Baywide Recreational Fishery Surveys Sub-Program

Progress Report No. 2 (Edition 2)

(May–Sept. 2008).

Simon Conron, Natalie Bridge, Daniel Grixti and Karina Ryan

April 2009 Fisheries Technical Report Series No. 24

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Conron S, Bridge N, Grixti D and Ryan K (2008). Published: Fisheries Victoria Recreational Fishery Surveys Progress Report Department of Primary No.2 (Edition 2)(May–September 2008). Technical Industries, Queenscliff Centre Report Series No.24, Fisheries Victoria, April PO Box 114, Queenscliff, Victoria 2009. Department of Primary Industries, 3225 . Queenscliff, Victoria, Australia. 10 pp.

General disclaimer This publication may be of assistance to you but ISSN 1835-4785 the State of Victoria and its employees do not guarantee that the publication is without flaw of ISBN 978-1-74217-572-0 any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

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Table of Contents

Introduction...... 1 This report...... 1

Project Design and Methods...... 2 On-site surveys...... 2 Catch rate ...... 2 Catch length composition...... 2 Statistical analysis ...... 2 Exceptions ...... 3

Results...... 4 On-site survey methods...... 4 Catch rate ...... 4 Catch length composition...... 4 Raw data ...... 5

Discussion...... 8

References ...... 9

Appendix...... 10

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List of Tables Table 1. On-site survey sample days required, undertaken and used for analysis in each region of PPB for January −April and May–September 2008...... 6

List of Figures Figure 1. Boat ramps of PPB selected for on-site surveys...... 3 Figure 2. Estimated mean catch rates (± 95% confidence limits) of combined species (snapper, and flathead) retained by boat-based anglers fishing within the Melbourne, Mornington and Bellarine regions of PPB during January −April and May −September 2008...... 6 Figure 3. A comparison of the length (TL) frequency distribution of snapper, King George whiting and flathead (all species) retained by boat-based anglers fishing in PPB during January −April and May −September 2008 (n=number of fish measured)...... 7

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Introduction

Fish are an important component of the experienced anglers) record ‘diary’ ecosystem in Port Phillip Bay (PPB). They form information on all fish caught, including the basis of a significant commercial fishery and those below the LML. the largest recreational fishery in Victoria. This sub-program is described in the CDBMP The main species of interest to recreational Recreational Fishery Surveys Detailed Design - anglers in PPB are snapper ( Pagrus auratus ), CDP_ENV_MD_017 Rev 0 (PoMC 2007). flathead (several species; Family Platycephalidae) and King George whiting ( Sillaginodes punctata ). The objective of this sub-program is to detect changes in the abundance and recruitment of key The Recreational Fishery Surveys Sub-Program recreational fishery species outside of expected of the Channel Deepening Baywide Monitoring variability. Programs (CDBMP) for PPB consists of two components: This report • On-site surveys to assess the recreational This report summarises progress results for the catch rates of boat-based anglers: on-site survey component of the sub-program for anglers interviewed on return to the boat the period from late autumn to early spring ramp and detailed data recorded on fishing (May–September 2008). effort and retained catch (i.e. fish above the Legal Minimum Length, LML) • Angler-based assessments of fish stocks: research anglers (a select group of

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Project Design and Methods

The methods and statistical analysis for this sub- • Snapper program are described in the Detailed Design for TL=1.125FL+1.38 (Francis and Winstanley 1989) the sub-program (PoMC 2007). • King George whiting TL=1.0644FL–0.3708 (DPI unpublished data). On-site surveys The primary sampling unit for the on-site survey Catch rate Combined catch rates (measured in fish per component is the number of ‘face to face’ survey angler hour) of the three most commonly caught days. fish species/taxa (snapper, King George whiting Angling in PPP decreases during winter from the and all flathead) for each region during the activity levels seen in spring, summer and survey period were used as an indicator of fish autumn. To maximise contact with anglers, the stock abundance. Catch rates were calculated sampling schedule for the winter reporting using the ratio-of means estimator (Jones et al. period (May–September 2008) were conducted 1995). only at weekends (see Detailed Design). Analysis was based on daily harvest rates, which Surveys were undertaken from May to represent the appropriate level of sampling September 2008 (Table 1), at selected boat ramps around PPB (Figure 1)(see also Exceptions). Boat (Steffe 2008). A review of variation on catch rates ramps were grouped into three key regions: by the number of interviews recorded per survey day indicated comparable variation for two or • Melbourne more interviews. The analysis threshold used for • Mornington this report was based on two or more interviews • Bellarine. per survey day, which is less than those indicated in the Detailed Design (PoMC 2007; see also Anglers were asked to provide information about Exceptions). the fishing trips they completed including: • Target species Catch length composition Length frequency distributions were plotted for • Number of fish of each species retained and snapper, King George whiting and flathead. released • Time spent fishing Statistical analysis • Location fished Catch rate • Level of fishing experience. The Detailed Design for this sub-program A sample of the important recreational species in prescribes that the three most commonly caught the retained catch, namely snapper, King George fish species/taxa (snapper, King George whiting whiting, flathead (all species), Australian and all flathead) will be statistically compared ( trutta ), calamari ( Sepioteuthis australis ) with data from the past 5 years during and garfish (Family Hemiramphidae), were comparable survey periods (PoMC 2008). As inspected, species identified and individuals there were no comparable data for the May– counted and measured. September reporting period prior to 2008, these analyses could not be performed and qualitative Total length was recorded for species with comparisons only were undertaken for other truncate or rounded caudal fins (including reporting periods in 2008. flathead). Fork length (distance from the tip of the snout to the base of the tail fin) was recorded Data were collected from anglers who targeted for species with emarginate or forked caudal fins key species. Estimating mean catch rates from (including snapper and King George whiting). this group of anglers increases consistency in the sampling effort and the reliability of the analyses. For use in all analyses, fork length (FL) was converted to total length (TL) using the following Catch and effort data are aggregated for each regression equations: interview day (to produce a mean daily catch and a mean daily effort). Analysis occurs at the level of these daily aggregates.

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Catch length composition (PoMC 2007) have been documented separately Length-frequency distributions for the reporting in Exception Report ER2008#21 and ER2009#26, period were combined by region and compared and summarised as follows: − statistically with January April 2008 (Conron et • ER2008#21: Late submission of progress report al. 2008) by a Kolmogorov-Smirnov (K-S) two • ER2008#21: Analysis threshold for 'survey sample asymptotic test using SAS PROC days' was lower than the requisite 10 NPAR1WAY (SAS Institute 1989; PoMC 2007). interviews/day. Exceptions • ER2009#26: Incorrect catch rate estimates were provided in Edition 1 of this report. Exceptions for this study period according to the Detailed Design-CDP_ENV_MD_017_Rev 0

Port Phillip Bay catches 2003-08 – Spatial distribution Melbourne

Bellarine

Mornington

Figure 1. Boat ramps of PPB selected for on-site surveys.

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Results

combined species in all regions in On-site survey methods May −September 2008 compared with During the reporting period, catch data were January −April 2008 (Conron et al. 2008). recorded from a total of 327 boat fishing trips. Those trips reported a combined retained catch Catch length composition of 1,015 snapper, King George whiting and The length-frequency composition of the flathead, of which 393 were measured. Across retained catches of snapper, King George the three regions, 36 survey days were whiting and flathead are shown in Figure 3. undertaken (Table 1). Snapper The number of interviews required for May– The TL range for snapper during May– September was determined from a sampling September was 27 to 80 cm, with a mode at 29 schedule of two ‘weekend days’ per region per cm (accounting for 24% of the catch). During month (PoMC 2007). This target was met (Table January–April, snapper TL in retained catches 1). Fewer interviews were recorded during the ranged from 25 to 95 cm, with a mode of 30 cm May–September 2008 study period when (15%). compared with January–April 2008 (Conron et Less than 2% of the snapper catch for the period al. 2008) because fewer anglers fish in PPB January–April and May–September were below during winter. the LML (28 cm). Fish in the size range 28 to 33 Anglers fishing in May–September 2008 were cm comprised 70% of the May–September catch, more likely to be ‘avid’ anglers. When asked compared with 56% of the catch in January– how often they fished in the previous year: April. The proportions of fish > 33 cm TL comprised 28% of the catch in May–September • 8% in January–April fished < 5 days in the previous 12 months compared with 6% in and 42% in January–April 2008 (Conron et al. May–September 2008). • 22% in January–April fished 5 to 14 days in King George whiting the previous 12 months compared with 16% The TL of King George whiting in retained in May–September catches ranged from 24 to 40 cm in May −September and from 25 to 44 cm in • 70% in January–April fished 15 days or January–April 2008. Fish of 28 cm TL were the more in the previous 12 months compared − with 78% in May–September. most common in May September, comprising 17% of the catch. In January–April 2008, fish of The total recreational catch retained by boat 32 cm TL were the most common, comprising based anglers in PPB differed between the 13% of the catch (Conron et al. 2008). reporting periods: The proportion of fish in January–April under • 89% of snapper was taken in January–April the current LML (27 cm) was 1%, compared with compared with 11% in May–September 3% for May −September 2008. Whiting in the size • 90% of King George whiting was taken in range of 27 to 39 cm TL comprised 96% of the January–April compared with 10% in May– catch in May −September, compared with 94% of September the catch in January–April. The proportion of • 68% of flathead was taken in January–April fish > 40 cm TL comprised 1% of the catch in − compared with 32% in May–September. May September, compared with 5% in January– April 2008 (Conron et al. 2008). Catch rate Flathead The mean retained catch rates for all species The TL of flathead in the retained catch ranged combined (snapper, King George whiting and from 24 to 58 cm during May–September 2008, flathead) for each region in the period May- compared with a range of 22 to 55 cm in September 2008 are presented in Figure 2. January–April 2008 (Conron et al. 2008). Fish of There was an apparent decrease in the mean 27 cm TL were most common in the retained retained catch rates (fish per angler hour) for

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catches in May–September compared with 28 May–September and January–April 2008 and 30 cm in January–April. reporting periods were not significantly different for: The proportions of flathead under the current • LML (25 cm) were the same (2%) for May– snapper (K-S test statistic=0.946, p=0.33) September and January–April. The proportion • King George whiting (K-S test of fish above the LML to 34 cm was 86% in statistic=1.139, p=0.15) May–September and 79% in January–April. The • flathead (K-S test statistic=0.804 p=0.54). proportion of fish above 34 cm was 12% in May– September 2008 and 19% in January–April 2008 Raw data (Conron et al. 2008). • Missing data: none. Length distribution Data sets are provided with this report The length-frequency distribution comparison of electronically as two MS Excel worksheets (see the catches retained by boat anglers between the Appendix).

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Table 1. On-site survey sample days required, undertaken and used for analysis in each region of PPB for January −−−April and May–September 2008.

Region

Survey period Sampling days Melbourne Mornington Bellarine Total

January–April Required 10 23 15 48

Undertaken 14 28 18 60

Above survey threshold* 12 17 15 44

Used for analysis** 14 26 18 58

May–September Required # 10 10 10 30

Undertaken 13 12 11 36

Above survey threshold* 5 4 5 14

Used for analysis** 12 11 10 33

# The number of interviews required for May −September was determined from a sampling schedule of 2 ‘weekend days’ region per month (PoMC 2007) * Sample days with less than ten interviews per sample day are considered below the survey threshold (PoMC 2007) ** Sample days with less than the minimum of two interviews per sample day were not used in the analysis

2.5 January-April May-September

2.0

1.5

1.0

0.5 Catchrate (fish/angler hr) 0.0 Melbourne Mornington Bellarine

Figure 2. Estimated mean catch rates (± 95% confidence limits) of combined species (snapper, King George whiting and flathead) retained by boat-based anglers fishing within the Melbourne, Mornington and Bellarine regions of PPB during January −−−April and May −−−September 2008.

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30 snapper

20 May-Sep (n = 50) Jan-Apr (n = 346)

10 Percentage Frequency 0 10 20 30 40 50 60 70 80 90

Total Length (cm) 20 King George whiting

15 May-Sep (n = 106) Jan-Apr (n = 581) 10

5 Percentage Frequency 0 10 20 30 40 50 60 70 80 90

Total Length (cm) 15 flathead

10 May-Sep (n = 237) Jan-Apr (n = 337)

5 PercentageFrequency 0 10 20 30 40 50 60 70 80 90

Total Length (cm)

Figure 3. A comparison of the length (TL) frequency distribution of snapper, King George whiting and flathead (all species) retained by boat-based anglers fishing in PPB during January −−−April and May −−−September 2008 (n=number of fish measured).

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Discussion

Boat-ramp surveys of fish retained by anglers in probable that seasonal responses of fish PPB during May–September 2008 sampled 1,015 populations are affecting catchability. snapper, King George whiting and flathead The length-frequency distributions of snapper, from 327 interviews during 36 survey days. King George whiting and flathead from retained A quantitative assessment of the May- catches by boat based anglers in May– September 2008 survey period in relation to September were within the range of variability levels of natural variability in PPB could not be for these species observed between January– made because there are no comparable historical April 2008. data available for a meaningful statistical The similarity in length-frequency distributions analysis. indicates there has been no change in the The mean retained catch rates of combined population size structure of fish caught by species (snapper, King George whiting and anglers in PPB during May–September 2008, flathead) were variable between regions during compared to January −April 2008. May–September 2008.

A reduction in overall recreational catch rates was apparent in May-September 2008 when qualitatively compared with January-April 2008 (Conron et al 2008). The cause of this reduction cannot be determined categorically, but it is

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References

Conron, S., Bridge, N., Ryan, K.L., Grixti, D. PoMC (2007). Fish stock and recruitment. (2008). Recreational Fishery Surveys Progress Subprogram 1— Recreational surveys. Detailed Report No.1 (Jan.–April 2008). Technical Report design CDP_ENV_MD_017 Rev0. Port of Series No. 9, Fisheries Victoria, June 2008. Melbourne Corporation. Department of Primary Industries, Queenscliff, (www.channelproject.com ). Victoria, Australia. 17 pp. Ryan K, Bridge N, Grixti D and Conron S (2008) Efron, B., Tibshirani, R. (1993). An Introduction to Recreational Fishery Surveys Milestone Report the Bootstrap . Chapman and Hall, New York. No.1 2008. (January–April 2008). Technical Report Series No. 18, Fisheries Victoria, October Francis, R.I.C.C. and Winstanley, R.H. (1989). 2008. Department of Primary Industries, Differences in growth rates between habitats of Queenscliff, Victoria, Australia. 25 pp. and south-east Australian snapper. Aust. J. Mar. Appendices Freshwater Res. 40, 703-710 SAS Institute (1989). SAS/STAT User's Guide, Hoyle, S.D. and Cameron, D.S. (2003). Version 6, Fourth Edition, Volumes I and II, Confidence intervals on catch estimates from a Cary, NC: SAS Institute Inc. recreational fishing survey: a comparison of bootstrap methods. Fisheries Management and Steffe, A. (2007). Peer review for CDPMP Fish Ecology 10, 97-108 Stock and Recruitment Sub-program 3 – Recreational Fishery Surveys Detailed Design. Jones, C.M., Robson, D.S., Lakkis, H.D., Kressel, J. (1995). Properties of catch rates used in analysis of angler surveys. Transactions of the American

Fisheries Society 124, 911–928

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Appendix

Attached EXCEL spreadsheet (Fish3_P2.xls) with two data worksheets: On-site_catch_P2 On-site_length_P2 and relevant metadata as additional worksheets.

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