. The commercial catch of species from Lake Illawarra, although variable from year to year and species to species,
I does not indicate substantial changes overall in the amount of fish caught in the short-term, between 1985 and 1992. There are several aspects of the current proposal which would effect I commercial fishing operations around Griffins Bay and this may in turn effect the production of Lake Illawarra. These issues will be discussed further in Section 4.2.
Most recreational fishing and prawning occurs at the entrance channel into Lake Illawarra. The current proposal is unlikely to impact on the activities of recreational anglers.
1 4.0 ASSESSMENT OF IMPACTS
1 4.1 Brief Description of the Proposal
The proposed extraction of sand would be done by dredging in stages over a period of 10 to 13 years and involve three major components; i) dredging of 4 major areas (denoted Areas A to D), ii) dredging an extension of the channel already in Griffins Bay and iii) creation of an island off Purry Burry Point (Figure 15). The duration of the project would depend on i) the demand for sand and ii) which channel option is adopted (GI-ID, 1995). A summary of the details of these works considered relevant to assessing the impacts on the aquatic environment of dredging the different areas is in Table 14. More information is provided by the EIS (GHD, 1995).
Material dredged from the lake would be screened for rocks, shells and other debris greater than 5 mm before being transported to sandwashing and stockpiling facilities at Korrungulla Swamp. The material would be washed, the sand stockpiled for sale and the residue (sediment finer than 150 xm) returned via pipeline to the lake (SCE pers. comm.). The residue would be added to the coarse material already screened from the sediment to form an island and be used as back fill for dredged Area A.
31 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
The first stage of the dredging operation is the creation of embankments around the perimeter of the area designated to form the island and Area A before any dredging starts. The embankments would be made from the surrounding sediment, have a crest height of 1.5 m Al-ID (i.e. 1.2 m above the water level), outward facing slopes of 1:15 and function to prevent erosion of the island during the dredging process. The embankments would stay in place throughout the project and would be used as fill for Area A before capping the area with 50 cm of sand.
The island would be built in two phases. First, the residues from the dredging of Area A would be used to form the first part of the island. Any runoff water from the island would be channelled to Area A which would act as a sedimentation pond, allowing fine sediments to settle out before the water flowed into the lake. This first phase would take 4 months to complete. This part of the island would then be capped by 50 cm of sand which would be suitable for vegetation by native grasses and shrubs (GI-ID, 1995). The second phase would involve placing a floating geofabric curtain on the western side of the island and filling behind it with residues from dredging Area B, Area C and the channel extension. This phase would be complete after 6 years.
Areas A, C and D would be dredged to a depth of -14 m Al-ID and only Area A would be backfilled to a depth sloping between -0.9 m to -1.6 m Al-ID as part of the current proposal. The backfilling of Areas C and D depend on receiving fill from other dredging programs under the control of the Lake Illawarra Authority and are subject to separate approval. Areas C and D would be isolated from the rest of the lake by embankments while they were being dredged. The embankments would be made from material excavated in the surrounding area. The description of the proposal in the previous EIS (KayBond Pty Ltd, 1993) did not involve the isolation of these areas from the rest of the lake. In response to comments on the previous EIS, the dredging proposal now includes the embankment surrounding the deep hole as a way to reduce the risk of movement of stagnant water from the deep hole to the rest of the lake and reduce the potential for the deep hole to be a 'sink' for debris such as dead seagrass and algae. After completion of the dredging contract, the maintenance of the island and embankments around dredge Areas C and D would become the responsibility of the Lake Illawarra Authority (GI-[D, 1995).
Previous dredging in Griffins Bay has created a 50 m foreshore buffer zone which runs adjacent to the shore and is -0.8 m deep Al-ID. Seaward of the buffer zone is a horses hoe-shape d channel, 50 m wide with a slope of 1:6, which was dredged to -1.5 m deep AHD around Griffins Bay. As part of this proposal the existing channel on the southern side of Griffins Bay would be extended out into the main bodv of the lake. The proposed extension of the channel would be 50 m wide, with
32 The Ecology Lab Pt y Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
side slopes of 1:6 except where the channel cuts the underwater sand bank, reducing the side slopes to 1:12. Two options are being evaluated for the positioning of the channel extension I (G1-[D, 1995). Option I would pass north of Purry Burry Point and due west. Option 2 would cut through the northern tip of Purry Burzy Point and head in a more north-westerly direction. More I sand would be removed from Areas C and D under Option 2 (Table 14).
In summary, the main parts of this proposal that need to be considered in assessing the impacts on the aquatic environment are:
I i) the direct removal of habitat such as seagrass and unvegetated benthic substratum by dredging,
I ii) the indirect effects of dredging on surrounding habitats;
the direct creation of new habitats such as the island, the channel and the enclosed deep hole; and
the indirect effects of the newly created habitats.
4.2 Dredging Areas A to D and the Channel Extension
The impacts of the dredging part of the proposal are discussed below in two sections: impacts during dredging (Section 4.2.1) and long term impacts after dredging is completed (Section 4.2.2).
I 4.2.1 Impacts During Dredging
Changes to the marine environment associated with the dredging activity which may lead to I impacts on biota include:
i) the release and circulation of suspended fines, nutrients, heavy metals and other contaminants I from the removal and backfilling of sediments in the dredged areas;
ii) changes in water quality (turbidity, salinity, temperature, dissolved oxygen, and nutrients);
iii) physical damage and alteration of the bottom topography of the lake through the activities of boats, equipment and people associated with dredging operations;
iv) creation of barriers to movement of fish and mobile invertebrates e.g. embankments and island;
33
I
The Ecology Liib Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
removal and burial of seagrasses;
changes to patterns of water circulation; and vii) the presence of potential acid sulphate soils.
The responses of various biota and fisheries to these changes during dredging (except for acid sulphate soils) are discussed in the following subsections; seagrass beds, benthic macrofauna, fish and mobile invertebrates, commercial fisheries and recreational fisheries.
Acid Sulphate Soils Acid sulphate soils (ASS) are found in many places along the Australian coast. They contain iron pyrite, a naturally occurring mineral in estuarine sediments. Iron pyrite is stable under waterlogged (reducing) conditions where it is no threat to the environment. When exposed to air, however, it reacts rapidly with oxygen to produce sulphuric acid and iron. Exposure to air can happen naturally (e.g. during drought) or through a human activity such as dredging and some agricultural practices. The oxidation of pyrite to sulphuric acid and iron decreases the pH of the sediment making it acidic. The lowered pH levels may affect groundwater as well as surface water bodies. Elements such as aluminium and iron can dissolve and reach concentrations high enough to be detrimental to aquatic biota (Creagh, 1993). The influx of acidic water high in aluminium and iron clogs the gills of fish, crustaceans and oysters causing 'fish kills' (Sammut et al., 1993).
The EPA (1993) have published draft guidelines on the assessment and management of coastal developments in areas of acid sulphate soil. These guidelines, which are described as tentative, provide levels of oxidisable sulphur in sediments that are considered to constitute a risk to the environment if exposed. Bowman (1993) has developed criteria to judge the potential for acid sulphate soils based on the oxidisable sulphur content (as pyrite %S) of sediments. Management strategies for dealing with acid sulphate soils and their detrimental effects on the environment are being developed in Australia and were recently the subject of a national conference (Bush, 1993). NSW Fisheries Estuarine Habitat Management Guidelines (Burchmore et al., 1993) also provide recommendations concerning the management of acid sulphate soils and various developments.
The preliminary tests done by CF-ID (1995) on the sediments in Griffins Bay indicated that there was the potential for acid sulphate soils to occur in Griffins Bay. Cl-iD (1995) recommended that a more comprehensive survey be undertaken prior to dredging. An assessment of the effects of acid
34 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
sulphate soils on aquatic biota cannot be made using the data collected to date. Therefore, the potential for acid sulphate soils needs to be quantified and investigated further. Measures such as those developed by Bowman (1993) are recommended to assess the potential for impacts on the aquatic biota in Griffins Bay and Lake Illawarra. I 4.2.1.1 Seagrass Beds The dredging of Areas A to D and the channel extension would result in the direct removal of seagrass from the entrance to Griffins Bay. Estimates of the actual area of seagrass that would be lost depend on the estimate of seagrass cover used initially (see Section 1.2.2). By superimposing the area of the dredging operations and the island onto the map of seagrass given by West et al., 1985, the total area of seagrass to be removed was estimated as 26.4 hectares (25.4 hectares of
Zostera and 1 hectare of Halophila). This is 5% of the total area of seagrass in Lake Illawarra using
data from West et al., 1985. Using data from King (1991) for the total area of seagrass in Lake Illawarra (10.9 km2), then 2.4% of the total area of seagrass would be removed. Using a more recent map of the cover of seagrass (WBM Oceanics, 1993), the area of seagrass to be removed was estimated to be 25 hectares (15.8 hectares of dense Zostera and 9.2 hectares of dense Ruppia) but because the total area of seagrass in Lake Illawarra was not estimated by WBM Oceanics, so the proportion of seagrass removed by dredging cannot be estimated in this case.
The rate of removal of seagrass would depend on the progress of the dredging operations (Table 14). Thus, the loss of seagrass calculated above represents the maximum amount which would be removed over a period of 10 to 13 years. It may, however, be possible for seagrass to revegetate the substratum in dredged Areas A and B because the depth of these areas would be within the range possible for the growth of seagrass in Lake Illawarra (WBM Oceanics, 1993; Yassini, 1993). The maximum area that may be at a depth suitable for the regrowth of seagrasses would be 5.2 ha or 20.8 % of the area lost and 2.4 ha. or 9.6% would be available 2 years after the project commenced (Table 14). If Areas C and D were backfilled, then a further 21.3 ha. (or approximately 80%) of the initial area lost would be available and this would occur a minimum of 10 years after the project commenced. It should be noted, however, that the depth of these areas is deeper than the pre-dredging depths and thus, it cannot be assumed that the seagrass would grow at the same rates or to the same densities as pre-dredging levels. Should seagrass grow back in these areas, it would reduce the final overall area of seagrass that would be removed by the proposal. The possibility for rehabilitation of areas of seagrass is discussed further in Section 4.7.2.
35 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Seagrass may also be lost, damaged by smothering or its growth reduced due to an increase in turbidity of the water from; I) the escape of fine sediments during dredging, ii) the settling out of fine sediments in the 'return-water' from the washing facility and iii) the erosion of disturbed areas such as the boundaries of the dredged areas. The use of silt-curtains around the head of the dredge would reduce the risk of the escape of fines during dredging and is recommended by NSW Fisheries in their Estuarine Habitat Management Guidelines (1993). The 'return water' from the washing facility would be directed to flow from the island into dredge Area A, allowing the fines to settle out before this water enters the rest of the lake (GHD, 1995). These measures would reduce the risk to seagrass being damaged adjacent to the dredged areas.
Other changes in water quality such as water temperature, salinity and dissolved oxygen may lead to a decrease in growth and a loss of productivity of seagrass. This is not considered likely for this proposal, however, as GHD (1995) predicts that the temperature, salinity and dissolved oxygen levels of Griffins Bay would not change substantially from pre-dredging conditions but would be more similar to those of the rest of Lake Illawarra due to the increase in circulation (once the channel is completed) and decrease in residence time of water in Griffins Bay. The 'return-water' from the washing facility to the lake would have a reduced salinity (GHD, 1995), however, it would still be within the range of salinities that Zosterci capricorni grows in within Lake Illawarra (Harris et cii., 1980).
Seagrass may also be lost or damaged incidentally, by the activities of boats, equipment and humans associated with the dredging operations. For example, boat moorings in seagrass beds in Western Australia have been found to produce circular scours ranging from 3 to 300 m2 (Walker et cii., 1989). The movement of the screen which is used to filter the dredged material and the laying of the dredge pipelines are examples of activities that could damage the lake bed. Therefore, movement of screens and boats should be done in such a way to minimise the impacts of physical damage to the seagrass bed. This damage would be in addition to other damage which may be associated with recreational and commercial boating and fishing activities.
4.2.1.2 Benthic Macrofauna
Dredging activities can cause changes to existing benthic assemblages which range from a temporary depletion of the original assemblage through to a permanent change in the structure of the assemblage, including the elimination of some species (ICES, 1991). Many studies have demonstrated that macrofauna are able to recolonise disturbed bottom sediments but the rates of
36 I The Ecology Lab Pty Ltd Griffins Bay sand extradion - Marine Ecology - Final Rqxrt, April 1995 colonisation and the composition of the colonising fauna may be different to the original assemblages (e.g. Levin, 1984 Thrush and Roper, 1988; Savidge and Taghon, 1988; Diaz-Castaneda et al., 1993). The nature of the assemblage that recolonises after dredging would depend on the I magnitude and duration of the dredging operation, the type of sediment that remains or subsequently accumulates at the extraction site, the ability of adults to migrate into the sediment, the ability of larvae to settle from the water column and the range of stresses which the I assemblage can withstand (ICES, 1991).
I Removal of Habitat
The removal of seagrass and unvegetated sediments in dredge Areas A to D would cause the I removal of the benthic macrofauna associated with these habitats immediately after dredging. This would lead to changes in the structure, distribution and abundance of benthic macrofauna that I recolonise the areas that have been dredged. It would be expected, however, that recolonisation of dredged areas would be progressive and occur for the duration of the project and after dredging is I complete. The recolonisation rates of benthic macrofauna reported in the scientific literature are highly variable, making predictions about specific rates of recolonisation to bottom sediments in Griffins Bay difficult. For example, recolonisation of benthic macrofauna from dredging in muddy Ii sediments where the sediment did not change as a result of dredging occurred within 3 months after dredging (Van Dolah et al., 1984). Alternatively, Poiner and Kennedy (1984) reported a [j decrease in the number of species and the abundance of individuals of macrofauna after dredging of a shipping channel in Moreton Bay, Queensland. Their samples were collected several months I after dredging was complete and the sediment, predominantly fine to medium sand, was similar to that prior to dredging.
The staging of dredging in Griffins Bay would lead to the availability to colonisers of areas that were also different in the type of sediment, the cover of seagrass, water depth and possibly the chemical and physical nature of the water itself (Table 14). Thus, the impacts on benthic macrofauna may vary according to the characteristics of the areas that remain. Benthic assemblages and populations varied with type of sediment and location in Lake Illawarra and the assemblages in Griffins Bay were different to the others sampled (Section 3.1). In addition, the benthic fauna associated with seagrass is often different to that of adjacent unvegetated sediments (reviewed by Howard et al., 1989). Dredged areas once covered by seagrass would be unvegetated for some time (depending on recolonisation rates of seagrass, Section 4.2.1.1) or remain unvegetated and may contain a different benthic assemblage than what was there prior to dredging.
37 The Ecology Lab Pt y Ltd Griffins Bay sand extraction Marine Ecology - Firoil Report, April 1995
It seems likely then that only dredge Area B (Figure 15, Table 14), which would be similar to pre- dredging areas in Griffins Bay in terms of water depth and sediment type, could potentially be recolonised by an assemblage of benthic macrofauna similar to that found prior to dredging. The other areas to be dredged would be very different in water depth and sediment type after dredging, thus, differences in the structure of benthic assemblages would be expected in these areas. Area A would be dredged to a depth of -14 m and eventually backfilled with a combination of very coarse and fine sediment (rejected by the sand extraction process) to a depth of -0.9 to - 1.6 m Al-ID. Dredging of Area A would be complete after 2 years but backfilling could take 13 years. Areas C and D would be dredged to a depth of -14 m Al-ID over 6 years and could remain at this depth unless fill from other projects was obtained.
Deposition of Fines
The deposition of fine materials that may escape from the dredge and/or from the 'return water' may result in a change in structure of assemblages of benthic macrofauna in adjacent areas to the dredging because the assemblages associated with finer (muddier) sediments are different to those associated with sandy habitats in the lake (Section 3.1.1). If the escape of fines were severe the fauna may be smothered but this would depend on the abilities of the fauna to escape or tolerate these conditions, the deposition rate of the fine sediment and the increase in water turbidity relative to natural background levels. Given the safeguards suggested for this project, such as the use of the silt curtain and bunding of Areas A, C and D, it is unlikely that such impacts would occur as a direct result of the dredging.
The extension of the channel, however, is predicted to redistribute silt, over a period of 6 months, as a consequence of an increase in the flow velocity in this area (GHD, 1995). Silt and ooze within 50 m of the channel would move into the channel and be deposited at the western end of the channel over an area of 2 ha and to a maximum depth of 3 cm (GHD, 1995). The fauna in this area may be smothered at this rate of deposition or they may have the ability to burrow through fine deposited material and escape burial (Kranz, 1974; Brenchley, 1981; Engler ef al., 1991). For instance, Poiner and Kennedy (1984) concluded that deposition rates of sand (not fine material) ranging from 6 to 23 mm/m 2 were not sufficient to cause smothering of macrofauna or detrimental effects from increases in water turbidity. Removing the silt (by skim dredging) prior to work on the channel would substantially reduce the risk of adverse effects on the benthic macrofauna at the western end of the channel extension and is recommended. Monitoring of this area should also be considered.
38 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Potential Mobilisation of Contaminants
Heavy metals and other contaminants may be mobilised in several ways by the dredging proposal. The release and movement of contaminants (e.g. chromium and zinc) could have toxic effects on biota such as benthic macrofauna. During dredging, contaminants in the sediment may be disturbed in areas not directly dredged but adjacent to dredged areas. Thus, some redistribution I of heavy metals and contaminants would result directly from the dredging but could be minimised by the use of a silt-curtain around all dredging operations. As a consequence of extending the channel on the southern side of Griffins Bay, heavy metals and other contaminants associated with silt in Primbee Bay located within 50 m of the channel, would be deposited in the channel and moved to the deeper parts of the lake outside of Griffins Bay (GHD, 1995). This would also result in the redistribution of contaminants. The likelihood of release of contaminants into the water column is, however, unknown.
All sediment removed by dredging would be washed at the sand washing facility and the fine fraction returned to the lake. A preliminary test of the elutriate from sediment collected in Griffins Bay and washed in distilled water found no detectable levels of heavy metals (GHD, 1995). Thus, the concentration of heavy metals in the 'return' water from the sand washing plant may be negligible and implies that the heavy metals would remain attached to the fine fraction of the sediment and therefore, would be deposited as part of the island or backfill for Area A.
Changes in Water Quality
Other impacts on the benthos may arise through changes in water quality. For instance, an increase in turbidity due to suspended fines in the water column may decrease primary productivity temporarily affecting the benthos in turn. Overall, water quality is predicted to improve slightly due to the dredging of the circulation channel out of Griffins Bay (GHD, 1995).
4.2.1.3 Fish and Mobile Invertebrates
During the dredging, many fish and mobile invertebrates would be able to avoid being sucked into the head of the dredge. However, small fish and mobile invertebrates associated with seagrass would probably be lost at the commencement of the operation. This includes fish and crustaceans of economic value utilising seagrasses as nursery areas. It may be possible to minimise the potential loss of post-settlement fish by commencing dredging at times of the year when settlement is not expected. Juvenile fish are unlikely to move out of the seagrass to escape the dredge head. Therefore, if seagrass is removed by skim dredging prior to settlement in
39 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995 spring/summer, the juvenile fish may settle in other seagrass beds in Lake Illawarra rather than in seagrasses about to be dredged. Thus, these fish may be able to grow into adults in other parts of Lake Illawarra. Adults that may occasionally be trapped by the dredge head include some leatherjackets (Monacanthidae) and flathead (P/atycephalus spp.). The extent of impact to fish and mobile invertebrate assemblages would therefore depend upon; i) the behavioural responses of fish to the dredging operations, ii) the removal of habitat such as seagrass, iii) changes to assemblages of benthic macrofauna affected by dredging and iv) changes in water quality and circulation, which have been addressed by GI-ID (1995).
The removal of seagrass from the dredged areas would result in a direct loss of habitat for adult and juvenile fish and mobile invertebrates. Because seagrass beds are important habitat for these animals (Section 1.2.5), this removal would be significant. It is uncertain, however, if this would lead to an overall decrease in the number and species of fish that settle out of the plankton in the lake or whether they would settle out into other suitable areas of seagrass. In general, the fish and mobile invertebrate assemblages sampled in the proposed dredge area of Griffins Bay were not unique and fell within the range found for other areas of the lake (Section 3.2). Thus, the direct removal of seagrass habitat in the proposed dredge area of Griffins Bay would not represent the loss of a unique or uncommon species of fish or mobile invertebrate but may lead to a decrease in the abundance of some species especially in the immediate vicinity of the dredge operations.
The northern shore at the entrance to Griffins Bay, near the proposed dredging operations, was found to support a greater abundance of juvenile fish of commercial importance compared to other areas sampled (Section 3.2). It is likely that fish and mobile invertebrates in the vicinity of the dredging operations would be disturbed which may result in a redistribution of fish away from the dredge areas. This may, for instance, lead to a decrease in the relative importance of the northern shore of Griffins Bay as a habitat for juvenile fish.
Disturbance to the bottom sediments in Griffins Bay, as a consequence of dredging, may also attract some species of fish due to the exposure of benthic macrofauna which some fish feed on. This has been observed around a discharge pipe returning a sand slurry laden with macrofauna at Wallis Lake (M. Lincoln Smith, pers. obs.). Such a disturbance would only occur over a relatively small spatial scale, in the immediate vicinity of the head of the dredge near freshly exposed bottom sediments. On a larger spatial scale, however, there may be a reduction in food for fish because the benthic macrofauna and algae associated with seagrass and unvegetated sediments would be removed. Until recolonisation of the dredged areas by benthic macrofauna occurred,
40 I The Ecology Lab Ply Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995 there would be a loss of food for fish. In addition, the composition and abundance of species of riiacrofauna that recolonise the dredged areas may represent a different quality of food for fish and
mobile invertebrates (Section 4.2.1.2).
Overall, it is likely that fish would move away from the dredging operations. Their movements I may be affected by the embankments surrounding dredge Areas A, C and D and the island. 4.2.1.4 Commercial Fisheries
The commercial fishing operations that currently take place in Lake Illawarra would be impacted
during dredging in the following ways:
loss of recognised fishing and prawning grounds through direct loss of fishing areas where
dredging is occurring;
reduction in productivity of Lake Illawarra if loss of fishing areas near Griffins Bay results in an
overall decrease in the amount caught by fishers; and
interference with currents affecting the movements of prawns and fish.
The likelihood of impacts during dredging on the different methods of fishing (described in
Section 3.3.1) are summarised in Table 15.
Commercial hauling and meshing for fish and crabs occurs in many parts of Lake Illawarra including the area where dredging would occur (Section 3.3.1). Throughout the duration of the
dredging operation, parts of the dredged area would be unavailable for commercial fishing. Fishers may therefore be forced to rely on other areas of Lake Illawarra as a substitute for the loss of grounds near Griffins Bay, potentially leading to an increase in fishing pressure in other areas of
Lake Illawarra.
There would be a decrease in productivity of the area where dredging takes place near Griffins Bay. There may, however, also be a reduction in the productivity of the entire lake if the loss of the seagrass habitat near Griffins Bay leads to a reduction overall in juvenile fish settling from the
plankton in Lake Illawarra.
41 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology Final Report, April 1515
Prawning using running nets relies on the movement of prawns in currents and snigging nets disturb the bottom sediments to make the prawns move. During dredging the movement of prawns may change due to the removal of shallow benthic habitat, the large increase in depth in some areas, the placement of barriers such as the island and bund walls around dredge Area A, C and D and the disturbance in the immediate vicinity of the head of the dredge. Thus, changes in the movements of prawns may influence the amount caught by fishers and the location where they are caught. Once the channel is completed, it may be possible to deploy running nets in the channel all around Griffins Bay.
The fishery for cockles is unlikely to be affected adversely because the areas where they are hand- collected do not overlap with the dredge areas. Areas close to Griffins Bay on the eastern foreshore are unlikely to be affected by the settling of suspended fines from the dredge operations given the use of silt curtains and Area A as a settling pond, although there may be some smothering of the seabed from fines transported out of Griffins Bay following dredging of the channel, as discussed previously in Section 4.2.1.2.
4.2.1.5 Recreational Fisheries
The area of the lake to be dredged in this proposal is not used often, as far as we can ascertain, by recreational anglers. Therefore, we predict no adverse impacts on recreational fishing activities. Bait collecting on the eastern foreshore near Griffins Bay is also unlikely to be affected given the large area available to collect from. The potential impacts during dredging on the different methods of recreational fishing (described in Section 3.4.1) are summarised in Table 15.
4.2.2 Impacts after Dredging
In this section the long-term impacts of the dredging proposal are discussed. These are impacts that may arise after the completion of dredging. Some impacts discussed in the previous section, however, may also persist after the dredging is finished and these are noted.
Furthermore, the assessment of impacts after dredging is based on the maintenance of the embankments surrounding the deep hole by the Lake Illawarra Authority until these areas are backfilled (Cl-ID, 1995). Discussion of the consequences of removal of these embankments prior to complete backfilling is in Section 4.3.
42 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Modelling of the water circulation patterns around Griffins Bay after the project is completed produced the following predictions (GHD, 1995):
I) Water circulation would be altered around the mouth of Griffins Bay, due to the presence of embankments surrounding the deep hole, formation of the southern channel and creation of the island;
There would be no strong tidally-induced flows in the channel in Griffins Bay with a maximal predicted current of 0.1 m/s;
The island would provide a sheltered area to the immediate east which would restrict mixing because of the reduction in the amount of water entering Griffins Bay;
There would be no significant change to present conditions along the northern foreshore of Lake Illawarra with a maximal variation of 0.05 m/s in the velocity of currents. Increases or decreases in current speed would depend on the wind;
There would be a tendency for more uniform salinity, dissolved oxygen and temperature of the water around Griffins Bay with the rest of the lake due to water circulation in the southern channel extension
There would be continued movement of sand along the eastern shore of the lake northwards to the mouth of Griffins Bay;
There would be greater wind waves for westerly and south westerly wind conditions into Griffins Bay; and
There would be increased movement of water along Primbee Bay when the channel was extended compared to present conditions.
4.2.2.1 Seagrass Beds
Aside from the direct loss in aerial extent of seagrass as a result of the dredging (Section 4.2.1.1) there may be several other longer term impacts on seagrasses. There are several ways in which changes in water flow can affect the productivity of seagrasses. For example, an increase in
43 The Ecology Lab Ply Ltd Gnffins Bay sand extraction - Marine Ecology - Final Report, April 1595
current flow may enhance nutrient uptake at the leaf surface of seagrasses thereby, increasing productivity (Harlin and Thorne-Miller, 1981). Evidence for this is limited, however, and is likely to vary considerably among species (Fonseca and Kenworthy, 1987). Zostera marina and other seagrasses can exist in currents of up to 120 - 150 cm/s but the standing stock of Zostera marina drops dramatically in current regimes greater than 50 cm/s. Alternatively, increased current flow may cause erosion of the outer edge of the seagrass bed or scouring may create 'halos' or 'blowouts' within the bed. The changes to current flow predicted by GHD (1995) are so small that they would be unlikely to cause changes in the productivity of the seagrass remaining after dredging is completed in this manner.
The edges of the remaining seagrass bed near the embankments surrounding the deeply dredged hole may be susceptible to damage because of a decrease in light reaching them or change in water flow and turbulence due to the presence of the embankment. Fisheries Estuarine Management Guidelines state that the bottom of dredged areas must be even, battered to a slope of 1:7 and be free of holes which allow the build-up of stagnant waters (Burchmore et al., 1993). The hole left by this proposal would have slopes of 1:1 (GHD, 1995), however, because they would be bunded the potential for slumping is minimised and the possibility of stagnant waters impacting the rest of the lake is also minimised.
The rehabilitation of areas where seagrass has been removed is discussed in detail in Section 4.7.2.
4.2.2.2 Benthic Macrofauna
In the long term, the benthic macrofauna in the areas that would be dredged would be different to those prior to dredging due to major changes in their habitat. It is predicted that benthic macrofauna adjacent to the dredged areas in Griffins Bay would be unaffected by the dredging if mitigative procedures are adopted.
Changes in water circulation may affect the dispersal of larval, juvenile and adult animals resulting in changes to the distribution of settled adults in seagrasses and unvegetated sediments. For this project, however, the predicted changes in water circulation are relatively small and are unlikely to affect macrofaunal assemblages in this way.
44 The Ecology Lab Ply LId Griffins Bay sand extradion - Mirine Ecology - Final Report, April 1995
4.2.2.3 Fish and Mobile Invertebrates
After dredging is completed, there is a potential for fish to inhabit the areas that have been dredged except for the deep hole because it would be surrounded by an embankment. In the long term, the movements of fish would be altered by the presence of the embankment and the island. Changes in water circulation in this area may also alter the movements of fish compared to before dredging. Specific predictions such increases, decreases or no change in the abundance of fish in these dredged areas are difficult to make due to the lack of information on the effect of changes in depth and bottom topography due to dredging on the movement of fish.
4.2.2.4 Commercial Fisheries
Commercial fishing operations in the lake would be impacted adversely because of the permanent loss of fishing grounds where dredging and construction of the island took place. The depth of this area after dredging would be at a minimum of -1.5 m and therefore too deep for hauling. It may also be too deep for meshing for fish and crabs (Table 14).
Changes in the circulation of water along the northern foreshore are predicted to be minimal (GI-ID, 1995). On this basis it would be expected that prawning in this area would be viable and similar to pre-dredging conditions. The extension of the channel in the southern part of Griffins Bay may provide another area available for prawning. If, however, the movement and behaviour of prawns had been altered by the dredging works, this may not be the case. As far as we are aware, there is no information on the movements of prawns within estuaries that would help to assess the potential for this to occur.
4.2.2.5 Recreational Fisheries
Access into Griffins Bay would improve after completion of the project because of the deeper channel on the southern side of the bay and jetties built into Griffins Bay from the shore. This may encourage anglers into this area whereas at present, it is not used often (Section 3.4.1).
4.3 Creation of Deep Hole
Cl-ID (1995) predict that water quality and circulation would be different in the deep hole compared to elsewhere in the lake. A decrease in water circulation could lead to a decrease in
45 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine &olgy - Final Report, April 1995 water temperature by 2-3° (compared to the rest of the lake) and a depletion of oxygen. Thus, water in the hole could become de-oxygenated and stagnant with the potential to stratify and mix with waters in the rest of the lake. Under the proposal, this problem would be mitigated by the isolation of the hole using embankments and the use of an aeration system to mix the water in the deep hole (GHD, 1995). Furthermore, if the deep hole was not isolated from the rest of the lake it may act as a sink for solids such as seagrass, algae and gross-pollutants. Although embankments I create a physical barrier to movement of fish and crustaceans, if the hole were not bunded it may still create a barrier to movement because of the different depth and/or disturbance caused by aeration.
If the deep hole remained isolated from Lake Illawarra until filled, it is likely to be inhabited only I by animals or plants arriving in the return slurry water. If the hole was not isolated following completion of the dredging of Griffins Bay, it would provide a new habitat in Lake Illawarra. I Therefore, it is difficult to assess what, if any, fauna would use this habitat as it is not possible to sample any similar habitats in Lake Illawarra. Some species of benthic macrofauna found in the lake have been recorded in depths of up to 20 m in other estuaries suggesting that they could potentially live in the sediment at a depth of -14 m AHD in Lake Illawarra provided the salinity, temperature and dissolved oxygen levels were also suitable. These species cover a broad taxonomic range and include polychaetes (e.g. Oweniafusiformis, Australonereis ehiersi and (Hutchings and Murray, 1984)), crustaceans (e.g. Urohaustorius metungi, Cirriformia filigera I Victoriopisa australiensis and Corophium cf vol utator (Jones et al., 1986)) and bivalves (e.g Spisula trigonella (Jones et al., 1988)).
In a naturally occurring, 7.5 m deep basin in Port Hacking, New South Wales, the abundance and biomass of benthic macrofauna were considerably less compared to adjacent shallow sediments covered by seagrass (Zostera capricorni and Posidonia australis)(Rainer and Fitzhardinge, 1981). These authors concluded that the reason for this impoverishment was low dissolved oxygen levels rather than differences in sediment size and water depth among the habitats studied. This study adds weight to the suggestion that it is possible for benthic macrofauna to live in the sediments of the deep hole, but only if dissolved oxygen levels are maintained at an acceptable level, either naturally or by the proposed aeration system. I
The use by fish of deep holes caused by dredging was examined in Botany Bay by the SPCC (1981). Two holes were sampled for fish (one was 7 m deep and 1.5 km long x 0.5 m wide and the other was 21 m deep and 1 km long x 0.3 km wide) and compared to other areas in Botany Bay.
46 1 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
Fish such as trumpeter whiting, red gurnard, John Dory, nannygai, Port Jackson sharks, fortesques, stingrays, tarwhine, dusky flathead, tailor, bream and flounder were found in the holes but were not considered to be permanent residents there. They concluded that the deeper muddy habitats of the deep holes provided feeding areas for some commercial fish, particularly during winter. Botany Bay, however, is very different to Lake Illawarra especially in terms of water circulation and mixing. Therefore, extrapolation of these results to Lake Illawarra is questionable.
Given the risk of stagnant water from the deep hole mixing with the rest of the lake and the deep hole acting as a sink if unbunded, it is strongly recommended that the hole remain isolated until backfilling is complete.
4.4 Creation of Channel
The extension of the channel on the southern side of Griffins Bay out into the rest of the lake is expected to change the water circulation patterns in Griffins Bay. Modelling predicted that there would be an overall increase in water flow into and out of Griffins Bay for two reasons; i) water would pass westward on falling tides in the southern channel and ii) water would pass eastward on rising tides in the southern and northern parts of the channel (GHD, 1995). The maximal increase in velocity of water flow in the channel was less than 0.2 m/s with no increases in water flow at the eastern end of Griffins Bay. These predictions are independent of the route of the channel (GHD, 1995).
The extension of the channel on the southern foreshore would allow power boats better access to this area of the lake. This in turn may lead to increased turbidity levels in adjacent areas, areas where seagrass may be effected by the reduced light availability. This may also impede natural recolonisation of the unvegetated substratum of Area A. Regular maintenance dredging may be required to keep the channel open (GHD, 1995) and disturbance to the sediments by these operations may adversely affect seagrass unless safeguards such as silt-curtains were used.
The impacts of the short-term mobilisation of silt and ooze in Griffins Bay due to the extension of the channel in Griffins Bay were discussed previously in Section 4.2.1.2 and the impacts on commercial fishing were discussed in Section 4.2.2.4.
47 'The Ecology Lab Ply Ud Griffins Bay sand extraction - Marine Ecology Final Repori, ApiI 1995
4.5 Creation of Island
The position of the island influences the amount of water flowing into and out of the southern channel in Griffins Bay such that the more south westerly position would allow more water to I circulate in Griffins Bay (Gi-ID, 1995).
The island is intended to provide a habitat for birds that is free from humans and predators such as dogs and cats. Sand would be placed on the surface of the beach facing north east to provide an environment suitable for wading birds (GHD, 1995). Dames and Moore (1993) provided a list of birds that are likely to use constructed wetlands and surrounding areas in Lake Illawarra which includes pelicans, cormorants, herons, egrets, ducks, swamphens, curlews, sandpipers and gulls.
4.6 Interactions with Other Proposals for Lake Illawarra
An EIS has recently been published which examines the proposal to dredge the entrance channel to Lake Illawarra for the Public Works Department (Mitchell McCotter, 1994). The proposal involves increasing the throat area of the entrance to Lake Illawarra by dredging a channel 750 m long with a nominal base width of 20 m. Hydraulic modelling indicates that this would lead to; i) no change in the overall tidal range, ii) mean high water levels staying within the range of previous levels, iii) a decrease by 4 cm compared to levels since 1991 in the median lake water level, iv) an increase of 6 cm in the daily range in the lake water level caused by tides, and v) increased tidal exchange which would improve water quality due to a decrease in flushing time provided the ocean water is of a better quality than the lake water. The ELS argues that, because the levels of water in the lake over the last 2/2 years have been at least 10 cm below the long term average and the throat of the channel has been wider in the past, the proposed works are within the bounds of the natural variability of the system and thus impacts on the biota of the lake would be minimal.
Some of the conclusions regarding impacts for this study are relevant to the proposal for dredging in Griffins Bay. The change in water level is predicted to have no adverse impact on the benthic communities of the lake and, for sites remote from the entrance channel, there would be little impact on shallow water and intertidal benthic communities, including seagrass and saltmarsh. The quicker flushing time of the lake may cause a temporary increase in the removal of nutrients from the lake temporarily but this may be compensated for by the regeneration of nutrients from
48 The Ecology Lab Pty Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995
within the lake. Tuthidity of water is predicted to improve near the entrance channel and perhaps marginally throughout the remainder of the lake because of the increase in penetration of flood- tide water into the lake. This should also mean a slight increase in salinity with less variation than at present. In response to an increase in salinity, Ruppia megacarpa along the shallow foreshores of Windang and around Bevans Island may be replaced by Zostera capricorni.
The impacts on fish, prawns and other biota that use the entrance channel as passage between the ocean and lake are predicted to be neutral or marginally beneficial because of the creation of a larger, more permanent entrance channel especially d ring heavily shoaled entrance conditions and low rainfall years. Recreational fishing in the entrance channel should be enhanced by the increase in rocky habitat and deeper water. It is proposed to dredge the channel and carry out the associated construction activities from July to September to reduce interference with the recruitment of fish and prawns to the lake.
On the basis of this information, it is concluded that the cumulative effects of the project to dredge the entrance channel of Lake Illawarra with the one to dredge in Griffins Bay would not be adverse. GHD (1995) calculate that if the tidal range increases to 10 cm because of dredging the entrance channel to Lake Illawarra then the exchange of water between Griffins Bay and the rest of the lake would increase from 40.6 ML to 135 ML per tidal cycle. A larger tidal range is predicted to increase current velocity within Griffins Bay (GHD, 1995).
The remaining deep hole of Areas C and D at the entrance to Griffins Bay would be used as a location for the placement of mud and silt removed from other areas of Lake Illawarra (GHD, 1995). The backfilling of Areas C and D are reliant on these other dredging works programs run by the Lake Illawarra Authority (LIA). If this filling proceeds, in the long term the water depth of the dredged areas may be -1.5 m and therefore may become colonised by seagrasses. If these dredging works proposed by the LIA were to proceed, there would be further decreases in the area of seagrass removed by the proposal to dredge in Griffins Bay. The losses to Lake Illawarra as a whole, however, need to be considered in relation to any loss of seagrass from the areas intended to provide fill for the deep hole in Griffins Bay.
49 The Ecology Lab Pty Ltd Griffins Bay sand extradion - Marine Ecology - Final Reprt April 1995
4.7 Recommendations
4.7.1 Mitigation of Impacts
The impacts of the proposal to dredge at the entrance to Griffins Bay could be mitigated in a number of ways by:
minimising the overall loss of seagrass habitat;
preventing the escape and spread of fine sediments (plus nutrients, heavy metals and other contaminants);
minimising the frequency and extent that bottom sediments are disturbed;
bunding of the deep hole
aerating the deep dredge hole to prevent stratification; and
allowing fishers to use dredge areas that are not actually being dredged at that point in time. SCE aim to return the dredge areas to the public, including fishers, as soon as possible. There would be no access to dredge Areas A, C and D by fishers until these areas were backfilled because they would be surrounded by embankments. Access to all other areas that would be dredged e.g. Area B and the channel, would be restricted only during the dredging of that particular area and, even then, access to within 10-15 m of the area being dredged would be possible (SCE pers. comm.).
Most of these mitigative measures have been discussed in previous sections and will not be repeated here (seagrass loss - Section 4.2.1.1; escape of fine sediments - Section 4.2.1.1; disturbance to bottom sediments - Section 4.2.1.2; aerating deep hole - Section 4.3). Measures to rehabilitate areas of seagrass are discussed in detail in Section 4.7.2.
Given the extent of this project and the value of the estuarine habitats of Lake Illawarra it is recommended that the effects of this proposal be monitored. Section 4.7.3 discusses the elements that should be incorporated into a cost-effective monitoring programme.
50 The Ecology Lab Pty Ltd Grns Bay sand extradion - Marine Ecology - Final Report, April 1995
4.7.2 Rehabilitation of Seagrass
In both the Environmental Assessment Act and the Fisheries and Oyster Farmers Act there are provisions for the ordering of restoration works of estuarine habitats whenever 'an opportunity for remedying past damage is presented' (Burchmore et al., 1993). The toss of areas of seagrass in this project may fall into this category. There are two means by which areas of seagrass may be restored, passively by natural revegetation and actively, by planting seeds, seedlings or vegetative parts of plants. The advantage of natural revegetation is the low financial cost but its success is dependent on the extent of degradation of the site and on the ability of the surrounding environment to supply propagative material. The area to be rehabilitated would need to be of suitable substratum and depth and be protected from excessive wave action and water movement, excessive pollution and siltation, and from damage related to other human activities (e.g. damage from anchors, propeller from power boats, etc).
Transplanting of seagrasses into areas that have been disturbed by humans has been attempted since the 1940's, primarily in the U.S.A., but also in Europe (Phillips, 1974). Transplantation has been most often attempted using Zostera marina and Thai assia testudinum, by planting seeds and vegetative stock (Phillips, 1974; Thorhaug, 1974). Large scale transplanting programmes, aimed at restoring seagrass beds to areas where seagrass has been lost, have met with limited success. Fonseca (1992) reviewed transplanting programmes in the United States and concluded that there has never been a seagrass restoration project which has restored more acreage than what was lost. These studies, however, provide a background of information on the attributes of various transplanting techniques and the environmental conditions required. Kenworthy and Fonseca (1977) suggest that successful methods of transplantation require a knowledge of the biology of the species of seagrass concerned with respect to the parameters that influence its growth.
Only limited information is available on the demography of Zostera capricorni in New South Wales. There is little information, for example, on the relative rates of seed production and germination and on the colonisation of new areas by seedlings. Erect flowering shoots of Zostera capricorni are produced in spring and are most abundant in summer (Larkum et al., 1984) and vegetative shoots are present throughout the year at most locations. Aerial photographs have shown large year to year variation in the areal extent of beds of Zostera in a number of estuaries in central New South Wales (West et al., 1985; Larkum and West, 1983; 1990), including Lake Illawarra (Section 1.2.2). In most cases, however, the mechanisms of decline and colonisation have not been determined.
51 The Ecology Lb Pty Ltd Griffins Bay sand extrathon - Marine Ecology - Final Report, April 1995
Zostera appears capable of recolonising unvegetated areas relatively rapidly through both vegetative and sexual modes of dispersal (Larkum and West, 1983; 1990). 1
WBM Oceanics (1993) reported that Zostera had recolonised and grown back in Koonawarra Bay, Lake Illawarra after skim dredging operations which removed 5.7 hectares of seagrass, mostly from very shallow (< 0.5 m) subtidal areas. In contrast, dredging of areas within Griffins Bay using a cutter-suction dredge resulted in the removal of 5 hectares of Zostera to a depth of -1.5 m Al-ID and have shown only a slight recovery after two years. WBM Oceanics concluded that
Zostera is able to rapidly recolonise dredged areas provided that the type of substrate and the light penetration are suitable for the growth of seagrass. The sediments remaining after previous dredging operations in Lake Illawarra have been suitable for Zostera colonisation as the dredging has removed ooze and silt leaving sandy sediments.
In Lake Illawarra, the natural depth limit for Zostera growth appears to be between 1.5 and 2 m, although density decreases with depth (Section 1.2.2). Thus, the extent and rate of recovery would be determined by the depth and turbidity of the dredged area. Works which improve water circulation and flushing of the lake may reduce tuthidity and enhance light penetration (Section 4.6). If so, the depth distribution of seagrasses may be extended and additional habitat may become available. WBM Oceanics (1993) recommended that dredging to depths of -1.2 m will generally have no major long-term impacts whereas dredging below - 1.5 to -2 m Al-ID may have long-term impacts because recovery would be slow. Given this information, we predict that seagrass may naturally but slowly recolonise Areas A and B because these areas would be restored to within the depth range that seagrass can grow in Lake Illawarra, albeit at the deeper end of the range. The colonisation of Area B would be possible 2 years after the dredging proposal commences whereas the colonisation of Area A would take place only at the end of the project when this area would be backfilled to a suitable depth range of -0.9 to -1.6 m Al-ID (Table 14). Most of the channel extension is likely to be too deep for seagrass to grow and Areas C and D are far too deep, at -14 m, for seagrass to grow. When Areas C and D are restored to a depth of -1.5 m they may also be suitable for the regrowth of seagrass. The Lake Illawarra Authority is committed to backfilling these dredged areas as quickly as possible (GHD, 1995).
Given that Zostera has returned to areas that have been dredged previously in Lake Illawarra, it is possible that Zostera will naturally colonise these areas when dredging is completed if water quality is improved from its present condition. Areas to be skim-dredged, such as Area B and the areas adjacent to the channel extension, may support a more rapid colonisation of seagrass than
52 The Ecology Lb Pty Ltd Griffins Bay sand extradion - Marine Ecology - Final Report, April 1995
the other dredged areas due to the type of dredging and the shallower depth and sandy substratum that would remain after dredging. Therefore, transplanting programmes may be unnecessary and possibly risk damaging the beds where the seagrass transplants are taken from (=donor bed). In addition, if conditions are not suitable for the colonisation and growth of Zostera I after dredging and colonisation has not occurred, then transplanted material is unlikely to survive unless the conditions change (Fonseca, 1992). Thus, transplanting Zostera into the dredged areas is I not recommended at this stage until sufficient time has passed to allow colonisation to occur naturally. The value of transplanting Zostera should then be reassessed as part of the plan of I management for seagrasses.
The natural colonisation of Zostera capricorni has been recorded in other places after major disturbances which led to loss and damage of large areas of seagrass. For example, the natural recovery of 15 km2 of Zostera took 5 years between 1975 and 1980 in Deception Bay, Queensland when excess sediment due to land clearing was no longer transported from the river into the bay (Kirkman, 1992). Thus, it may take many years for the areas suitable for colonisation in Griffins Bay to have a cover of seagrass similar to pre-dredging conditions. We strongly recommend that the natural colonisation of Zostera is monitored so that measures may be taken, if necessary, to enhance this process. An outline of a suitable plan of management including objectives, goals and methods will be discussed in Section 4.7.3.2.
4.7.3 Environmental Monitoring Programme
4.7.3.1 General Considerations
The requirements of the Director of the Department of Planning specify that the EIS should formulate a proposal for monitoring the effects of the proposal to dredge in Griffins Bay (GI-ID, 1995).
The aims of the monitoring programme should be to:
distinguish impacts associated with the dredging proposal from natural variation or other human induced impacts;
test predictions of the effects of the dredging proposal made in the EIS; and
53 The Ecology Lab Ply Ltd Griffins Bay sand extraction - Marine Ecology - Final Report, April 1995 iii) assist in formulating strategies to mitigate any unforeseen impacts after dredging has commenced. I
A monitoring programme needs to distinguish between changes in biota associated with the dredging activity and changes associated with natural variability or other activities such as residential development, urban run-off or sewage discharge. This can be done only by monitoring the biota several times before and after dredging in areas where changes are predicted to occur and, importantly, in similar areas that are unlikely to be affected by the dredging. Recently, Underwood (1991; 1992; 1993) has highlighted the necessity of estimating adequately the spatial and temporal variation of the biota of interest and has provided formal, rigorous procedures for examining the impacts of proposals on biota. This requires that sampling be done at least twice before and twice after an impact event and at two or more control sites. Control sites must be selected on the basis of similarity to the potentially impacted sites and on the assumption that they would be unaffected by the dredging activities.
The biota of estuaries consists of complex, highly variable and diverse assemblages of micro- organisms, plankton, attached plants (e.g. macroalgae and seagrasses), benthic invertebrates, fishes and mobile invertebrates. The choice of which biota to monitor depends on several factors, such as; current scientific knowledge of the biota, ability to measure changes in their populations or assemblages, importance to other biota and humans and the nature of the proposal being monitored.
We recommend that seagrasses, benthic macrofauna, fish and mobile invertebrates be monitored for the current proposal. We now have some baseline information on these groups, such as natural variability in abundance and distribution at several spatial scales within the lake. These data can then be used to design the most cost-effective and powerful sampling design, given the range of natural variability in space, with the ability to detect changes coincident with the dredging operations.
The data provided in this report together with existing information have described the distribution and abundance of benthic macrofauna, fish and mobile invertebrates at several spatial scales i.e. from 10's metres through to kilometres across the lake. Essentially, this is a 'snapshot' view because there is no information on the temporal changes of these biota. Understanding the magnitude of change that can happen through time naturally must be addressed prior to dredging and forms an essential part of monitoring.
54 The Ecology Lab Pty Ltd Gnffins Bay sand extraction - Marine Ecology - Final Rexrt, April 7995
Furthermore, the techniques used to monitor these particular biota have already proven effective in the field and changes in these biota would be of significance to humans, for instance, changes in abundance of fish leading to a decrease in the commercial catch from Lake Illawarra. Monitoring these biota would allow an assessment of the impacts of the dredging activities in the short-term (i.e. as a direct consequence of dredging activities) and in the long-term (i.e. as a consequence of the creation of new habitats, changes to benthic topography due to the deep hole, changes to water circulation and quality).
The deep hole that would remain after dredging is completed may be a new habitat for fauna in the lake depending on whether the hole is bunded until backfilling is completed. If the embankment surrounding the hole is removed prior to backfilling, the monitoring of the fish and mobile and benthic invertebrates would address whether these animals use this habitat and whether they differ in composition to other habitats such as vegetated, shallow sediments. Obviously, there would be no comparison between before and after dredging as this habitat did not previously exist.
It is advisable to monitor the impacts of this dredging proposal because more dredging in Lake
I Illawarra is likely, for instance, the backfilling of Areas C and D of the current proposal relies on fill from other dredging projects in the lake (GHD, 1995). Information derived from a monitoring programme for the current proposal would be useful for predicting and assessing the impacts of I other similar projects. Thus, monitoring would not only test specific predictions made by this I proposal, it would provide information for the better management of future projects. 4.7.3.2 Seagrasses
Seagrasses are important to monitor in Lake Illawarra because they are valuable habitats for I juvenile (Section 3.2) and adult fish (Section 3.3) and they contribute substantially to the productivity of the estuary (Larkum et al., 1989). They may be affected by the proposal in several ways: by their removal from the dredged areas and potentially, by incidental loss or damage in I areas surrounding the dredging activity.
I Two programmes are suggested to monitor seagrasses for this proposal; i) monitoring the dredged areas where seagrass has been removed for natural colonisation (Section 4.7.3.2.1) and ii) I monitoring the areas of seagrass surrounding the dredged areas where seagrass may be damaged or lost (Section 4.7.3.2.2).
55
I The Ecology Lab Pty Ltd Griffins Bay sand extradion - Marine Ecology - Find Reporl, April 1.495
4.7.3.2.1 Natural Colonisation of Dredged Areas
An area of approximately 25 ha. of seagrass would be removed as a result of this dredging proposal. The potential exists, however, for some of this area to be colonised naturally by seagrass after dredging is completed. Table 14 indicates the suitability and timing of availability of each dredge area for the colonisation of seagrass.
In order to assess whether the dredged areas have been colonised successfully by Zostera capricorni, as predicted from existing information and previous experience of dredging in Lake Illawarra, a plan of management and monitoring programme should be implemented. The criteria to judge success should be determined prior to the dredging proposal commencing. In addition, criteria should be quantitative and explicitly stated so that an unambiguous and unbiased means of assessing whether colonisation has been successful or not is provided.
The recommended plan of management is outlined as follows:
Step 1. Areas where seagrass had been removed and where dredging and backfihling is completed should be inspected for, i) the presence of seagrass and ii) the growth of seagrass from adjacent undredged areas, at regular intervals (e.g. 3 monthly) over two years to observe if and how seagrass is colonising the dredged area.
Step 2. If seagrasses are detected during the inspection period, patches of seagrass should be mapped accurately and their area determined. In addition, measurements of the density and length of leaves of seagrass should be obtained in the colonised patches and compared to measurements obtained in reference (i.e. undisturbed) beds. Inspections of the dredged area should continue regularly to identify any new patches.
Step 2a. The growth of colonising patches should be monitored through time, so that the rate of patch growth (i.e. increase in area) and the proportion of the dredged area covered by seagrasses may be determined. There is no information available to suggest how quickly patches of seagrass should grow, or what the rate of development of new patches should be, so it is difficult to assign a period of time for complete recolonisation (defined here as the areal coverage of seagrass equivalent to what was removed). At this stage, it is suggested that an arbitrary criterion of 10% of the dredged area be recolonised per year, after a 1 year period of stabilisation following dredging and backfilling. At this rate, complete recolonisation would be expected to The Ecology Lab Pty Ltd Griffins Bay sand extradion - Marine Ecology - Final Report, April 1995
take 11 years after dredging of a particular area was completed. For example, Dredged Area B would be the first area available for colonisation of seagrass approximately 3 years after the dredging proposal commenced. Area B is 2.4 ha thus, the criteria for growth of seagrass would be 0.24 ha per year. If seagrasses are present but the 10% rate of growth is not being achieved after five years, transplantation of seagrasses should be considered to assist with seagrass growth and to help meet the objective of complete recolonisation.
Step 3. If seagrasses are not detected during the inspection period of two years, two I- options should be considered First, if the area is at the depth limit for growth of seagrass in Lake Illawarra (i.e. 1.5 - 2.0 m below Al-ID), consideration should be given to further backfilling with sand to make the substratum shallower either over the whole of that particular dredged area, or within a portion of it, as an experiment. If backfilling is done, a further period of inspection should be initiated and Step 2a followed. Second, if the area is already suitably shallow (i.e. <-1.5 I m Al-ED), transplantation of seagrass should be initiated.
Step 4. If seagrass recolonisation does not occur following Step 3 - which is considered most unlikely, given that seagrasses have already recolonised other dredged areas in Lake I Illawarra - further research and remediation works should be considered to facilitate the growth of seagrasses (e.g. further backfilling).
One further advantage of the above plan of management is that monitoring of colonisation of Area B would take place after 3 years from the start of the dredging programme and run for 7 to 10 I years before any other dredged areas would be ready for seagrass to colonise. Thus, the plan of management for Areas A and possibly Areas C and D can be modified, if necessary, to incorporate I the information collected from Area B. The monitoring of Area B would provide a good test case of the management plan.
Clearly, there are a number of possible approaches that could be adopted for a plan of management for seagrasses in the proposed dredge areas. The final approach should be determined in consultation between SCE, the Lake Illawarra Authority and other relevant organisations, such as the NSW Environment Protection Authority (EPA), NSW Fisheries and the Commercial Fisherman's Advisory Council (CFAC).
57 The Ecology Lab Pty Ltd Griffins Bay 9and extraction - Marine Ecology - Final ReporL April 7995
4.7.3.2.2 Indirect Loss or Damage
Seagrass may be influenced indirectly by the dredging proposal in several ways. First, there may be incidental loss of more seagrass near the dredging areas by smothering (due to the re-settlement of fines from the dredging operations), a reduction in growth (e.g decreased light due to water turbidity), disturbance (e.g. boat anchors) and erosion (at the boundaries of the deep hole). Second, in the longer term, changes to water circulation and bottom topography may also effect the remaining seagrass. These impacts would be manifested by changes to the structure of the seagrass such as a decrease in the density of shoots and/or a reduction in the height of leaves and changes in the cover of seagrass. If such effects are detected, mitigative measures should be considered in the context of the magnitude of effects.
4.7.3.3 Benthic Macrofauna
Sampling procedures used to describe the benthic macrofauna for this report (Section 2.1) would be appropriate to use for a monitoring programme. Changes to the habitat of these animals such as removal or reduction in seagrass cover, changes to size of the sediment, depth of the substratum and speed of water flow and direction may influence the assemblages and populations of these animals. This monitoring would complement the seagrass monitoring, which involves only a few species of plants whereas the benthic macrofauna consists of a diverse assemblage of animals that are very important to fish and larger mobile invertebrates as a source of food.
Given that the deep hole would be surrounded by an embankment, it is unlikely to be colonised by benthic macrofauna and therefore, monitoring of the deep hole is not recommended. Monitoring of water quality in the deep hole, however, would be needed and is included as part of the dredging proposal (GHD, 1995). In the event that the embankments were removed before complete backfihling of the hole, it would be advisable and informative to monitor the colonisation of the deep-hole habitat by benthic invertebrates. This habitat was not previously available to these animals in Lake Illawarra and, as such, little is known about what species may inhabit it. This assemblage is likely to be very different to the pre-dredged one in shallow seagrass and its value as a habitat could be assessed.
58
I The Ecology Lab Pty Ltd Gnffins Bay sand extraction - Marine Ecology - Final Report, April 1995
4.7.3.4 Fish and Mobile Invertebrates I Sampling procedures used to describe the fish and mobile invertebrate fauna for this report I (Section 2.2) would be appropriate to use for a monitoring programme. Under the current proposal, the movements of these animals would be impeded by the island and the embankment when it is in place and may be different to pre-dredging behaviour due to changes in water I circulation and the presence of the deep hole. Assemblages of fish and mobile invertebrates would be sampled by beach seining and beam trawling in areas in the vicinity of the dredge I operations and in control areas that are unlikely to be affected.
I Given that the deep hole would be surrounded by an embankment, it is unlikely to be colonised by fish and mobile invertebrates. In the event that the embankments were removed before complete backfilling of the hole, the monitoring of colonisation of the deep hole by fish and mobile I invertebrates would be recommended. This assemblage is likely to be very different to the pre- dredged one in shallow seagrass and its value, as a habitat could be assessed. Questions regarding I whether any fish would use these habitats could be addressed by sampling this habitat with gill nets and contrasting the assemblage with that from other areas within Lake Illawarra. Monitoring I of fish and mobile invertebrates in the deep hole is not recommended for this dredging proposal.
1 4.7.3.5 Commercial Fisheries
The commercial catch of fish in Lake Illawarra should be monitored by using NSW Fisheries Statistics compiled on a monthly basis. Data presented in this report (Section 3.3.2) demonstrated large variability through time over a period of 7 years in the catch from Lake Illawarra. Any I changes in catch as a result of the dredging should be reflected in the catch statistics as a change in the productivity of Lake Illawarra greater than that of natural variability of the pre-dredging I years.
Because the fisheries data are only available on a lake-wide basis, it would not be possible to unambiguously ascribe reductions in fisheries to the dredging operation, other human activities (such as pollution or overfishing) or natural variability. It may, therefore, be beneficial to obtain quantitative information on fishing on various parts of Lake Illawarra, for example, by I questionnaires or direct surveys of commercial fishing.
WE The Ecology Lab Pty Ltd Griffins Bay sand extradion - Marine Ecology Final Report, AFril 1995
Acknowledgments
This report was written by Libby Howitt and Marcus Lincoln Smith of The Ecology Lab Pty Ltd. The field work was done by Marcus Lincoln Smith, Adam Smith, Roberta Dixon and John Runcie. Graeme White, Adam Pope and Roberta Dixon assisted with preparation of maps, graphs and tables. Identification of molluscs and crustaceans in the benthic samples was done by staff at The Australian Museum. Polychaetes from the benthic samples were identified by Libby Howitt. Fish and mobile invertebrates were identified by Sally McNeil! and Roberta Dixon. Rough sorting of samples was done by Roberta Dixon, Adam Pope, John Runcie, Marcel Green and Leslie Diver. We acknowledge the assistance of Warren Winter (NSW Fisheries Inspector) who provided information on the commercial and recreational fishing activities in Lake Illawarra. Helpful discussions concerning the fishing activities of Lake Illawarra were held with Shirley and Russell Massey, Frank Krizak, Graham Burns and members of the Windang Hotel Fishing Club. Comments from participants at a public meeting at Lake Illawarra Yacht Club on the 22nd April, 1994 were also considered.
ZE I I
The Ecology Lab Pty Ltd Gnfflns Bay sand extraction - Marine Ecology - Final Report, Apr11 1995
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Yassini, I. and B.G. Jones (1987) Ostracods in Lake Illawarra: Environmental factors, assemblages 1 and systematics. Aust J. Mar. Freshw. Res. 38: 795-843. Yassini, I. (1992) Heavy metal concentrations in algae, marine angiosperms and molluscs in Lake Illawarra, New South Wales. Proceedings of a Bioaccumulation Workshop. Edited by A.G. I Miskiewicz. Published by Water Board and Australian Marine Sciences Association Inc. I TABLES Table 1: Range of concentration of heavy metals and their detection limits in sediment samples from different locations in and around Griffins Bay (data from GHD, 1994). The screening level and probable effect level are given as indicators of sediment quality modified from MacDonald 1992, except* from Irvine 1980.
A. Data are from 8 sampling locations in Gri (fins Bay with 2 replicate samples per location.
Range Detection Limit Screening Level (SL) Probable Effect Level (PEL) - (mg/kg dry weight) (mg/kg wet weight) (mg/kg dry weight) (mg/kg dry weight)
Cadmium not detected 2.5 1 8.6 Chromium 5.4 - 254.6 5 51* 230 1 Copper 6-45.2 5 30 200
Lead 9.4 - 20 5 33* 170 Mercury not detected 0.25 0.15 1.4 I Zinc 7.6- 1692 5 70 280 I B: Data are from 2 sampling locations in the proposed dredge areas in Griffins Bay and were analysed at lower detection limits than A above.
Range Detection Limit Screening Level (SL) Probable Effect Level (FEL) (mg/kg dry weight) (mg/kg wet weight) (mg/kg dry weight) (mg/kg dry weight)
Cadmium 0.1 - 0.2 0.05 1 8.6
Chromium 1.3-3.6 0.5 51* 230 Copper 1.3-7.1 05 30 200 1 Lead 1.0-4.8 0.5 33* 170
Mercury <0.01 0.01 0.15 1.4 Zinc 9.8-20.2 1 70 280 1 I Table 2: Average abundance of the 10 most important benthic species in contributing to the average dissimilarity between two groups.
Species or taxa contributing to the average dissimilarity O (=70.58) between the two groups, group a=Griffins Bay sandy sediment and group b=muddy sediment. Species or Taxa Group a Group b Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Theonzfragilis 0.07 2.45 435 2.38 1.91 Oweniafrstformic 40.46 9.35 4.36 4.24 1.03 Victoriopisa australiensis 0.97 3.85 4.22 2.97 1.42 Australonereis eMeisi 9.77 3.50 4.22 3.56 1.18 Soletellina alba 3127 0.00 4.01 4.31 0.93 Tellina deltoidalis 4.67 11.05 3.95 2.81 1.41 Spisula trigonelia 7.93 6.05 3.44 3.45 1.00 Barantolla lepte 4.00 4.25 3.21 2.76 1.16 Nephtys australiensis 0.07 1.55 3.17 3.26 0.97 Cirriformia filiera 4.43 0.25 3.13 3.25 0.96 Species or taxa contributing to the average dissimilarity O (=64.15) between the two groups, group a=Griffins Bay sandy sediment and group c=Eastern Shore sandy sediment. Species or Taxa Group a Group c Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Llrohaustorius metungi 0.17 32.40 6.11 3.06 2.00 Soletellina alba 3127 20.30 4.43 2.95 1.50 Tellina deltoidalis 4.67 0.03 3.90 1.63 2.39 Mysella sp. 2.50 13.00 3.85 2.91 1.32 Owenia fusiformis 40.60 2.47 3.30 3.28 1.01 Cirriformia fihigera 4.43 8.83 3.02 2.53 1.19 Spisula trigonella 7.93 3.03 2.68 2.14 1.25 Family Orbiniidae 2.03 4.40 2.60 2.22 1.17 Corophium volutator 1.57 6.27 2.59 2.57 1.01 Barantolla lepte 4.00 0.67 2.29 1.97 1.16 Species or taxa contributing to the average dissimilarity O (=82.93) between the two groups, group b=muddy sediment and group c=Eastern Shore sandy sediment. Species or Taxa Group b Group c Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Llrohaustorius metungi 0.35 32.40 7.93 323 223 Soletcllina alba 0.00 20.30 6.44 2.56 2.52 Mysella sp. 0.00 13.00 5.73 2.58 2.22 Victoriopisa australiensis 3.85 0.03 4.57 2.19 2.09 Australonereis eh!ersi 3.50 17.23 4.35 3.44 1.26 Theora fragilis 2.45 0.00 424 1.64 2.59 Cirriformia fihigera 0.25 8.83 3.64 3.16 1.15 Tellina deltoidalis 11.05 0.03 3.61 3.10 1.17 Family Orbiniidae 0.00 4.40 3.49 2.61 1.34 Nephts australiensis 1.55 0.10 2.79 2.75 1.01 Table 3: Summary of ANOVAs and SNKs comparing the number of benthic invertebrates collected by corer among Areas, Locations and Sites In Lake Illawarra in November 1993. Data were not transformed unless stated. Areas, Locations and Sites not underlined had significantly different means at alpha levels given. * Mean square has been tested over pooled mean square for Site and Residual. GB= Griffins Bay; GBA= Gnffins Bay A, GBB=Griffins Bay B, GBC=Griffins Bay C. ES=Eastern Shore; ESM=Eastern Shore Middle, ESN=Eastern Shore North, ESS=Eastern Shore South. (see Figure 3). Variate Source df MS F p SNK
Total Number of Taxa Area 1 15 0.26 >0.25 a =0.05 Location(Area) 4 58.7333 3.09 >0.10 Site(Location) 6 19 1.66 >0.10 Residual 48 11.4583
Total Abundance Area 1 3.9531 0.45 >0.25 Area GB ES log e(x+1) Location(Area) 4 8.7659 15.76 <0.01 Location GBB GBC GBA ESS ESN ESM a =0.05 Site(Location) 6 0.5561 1.97 >0.05 Residual 48 02828
POLYCHAETES Australonereis ehiersi Area 1 0.8105 0.14 >0.25 Area GB ES log e(x+1) Location(Area) 4 5.6911 1.90 >0.10 Location GBA GBB GBC ESM ESN ESS a =0.05 Site(Location) 6 2.9889 7.80 <0.001 Site 2 1 3 4 6 5 12 11 13 14 15 16 Residual 48 0.3834
Barantolla lepte Area 1 7.0125 1.98 >0.10 Area GB ES log e(x+1) Location(Area) 4 3.5498 7.32 <0.01 Location GBB GBC GBA ESN ESM ESS a =0.05 Site(Location) 6 0.3594• 0.72 >0.25 Residual 48 0.5008
Cirriformiafiligera Area 1 2.8333 0.29 >0.25 Area GB ES log e(x+1) Location(Area) 4 9.849 2.76 >0.10 Location GBA GBB GBC ESM ESN ESS a =0.05 Site(Location) 6 3.5893 6.32 <0.001 Site 2 1 4 3 6 5 11 12 13 14 15 16 Residual 48 0.5681
Owen ia fusiformis Area 1 21812.267 1.03 >0.25 Area GB ES Location(Area) 4 21205.967 13.36 <0.01 Location GBB GBC GBA ESS ESM ESN Site(Location) 6 727.5333 * 0.43 >0.25 a =0.01 - - - -Residual - -48 1697.2------Table 3: (continued)
Variate Source df MS F p SNK AMPHIPODS Corophium vol utat or Area 1 2.4923 0.23 >025 Area GB ES log e(x+1) Location(Area) 4 10.932 5.09 <0.05 Location GBC GBB GBA ESS ESM ESN a =0.05 Site(Location) 6 2.1484 7.71 <0.001 Residual 48 0.2785 Area GB ES Location GBA GBB GBC ESM ESN ESS Site 2 1 4 3 5 6 12 11 13 14 16 15 ljrohaustorius metungi Area 1 15584.817 6.00 >0.05 Area GB ES Location(Area) 4 2597.6667 * 13.92 <0.01 Location GBB GBC GBA ESN ESS ESM a =0.01 Site(Location) 6 49.3833 0.24 >0.25 Residual 48 9780.4
BIVALVES Soletellinoalba Area 1 1804.0167 0.12 >0.25 Area GB ES Location(Area) 4 15227.117 6.23 >0.01 Location GBA GBB GBC ESM ESN ESS a =0.01 Site(Location) 6 2444.4167 7.14 <0.001 Site 2 1 3 4 6 5 12 11 13 14 15 16 Residual 48 342.525
Tellina deltoidalis Area 1 322.0167 7.81 >0.01 Area GB ES Location(Area) 4 41.2333 * 6.54 <0.01 Location GBB GBC GBA ESN ESS ESM a =0.01 Site(Location) 6 0.9167 0.13 >0.25 Residual 48 6.9833
Spisula trigonella Area 1 3.2186 0.31 >0.25 Area GB ES * log e(x+1) Location(Area) 4 10.5247 20.78 <0.01 Location GBB GBC GBA ESM ESS ESN a =0.05 Site(Location) 6 0.5879 1.18 >0.25 Residual 48 0.4962
Mysella sp. Area 1 28.7997 6.01 >0.05 Area GB ES * log e(x+1) Location(Area) 4 4.7941 6.04 <0.05 Location GBB GBC GBA ESM ESN ESS a =0.05 Site(Location) 6 0.9753 1.27 >0.25 Residual 48 0.7709 Table 4: Pairwise comparisons of locations for the ANOSIM randomisation test for assemblages of fish and mobile invertebrates collected by beam trawling. A comparison is considered significant at p <0.005 to adjust for the number of comparisons being made (Bonferroni correction; Winer, 1971).
Comparison between locations ANOSIM R significance
Griffins Bay A and Griffins Bay B 0213 not significant
Griffins Bay A and Windang Channel South 0.702 not significant
Griffins Bay A and Windang Channel North 0.335 not significant
Griffins Bay A and Eastern Shore 0.480 not significant
Griffins Bay B and Windang Channel South 0.948 p < 0.005
Griffins Bay B and Windang Channel North 0.632 p < 0.005
Griffins Bay B and Eastern Shore 0.677 p < 0.005
Windang Channel South and Windang Channel North 0.765 p < 0.005
Windang Channel South and Eastern Shore 0.742 p < 0.005
Windang Channel North and Eastern Shore 0230 not significant I Table 5: Average abundance of 4 species of fish and mobile invertebrates caught by beam trawling that contributed most to the average dissimilarity between two locations identified as having different assemblages in the ANOSIM test. I
Species contributing to the average dissimilarity O (=46.59) between Griffins Bay B (GBB) and Windang Channel South (WCS).
' Species GBB WCS Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Macrobrachium intermedium 346.35 3901.08 7.18 2.46 2.92 Redigobius macrostoma 0.00 46.96 5.34 0.65 825 I Stigmatoxra nigra 021 33.46 4.47 1.15 3.90 Gobiopterus semivestitus 83.23 7.75 323 2.07 1.56
Species contributing to the average dissimilarity 6 (46.73) between Griffins Bay B (GBB) and Windang Channel North (WCN).
Species GBB WCN Av. S. D. Ratio - I Av. abund Av. abund dissimilarity Av. dissim./S.D. Pseudogobius olorum 122.60 1.46 8.33 2.85 2.92 Stignatopora nigra 021 12.46 4.66 1.43 3.26 I Gobiopterus semivestitus 8323 12.67 3.82 2.56 1.49 Urocampus carinirostris 13.02 2.37 3.15 229 1.37
I c) Species contributing to the average dissimilarity ô (=64.31) between Griffins Bay B (GBB) and Eastern Shore (ES).
Species GBB ES Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Pseudogobius olorum 122.60 0.83 10.70 3.63 2.94 Macrobrachium intermedium 346.35 30.42 8.06 3.52 2.29 Gobiopterus semivestitus 83.23 13.33 6.49 4.53 1.43 Arenisobius bifrenatus 4.48 0.00 4.46 1.94 2.30 Species contributing to the average dissimilarity 6 (=50.83) between Windang Channel South (WCS) and Windang Channel North (WCN).
Species WCS WCN Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Macrobrachium intermedium 3901.08 292.21 8.80 3.56 2.47 Redigobius macrostoma 46.96 0.00 5.87 0.89 6.62 Pseudogobius olorum 17.63 1.46 3.77 1.79 2.10 Pavonoobius tamarensis 8.00 0.00 3.45 0.82 4.21 Species contributing to the average dissimilarity 6 (=67.01) between Windang Channel South (WCS) and Eastern Shore (ES).
Species WCS ES Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Macrobrachium intermediurn 3901.08 30.42 15.37 3.73 4.12 Redigobius macrostoma 46.96 0.62 629 2.11 2.97 Pseudogobius olorum 17.63 0.83 4.62 2.16 2.14 Favonoobius tamarensis 8.00 0.00 4.11 0.99 4.14 Table 6: Summary of ANOVAs and SNKs comparing the number of fish and mobile invertebrates caught in beam trawl nets among Locations and Sites in Lake Illawarra. Data were not transformed unless stated. Locations and sites not underlined had significantly different means at alpha levels given. * Mean square has been tested over pooled mean square for Site and Residual. GBA=Griffins Bay A GBB=Grifflns Bay B WCS=Windang Channel South WCN=Wingdang Channel North ES=Eastern Shore
Variate Source df MS F p SNK
Total Number of Taxa Location 4 64.56 * 6.89 <0.01 Location ES GBB GBA WCN WCS log e(x+1) Site (Location) 5 11.48 1.27 >0.25 a =0.05 Residual 30 9.03
Total Abundance Location 4 18.21 10.67 <0.05 Location ES GBA WCNGBB WCS log e(x+1) Site (Location) 5 1.71 4.08 <0.01 a =0.05 Residual 30 0.42 Location GBA GBB WCS WCN ES Site 2 1 4 3 5 6 7 8 10 9 Total Abundance of Species of Commercial Value Location 4 54.51 3.73 <0.05 Location ES GBA WCN GBB WCS Site (Location) 5 14.16 0.97 >0.25 a =o.os Residual 30 14.67
Blue Groper * (Achoerodus viridis) Location 4 7.28 2.57 >0.05 Site (Location) 5 1.12 0.40 >0.25 a =0.05 Residual 30 2.81
Bridled Goby (Arenigobius bifrenatus) Location 4 3.67 5.66 <0.05 Location ES GBA WCNWCS GBB log e(x+1) Site (Location) 5 0.65 1.95 >0.10 a =0.05 Residual 30 0.33
Eastern Fortesque (Cent ropogon aust rails) Location 4 4.70 4.17 >0.05 log e(x+1) Site (Location) 5 1.13 2.05 >0.10 a =0.05 Residual 30 0.55
Table 6: (continued)
Variate Source df MS F p SNK
Three -barred Porcupinefish (Diaitolichthys punctulatus) Location 4 1.07 * 3.52 <0.05 Location WCS GBA GBB ES WCN log e(x+1) Site (Location) 5 0.02 0.07 >0.25 a =0.05 Residual 30 0.35
Transparent Goby (Gobiopterus semivestitus) Location 4 8.21 * 4.71 <0.01 Location ES WCS WCN GBA GBB log e(x+1) Site (Location) 5 1.20 0.66 >0.25 a =0.05 Residual 30 1.84
Leatheriacket (Meuschenia spp.) Location 4 2.72 5.30 <0.01 Location ES GBA WCN GBB WCS log e(x+1) Site (Location) 5 0.55 1.09 >0.25 a =0.05 Residual 30 0.51
Swan River Goby (Pseudogobius olorum) Location 4 26.94 36.81 <0.01 Location ES WCN WCS GBA GBB log e(x+1) Site (Location) 5 0.73 1.41 >0.10 a =0.05 Residual 30 0.52
Large-mouth Goby (Redigobius macrostoma) Location 4 21.09 * 107.12 <0.01 Location GBB WCN ES GBA WCS log e(x+1) Site (Location) 5 0.18 0.89 >0.25 a =0.05 Residual 30 0.20
Wide-bodied Pipefish (Stigmatopora nigra) Location 4 13.16 9.15 <0.05 Location GBB GBA ES WCN WCS
log e(x+1) Site (Location) 5 1.44 2.86 <0.05 a =0.05 Residual 30 0.50 Location GBA GBB WCS WCN ES Site 2 1 4 3 5 6 7 8 10 9 Table 6: (continued)
Variate Source df MS F p SNK
Snub-nosed Pipefish WCN GBA WCS GBB (Urocarn pus airinirostris) Location 4 185.68 * 6.95 <0.01 Location ES Site (Location) 5 12.96 0.45 >0.25 a =0.05 Residual 30 29.02
Carid Shrimp (Macrobrachium intermedium) Location 4 21716231.46 13.82 <0.01 Location ES WCN GBA GBB WCS Site (Location) 5 1571215.27 2.11 >0.05 a =o.oi Residual 30 743965.71
Eastern King Prawn (Pen aeus plebejus) Location 4 2.88 * 1.11 >0.25 Site (Location) 5 2.64 1.02 >0.25 a =0.05 Residual 30 2.59
Squid WCS WCN (Idiosepius notoides) Location 4 1.37 0.57 >0.25 Location GBA GBB ES Site (Location) 5 2.39 2.64 <0.05 Site 2 1 3 4 5 6 7 8 9 10 a =o.os Residual 30 0.91 Table 7: Data on size of species of commercial Importance caught by beam trawling.
Species Common Name Number Range Mean +1- SE Life History stage I measured (mm) (mm) Aainthopagrusaustralis yellow-finned bream 4 32-49 40.75 +1- 3.50 <205 mm=juvenile I Achoerdus viridis blue groper 29 26-62 44.07 +1-2.00 <118 mm=juvenile Girdla tricuspidata luderick 15 11-31 19.40 +1- 1.64 <285 mm=juvenile I Meuscheniafreycineti six-spined leatheqacket 49 21-68 44.16 +1- 1.50 <150 mm=juvenile Meuscheniatrachylepis yellow-finned leatherjacket 9 22-150 61.89 +1- 16.80 <225 mm=juvenile I Rhabdosarc1us sw-ba tarwhine 2 29-30 29.50 +1-0.50 <215 mm=juvenile * Data from SPCC (1981) Table 8: Palrwlse comparisons of locations for the ANOSIM randomisation test for assemblages of fish and mobile Invertebrates collected by beach seining. A comparison is considered significant at p < 0.005 to adjust for the number of comparisons being made (Bonferroni correction; Winer, 1971).
Comparison between locations ANOSIM R significance
Griffins Bay A and Griffins Bay B 0.982 p < 0.005
Griffins Bay A and Windang Channel 0.999 p < 0.005
Griffins Bay A and Boat Harbour 0.996 p < 0.005
Griffins, Bay A and Hennegar Bay 0.850 p < 0.005
Griffins Bay B and Windang Channel 0.855 p < 0.005
Griffins Bay B and Boat Harbour 0.563 not significant
Griffins Bay B and Hennegar Bay 0.669 p < 0.005
Windang Channel and Boat Harbour 0.987 p < 0.005
Windang Channel and Hennegar Bay 0.820 p < 0,005
Boat Harbour and Hennegar Bay 0.443 p <0.005 I Table 9: Average abundance of 4 species of fish and mobile invertebrates caught by beach seining that contributed most to the average dissimilarity between two locations identified as having I different assemblages in the ANOSIM test.
a) Species contributing to the average dissimilarity ô (=57.94) between Griffius Bay A (GBA) and Griffins Bay B (GBB).
Species GBA GBB Av. S. D. Ratio - I Av. abund Av. abund dissimilarity Av. dissim./S.D. Ambassisjacksoniensis 0.00 301.00 7.60 125 6.06 Atherinosoma microstoma 285.13 7.13 4.46 3.11 1.43 I Rhabdosargus sarba 0.00 28.88 4.06 1.83 2.22 Liza arentea 0.00 29.62 3.46 2.01 1.72
b) Species contributing to the average dissimilarity 6 (=63.50) between Griffins Bay A (GBA) and I Windang Channel (WC). Species GBA WC Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. I Macrobrachium internw4ium 306.00 2596.38 5.78 3.37 1.71 Atherinosoma microstonia 285.13 0.62 5.39 3.55 1.52 I Girella tricuspidata 0.00 22.38 421 0.76 5.54 Ambassis jacksoniensis 0.00 71.13 4.19 1.84 2.28 I Species contributing to the average dissimilarity 6 (=57.40) between Griffins Bay A (GBA) and Boat Harbour (BH).
Species GBA BH Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Macrobrachium intermedium 306.00 1.88 8.02 3.03 2.65 Atherinosorna microstonia 285.13 2.75 5.87 4.01 1.46 Ainbassisjacksoniensis 0.00 18.50 4.37 1.51 2.90 Gircila tricuspidata 0.00 5.88 3.70 0.64 5.75
Species contributing to the average dissimilarity 6 (=61.61) between Griffins Bay A (GBA) and Hennegar Bay (FIB).
Species GBA HB Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Atherinosoma microstoma 285.13 0.00 8.70 5.30 1.64 Macrobrachium intermedium 306.00 8.75 829 3.85 2.15 Pseudogobius olorum 131.13 14.50 4.30 1.55 2.77 Miixus c1ancntus 2.50 11.38 3.79 3.06 1.24 Table 9: (continued) e) Species contributing to the average dissimilarity 6 (=49.77) between Griffins Bay B (GBB) and Windang Channel (WC).
Species GBB WC Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Macrobrachium intermedium 140.38 2596.38 5.37 2.67 2.02 Ainbassis jacksoniensis 301.00 71.13 2.92 1.46 2.05 Rhabdosargus sarba 28.88 0.62 2.61 1.46 1.79 Favonoobius Iateralis 0.00 21.75 2.48 1.18 2.11
Species contributing to the average dissimilarity 6 (=56.40) between Griffins Bay B (GBB) and Hennegar Bay (HB).
Species GBB WC Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Ambassis jacksoniensis 301.00 6.50 5.96 2.47 2.41 Macrobrachium intermedium 140.38 8.75 351 2.25 1.56 Liza argentea 29.62 0.25 3.36 2.10 1.60 Gobiopterus semivestitus 186.63 21.50 3.35 221 1.51
Species contributing to the average dissimilarity 6 (=56.06) between Windang Channel (WC) and Boat Harbour (BH).
Species WC BH Av. S. D. Ratio.. Av. abund Av. abund dissimilarity Av. dissim./SD. Macrobrachium intermedium 2596.38 1.88 10.55 3.08 3.42 Meuschenia spp 11.13 0.00 2.88 0.77 3.74 Favonogobius lateralis 21.75 0.13 2.83 1.40 2.02 Stig,natopora nigra 8.00 0.13 2.64 0.68 3.91
Species contributing to the average dissimilarity 6 (=62.55) between Windang Channel (WC) and Hennegar Bay (HB).
Species WC HB Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Macrobrachium intermedium 2596.38 8.75 11.18 3.66 3.06 Gobiopterus sernivestitus 96.50 21.50 3.28 1.82 1.81 Girella tricuspidata 22.38 1.25 3.11 1.47 2.11 Redicobius macrostoma 14.38 0.75 2.95 1.63 1.82
Species contributing to the average dissimilarity 6 (=49.36) between Boat Harbour (BH) and Hennegar Bay (HB)
Species BH HB Av. S. D. Ratio - Av. abund Av. abund dissimilarity Av. dissim./S.D. Penacus plcbcjus 29.37 4.00 320 2.17 1.48 Urocarn pus carinirostris 5.38 0.38 3.14 1.43 2.20 Arnbassis jacksoniensis 18.50 6.50 2.90 2.14 1.36 Acanthoparus oust ralis 4.75 0.50 2.66 1.57 1.69 Table 10: Summary of ANOVAs and SNKs comparing the number of fish and mobile macroinvertebrates caught in beach seine nets among Locations and Sites in Lake Illawarra in November 1993. Data were not transformed unless stated. Locations and sites not underlined had significantly different means at alpha levels given. * Mean square has been tested over pooled mean square for Site and Residual. GBA=Griffins Bay A GBB=Griffins Bay B WC=Windang Channel BH=l3oat Harbour HB=Hennegar Bay (see Figure 5). Variate Source df MS - F p SNK
Total Number of Taxa Location 4 164.28 7.79 <0.05 Location GBAHB BH GBB WC a =0.05 Site (Location) 5 21.10 2.79 <0.05 Residual 30 7.55 Location GBA GBB WC BH HB Site 12 43 6 5 87 910
Total Abundance Location 4 14.31 9.63 <0.05 Location HBBH GBA GBB WC log e(x+1) Site (Location) 5 1.49 5.02 <0.01 a =0.05 Residual 30 0.30 Location GBA GBB WC BH HB Site 12 4 3 5 6 87 910 Total Abundance of Species * of Commercial Value Location 4 40196.16 7.27 <0.01 Location GBAHB WCBH GBB a =0.05 Site (Location) 5 2937.48 0.49 >0.25 Residual 30 5961.59
Blue Groper (Achoerodus viridis) Location 4 136.31 1.90 >0.10 Location GBA GBB WC BH HB Site (Location) 5 71.78 4.66 <0.01 Site 12 4 3 6 5 7 8 910 a =o.oi Residual 30 15.41 Perchlet (Ambassis jackson iens is) Location 4 33.29 9.36 <0.05 Location GBAHB BHWC GBB log e(x+1) Site (Location) 5 3.56 3.35 <0.05 a =o.os Residual 30 1.06 Location GBA GBB WC BH HB Site 12 43 5 6 87 910 Transparent Goby (Gobiopterussemivestitus) Location 4 11.57 1.73 >0.25 Location GBA GBB WC BH HB log e(x+1) Site (Location) 5 6.69 5.29 <0.01 Site 21 4 3 65 78 910 a =0.05 Residual 30 1.26 Table 10: (continued)
SNK Variate Source df MS F p Luderick Location GBA GBB WC BH I-LB (Girella tricuspidata) Location 4 11.38 3.71 >0.05 <0.001 Site 1 2 4 3 5 6 8 7 9 10 log e(x+1) Site (Location) 5 3.06 8.24 a =0.05 Residual 30 0.37
Flat-tail Mullet * 3.63 <0.01 Location GBA GBB WC BH HB (Lizaargcntca) Location 4 1348.66 C;f. IT r,-Hnn\"'_'/ 1.58 0.07 >0.25 a =0.01 Residual 30 428.11
Sand Mullet 3.39 >0.05 (Myxus don gut us) Location 4 5.64 1.00 >0.25 log e(x+1) Site (Location) 5 1.67 a =0.05 Residual 30 1.66
Swan River Goby 13.18 <0.01 Location WC HB BH GBB GBA (Pseudogobius olorum) Location 4 10.65 2.28 >0.05 log e(x+1) Site (Location) 5 0.81 a =0.05 Residual 30 0.35
Tarwhin e 6.85 <0.05 Location GBA WC RB BH GBB (Rhabdosargus sarba) Location 4 9.57 2.42 >0.05 log e(x+1) Site (Location) 5 1.40 a =0.05 Residual 30 0.58
Hardyhead 2.19 >0.10 Location GBA GBB WC BH FIB (Atherinosoma micros toma) Location 4 18.37 8.07 <0.001 Site 1 2 3 4 5 6 8 7 9 10 log e(x+1) Site (Location) 5 8.40 a =0.05 Residual 30 1.04
Yellowfin Bream 2.62 >0.05 (A cant hopagrus oust ralis) Location 4 121.63 * Site (Location) 5 56.63 1.27 >0.25 a =0.01 Residual 30 44.76 Table 10: (continued)
Variate Source df MS F p SNK River Garfish * (Hyporhamphus regularis) Location 4 55.06 9.92 <0.01 Location HB WC BH GBA GBB Site (Location) 5 1.88 0.17 >0.25 a =o.oi Residual 30 11.25
Sea Mullet (Muglcepha1us) Location 4 1.41 2.38 >0.05 Loge (x+1) Site (Location) 5 0.35 0.55 >0.25 a =0.05 Residual 30 0.63 -
Sand Whiting * (Sillago ciliata) Location 4 64.56 2.58 <0.05 Location WC GBA I-TB BH GBB Site (Location) 5 5.15 0.18 >0.25 a =0.05 Residual 30 28.38
Eastern King Prawn (Penaeus plebejus) Location 4 5.28 1.30 >0.25 Location GBA GBB wc BH I-LB log e(x+1) Site (Location) 5 4.07 5.05 <0.01 Site 1 2 3 4 6 5 8 7 10 9 a =0.05 Residual 30 0.81
Carid Shrimp (Macrobrachiunz intermediurn) Location 4 62.00 24.51 <0.01 Location BH HB GBB GBA WC log e(x+1) Site (Location) 5 2.53 2.87 <0.05 a =0.05 Residual 30 0.88 Location GBA GBB wc BH 1-LB Site 2 1 4 3 5 6 8 7 9 10 Table 11: Data on size of species of commercial importance caught by beach seining.
Species -- Common Name Number Range Mean + I- SE Life History stagl measured (mm) (mm) Acanthogrus australis yellow-finned bream 125 15-58 34.53 +1- 0.76 <205 mm=juvei Achcrdus viridis blue groper 154 22-76 51.05 +/-0.91 <118 mm=juvenile Annnotretis rtratus long-snouted flounder 1 84 juvenile Gerres subfasciatus silverbiddy 6 22-71 58.33 +1- 7.67 <125 mm=juvenile Girella tricuspidata luderick 358 11-134 28.34 +1- 0.59 <285 mm=juvenil1 Hyporhamphus regularis river gathsh 61 16-134 34.97 +1- 3.22 <170 mm=juvenile Liza argentea flat-tail mullet 257 15-250 33.05 +1- 1.54 <205 mm=juvenil1 Meuscheniafreycineti six-spined leatherjacket 113 19-76 51.34 +1- 1.07 <150 mm=juvenile Meuschenia trachylepis yellow-finned leatherjacket 8 22-52 39.88 +/-2.78 <225 mm=juvenil1 Mugilcepha!us sea mullet 66 24-300 118.71 +1- 8.47 <230 mm=juvenile Myxus elongatus sand mullet 505 22-256 60.73 +1-0.84 <225 mrn=juvenil1 Ne! usetla ayraudi chinaman leatherjacket 1 33 juvenile Platycephalus caeruleopunctatus blue spotted flathead 1 57 juvenile I Platycephalusfuscus dusky flathead 5 48-82 57.20 + I- 6.28 <325 mm=juvenile Pomatomus saltatrix tailor 3 22-61 39.33 +1- 11.46 <245 mm=juvenil Rhabdosargus sarba tarwhine 289 16-121 35.09 +1- 0.51 <215 mm=juvenile Sillago ciliata sand whiting 150 26-155 80.51 +1-2.35 <245 mm=juvenil Synaptura nigra black sole 1 50 <170 mm=juvenile Upeneichthys poimus goatfish 1 44 juvenile * Data from SPCC (1981) Table 12: Summary of ANOVAs and SNKs comparing the weight (kg) of species caught by commercial fishers among years (1985-92) In Lake Illawarra. The 12 Months of the year were used as replicates, except those marked as follows; a n=5, b n=8, c n=3.
Variate Source df MS F p SNK
River Garfish log e(x+1) Year 7 4.37 0.68 >0.25 a =0.05 Residual 88 6.44
Total Flathead log e(x+1) Year 7 6.20 2.36 <0.05 Year 19- 85 86 87 91 92 88 90 89 a =0.05 Residual 88 2.63
Yellow-fin Bream log e(x+1) Year 7 4.03 5.65 <0.001 Year 19- 89 92 90 91 88 85 86 87 a =0.05 Residual 88 0.71
Luderick log e(x+1) Year 7 1.79 3.57 <0.01 Year 19- 85 91 86 92 90 89 88 87 a =0.05 Residual 88 0.50
Sea Mullet Year 7 19182960.42 2.52 <0.05 Year 19- 85 90 86 92 91 88 87 89 a =0.05 Residual 88 7616902.26
Leatheijacket log e(x+1) Year 7 19.06 5.60 <0.001 Year 19- 92 91 85 90 89 86 87 88 a =0.05 Residual 88 3.40
Total Whiting a log e(x+1) Year 7 14.60 6.60 <0.001 Year 19- 85 88 90 91 92 86 87 89 a =0.05 Residual 32 2.21
Silver Biddy b log e(x+1) Year 7 9.65 1.90 >0.05 a =0.05 Residual 56 5.08 Table 12: (cont).
SNI( Variate Source df MS F p
Total Finfish 19- 85 90 92 91 88 86 89 87 Year 7 107970759.84 3.91 <0.001 Year a =0.05 Residual 88 27614005.06
Eastern King Prawn a 19- 92 88 87 89 86 90 91 85 Year 7 8552485.09 3.22 <0.05 Year a =o.os Residual 32 2655297.65
School Prawn C Year 7 1486617.60 3.30 >0.01 a =o.oi Residual 16 451031.83
Mud crab Year 19- 87 86 85 89 88 90 91 92 log e(x+1) Year 7 11.55 5.76 <0.001 a =0.05 Residual 88 2.01
Blue Swimmer Crab 88 89 90 85 87 91 86 92 Year 7 51387.19 4.20 <0.001 Year 19- a =o.oi Residual 88 12246.13
Total Species Year 19- 85 90 86 89 92 88 91 87 Year 7 170130180.81 6.84 <0.001 a =o.os Residual 88 24875426.34 I Table 13: Production (in kg) of 15 major species, total finfish and total for all species from Lake Illawarra and 6 other lakes in NSW from July 1990 to June 1991. Data from New South Wales Commercial I Fisheries Statistics 1990/1991, NSW Fisheries (1993).
I Lake Wallis Smiths Myall Lake Tuggerah St. George Illawarra Lake Lake Lakes Macguarie Lakes Basin I Bream 18 23815) 20 080(4) 1 403(7) 7 933(6) 23 316(3) 32 444(2) 35493(1) Dusky Flathead 20 876(2'! 33347(1) 2 326(6) 991(7) 7943(4) 16 385(3) 6 626(5) I River Garfish (2) 5 318(3) 20(7) 90(6) 5 083(4) 4279(5) 6 793(1) Leatheijackets i7(4) 9502(1) 244(6) 5(7) 1 128(3) 357(5) 1 233(2) I Luderick 15 156(5) 45543(1) 6 632(7) 13 %9(6) 33 720(4) 38559(2) 37968(3) Fantail Mullet 3 321(5) 11 277(1) 678(7) 679(6) 5081(3) 3402(4) 6 725(2) Sea Mullet 5 718(5) 145 232(1) 25 815(7) 78 911(4) 99409(3) 110 292(2) 29 596(6) I Mulloway 30) 1 044(3) 157(5) 80(7) 1 781(2) 2293(1) 175(b) Silver Biddy .36(3) 165(5) 0(7) 50(6) 35488(2) 672(4) 37504(1) I Sand Whiting 7215(2) 7 131(3) 248(7) 4448(4) 3 074(5) 9 885(1) Cockles 21 57ói) 0(4) 0(4) 0(4) 15(3) 0(4) 6498(2) I Blue Swimmer Crabs 416(5) 33 955(1) 314(6) 1 278(3) 2 788(2) 607(4) 6(7) Mud Crabs 537(4) 8 941(1) 245(6) 175(7) 1 443(3) 2220(2) 288(5) I Eastern King Prawns 20212(1) 3216(4) 129(7) 169(6) 1 337(5) 4737(3) 7012(2) School Prawns 13 823(3) 18 330(2) 232(7) 8 679(4) 1 418(6) 38495(1) 2 028(5) I Total finfish 137 257(5) 300 919(1) 51 294(7) 119 635(6) 278 205(2) 222 397(3) 217 897(4) All species 2256692 468 721(1) 54 043(7) 131 259(6) 363 991(2) 286 574(3) 236 187(4) I I I I I Table 14: Summary of details of the proposal to dredge in Griffins Bay by Stage and Area to be dredged. Option 1 is dredging the channel north of Furry Burr)' Point and option 2 is dredging through the northern tip of Purry Burry Point. a = area was not calculated by GHD (1994) and b = cannot be calculated because original area is unknown.
Development Stage Stage I Stage 2 Stage 3 Stage 4 Dredging Areas Area A Area B channel Area C Area D extension option 1 option 2 option 1 option 2
14.6 size of area (ha.) 6, island = 3.2 2.4 1.6 a 6.7 a
depth prior to dredging <0.5m <1.0m <1.0m <1.5m <1.5m <1.5m <1.5m
maximum depth after dredging -14 m -1.5 m -1.5 m to -3 m -14 m -14 m -14 m -14 m
slopeof area 1:1 noslope 1:6to1:12 1:1 1:1 1:1 1:1
would dredged area be filled in? yes no no not by this not by this not by this not by this proposal proposal proposal proposal - how long would it take 10 -13 years - depth on completion 0.9 to -1.6m AT-ID
enclosing embankment present yes no no no no no no
sequence of dredging first, 2 phases after Area A after Area B after channel after channel after Area C after Area C
time since start of project 0 1.9 2.1 3.2 3.2 5.7 6.3 (in years)
time taken to complete dredging 1.9 0.2 1.1 2.5 3.1 4 6.4 (in years) Phase 1 Phase 2 amount of material taken (m3) 57 000 301 000 35 000 167 000 460 000 580 000 645 000 1 000 000
amount of residue returned (m3) 8 000 42 000 5000 29 000 64 000 81 000 105 000 170 000
residue used for. island island island island island island, Area A island, Area A Area A
sediment same size as before no no yes yes no no no no
suitable for seagrass to grow? no yes yes no if backfilled if backfilled if backfilled if backfllled - area available 2.8 2.4 0 b 0 - 6.7 b 0- 14.6 - - MMMMM - - MMMMM MMMMMM ------
Table 15: Summary of fishing methods and the likelihood of impact from the proposal to extract sand from Griffins Bay.
Done within Done near Likely to Dredged Dredged be impacted Fishing Method Areas Areas by project Why?
COMMERCIAL
Prawning Pocket set nets No No No only done in entrance channel Snigging nets No Yes Yes done lakewide but disturbance to area may alter prawn behaviour and movement Running nets No Yes Yes done lakewide but disturbance to area may alter prawn behaviour and movement
Meshing for Fish and Crabs Splash method Yes Yes Yes loss of fishing ground, during and after dredging Set net Yes Yes Yes loss of fishing ground, during and after dredging
Hauling for Fish Yes Yes Yes loss of fishing ground, during and after dredging
Hand-collecting of Cockles No Yes Unlikely only if smothering by settling of fines over seagrass on eastern foreshore
RECREATIONAL
Frawning scoop nets No No No only done in entrance channel and on eastern shore
Line fishing No Rarely No usually done around entrance channel and Bevan Island
Bait collecting No Yes No other areas where bait could be collected away from dredging operations FIGURES Hooka Ck
Brooks Ck
Eastern Shore
Duck Ck g channel
Lake Entrance
Macquari Rivulet Hennegar Bay
Koona Ba
0 1 2km Scale Seagrass (West et al. 1985)
j Seagrass (King et al. 1991) 11111 Saltmarsh (West et al.1985)
Figure 1: Distribution of the total area of seagrass and saltmarsh in Lake Illawarra as mapped by West et al., 1985 and King et al., 1991. MARCH 1988
LIMIT OF STUDY
LHT OF STUDY AREA AREA
I I GRFFLNS BAY I I 4 l)
- LEGEND I / Dense I I PI T Zostera POINT 0 100 200 300 £10 SOOm [' Moderate I Ruppia I AUGUST 1993
LIMIT OF STUDY I AREA I I
I GRIFFINS BAY I I V7 LEGEND p5Y LIMIT OF , EI Dense / PW STUDY AREA / Zorlera I Dense o 100 200 300 L00 sOOrn Ruppia I --Transects Figure 2: Distribution of the total area of seagrass in Griffins Bay at two different times (1988 and I 1993). Maps are reproduced from WBM Oceanics (1993). Hooka Ck
Mullet Ck
,43-'±criffins 2 1_6 Bay BrooksCk - 14 13
Eastern Shore Koonawarra Bay '12 11
Lake Illawarra 0 11
Duck Ck Bevans Is. indang channel Lake Entrance
N Macquarie Rivulet Hennegar Bay -
91 Koona Ba Burroo Bay
0 1 2km I I Scale Area of seagrass cover
Figure 3: Location of sampling sites for collection of benthic macrofauna by corer. The area of seagrass cover is from West et al., 1985. Hooka Ck
Mullet Ck
B A a y Brooks Ck
Koonawarra Bay Eastern Shore
j Lake illawarra
{
Duck Ck indang channel S Lake Entrance
N Macquarie Rivulet Hennegar Bay
Koona Ba Burroo Bay
0 i 2km Scale Area of seagrass cover
Figure 4: Location of sampling sites for collection of fish and mobile invertebrates by beam trawling. The area of seagrass cover is from West et al., 1985. Hooka Ck Boat Harbour Mullet Ck B
riffins Bay Brooks Ck A
Koonawarra Bay Eastern Shore
Lake illawarra 0
Duck Ck Bevans Is. indang channel
Lake Entrance
N Macquarie Rivulet Hennegar Bay -
Koona Ba Burroo Bay
0 1 2km Scale Area of seagrass cover II
Figure 5: Location of sampling sites for collection of fish and mobile invertebrates by beach seining. The area of seagrass cover is from West et al., 1985. I I I I Figure 6: Two-dunensional plot of the MDS ordination of benthic macrofauna collected from 2 I sites in 8 locations in Lake Illawarra. Each symbol represents a sample. I
I proposed Eastern Shore dredge Area A 0 muddy sediment sandy sediment I sandy sediment I 1 I
I A A
I stress = 0.191 Figure 7 a-f: The mean (i-SE) of the number of taxa, number of individuals and abundance of 4 species of benthic macrofauna collected in cores at 2 sites in 8 locations in Lake fliawarra. Locations are; GBA=Grifflns Bay A (Sites 1 & 2 Figure 3), GBB=Griffins Bay B (Sites 3 & 4), GBC=Griffins Bay C (Sites 5 & 6), ESM=Eastern shore mid (Sites 11 & 12), ESN=Eastern shore north (Sites 13 & 14), ESS=Eastern shore south (Sites 15 & 16), GBM=Griffins Bay mud (Sites 7 & 8) and BBM=Burroo Bay mud (Sites 9 & 10). GBM and BBM were not included in the analyses of variance (Table 3).
a) Number of taxa b) Number of individuals 40
30
Eli
10
GBA GBB GBC ESM ESN ESS GBM BBM GBA GBB GBC ESM ESN ESS Griffins Bay Area Eastern Shore MUDDY Griffins Bay Area Eastern Shore SANDY SEDIMENT SEDIMENT SANDY SEDIMENT
r12 — c) Tellina deltoidalis d) Barantolla lepte IV 15 0 '-4 0 o 30 '-4 10 0 04 20 0 5
1 10 GBA GBB GBC ESM ESN ESS GBM BBM GBA GBB GBC ESM ESN ESS Griffins Bay Area Eastern Shore MUDDY Griffins Bay Area Eastern Shore SANDY SEDIMENT SEDIMENT SANDY SEDIMENT
e) Owenia fusiformis f) Mysella sp. 200 401
150 30
100 20
50 10
GBA GBB GBC ESM ESN ESS GBM BBM GBA GBB GBC ESM ESN ESS Griffins Bay Area Eastern Shore MUDDY Griffins Bay Area Eastern Shore SANDY SEDIMENT SANDY SEDIMENT Figure 7 g-l: The mean (+ SE) of 6 species of benthic macrofauna collected in cores in 2 sites at 8 locations in Lake Illawarra. Locations are; GBA=Griffins Bay A (Sites 1 & 2, Figure 3), GBB=Griffins Bay B (Sites 3 & 4), GBC=Griffins Bay C (Sites 5 & 6), ESM=Eastern shore mid (Sites 11 & 12), ESN=Eastern shore north (Sites 13 & 14), ESS=Eastern shore south (Sites 15 & 16), GBM=Grifflns Bay mud (Sites 7 & 8) and BBM=Burroo Bay mud (Sites 9 & 10). GBM and BBM were not included in the analyses of variance (Table 3).
g) Urohaustorius metungi h) Corophium volutator 75-. 40
60-i T 1 30
45 20 30
10 15
GBA GBB GBC ESM ESN ESS GBM BBM GBA GBB GBC ESM ESN ESS GBM BBM Griffins Bay Area Eastern Shore MUDDY Griffins Bay Area Eastern Shore MUDDY SANDY SEDIMENT SEDIMENT SANDY SEDIMENT SEDIMENT
i) Spisula trigonella j) Soletellina alba 30 140 120
100 20 80
60 10 40
20
GBA GBB GBC ESM ESN ESS GBM BBM GBA GBB GBC ESM ESN ESS GBM BBM Griffins Bay Area Esstern Shore MUDDY Griffins Bay Area Eastern Shore MUDDY SANDY SEDIMENT SEDIMENT SANDY SEDIMENT SEDIMENT
k) Austrolenereis ehiersi 1) Cirriformia filigera 50 50
40 40
30
20
10 10
GBA GBB GBC ESM ESN ESS GBM BBM GBA GBB GBC ESM ESN ESS GBM BBM Griffins Bay Area Eastern Shore MUDDY Griffins Bay Area Eastern Shore MUDDY SANDY SEDIMENT SANDY SEDIMENT SEDIMENT Figure 8: Two-dimensional plot of the MDS ordination of fish and mobile invertebrates collected In beam trawls at five locations in Lake illawarra. GBA=Griffins Bay A, GBB=Grifflns Bay B, WCS=Windang Channel South, WCN=Windang Channel North and ES=Eastern Shore (see Figure 4).
GBA 40 GBB 0 wcs A WCN 0 ES
a a A ••—
A A
AA 0?(
stress=0.157 I
I Figure 9 a-fl The mean number (+SE) of taxa, total abundance, abundance of all commercial species and 3 species of fish caught in beam trawis in 2 Sites at 5 Locations in Lake illawarra. Locations are; GBA=Griffins Bay A, GBB=Griffins Bay B, WCS=Windang Channel South, I WCN=Windang Channel North and ES=Eastern Shore (see Figure 4). There were 4 replicate trawis per site. I I a) Number of Taxa b) Total Abundance 20
I 15
I 10 I 5 I GBA GBB WCS WCN ES GBA GBB WCS WCN ES I c) Abundance of Commercial Species d) Achoerodus viridis + 15 5 I - 4 10 3 04 4.4 2 5
GBA GBB WCS WCN ES GBA GBB WCS WCN ES
e) Meuschenia spp. f) Pseudogobius olorum
GBA GBB WCS WCN ES GBA GBB WCS WCN ES
Figure 9 g-l: The mean number (+SE) of 6 species of fish and mobile invertebrates caught in beam trawis in 2 Sites at 5 Locations in Lake lilawarra. Locations are; GBA=Griffins Bay A, GBB=Grifflns Bay B, WCS=Windang Channel South, WCN=Windang Channel North and ES=Eastern Shore (see Figure 4). There were 4 replicate trawis per site.
g) Centropogon australis h) Urocampus carinirostris
GBA GBB WCS WCN ES GBA GBB WCS WCN ES
i) Gobiopterus semivestitus j) Penaeus plebejus
4
3 I
2
I
GBA GBB WCS WCN ES GBA GBB WCS WCN ES
k) Macrobrachium intermedium 1) Idiosepius notoides
2
GBA GBB WCS WCN ES GBA GBB WCS WCN ES Figure 10: Two-dimensional plot of the MDS ordination of fish and mobile invertebrates collected in beach seines at five locations in Lake illawarra. GBA=Grifflns Bay A, GBB=Griffins Bay B, WC=Windang Channel, BH=Boat Harbour and HB=Hennegar Bay.
U GBA • GBB 0 WC A BH 0 HB
4 AA o a0 AA
0
stress=0.197 Figure 11 a-ft The mean number (+SE) of taxa, total abundance, abundance of all commercial species and 3 species of fish caught in beach seines in 2 Sites at 5 Locations in Lake Illawarra. Locations are; GBA=Griffins Bay A, GBB=Griffins Bay B, WC=Windang Channel, BH=Boat Harbour and HB=Hennegar Bay (see Figure 5). There were 4 replicate hauls per site.
a) Number of Taxa b) Total Abundance
25 7000 6000 20 5000
15 4000
3000 10 2000 5 1000
GBA GBB WC PH HB GBA GBB WC BH HB
c) Abundance of Commercial Species d) Sillago ciliata
15-
ii
61
Cd GBA GBB WC BH ES GBA GBB WC BH HB
e) Acanthopagrus australis f) Mugil cephalus
GBA GBB WC BH HB GBA GBB WC BH HB Figure 11 g-l: The mean number (+ SE) of all species and 6 species of fish and mobile invertebrates caught in beach seines in 2 Sites at 5 Locations in Lake illawarra. Locations are; GBA=Griffins Bay A, GBB=Griffins Bay B, WC=Windang Channel, BH=Boat Hathour and HB=Hennegar Bay (see Figure 5). There were 4 replicate hauls per site.
g) Achoerodus viridis h) Girella tricuspidata
40 20
30 15
20 10
10 5
GBA GBB WC BH HB GBA GBB WC BH HB
i) Penaeus plebejus j) Hvprohamphus regularis
40 15
30 10
20
5 10
GBA GBB WC BH ES GBA GBB WC BH HB
k) Macrobrachium intermedium 1) Ambassis jacksoniensis
600
400
200
GBA GBB WC BE! HB GBA GBB WC BH HB Figure 12: The length frequency distribution of sand mullet at 5 locations in Lake Illawarra collected by beach seining.
Griffins Bay A Griffins Bay B 20 100
15 75
10 50
5 25
20-39 60-79 100-119 140-159 180-199 220-239 20-39 60-79 100-119 140-159 180-199 220-239 40-59 80-99 120-139 160-179 200-219 240-259 40-59 80-99 120-139 160-179 200-219 240-259
Windang Channel Boat Harbour 40 100 0 0 30 75 0 '4
20 50
10 25
20-39 60-79 100-119 140-159 180-199 220-239 20-39 60-79 100-119 140-159 180-199 220-239 40-59 80-99 120-139 160-179 200-219 240-259 40-59 80-99 120-139 160-179 200-219 240-259
Hennegar Bay 80
60
40
20
20-39 60-79 100-119 140-159 180-199 220-239 40-59 80-99 120-139 160-179 200-219 240-259 Length Classes (mm)
Hooks Ck ily Bay Mullet Ck
Griffins Bay
Brooks Ck Joes Bay
Bay
Koonawarra Bay Eastern Shore
Lake illawarra
DuckCk ' I Windang channel 0 Lake Entrance
Macquarie
Koona Ba\ k Burroo Bay
0 1 2km I I Scale
Figure 13: A map showing the approximate location of recognised areas where prawn running nets are set in Lake Illawarra. Stippled areas = area where nets are set. Figure 14 a-f: The total weight per year (in 1000 kilograms) of all commercial species, all finfish - and 4 selected species caught by commercial fishers in Lake ifiawarra from 1985 to 1992. -
a) All species
300 200
250 150 200
150 100
100 50 50
1985 1986 1987 1988 1989 1990 1991 1992
c) river garfish
12 40
10 30 8
6
4
2
1985 1986 1987 1988 1989 1990 1991 1992
e) luderick f) flathead
35 25
30 20 25 15 20
15 10 10 5 [T 5
1985 1986 1987 1988 1989 1990 1991 1992
Figure 14 g-l: The total weight per year (in 1000 kilograms) of 6 selected species caught by commercial fishers in Lake Illawarra from 1985 to 1992. i 1 I g) sea mullet h) leatherjackets
91 1 80
60 2
40
1 20
1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992
i) eastern king prawn j) school prawn
Il 15 30
1-4
10 20 bo
10 5
bo
1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992
k) blue swimmer crab 1) cock.les I
60
I 50
2 40
30
20
10 I 1985 1986 1987 1988 1989 1990 1991 1992 1985 1986 1987 1988 1989 1990 1991 1992 I I
N iFFE
-. 911 N. •/ 4_t #4' ---.12____...______...-- tN'4 (I3TING INV I 0 CHANNEt. ' — - 4VStage2 N -- - - Area B GRIFFINS BAY ----Ama C Phase I
/. 72 Area A / / Stage 4 •1 -.-..-..---. -.... , Stage 1 noo Area D -. ( ( • ase 2 -
- CIIANN(t zu .- 26 lit /i
.. . I! I
/ EXtSTING CONTOURS - - / NEW CONTOURS / CONTOUR VALUESARE ON AUSTRALIAN ' KORp / HEIGI-IT DATUM (AND.)
Figure 15: Map of Griffins Bay indicating the stages and areas to be dredged for sand extraction in Griffins Bay. APPENDICES samples Collected in Lake lllawarrra on 8-9/11J93 I Appendix A: Mean and standard error of Benthic Macrofauna - C GBM=Griffins Bay Mud GBA=Griffins Bay A GBBrGriffins Bay B GBC=Griffins Bay GBC 6 GBM 71 GBM 8 GBA I GBA 2 ____ GBB 3 GBB 4 GBC5 LOCATION s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean 9.74 34.00 12.51 46.60 20.40 48.70 155.80 49.02 4.00 0.55 10.60 3.41 57.40 13.08 37.60 138.20 1 Total Polychaetes 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 Armandia internwdia 6.80 1.02 4.20 1.39 9.60 2.18 20.00 2.51 13.20 2.01 2.00 0.45 7.00 1.67 9.60 3.33 Austrolenereis ehiersi 6.40 4.20 9.00 4.30 8.00 3.10 10.00 2.92 3.40 1.12 0.00 0.00 0.40 0.40 3.80 1.50 Barantolla lepte 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.40 0.40 Capitella sp. 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Caulleriella sp. 4.60 1.47 0.80 0.80 020 0.20 0.80 0.49 0.00 0.00 0.60 024 0.60 0.40 20.00 4.62 Cirriforniiafihigera 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Leitoscolo plus normalis 0.00 0.00 0.00 0.00 0.00 0.20 0.20 3.00 1.48 2.80 1.62 0.00 0.00 0.00 0.00 0.00 F. Lumbrineridae 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Marphysa sanguinea 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.20 0.20 0.00 Nephtis oust raliensis 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Nephtys longipes 2.82 2.20 0.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 13.20 F. Nereidae (except A. ehlersi) 0.97 1.40 0.60 5.40 2.09 1.20 0.97 1.00 0.45 0.60 0.40 0.20 0.20 1.00 0.55 1.20 - Notomastus sp. 0.00 0.00 3.00 1.30 1.40 0.60 1.20 0.80 020 0.20 0.40 0.24 0.00 0.00 0.00 0.00 F. Opheliidae 3.67 4.00 0.63 0.00 0.00 0.00 0.00 0.80 0.58 020 0.20 0.00 0.00 0.80 0.37 6.40 F. Orbiniidae 1.50 10.00 5.03 11.40 527 26.00 14.95 96.20 41.86 135.00 46.98 0.00 0.00 0.20 0.20 2.20 Oweniafusiformis 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.40 1.17 0.00 0.00 0.00 0.00 0.00 0.00 0.00 F. Sabellidae 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 F. Sigalionidae 0.24 2.00 0.84 0.00 0.00 0.00 0.00 3.80 1.66 020 0.20 0.60 -0.24 020 0.20 0.40 F. Spionidae 1.52 3.20 0.66 4.40 1.17 5.40 0.81 11.40 3.57 3.80 1.36 8.80 1.50 3.20 1.59 5.00 Total Crustacea 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 - 0.00 0.00 0.00 Callianassa arenosa 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Caprella scaura 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6.20 1.59 1.40 0.60 1.20 0.97 0.60 0.60 0.00 Corophium cf. volutator 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.40 0.24 0.20 0.20 0.40 0.24 0.00 Haplostylis dakini 0.37 0.60 0.40 0.20 020 120 0.73 120 0.49 1.40 0.68 1.20 0.37 0.00 0.00 1.20 LimnoporeiayarragUe 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.20 Macrobrachiufli intermedium 0.00 0.60 0.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Malita matilda 0.66 1.60 0.24 0.60 0.24 020 0.20 2.20 1.50 0.20 0.20 0.60 0.40 1.40 0.98 2.20 Paracalliope australis 0.40 0.40 0.40 0.24 0.00 0.00 0.60 0.40 0.60 0.40 0.20 0.20 0.40 0.40 0.40 0.40 Paracorophium excava'qum 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Pseudolara towrae 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 F. Tatrilidae 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.40 0.24 0.00 Urohaustorius metungi 0.40 - 0.40 1.29 3.40 0.40 5.00 1.58 0.20 0.20 0.40 0.24 0.00 0.00 3.60 Victoriopisa australiensis 020 0.20 0.00 0.00 0.00 020 0.20 0.20 0.20 0.20 0.00 0.00 0.00 0.00 0.00 Am hipod s . D 0.00 0.00 0.00 0.00 020 -_ _ EU p • __ ------
BBM=Burroo Bay Mud ESM=Eastern_Shore-Mid ESN=Eastern_Shore-North ESS=Eastern_Shore-South LOCATION BBM 9 BBM 10 ESM 11 ESM 12 ESN 13 ESN 14 ESS 15 ESS 16 mean s.e. I mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean S.C. Total Polychaetes 3.20 0.581 4.00 1.05 57.20 14.93 46.60 6.87 31.20 9.73 61.80 16.74 8.40 1.50 19.80 5.03 Armandia interinedia 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1 0.00 0.00 0.00 0.00 Austrolenereis eblersi 0.00 0.00 0.20 0.20 35.80 10.70 2.40 0.87 25.60 6.65 29.00 3.78 2.80 1.02 7.80 2.85 Barantolla lepte 0.00 0.00 0.00 0.001 0.80 0.58 0.60 0.40 0.001 0.00 0.60 0.24 0.80 0.58 1.20 0.73 Capitella sp. 0.00 0.00 0.00 0.001 0.80 0.58 0.00 0.00 0.001 0.00 0.60 0.60 0.00 0.00 0.00 0.00 Caulleriella sp. 0.00 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.40 0.40 0.40 0.40 Cirriforrniafiligera 0.00 0.00 0.00 0.00 4.20 2.58 39.00 6.45 1.60 1.03 3.00 1.38 1.40 0.51 3.80 2.65 Leitoscoloplos normalis 0.00 0.00 0.00 0.00 1.60 1.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 F. Lumbrineridae 0.20 0.20 0.40 0.24 0.20 0.20 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 Marphisa sanguinea 0.00 0.00 0.00 0.00 0.00 0.00 0.201 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Nephti,'s australiensis 2.60 0.401 3.40 0.931 0.20 0.20 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.40 0.40 Nephtys longipes 0.00 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 F. Nereidae (except A. ehiersi) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 Notomastus sp. 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 F. Opheliidae 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5.09 1.80 0.66 4.00 1.41 F. Orbiniidae 0.00 0.001 0.00 0.00 8.20 2.87 0.80 0.80 3.201 1.77 8.40 Owen ia fusiformis 0.00 0.00 0.00 0.001 0.20 0.20 0.60 0.40 0.001 0.00 13.40 9.25 0.20 0.20 0.40 0.24 F. Sabellidae 0.00 0.00 0.00 O.Ool 0.00 0.00 0.20 0.20 0.201 0.20 3.00 2.14 0.00 0.00 0.00 0.00 F. Sigalionidae 0.00 0.00 0.00 0.00 0.40 0.24 1.00 0.45 0.001 0.00 0.00 0.00 0.20 0.20 1.00 0.32 F. Spionidae 0.40 0.40 0.00 0.00 4.60 2.68 1.80 0.58 0.601 0.40 3.60 1.96 0.40 0.24 0.80 0.20 Total Crustacea 6.00 0.321 4.80 0.97 51.80 11.89 60.40 15.01 20.201 9.18 42.00 3.58 39.40 8.45 51.80 9.51 0.24 0.40 0.24 Callianassa arenosa 0.00 0.001 0.00 0.00 0.00 0.00 0.401 0.24 0.001 0.00 0.00 0.00 0.40 000r 0.00 0.00 1.40 1.17 Caprella scaura 0.00 0.06L 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.93 0.40 0.24 0.00 0.00 Corophiurn cf. volutator 0.00 0.00 0.00 0.00 0.60 0.40 0.20 0.20 5.00 1.82 31.40 0.40 0.20 0.20 1.40 0.24 Haplostylis dakini 0.00 0.001 0.00 0.00 1.00 0.63 2.60 0.60 0.40 0.24 0.40 0.40 0.20 0.20 0.20 0.20 Limnoporeia yarrague 0.00 0.00 0.00 0.001 0.00 0.00 0.20 0.20 0.20 0.20 1.60 0.00 0.00 0.00 0.00 0.00 Macrobrachium intermedium 0.00 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Malita matilda 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.20 0.20 0.80 0.49 1.80 1.07 Paracalliopeaustralis 0.00 0.00 0.00 0.00 2.00 1.05 3.40 1.21 4.00 2.26 1.20 0.80 0.20 0.20 0.80 0.37 Paracorophiumexcavayum 0.60 0.601 0.20 0.20 0.80 0.58 1.20 0.37 1.20 0.37 2.80 0.73 0.20 0.00 0.00 0.00 0.00 Pseudolara towrae 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.00 0.00 0.00 0.00 0.00 0.00 F. Tatrilidae 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.51 37.00 8.38 45.60 7.91 Urohaustorius metungi 1.40 1.40 0.00 0.00 47.20 11.19 51.60 13.96 9.00 5.45 4.00 0.00 Victoriopisa australiensis 3.80 1.11 4.601 0.87 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.201 0.201 0.20 0.20 Amphipod sp. D 0.00 0.00 0.001 0.001 0.001 0.00 0.60 0.24 0.40 0.24 0.20 Appendix A. Mean and standard error of Benthic Macrofauna samples - Collected in LakeIllawarrra on 8-9/11/93 GBA=Griffins Bay A GBB=Griffins Bay B GBC=Griffins Bay C GBM=Griffins Bay Mud GBM 7 GBM 8 LOCATION GBA I GBA 2 GBB 3 GBB 4 GBC 5 GBC 6 mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. 10.40 2.91 35.80 9.76 24.60 3.20 Total Molluscs 148.80 16.57 98.80 26.16 2.00 0.32 2.80 0.37 18.40 5.55 0.00 0.00 0.20 0.20 0.00 0.00 Art hritica he! msi 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 Laternula marilina 0.60 0.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.00 0.001 0.00 0.00 0.00 0.00 Laternula sp. 0.20 0.20 0.20 0.20 0.00 0.00 0.20 0.20 0.20 4.92 2.00 1.10 0.00 0.00 0.00 0.00 Mysella sp. 2.80 0.73 4.80 2.27 0.00 0.00 0.00 0.00 5.40 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 Nassarius burchardi 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001 0.00 Nassariusjonasii 0.40 0.24 0.40 0.24 0.00 0.00 0.00 0.00 0.00 3.20 1.07 1.20 0.80 0.00 0.00 0.00 0.00 Soletellina aTha 118.20 12.97 65.00 19.46 0.00 0.00 0.00 0.00 1.36 1.60 0.68 7.20 2.03 5.00 0.89 Spisula trigonella 19.80 5.14 20.80 4.97 0.60 0.40 0.60 0.40 4.20 5.20 1.77 5.60 1.63 25.80 9.09 17.80 2.63 Tellina deltoidalis 6.60 2.82 7.60 1.60 1.00 0.45 2.00 0.45 0.00 0.00 0.00 0.00 2.60 0.81 1.60 0.51 Theorafragilis 0.20 0.20 0.00 0.00 0.20 0.201 0.00 0.00 0.00 1.20 0.58 1.40 0.51 3.40 1.40 2.80 1.07 C. Holothuroidea 0.20 0.20 1.40 0.40 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 C. Hydrozoa 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.58 0.00 0.00 0.20 0.20 2.20 0.86 3.00 0.77 P. Nemertinea 2.80 1.32 0.20 0.20 1.40 0.68 0.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 C. Oligochaeta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 162.80 27.83 104.00 17.54 154.20 41.69 159.00 45.10 Total individuals 526.60 126.35 518.40 124.11 31.00 3.30 34.00 8.06 1.03 6.20 1.24 6.60 0.75 4.40 0.68 4.00 0.95 No. taxa of polychaetes 6.20 1.39 4.60 0.93 3.00 0.55 3.60 0.60 3.00 0.71 2.00 0.32 1.60 0.24 2.20 0.37 No. taxa of crustacea 3.80 0.86 2.40 0.75 3.00 0.71 1.60 0.24 3.40 0.51 2.601 0.51 3.20 0.20 3.00 0.00 No. taxa of molluscs 5.00 0.55 4.20 0.20 1.40 0.24 1.60 0.40 0.24 0.60 0.24 1.00 0.32 1.80 0.20 1.60 0.40 No. of other taxa 0.801 0.371 1.20 0.20 0.60 0.24 1.53 13.20 1.91 12.20 0.49 11.00 1.05 10.80 0.97 Total No. of taxa 15.80 2.27 12.40 1.57 8.00 1.10 7.20
- - - - MMMMMMMMMM ------MMMMM ------
BBM=Burroo Bay Mud ESM=Eastern_Shore-Mid ESN=Eastern_Shore-North ESS=Eastern_Shore-South LOCATION BBM 9 BBM 10 ESM 11 ESM 12 ESN 131 ESN 14 ESS 15 ESS 16 mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. mean s.e. Total Molluscs 9.00 1.22 9.80 2.94 8.00 1.90 29.20 9.40 23.20 4.84 83.40 17.48 34.40 10.78 46.20 11.94 Arthritiai 1ielmsi 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 L.aternula marilina 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 Laternula sp. 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mysella sp. 0.00 0.00 0.00 0.00 2.60 1.89 15.80 7.07 4.80 1.59 7.80 2.82 28.40 10.67 18.60 5.42 Nassarius burchardi 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 020 0.20 Nassariusjonasii 0.60 0.40 0.00 0.00 1.60 0.51 0.00 0.00 0.40 0.24 1.20 0.58 0.60 0.40 1.60 0.68 Soletellina alba 0.00 0.00 0.00 0.00 3.60 0.68 12.20 3.94 14.80 4.83 66.40 13.22 3.80 0.97 21.00 7.62 Spisula frigonella 4.80 1.16 7.20 1.93 0.00 0.00 1.20 0.80 3.20 0.58 7.80 3.65 1.40 0.51 4.60 1.50 Tellina deltoidalis 0.60 0.401 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Theorafragilis 3.00 0,631 2.60 1.12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 C. Holothuroidea 0.00 0.001 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 C. Hydrozoa 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 P. Nemertinea 0.00 0.00 0.00 0.00 0.60 0.24 0.20 0.20 0.20 0.20 0.40 0.40 0.40 0.40 0.40 0.24 C. Oligochaeta 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.20 0.00 0.00 0.20 0.20 0.00 0.00 0.00 0.00 Total individuals 36.40 2.23 37.20 9.22 234.60 34.54 273.00 55.27 149.40 31.88 375.20 63.89 164.80 37.071 236.00 31.04 No. taxa of polychaetes 1.40 0.24 1.60 0.24 5.40 0.87 4.60 0.51 2.60 0.8 5.00 1.38 4.20 0.731 5.60 0.68 No. taxa of crustacea 1.40 0.24 1.20 0.20 3.00 0.55 5.40 0.51 4.20 0.73 5.20 0.58 3.00 0.321 4.60 0.68 No. taxa of molluscs 2.80 0.37 2.00 0.00 2.60 0.51 2.40 0.24 3.40 0.24 3.60 0.24 3.40 0.24 4.00 0.32 No. of other taxa 0.00 0.00 0.00 0.00 0.60 0.24 0.60 0.401 0.20 0.20 0.601 0.24 0.20 0.20 0.40 0.24 Total No. of taxa 5.60 0.24 4.80 0.20 11.60 1.54 13.001 1.051 10.40 1.36 14.401 1.99 10.80 0.97 14.60 150 Appendix B: Mean and standard error per site of fish and mobile Invertebrates collected I N.B. * indicates species of commercial value by beam trawling In Lake illawarra on 8-9/11193. I WCS=Windang Channel South Location Key GBA=Griffins Bay A GBB=Griffins Bay B WCS 6 Sites 1-10 GBA 1 GBA 2 GBB 31 GBB 4 WCS 5 mean s.e. mean s.e. meanj s.e. mean s.e. Scientific Name Common Name mean g.e. mean s.e. FISH 0.00 0.00 0.00 0.00 *Açnthgyits aust rails yellow-finned bream 0.00 0.00 0.00 0.00 1.25 1.25 0.42 0.42 1.18 0.25 0.25 0.67 0.41 *Achodu5 viridis blue groper 1.92 1.08 0.42 0.42 1.25 0.42 1.67 0.42 0.83 0.48 0.00 0.00 3.67 1.64 AmbassisjacksonieflSis perchlet 0.00 0.00 0.00 0,00 0.42 3.33 1.18 5.631 2.08 6.25 1.42 1.50 0.70 Arenigobius bifrenatus bridled goby 0.50 0.29 0.50 0.50 0.83 0.83 0.00 0.00 0.00 0.00 0.00 0.00 Bat hygobius kreffti goby 0.00 0.00 0.00 0.00 3.10 17.08 4.38 5.21 0.98 28.83 5.18 10.42 2.75 Centropogon australis eastern fortesgue 7.75 2.52 12.33 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Chlorotxelia leptorhynchus 0.00 0.00 0.00 0.67 0.42 0.42 0.88 0.88 0.00 0.00 0.00 0.00 Dicotolichthys punctulatus three-barred porcupinefisl 0.25 0.25 0.67 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Enoplosus armatus old wife 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.00 1.50 0.00 0.00 Favonigobius exquisitus goby 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.25 1.25 0.00 0.00 Favonigobius lateralis long-finned goby 0.00 0.00 0.25 0.25 0.00 0.00 0.00 0.00 9.92 6.23 6.08 1.74 Favonigobius tamarensis goby 0.00 0.00 0.00 0.42 0.42 0.00 0.00 1.50 0.70 1.33 0.82 *Girella tricuspidata blackfish/luderick 1.08 0.39 0.00 12.09 94.17 52.44 72.29 17.15 9.58 6.95 5.92 4.14 Gobiopterus semi vestitus transparent goby 19.08 10.72 21.33 0.00 0.00 0.00 0.00 0.42 0.42 0.00 0.00 *Hyperlophus translucidus sprat 0.00 0.00 0.00 0.00 0.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0,00 *Hypejlophus vittatus sandy sprat 0.00 0.00 0.25 1.67 1.18 1.04 0.63 3.08 1.08 6.67 2.04 *MeuschiiiapeyCineti six-spined leatherjacket 1.25 0.80 0.00 0.00 0.42 0.67 0.67 2.13 2.13 0.67 0.41 0.83 0.48 *MeuscIwllit1 trachylepis yellow-finned leatherjacke 0.83 0.83 0.42 0.42 0.42 2.33 1.05 3.17 2.64 3.75 0.80 7.50 1.60 Meuschenia spp. leatherjacket 2.08 1.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Microcanthus strigatus stripey 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 *Nelusetta ayraudi chinanian 1eathejacket 0.00 0.00 0.00 0.00 0.25 0.00 0.00 0.00 0.00 0.00 0.00 0.42 0.42 Pelates guadrilineatus trumpeter 0.67 0.41 0.25 6.77 98.75 29.98 146.46 30.27 21.83 4.65 13.42 6.09 Pseudogobius olorum swan river goby 16.50 7.68 29.17 0.00 0.00 0.00 0.25 0.25 0.00 0.00 *PsendorhijinhusjenynSii small-toothed flounder 0.00 0.00 0.00 0.00 0.00 0.75 0.75 0.00 0.00 0.00 0.00 49.67 13.19 44.25 2.02 Redigobius macrostoma large-mouth goby 1.25 0.80 0.42 0.42 0.42 0.00 0.00 0.00 0.00 0.00 0.00 *pJb3,rgus sarba tarwhine 0.00 0.00 0.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Stigmatopora argus spotted pipefish 0.25 0.25 0.42 0.42 0.42 0.42 0.00 0.00 19.25 3.15 47.67 18.44 Stiginatopora nigra snub-nosed pipefish 2.75 1.48 0.00 0.00 0.00 0.00 0.00 0.00 0.42 0.42 0.00 0.00 Tetractenos hamiltoni common toadfish 0.00 0.00 2.88 12.92 4.53 13.13 3.61 7.25 3.72 10.25 3.42 Urocampus carinirostris pipefish 9.25 1.44 7.33 CRUSTACEA 0.00 2.17 0.79 0.42 0.42 snanninslimD 0.00 0.00 0.00 0.00 0.00 0.00 0.00 - OO O.00.0C.00!3 - ) _C ------
N.B. indicates species of commercial value * Location Key WCN= indang Channel North ES=Eastern_Shore Sites 1-10 WCN 71 WCN 8 ES 9 ES 10 s.e. ScientificName CommonName mean s.e. mean s.e. mean s.e. mean FISH *Anthopagrus aust rails yellow-finned bream 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 *Achoodus viridis blue groper 2.92 1.25 2.50 1.44 0.42 0.42 0.25 0.25 0.00 0.00 Ambassisjacksoniensis perchiet 0.42 0.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Arenigobius bifrenatus bridled goby 1.67 1.67 0.42 0.42 0.00 0.00 0.00 Bat hygobius kreffti goby 0.00 0.00 0.42 0.42 0.00 0.00 1.97 1.33 0.82 Centropogon australis eastern fortesgue 14.50 8.57 7.08 3.49 2.92 0.00 0.42 0.42 Chlorotocella leptorhynchus 0.00 0.00 0.00 0.00 0.00 0.67 1.33 1.33 Dicotolichthys punctuiatus three-barred porcupinefis 2.00 0.67 2.08 0.70 0.67 0.00 0.00 0.00 Enopiosus armatus old wife 0.00 0.001 0.42 0.42 0.00 0.00 0.00 0.001 0.00 Favonigobius exguisitus goby 0.00 0.00 0.00 0.00 0.48 0.42 0.42 Favonigobius lateraiis long-finned goby 0.83 0.83 0.00 0.00 0.83 0.00 0.00 Favonigobius tamarensis goby 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 *Girella tricuspidata blackfish/luderick 0.42 0.42 1.25 0.42 0.00 0.00 2.39 Gobiopterus semivestitus transparent goby 4.83 2.531 20.50 10.95 22.92 18.16 3.75 0.00 *Hypjiophus transiucidus sprat 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 *Hyp.iophus vittatus sandy sprat 0.00 0.001 0.00 0.00 0.00 0.00 0.42 0.42 *Meuschniafrydneti six-spined leatheijacket 1.25 1.251 2.33 0.59 0.42 0.42 0.00 0.00 *Meuschenia trachylepis yellow-finned leatherjacke 0.00 0.00 0.83 0.83 0.00 0.00 0.42 0.42 0.42 0.42 Meuschenia spp. leatheijacket 1.25 1.25 3.17 1.27 0.00 0.00 0.00 0.00 Microcanthus strigatus stripey 0.00 0.00 2.08 2.08 *Nelusetta ayraudi chinaman leatherjacket 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.42 0.00 0.00 Pelates guadrilineatus trumpeter 0.00 0.00 0.00 0.00 0.42 1.67 1.18 0.00 0.00 Pseudogobius olorum swan river goby 2.50 250 0.42 0.42 small-toothed flounder 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Redigobius macrostoina large-mouth goby 0.00 0.00 0.00 0.00 1.25 0.80 *pJbargus sarba tarwhine 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Stigmatopora argus spotted pipefish 0.00 0.00 0.00 0.00 0.001 14.58 6.751 2.29 1.04 Stiginatopora nigra snub-nosed pipefish 7.33 2.15 17.58 6.67 0.00 0.00 0.00 Tetractenos hamiltoni common toadfish 0.42 0.42 0.00 0.00 0.00 0.42 0.42 Urocampus carinirostris pipefish 0.42 0.42 4.33 1.42 2.50 0.83 CRUSTACEA 0.00 0.00 0.00 0.00 Aipheid spp. snapping shrimp 0.00 0.001 0.42 0.42 €'.1 r....1,... 1.67 1.671 0.00 0.001 6.251 3.62L 0.42 0.42 collectea Appendix B. Mean and standard error per site of fish and mobile invertebrates I Illawarra on 8-9/11/93. ______I I I N.B. indicates species of commercial value by beam trawling In Lake B WCS=Windang Channel South * Location Key GBA=Griffins Bay A I __ GBB=Griffins Bay GBB 4 WCS 5 WCS 6 _____ Sites 1-10 GBA 1 GBA 2 GBB 3 ___ s.e. mean s.e. mean s.e. mean s.e. mean s.e. Scientific Name Common Name mean s.e. mean 0.48 0.83 0.83 0.42 0.42 1.83 1.07 0.00 0.00 Halicarsinus ovatus 0.25 0.25 0.75 57.34 275.00 84.87 417.71 40.99 2922.75 1066.92 4879.42 815.17 Macrobrachium intermedium carid shrimp 326.75 153.65 148.92 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Order Mysidacea 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.50 0.50 0.00 0.00 Nectocarcinus ovalipes 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 *p jnus pelagicus blue swimmer crab 0.00 0.00 0.00 0.71 0.83 0.48 2.50 1.08 0.00 0.00 1.25 0.80 *penus plebejus eastern king prawn 1.83 0.80 1.92 MOLLUSCA ______0.42 0.00 0.00 0.00 0.00 0.00 0.00 6.25 3.62 0.00 0.00 0.42 Bivalve sp. A 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Bivalve sp. B 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.08 2.08 4.17 3.63 Gastropod sp. A 0.42 0.42 1.67 1.67 0.00 0.00 0.00 0.00 16.25 9.39 11.67 6.16 Gastropod sp. B 0.25 0.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.42 0.42 Gastropod sp. C 0.00 0.00 0.00 0.00 0.00 0.00 1.46 0.86 0.25 0.25 1.83 0.82 Idiosepius notoides squid 1.08 0.79 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 cf Sublinella ______0.00 0.00 839.45 393.92 155.86 227.75 60.06 516.92 143.87 672.58 4-4.76 3109.92 1102.79 Total abundance E- 1.95 3.42 0.71 6.50 1.65 7.75 2.99 6.42 1.66 Total commercial species 6.92 2.32 8.50 1.19 10.00 1.22 10.00 0.71 15.50 2.47 0.75 Total number of taxa 11.75 0.85
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N.B. indicates species of commercial value * Location Key WCN=Windang Channel North ES=Eastern_Shore Sites 1-10 WCN 7 WCN 8 ES 9 ES 10 Scientific Name Common Name mean s.e. mean s.e. mean s.e. -mean s.e. Halicarsinus ovatus 0.42 0.42 0.42 0.42 0.00 0.00 0.00 0.00 Macrobrachium intermedium carid shrimp 185.08 59.71 399.33 129.59 50.42 30.85 10.42 2.08 Order Mysidacea 0.00 0.00 0.00 0.00 0.42 0.42 0.00 0.00 Nectocarcinus ovalipes 0.42 0.42 0.00 0.00 0.42 0.42 0.00 0.00 *p.tunus pelagicus blue swimmer crab 0.00 0.00 0.00 0.00 0.00 0.00 0.67 0.67 *penaeus plebejus eastern king prawn 1.25 1.25 0.42 0.421 1.25 1.25 0.00 0.00 MOLLUSCA ______Bivalve sp. A 5.83 5.83 0.42 0.42 16.25 16.25 0.75 0.75 Bivalve sp. B 0.42 0.42 0.00 0.00 2.08 2.08 0.00 0.00 Gastropod sp. A 7.92 4.581 1.25 0.80 1.67 1.67 0.25 0.25 Gastropod sp. B 22.08 17.451 11.67 2.26 15.00 6.27 1.50 1.19 Gastropod sp. C 0.42 0.421 0.00 0.00 0.00 0.00 0.00 0.00 Idiosepius not oides squid 0.00 0.00 0.42 0.42 0.00 0.00 0.00 0.00 cf. Sublinella 0.83 0.83 0.00 0.00 0.42 0.42 0.00 0.00
Total abundance 265.83 82.30 476.58 134.73 142.75 29.09 24.63 6.87 Total commercial species 5.831 2.101 7.33 2.151 2.08 1.58 1.33 1.03 Total number of taxa 10.251 1.491 12.25 1.801 9.501 2.06 5.75 1.44 Appendix C: Mean and standard error of fish and mobile invertebrates collected by beach N.B. * indicates species of commerical value seining in Lake illawarra on 8-9/11193 F7I ______I I Location Key (Sites 1-10) GBA=GriffinsBay A GBB=GriffinsBayB WC=Windang Channel I GBA 11 GBA 2 GBB 3 GBB 4 WC 5 WC 6 Scientific Name Common Name mean s.e. mean s.e mean s.e mean s.e mean s.e mean s.e FISH ______*Acanthopagrus aust rails yellow-fin bream 0.001 0.00 0.001 0.00 4.00 1.08 14.50 10.331 1.25 0.95 1.00 1.00 *Acho dus viridis blue groper 0.00 0.00 0.001 0.00 11.00 4.80 2.50 1.191 13.50 2.53 5.251 2.29 Ambassisjacksoniensis perchlet 0.00 0.00 0.00 0.00 454.001 68.67 148.00 40.53 5.50 2.06 136.75 105.62 *Allzlllof retis rostratus long-snou ted flounder 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 *Ancuilla aust rails short-finned eel 0.00 0.00 0.00 0.00 0.00 0.00 1.50 1.50 0.00 0.00 0.00 0.00 Arenigobius bfrenatus bridled goby 0.00 0.00 0.00 0.00 4.25 2.32 5.25 1.70 0.00 0.00 2.25 1.44 Atherinosoma microstoina hardy-head 18.001 16.35 552.251 252.63 2.75 2.75 11.50 7.68 0.00 0.00 1251 1.25 Centropogon aust rails eastern fortesgue 0.251 0.25 0.001 0.00 6.251 2.66 5.25 1.11 4.25 1.65 1.00 0.71 Dicotoiichthys punctulatus three-barred porcupinefish 0.001 0.00 O.00l 0.00 0.001 0.00 0.00 0.00 0.50 0.29 0.00 0.00 Enoplosus armatus old wife 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 Favonigobius exquisitus goby 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 Favonigobius lateralis long-finned goby 0.50 0.50 0.25 0.25 0.00 0.00 0.00 0.00 29.75 15.04 13.75 11.45 0.25 Favonigobius tamarensls goby 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 0.25 0.25 0.25 *Gerres subfas ciat us silverbiddy 0.00 0.00 0.25 0.251 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 *Girelia tricuspidata blackfish/luderick 0.00 0.00 0.00 0.001 28.50 7.641 2.25 1.931 19.25 8.39 25.50 4.50 Gobiopterus semivestitus transparent goby 10.00 5.29 4.25 1.49 364.00 142.68 9.25 6.42 109.75 28.66 83.25 26.36 *Hypo4jmphus regularis river garfish 1.00 0.41 1.25 0.75 7.25 2.78 5.25 4.311 0.25 0.25 0.001 0.00 0.48 *Liza argentea flat-tail mullet 0.00 0.00 0.00 0.00 25.50 11.79 33.75 30.451 0.50 0.29 0.75 *Meusclwniafrycineti six-spined leatherjacket 0.00 0.00 0.001 0.00 4.00 1.68 0.25 0.25 6.50 2.40 15.75 6.82 *Meuschenia trachylepis yellow-finned leatherjacket 0.001 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.75 0.48 1.25 1.25 0.00 0.00 Micrcanthus strigatus stripey 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.25 0.25 *Mugji cephalus sea mullet 0.001 0.00 0.00 0.00 4.25 3.92 5.00 3.54 0.75 0.75 0251 2.00 2.00 *M.yxus elongatus sand mullet 0.00 0.00 5.00 2.86 24.50 13.37 26.25 14.091 14.50 12.55 *Nelusetta ayraudi chinaman leatherjacket 0.00 0.00 0.001 0.00 0.50 0.50 0.00 0.00 0.00 0.00 0.25 0.25 0.25 Pandaculus lidwilli 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 Pelates guadrilineatus trumpeter 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 0.25 0.25 0.25 0.25 0.00 Philypnodon grandiceps gudgeon 0.001 0.00 0.00 0.00 0.50 0.291 0.00 0.00 0.00 0.00 0.00 *Piatycephaius caeruleopunctatus eastern blue-spoted flathead 0.00 0.00 0.00 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 *pycephalusfuus dusky flathead 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 *Po tus saltatrix tailor 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.00 Pantophilus intermedius 0.00 0.00 0.00 0.00 3.25 3.25 0.00 0.00 0.00 0.00 0.00 5.48 olor n rive OL 101.50 29.12 160.75 35.09 88.75 20.62 54.50 5.39 5.00 2.48 13.00 UUidrrr n w ieUI UIIltO flor' 00 öoo 00 0 00 00 OCI ------
N.B. indicates species of commerical value * Location Key (Sites 1-10) BH=Boat Harbour HB=Hennegar Bay BH7 BH8 HB9 HBIO Scient1ic Name Common Name mean s.e meanj s.e mean s.e mean s.e FISH *Acnutllopagrus australis yellow-fin bream 7.50 0.96 2.00 1.00 0.00 0.00 1.00 0.41 Ac/iocradus viridis blue groper 0.001 0.00 6.25 1.55 0.00 0.00 0.25 0.25 Auilassisiacks'onicnsiS perchlet 30.751 17.05 6.25 3.59 1.50 1.19 11.50 6.51 long-snouted flounder 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Au.uifIn nustmiis short-finned eel 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 Arcui'obius bifrenatus bridled goby 2.25 0.95 0.001 0.00 0.00 0.00 0.00 0.00 Atherinosoma rnicrostoma hardy-head 5.25 2.78 0.25 0.25 0.00 0.00 0.00 0.00 Centropogon aust rails eastern fortesgue 0.50 0.29 7.50 4.52 0.25 0.25 0.75 0.75 Dicotolichthys punctuiatus three-barred porcupinefish 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Enopiosus arm atus old wife 0.001 0.00 0.00 0.00 0.50 0.50 0.00 0.00 Favonicobius exguisitus goby 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Favonigobius interalis long-finned goby 0.251 0.25 0.00 0.00 0.75 0.48 0.25 0.25 Favoniçobius tnmarensis goby 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 *Gcrres subfasciatus silverbiddy 0.001 0.00 0.00 0.00 0.00 0.00 1.25 0.95 *Girella tricuspidata blackfish/luderick 8.751 2.10 3.00 0.82 0.75 0.48 1.75 1.44 Gobiopterus senzivestitus transparent goby 13.001 9.72 8.501 2.72 6.25 3.22 36.75 32.75 *Hyporhinzphus reguiaris river garfish 0.251 0.25 1.001 1.00 0.00 0.00 0.00 0.00 *Liw argentea flat-tail mullet 3.251 1.89 0.00 0.00 0.00 0.00 0.50 0.50 *Meuscheniafreycineti six-spined leatherjacket 0.001 0.00 0.00 0.00 0.25 0.25 0.75 0.75 *Meuschenia trachyiepis yellow-finned leatherjacket 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Micnxanthus strigatus stripey 0.001 0.00 0.00 0.00 0.00 0.001 0.00 0.00 *Mugil cephalus sea mullet 1.001 0.58 0.251 0.25 1.25 1.25 3.75 2.43 *Myys elan gatus sand mullet 9.501 3.59 31.751 21.83 18.00 9.08 4.50 2.10 *Neiusetta ayraudi chinaman leatherjacket 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 Pandaculus lidwilli 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.00 Pelates guadrilineatus trumpeter 0.00 0.00 0.251 0.25 0.001 0.00 0.00 0.00 Phiiypnodon grandiceps gudgeon 0.00 0.00 O.00j 0.00 0.001 0.00 0.00 0.00 *Platycephalus caeruleopunctatus eastern blue-spoted flathead 0.25 0.25 0.00 0.00 0.00 0.00 0.00 0.00 *pphalus frus dusky flathead 0.50 0.29 0.00 0.00 0.50 0.50 0.25 0.25 *Ptus saltatrix tailor 0.00 0.00 0.00 0.00 0.25 0.25 0.25 0.25 Pontophilus interniedius 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Pseudogobius olorum swan river goby 67.501 15.37 33.00 7.60 13.00 2.04 16.00 4.97 *ps dor fr( n4us ienvnsii small-toothed flounder 0.251 0.25 0.00 0,001 0.00 0.00 0.00 0.00 Appendix C Mean and standard error of fish and mobile invertebrates collected by beach N.B. indicates species of commerical value seining in Lake Illawarra on 8-9/11J93 1 I ______1 * Location Key (Sites 1-10) GBA=GriffinsBay A I GBBrGriffinsBay B WC=Windang Channel GBA I GBA 2 GBB 3 GBB 4 WC 5 WC 6 0.25 3.25 0.85 25.50 8.80 1i1?us nincrostonia large-mouth goby 1.50 1.50 0.001 0.00 2.00 0.91 0.25 0.00 0.00 *R 1nbdocnrssarba tarwhine 0.00 0.00 0.00 0.00 10.50 5.81 47.00 25.341 1.25 0.95 0.00 *Silklgociliata sand whiting 0.25 0.25 1.75 1.11 7.50 2.25 5.50 3.23 0.75 0.75 0.00 0.25 0.00 0.00 8.50 2.40 7.50 1.04 Stiginniopora nigra spotted pipefish 0.00 0.00 0.00 0.00 0.25 0.00 0.00 0.00 0.00 0.00 0.00 *Sy,lnpttlra nigra black sole 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.50 0.29 0.00 0.00 Tot ract coos glaher smooth toad fish 0.00 0.00 0.001 0.00 0.00 0.00 0.00 0.001 1.00 0.71 0.00 0.00 Tot ruotciws hamiltoni common toad fish 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.001 1.00 0.41 0.00 0.00 Torguigenerpleurogramnia banded toadfish 0.001 0.00 0.00 0.00 0.00 0.00 0.001 0.25 0.25 0.00 0.00 *Upeichthys porosus goatfish 0.001 0.00 0.00 0.00 0.00 0.00 0.00 7.15 8.50 6.031 3.50 1.44 1.75 0.75 Urocampus carinirostris snub-nosed pipeflsh 2.50 1.04 2.00 0.91 19.50 CRUSTACEA 250.25 147.27 30.50 5.24 944.251 224.36 4248.50 1320.30 Macrobrachium in! ermedium carid shrimps 413.75 268.65 198.25 16.361 0.00 0.00 0.50 0.50 0.75 0.75 0.00 0.00 Nectocarcinus tuberculosus 0.501 0.50 0.00 0.00 16.00 11.81 8.50 2.90 18.25 9.07 0.25 025 *penaeus plebejus eastern king prawn 3.751 2.59 21.50 6.40 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 pelagicus blue-swimmer crab 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.50 0.50 0.00 0.00 0.00 0.00 Grapsid Sp. A crab 0.25 0.25 0.00 0.00 0.00 0.00 0.25 0.25 0.00 0.00 0.00 0.00 Halicarsinus ovatus 0.00 0.00 0.00 - MOLLUSCA 0.75 0.7.51 0.00 0.00 1.00 0.41 0.75 0.48 Idiosepius not aides squid 0.00 0.00 0.00 0.00 272.02 1340.50 148.13 426.50 65.21 1197.75 220.73 4588.50 1401.56 Total abundance 553.75 291.03 947.50 201.00 38.31 214.75 68.21 108.50 53.2.51 57.00 11.03 Total commercial species 5.00 2.12 40.25 16.54 1.03 19.25 1.49 16.25 1.111 21.00 1.781 15.25 1.80 Total numberof taxa 7.00 1.22 8.25 ------
N.B. indicates species of commerical value * Location Key (Sites 1-10) BH=Boat Harbour HB=HennegarBay BH7 BH8 HB9 HBIO nu?crostoula large-mouth goby 1.00 0.71 0.001 0.00 1.00 1.00 0.50 0.50 RJinbdosarçus sarba tarwhine 7.00 2.42 3.25 2.63 1.75 0.48 1.25 0.63 Sii1nço cilbita sand whiting 4.50 1.66 6.75 2.87 4.75 4.42 5.75 4.80 Stiml1n,rn ni,cra spotted pipefish 0.00 0.00 0.25 0.25 0.25 0.25 0.25 0.25 5ninptura_nira black sole 0.25 0.25 0.00 0.00 0.00 0.00 0.00 000 TL'trwtcnos ghthcr smooth toadfish 0.00 0.00 0.001 0.00 0.00 0.00 0.00 000 /ui)Ui1!Oflj common toadfish 0.25 0.25 0.00 0.00 0.50 0.29 0.00 0.00 Torijuiçencrplcurogramnia banded toadfish 0.00 0.00 0.25 0.25 0.00 0.00 0.00 0.00 LJpencic1iihysporosus goatfish 0.001 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Llrocnnzpus carinirostris snub-nosed pipefish 6.00 0.91 4.75 2.17 0.50 0.50 0.25 0.25 CRUSTACEA ______Macrobraclijum interniediurn carid shrimps 2.00 1.68 1.75 1.44 2.00 1.08 15.50 9.73 Nectomrcintis tuberculosus 0.25 0.25 0.00 0.00 0.25 0.25 0.00 0.00 *pcflaclls plebeus eastern king prawn 31.251 3.84 27.50 6.54 4.00 1.83 4.00 216 *poI.tluil(s polo çicus blue-swimmer crab 0.251 0.25 0.50 0.50 0.00 0.00 0.00 0.00 Grapsid Sp. A crab 0.00 0.00 0.00 0.00 0.00 0100 0.00 0.00 Halicarsinus ovatus 0.00 0.00 0.001 0.00 0.25 0.25 0.00 0,00 MOLLUSCA Idiosepius not oides squid - 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total abundance 203.50 16.41 145.00 11.20 58.50 13.11 107.00 49.48 Total commercial species 95.50 14.81 146.25 61.74 70.00 35.69 44.25 16.28 Total number of taxa 16.251 0.631 13.501 0.65 10.25 1.65 11.50 1.71 Appendix D: Commercial Fishing Data - Lake Illawarra July 1984 - June 1993 Source: NSW Department of Fisheries, Database Section, Fisheries Research Institute
River garfish June Total July August Sept Oct Nov Dec Jan Feb March April May 1205 11103 1985 796 1687 1678 3431 225 45 0 222 464 589 761 502 10083 1986 1868 1066 2819 1634 0 0 0 722 351 800 321 423 6665 1987 1565 1708 691 322 40 0 23 4 205 1183 501 3040 1988 0 161 412 31 14 0 0 135 887 859 386 155 587 6192 1989 472 736 756 525 219 0 7 852 1433 96 509 31 9312 1990 285 1532 2129 1171 844 0 0 1654 905 405 356 6885 1991 96 49 3852 1327 80 0 0 96 267 470 569 79 296 11949 1992 683 741 5684 3009 445 0 5 436 185 142 323 8153.63 m eai 720.63 960 2252.6 1431.3 233.38 5.625 4.375 515.13 587.13 568 465.75 409.75 s.e. 238.96 231.18 641.78 435.49 101.9 5.625 2.8343 194.89 157.41 130.77 53.566 133.84 1052.13
Total flathead July August Sept Oct Nov Dec Jan Feb March_April May June Total 1985 1625 169 16 18 25 25 56 6 760 1232 1616 295 5843 1986 134 0 351 37 65 56 72 105 187 284 675 10892 12858 1987 2124 420 68 38 41 85 59 436 253 459 736 6752 11471 1988 596 377 110 166 199 168 373 480 717 989 2296 3462 9933 1989 1322 716 260 399 649 398 771 719 647 1097 2835 6745 16558 1990 1277 1419 428 113 118 169 214 1377 1866 938 2813 6753 17485 1991 7393 1353 125 598 43 16 97 106 116 275 1091 9899 21112 1992 4434 895 100 79 139 143 167 108 192 510 1193 5577 13537 meai 2363.1 668.63 182.25 181 159.88 132.5 226.13 417.13 592.25 723 1656.9 6296.9 13599.6 s.e. 1 850.9 18557 51.905 73.73 72.942 43.595 86.541 162.33 204.22 135.25 312.89 1189.9 1684.9
Total whiling - July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 1 0 0 0 0 0 0 0 80 19 29 31 160 1986 199 24 441 336 0 16 27 2 10 0 39 364 1458 1987 436 493 1031 237 5 39 6 10 30 97 178 55 2617 1988 18 32 2 16 4 14 11 0 26 48 18 671 860 1989 412 175 469 420 41 0 4 0 7 83 20 1432 3063 1990 225 193 15 0 0 14 0 97 4 50 56 184 838 1991 241 28 104 12 22 0 21 63 14 9 26 504 1044 1992 354 223 71 404 70 5 3 11 108 59 35 97 1440 mear 235.75 146 266.63 178.13 17.75 11 9 22.875 34.875 45.625 50.125 417.25 1435 s.e. 58.12 58.631 128.51 67.514 9.049 4.679 3.5456 12.968 13.543 12.227 18.759 165.93 341.049
silver biddy July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 0 217 83 128 72 60 10 0 0 0 217 174 961 1986 178 549 3546 1517 764 736 39 3 0 1 122 1556 9011 1987 3558 2769 1995 521 0 9 0 0 0 303 382 406 9943 1988 26 62 249 94 0 0 0 0 0 0 14 1179 1624 1989 1422 1093 817 396 121 0 30 42 5 0 2 2255 6183 1990 548 260 85 265 37 97 62 0 0 12 27 832 2225 1991 136 0 49 385 935 64 48 57 0 0 12 0 1686 1992 2509 2183 2351 2650 13 36 15 0 12 42 48 122 9981 mea 1047.1 891.63 1146.9 744.5 242.75 125.25 25.5 12.75 2.125 44.75 103 815.5 5201.75 s.e, 473.51 370.51 468.75 315.14 134.15 88.103 8.1196 8.152 1.5404 37.249 47.51 282.78 141925 Commercial Fishing Data - Lake illawarra July 1984 - June 1993 Source: NSW Department of Fisheries, Database Section Fisheries Research Institute
bream - July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 149 935 1309 3022 2459 759 474 1510 5901 4527 1233 1225 23503 1986 1136 537 1090 2183 1642 1450 5480 5353 7113 7065 3400 2715 39164 1987 1544 1171 2267 2350 1191 2229 3486 4563 4572 3649 4593 2140 33755 1988 1258 604 621 684 1420 608 1745 3539 1509 3963 3470 467 19888 1989 571 200 350 444 785 131 358 678 568 1317 2426 2065 9893 1990 278 378 365 463 921 241 429 904 1511 2387 1748 1460 11085 1991 2835 1604 3734 2731 758 132 331 309 593 1863 1819 1703 18412 1992 390 188 322 186 419 386 566 858 1152 2081 1665 1504 9717 meal 1020.1 702.13 1257.3 1507.9 1199.4 742 1608.6 2214.3 2864.9 33565 2544.3 1659.9 20677.1 s.e. 314.72 17657 424.33 414.11 226.95 262.33 674.71 696.49 918.28 661.89 410.86 238.53 3907.33
I mulloway Oct Nov Dec Jan Feb March April May June Total 1985 0 0 2 0 0 0 0 0 13 70 13 21 119 I 1986 5 0 50 0 0 0 45 17 37 68 40 140 402 1987 17 6 4 0 2 0 4 32 74 289 223 287 938 1988 38 2 0 0 0 0 73 29 101 0 5 48 296 I 1989 5 24 2 0 0 1 123 4 9 82 29 92 371 1990 132 59 1 0 2 0 0 0 16 7 1 79 297 1991 54 120 43 0 0 40 21 3 0 57 31 54 423 I 19921 107 2 0 18 90 37 61 376 172 254 40 31 1188 meal 44.75 26.625 12.75 2.25 11.75 9.75 40.875 57.625 52.75 103.38 47.75 94 50425 I s.e. 117.704 15.136 7.4084 2.25 11.183 6.2813 15.408 45.707 21.076 38.287 25.595 30.65 128.536 luderick July August Sept Oct Nov Dec Jan Feb March April May June Total I-1985 800 1252 1021 803 452 336 403 550 2183 1162 455 207 9624 1986 627 315 1041 458 539 307 1447 3546 4144 2663 2041 1638 18766 1987 1472 1235 3616 2165 1447 2708 3291 3586 4243 2889 3554 1002 30983 1988 669 818 518 737 1259 1895 3359 4161 5622 3317 3192 1655 27202 I 1989 2407 940 1353 1571 883 493 951 1811 2447 1053 3098 2477 19484 1990 535 1780 1890 596 636 771 1546 2565 3069 3082 1699 1439 19608 1991 967 979 1595 468 449 139 281 897 1546 3030 2736 2069 15156 I 1992 1679 1430 1510 933 640 413 1618 1505 2638 1358 1515 1060 16299 mear 1116.4 1093.6 1568 966.38 788.13 882.75 1612 2327.6 3236.5 2319.3 2286.3 1443.4 19640.3 I s.e. 22754 155.17 328.08 212.41 133.63 32527 413.45 475.02 47254 337.85 369.41 246.87 2383.82 sea mullet - July August Sept Oct Nov Dec Jan Feb March April May June Total I 1985 1755 2463 324 449 673 903 986 1220 3612 1520 4174 980 19059 1986 1198 3057 8032 2822 4423 3935 7338 6166 2772 1936 3292 1250 46221 1987 5954 2566 2201 649 1542 2518 10878 12439 8096 2421 4413 6261 59938 I 1988 8937 3384 1206 4629 2509 3116 9311 7048 9599 3497 3488 2313 59037 1989 2594 6614 1290 2347 3986 5186 10398 11486 12965 4836 4611 3849 70162 1990 1674 1849 1837 1809 2153 2197 5039 4716 5533 5433 2325 9322 43887 I 1991 6846 7376 3850 4579 1187 1645 4355 7947 7579 2970 2656 2851 53841 1992 4867 3444 4566 6276 3389 1469 4648 5070 9674 2884 905 4352 51544 mear 4228.1 3844.1 2913.3 2945 2482.8 2621.1 6619.1 7011.5 7478.8 3187.1 3233 3897.3 50461.1 I s.e. 1008.1 715.38 883.68 729.07 477.98 499.51 12205 12932 1200.4 4805 439.61 985.13 5364.18 Commercial Fishing Data - Lake Illawarra July 1984 - June 1993 Source NSW Department of Fisheries, Database Section, Fisheries Research Institute total mullet July August Sept Oct Nov Dec Jan Feb March April May June Total 980 19135 1985 1755 2463 324 449 685 903 986 1220 3612 1565 4193 1986 1210 3074 8316 2822 4423 4017 7370 7373 2965 2075 3460 1607 48712 1987 6644 2829 2357 1325 1544 2596 11399 12467 8638 2565 4726 8171 65261 1988 9042 3384 1206 4629 2509 3116 9311 7048 9599 3497 3488 2335 59164 1989 3447 7615 7224 2853 4034 5186 12845 11486 12965 4875 4683 7252 84465 1990 3198 3063 1951 1839 2204 2197 5039 5831 5585 5509 2644 10669 49729 1991 8804 8239 4136 4663 1231 1645 4376 7947 7587 2989 2661 2884 57162 1992 5254 3622 5483 6276 3440 1469 4648 5070 9674 2947 905 4721 53509 54642.1 meai 4919.3 4286.1 3874.6 3107 2508.8 2641.1 6996.8 7305.3 7578.1 3252.8 3345 4827.4 6478.41 s.e. 1069.7 805.94 1029.3 691.46 478.84 503.23 1410.6 1259.3 1192.3 475.35 450.46 1241.8
leatherjacket - July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 104 68 0 0 16 0 0 11 8 429 149 49 834 1865 1986 182 0 43 2 7 8 13 535 82 86 213 694 1987 575 290 134 14 18 4 25 37 20 51 150 219 1537 2586 1988 76 103 47 13 8 23 153 377 269 477 415 625 1218 1989 236 161 17 5 19 24 10 0 0 66 193 487 1990 258 27 12 0 0 20 45 46 48 55 95 51 657 1991370 0 3 4 0 0 0 0 1 130 0 9 517 1992 3 0 0 0 0 0 0 0 0 26 16 108 153 meai 225.5 81.125 32 4.75 8.5 9.875 30.75 125.75 53.5 165 153.88 280.25 1170.88 s.e. 64.463 36.187 15.96 2.0244 2.9155 3.7911 18.305 73.855 32.447 63.909 46.176 98.726 282.269
total finfish - July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 5426 8247 5118 8807 4124 2315 2328 4360 13374 10306 9223 4452 78080 1986 5799 5704 18277 9567 7954 7114 16656 21136 15335 13562 19627 24063 164794 1987 19613 17641 15362 13141 6596 9368 21936 22263 19757 12764 17017 22009 197467 1988 13939 5663 3450 10664 7179 10172 16586 21011 24505 18368 17253 14132 162922 1989 12036 12927 12761 8306 7398 7698 18313 16594 18710 10938 14725 25878 166284 1990 8046 10319 8157 4796 5318 3720 7890 13164 13808 12878 10195 23382 121673 1991 21584 12680 14544 11110 3875 2675 8115 10326 11508 12220 10934 18107 137678 1992 16034 9907 15777 14192 6175 5017 9468 10508 14960 11120 7150 15865 136173 meari 12810 10386 11681 10073 6077.4 6009.9 12662 14920 16495 12770 13266 18486 145634 s.e. 2162.6 1423 1920 1040.5 534.53 1066.3 2351.8 2266.3 14955 890.72 1587.8 2482.3 127262
cockles - July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 0 25 0 0 0 0 0 0 0 0 0 0 25 1986 0 0 0 0 0 0 0 0 0 0 0 68 68 1987 0 0 0 0 0 0 0 616 76 361 0 0 1053 1988 0 772 5366 4986 4497 105 0 0 79 0 0 0 15805 1989 98 0 0 962 0 0 78 0 0 0 0 0 1138 1990 0 0 0 0 0 0 0 0 99 0 132 67 298 1991 4445 3754 4251 3339 28 0 0 117 117 601 2580 2344 21576 1992 3111 3336 6994 8023 3666 3712 5163 2388 6110 4962 5331 3429 56225 meai 956.75 985.88 2076.4 2163.8 1023.9 477.13 655.13 390.13 810.13 7405 1005.4 7385 120235 s.e. 62853 567.61 10462 1067.8 671.84 462.31 644.05 295.14 757.31 608.37 694.46 479.93 6972.59 Commercial Fishing Data - Lake illawarra July 1984 - June 1993 I Source: NSW Department of Fisheries, Database Section, Fisheries Research Institute
eastern king prawn I - July August Sept Oct Nov Dec Jan Feb March April May June Total 1985 146 20 752 688 1554 3869 7580 8196 3336 2340 36 36 28553 1986 0 0 9 375 3535 2484 2401 2173 460 173 371 43 12024 10846 I 187 0 72 165 1045 1806 2646 503 1676 1038 1555 338 2 8611 1988 0 74 503 825 1768 2526 1092 1450 288 85 0 0 10720 1989 0 102 137 232 2060 1153 1751 1879 3092 278 36 0 I 1990 0 0 365 2095 5206 5567 3088 405 278 30 4 13 17051 1991 0 0 0 289 4813 4870 5290 2180 2615 133 22 0 20212 1992 0 0 7 359 186 404 3292 1430 1128 336 4 0 7146 m eai 18.25 33.5 242.25 738.5 2616 2939.9 3124.6 2423.6 1529.4 616.25 101.38 11.75 14395.4 s.e. 18.25 14.932 97.136 218.71 613.78 620.76 823.58 848.4 453.9 301.82 55.546 6.287 2532.17
1 school prawn - July August Sept Oct Nov Dec Jan Feb March April May June Total 3109 1985 0 0 187 152 189 603 80 259 414 170 1041 14 I 1986 0 0 94 282 665 581 232 88 153 66 138 97 2396 1987 9 0 60 602 809 423 114 266 40 145 79 0 2547 1988 0 51 174 415 485 831 397 76 95 28 0 0 2552 I 1989 0 11 94 230 765 1194 200 707 670 50 30 0 3951 1990 1020 0 200 462 1448 3678 3283 138 457 754 4 0 11444 1991 0 0 70 261 3450 4209 3131 2120 539 21 22 0 13823 I 1992 0 0 7 1035 302 232 1000 112 87 150 8 0 2933 mea 128.63 7.75 110.75 429.88 1014.1 1468.9 1054.6 470.75 306.88 173 165.25 13.875 5344.38 s.e. 127.34 6.3267 24.4 100.41 37359 551.5 480.96 246.56 85.345 85.523 12621 12.001 1615.56 I mud crabs July August Sept Oct Nov Dec Jan Feb March April May June Total I-19850 7 0 0 0 0 224 0 265 12 7 4 519 1986 0 0 3 4 0 0 1 4 15 3 12 19 61 1987 1 0 3 2 0 0 0 12 13 12 18 2 63 1988 0 0 1 5 12 16 130 42 26 84 41 20 377 I 1989 5 0 3 6 23 5 23 10 16 33 53 28 205 1990 0 14 2 8 8 14 15 72 98 571 97 75 974 1991 28 1 12 35 17 16 28 42 66 68 59 165 537 I 1992 45 7 9 20 39 56 48 79 179 165 54 41 742 mear 9.875 3.625 4.125 10 12.375 13.375 58.625 32.625 84.75 1185 42.625 44.25 434.75 I s.e. 6.0576 1.8414 1.4692 4.1619 4.8585 6.598 27.846 10.936 32.758 67.347 10.588 19.101 114.701 blue swimmer crabs - July August Sept Oct Nov Dec Jan Feb March April May June Total I 1985 0 0 0 0 0 2 16 0 0 28 37 15 98 1986 0 0 241 0 0 20 16 8 10 191 122 136 744 1987 1 0 1 2 12 10 14 19 8 0 32 0 99 I 1988 0 0 0 0 0 0 0 0 0 0 0 0 0 1989 0 0 0 0 0 0 0 0 0 0 0 0 0 1990 0 0 0 0 0 0 0 0 0 0 0 0 0 I 1991 0 0 0 0 0 0 0 0 0 39 163 214 416 1992 14 3 0 0 13 62 163 64 103 334 906 625 2287 I mear 1.875 0.375 30.25 0.25 3.125 11.75 26.125 11.375 15.125 74 1575 123.75 455.5 s.e. 11.7366 0.375 30.107 0.25 2.048 7.6105 19.738 7.8897 12.637 43.616 109.07 77.07 277.634 Commercial Fishing Data - Lake fllawarra July 1984 - June 1993 Research Institute Source: NSW Department of Fisheries, Database Section, Fisheries
total spedes Total July August Sept Oct Nov Dec Jan Feb March April May June - 110784 1985 5578 8299 6072 9647 5876 6789 10228 12821 17428 13065 10460 4521 184595 1986 5892 5704 19136 10409 12170 10251 19306 23449 15983 14667 21893 25735 24785 259855 1987 28284 22459 20278 20733 13630 17132 24643 27005 23926 16953 20027 16933 225740 1988 17669 8035 9867 16909 17408 15166 23918 27119 30001 22075 20640 213280 1989 16769 13831 16629 13093 16133 12643 21804 22557 24409 12730 15952 26730 25819 174247 1990 12644 14044 12189 10180 14146 13472 14431 14065 15518 15713 12026 20932 226115 1991 26060 16437 18897 15493 19140 19994 25921 19257 16522 13621 13841 218696 1992 19233 13254 22805 24682 11425 10747 23182 18296 23095 18536 13458 19983 201664 meaji 16516 12758 15734 15143 13741 13274 20429 20571 20860 15920 16037 20680 15974.8 s.e. 12945.5 1902.3 2041.4 1922.3 1452.7 1473.8 1940.5 1917 1858.7 1126.1 1524 2608.8 I