Survey of Sonar Test Sites, Phase 1, Literature Review

J.F Middleton, C.E James, J.L Luick, S. Goldsworthy, A. Tsolos, C.E.P Teixeira and L. Richardson

SARDI Publication No. F2011/000212-1 SARDI Research Report Series No. 566

ISBN: 978-1-921563-41-6 DSTO Contract No. 4500782641

SARDI Aquatic Sciences PO Box 120 Henley Beach SA 5022

August 2011

Final Report for the Defence Science and Technology Organisation 1

Survey of Sonar Test Sites, Phase 1, Literature Review

Final Report for the Defence Science and Technology Organisation

J.F Middleton, C.E James, J.L Luick, S. Goldsworthy, A. Tsolos, C.E.P Teixeira and L. Richardson

SARDI Publication No. F2011/000212-1 SARDI Research Report Series No. 566

ISBN: 978-1-921563-41-6 DSTO Contract No. 4500782641

August 2011

2 This publication may be cited as: Middleton, J.F., James, C.E., Luick, J.L., Goldsworthy, S., Tsolos, A., Teixeira, C.E.P. and Richardson (2011). Survey of Sonar Test Sites, Phase 1, Literature Review. Final Report for the Defence Science and Technology Organisation. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2011/000212-1. SARDI Research Report Series No. 566. 67pp.

South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024

Telephone: (08) 8207 5400 Facsimile: (08) 8207 5406 http://www.sardi.sa.gov.au

DISCLAIMER The authors warrant that they have taken all reasonable care in producing this report. This report has been through SARDI Aquatic Sciences internal review process, and has been formally approved for release by the Chief, Aquatic Sciences. Although all reasonable efforts have been made to ensure quality, SARDI Aquatic Sciences does not warrant that the information in this report is free from errors or omissions. SARDI Aquatic Sciences does not accept any liability for the contents of this report or for any consequences arising from its use or any reliance placed upon it.

© 2011 SARDI This work is copyright. Apart from any use as permitted under the Copyright Act 1968 (Cth), no part may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owner. Neither may information be stored electronically in any form whatsoever without such permission.

Printed in Adelaide: August 2011

SARDI Publication No. F2011/000212-1 SARDI Research Report Series No. 566

ISBN: 978-1-921563-41-6 DSTO Contract No. 4500782641

Author(s): J.F Middleton, C.E James, J.L Luick, S. Goldsworthy, A. Tsolos, C.E.P Teixeira and L. Richardson

Reviewer(s): M. Doubell and R. McGarvey

Approved by: T. Ward Assoc Prof – Wild Fisheries

Signed:

Date: 23 August 2011

Distribution: Defence Science and Technology Organisation, SAASC Library, University of Adelaide Library, Parliamentary Library, State Library and National Library

Circulation: Public Domain

3 Table of Contents:

Summary 9 Background 9 Data and Analyses 9 Additional Data Requirements – west zone, spring 14

1 Methodology 16

2 Sound Speeds 19 2.1 CTD Cast Data 19 2.2 Sea Surface Temperature (SST) data 35 2.3 Ocean Model Results 38 2.4 Ocean Glider Data 41

3 Monthly, Weekly, Hourly Sound Speed Variability 45 3.1 Month to Weekly Variability 45 3.2 Tidal Band Variability 46 3.3 Hourly Variability 47

4 Other Factors – Topography and Waves 48 4.1 Bottom Topography 48 4.2 Surface Wave Climatology 50

5 Other Factors – Marine Mammal Distributions 53 5.1 Australian Sea Lions 53 5.2 New Zealand Fur Seals 55 5.3 Blue Whales 57 5.4 Southern Right Whales 58 5.3 Other 61

6 Other Factors – Marine Vessel Activity 62

References 65

4 List of Tables:

Table S.1 Key indicators for SONAR testing by zone 14

Table 1.1 Summary of data types, public access and web sites for download And/or description. Data that is not public domain is either private Research data or commercial in confidence 16

5 List of Figures:

Fig S.1 Place names and the topography of the region including the 100 and 1000m isobaths 10 Fig S.2 The zones of study. The 20, 70, 300 and 5000m isobaths are indicated 11

Fig 1.1 The three regions used during analysis 17

Fig 2.1 Winter sound speed profiles for region 1 and the three zones 22 Fig 2.2 As in Fig 2.1 but for spring 23 Fig 2.3 As in Fig 2.1 but for summer 24 Fig 2.4 As in Fig 2.1 but for autumn 25 Fig 2.5 Winter sound speed profiles for region 2a (70 to 300m) and the three zones 27 Fig 2.6 As in Fig 2.5 but for spring 28 Fig 2.7 As in Fig 2.5 but for summer 29 Fig 2.8 As in Fig 2.5 but for autumn 30 Fig 2.9 Winter sound speed profiles for region 2b (300 to 5000m) and the three zones 31 Fig 2.10 As in Fig 2.9 but for spring 32 Fig 2.11 As in Fig 2.5 but for summer 33 Fig 2.12 As in Fig 2.5 but for autumn 34 Fig 2.13 A SST image illustrating very strong upwelling during summer 35 Fig 2.14 A SST image illustrating the relatively warm Leeuwin Current inflow during winter 36 Fig 2.15 SST image illustrating the relatively uniform temperatures during October (spring) 37 Fig 2.16 Output from the SARDIs numerical ocean model (Teixeira 2010) Obtained using forcing by a monthly atmospheric climatology and for summer (February 25th) 38 Fig 2.17 Output from the SARDIs numerical ocean model (Teixeira 2010) Obtained using forcing by a monthly atmospheric climatology and for autumn (April 20th) 39 Fig 2.18 Output from the SARDIs numerical ocean model (Teixeira 2010) Obtained using forcing by a monthly atmospheric climatology and for winter ( July 13th) 40 Fig 2.19 Output from the SARDIs numerical ocean model (Teixeira 2010) Obtained using forcing by a monthly atmospheric climatology and for spring (October 11th) 41 Fig 2.20 The Slocum glider path for 4 days in February 2010. 42 Fig 2.21 A 3D plot of temperature data for the glider path shown in Fig 2.20 42 Fig 2.22 The Slocum glider path for 10 days in November 2009 43 Fig 2.23 A 3D plot of temperature data for the glider path shown in Fig 2.22 44 Fig 2.24 A 3D plot of salinity data for the glider path shown in Fig 2.22 44

Fig 3.1 Time series of temperature and sound speed at the Reference Station, low pass-filtered with a cut-off period of 34 hours 45 Fig 3.2 Time series of temperature and sound speed at Coffin Bay, low pass-filtered with a cut-off period of 34 hours 46 Fig 3.3 Time series of temperature and sound speed at the Reference Station, band pass-filtered with cut-off periods of 10-26 hours (tidal band) 46 Fig 3.4 Time series of temperature and sound speed at the Coffin Bay, band pass-filtered with cut-off periods of 10-26 hours (tidal band) 47 Fig 3.5 Time series of temperature and sound speed at the Reference Station, high pass-filtered with a cut-off period of 4 hours 47

6 Fig 4.1 Topographic gradient in the western zone as computed from 1000*/grad(h)/ with units meters/kilometre. The depth contours 50,70, 100, 200, 500 and 1000 m are shown 48 Fig 4.2 Topographic gradient in the central zone as computed from 1000*/grad(h)/ with units meters/kilometre. The depth contours 50,70, 100, 200, 500 and 1000 m are shown 49 Fig 4.3 Topographic gradient in the eastern zone as computed from 1000*/grad(h)/ with units meters/kilometre. The depth contours 50,70, 100, 200, 500 and 1000 m are shown 50 Fig 4.4 Significant Wave Height in summer 51 Fig 4.5 Significant Wave period in summer 51 Fig 4.6 Significant Wave Height in winter 52 Fig 4.7 Significant Wave period in winter 52

Fig 5.1 Breeding and haul-out areas for Australian sea lions and NZ fur seals (URS 2010) 54 Fig 5.2 Examples of raw satellite derived at-sea positions and modelled densities at sea for Australian sea lions (a,b) and NZ fur seals (c,d) 56 Fig 5.3 Distribution of blue whale sightings between 2002-2007 in the DSTO areas of interest (a), raw data from Gill et al (2011) 60 Fig 5.4 Feeding areas of Beaked, Sperm and other whales (URS 2010) 61

Fig 6.1 The number of boat days for the scalefish and lobster fisheries for the “summer” (November to April) and “winter” (May to October) periods 62 Fig 6.2 The number of boat trips for the sardine fishery for the “summer” (November to April) and “winter” (May to October) periods 63

7 List of Acronyms:

ANFOG: Australian National Facility for Oceanic Gliders

AWD: Australian Warfare Destroyer

CARS: CSIRO Atlas of Regional Seas – data set

CSIRO: Commonwealth Scientific and Industrial Research Organisation

CTD: Instrument to measure Conductivity, Temperature, Depth

IMOS: Integrated Marine Observing System

ISS: integrated sonar system

MATLAB: a mathematical analysis package

MB: Middleton and Bye (2007) – an extensive review of oceanography for the South Australian region.

NOAA/NCEP: National Ocean and Atmospheric Administration/ National Center for Environmental Prediction (U.S. agencies)

RAN: Royal Australian Navy

SAIMOS: Southern Australian Integrated Marine Observing System

SARDI: South Australian Research and Development Institute

SONAR: Sound Navigation and Ranging

SST: Sea Surface Temperature (satellite data)

T&E: test and evaluation

XBT: Expendable Bathythermograph

8 SUMMARY Background The Royal Australian Navy (RAN) is currently acquiring three Air Warfare Destroyers (AWD) under project SEA4000 and the acceptance process of these platforms will include at sea testing of the integrated sonar system (ISS) suite. This report contributes to the identification of suitable at sea locations in South Australian waters for this testing. The criteria for suitable locations include: being near the build location of Adelaide, a relatively flat seafloor for about thirty kilometres, known underwater acoustic conditions and variability, with as benign conditions as possible (such as minimal frontal activity and constant sediment grain size) and contain minimal amounts of marine mammal activity, regular fishing, and traffic routes. The water depths of interest are a shallow (70 to 200 m), intermediate (2000 to 4000 m), and a deep water site (5000 m).

This review and report was under contract 4500782641 and required a literature and database search for information relevant to underwater acoustics for South Australian waters. The most extensive set possible of temperature and salinity data was assembled from the archives of CSIRO, IMOS and SARDI and includes data obtained from field surveys, tagged marine mammals, fixed moorings, satellites and ocean model output. This report is limited to oceanographic phenomena which affect the sound speed profile, seafloor slope, surface wave height, marine mammal distributions, and fishing vessel distributions. Other significant parameters, including sediment and sidescan data, are outside the scope of this report, however should be considered in the selection of the testing locations.

Data and Analyses To determine the best region and times for sonar test and evaluation (T&E), an analysis was made of around 6,700 conductivity, temperature, and depth (CTD) casts and two years of CTD time series to determine the acoustic properties of the South Australian (S.A.) region (Fig. S.1). These data are supplemented by sea surface temperature (SST), ocean model output, wave and topographic data and distributions of marine mammals and fishing vessel activity. The CTD data consists of all that stored by CSIRO and SARDI up until June 2010 and represents the most extensive database of its type for the region. The CTD time series (at two depths and sites) have been collected by SARDI through its involvement in the Southern Australian Integrated Marine Observing System (SAIMOS).

Fig. S.1. Place names and the topography of the region including the 200 and 1000 m isobaths. The +s denote the location of the SAIMOS Coffin Bay mooring (BC) and Kangaroo Island reference station (RS).

In order to determine the optimal area for sonar testing, we have split the region up into 3 zones as shown in Fig. S.2.

The central shallow zone (136.25 to 138 oE, 70 to 300 m) encompasses southern Kangaroo Island and is too small to provide the needed 30 km region of uniform topography due to the narrow and steeply sloping shelf. In addition, it is also subject to dense water eddy outflows during winter that are generally confined largely to the east of longitude 135.25 E and the bottom 10-20 m and flow past the western side of Kangaroo Island. However glider data from this region in early November 2009 does indicate that gulf outflows can occur in late spring. During summer, cold, fresh water is upwelled onto the shelf to the south of Kangaroo Island. This water follows the 70 - 100 m isobaths and surfaces off the western Eyre Peninsula. Both the upwelled and winter dense water outflows will affect sound speed on a seasonal and weekly time scale. Fishing vessel activity is also significant in the central zone.

The east shallow zone (138 to 140 oE, 20 to 300 m) does provide a 30 km region of uniform topography for shelf depths of 20 to 300 m. During summer, upwelling reaches the surface as a massive cold water plume that extends from Portland (Victoria) to the west of Robe (139 oE). The strong vertical and horizontal temperature gradients that result can vary on weekly to seasonal time scales. In addition, the temperature and sound speed for the region in water depths less than 10 100 m is relatively under-sampled compared to the west and central zones. Indeed, dense bottom water may be formed in the coastal regions during winter, although there is insufficient data to determine if this occurs.

Fig. S.2. The zones of study. The 20, 70, 300 and 5000 m isobaths are indicated. (Note for the east zone, data will be included for shelf depths 20 to 300 m, while for the other zones, data will be included for shelf depths 70 to 300 m.)

The west shallow zone (135 to 136.25 oE, 70 to 300 m) appears to be the most suitable region for T&E. A region 30 km in diameter exists for depths 70 to 300 m that has bottom slopes that are generally less than 50 m/km. Moreover, the temperature and sound speed variability is least during winter and spring suggesting that these months may be the most suitable for T&E of the sonar.

During winter, dense water outflows from coastal regions may be found (Petrusevics et al., 2009) although these are not apparent in the CTD profile data presented below. Over the shelf (70 – 300 m) the top 100 m of the water column is generally well mixed. Due to the effect of pressure, the mean sound speed increases with depth. This results in an acoustic surface duct approximately 100 m thick. During spring, atmospheric heating leads to temperatures and sound speeds that generally decrease with depth. On average, the acoustic surface duct existing in winter is not found. Glider data for the western zone in early November 2009 shows an anomalous upwelling of cold fresh

11 water in the bottom 30 m of the water column and over the 100 m isobath. This anomalous result indicates the need for additional data and is an important phenomenon needing investigation.

For the shallow region over all zones and seasons, the mean temperature and sound speed increase with depth from the surface to depths of 5 -10 m. This is attributed to atmospheric cooling during winter and evaporation during summer. Thus, a narrow (5 – 10 m) surface duct is expected. This narrow duct is not found offshore (water depths > 300 m).

For the deep region in all zones (>300 m) below the surface turbulent layer (Region 2b, fig 1.1) there is little variability in sound speed within and between seasons. All data indicate a well defined deep sound channel with axis at about 1100m. The strong linear increase in sound speed at greater depths results from the increase in pressure. The lack of variability is expected at such depths where atmospheric forcing of temperature and sound speed is minimal. The surface sound speeds for each zone are close to 1510 m/s and imply a critical depth of about 3200 m for convergence zone propagation.

For the deep region in all zones (>300 m) within the surface turbulent layer (Region 2a, fig 1.1) and for all seasons, (with the possible exception of winter), the overlying waters generally have sound speeds that increase towards the surface. Near surface sonar transmissions will therefore be focused down into the deep sound channel.

For all regions, SST data and ocean model results indicate the sound speed to be spatially uniform during spring which marks the transition between summer upwelling and wintertime cooling and gulf outflows. During winter, spatial temperature increases of around 2 oC are found within the Leeuwin Current compared to the other water over the shelf.

During summer and autumn, cold upwelled water lies below the 40 m deep surface mixed layer for both the western and central zones. The strong decrease in temperature and sound speed with depth within these two zones implies that an acoustic surface duct is rarely found.

Two years of CTD time series data in the western and central zones, shows that most of the sound speed variability (18 m/s) is seasonal. The daily variability is less significant at around 3 -10 m/s (10 – 20 day filter band). The sound speed variability under 1 day is less than 0.01 m/s, with no internal wave activity found. So if the Leeuwin current, upwelling zones, storms, and salinity currents can all be avoided, the sound speed should be fairly stable during the T&E trial. More measurements would be needed to confirm this.

12 Sonar testing during September-October in the western zone may affect the N.Z. Fur Seals and Australian sea lions which forage on the shelf and slope all year round. Whale activity in this region is least in spring prior to November. Fishing vessel activity is generally minimal between May and November and less in the western zone. Regular shipping routes do exist between Melbourne and Adelaide, via Backstairs passage, and Adelaide and Perth, via the southern tip of the Eyre Peninsula. Wave heights and periods are typically 2-3 m and 11-13 seconds with a swell directed from the south-west. Wave heights can exceed 8 m, 1.3% of the time and 5 m, 17% of the time.

The above is summarised in Table S.1 below where key testing indicators are evaluated for each zone. We conclude that testing in the west zone during spring (October) represents the optimal choice. This is based upon: a) the presence of a 30 km region of uniform topography b) the smaller variability found in sound speed with depth c) minimal upwelling and downwelling d) minimal horizontal variability in temperature and dense water outflows e) the overall uniformity of temperature and sound speed that is expected for spring – a transition period between summer and winter f) minimal marine mammal and fishing vessel activity. In addition, selection of the western zone means that the T&E can lever off the extensive data sets being collected by SAIMOS for this region. These include CTD surveys, moorings, marine mammal and glider data.

Indicator West Zone Central Zone East Zone 30 km region of Yes No Yes topographic uniformity Period of best Spring Spring Spring sound speed uniformity Other features: Weak or no Strong upwelled Strong upwelled summer upwelled water bottom plumes plumes (bottom except near Eyre and surface) Peninsula Other features: Dense bottom Downwelled dense Possible winter water plumes are water and eddies downwelled not evident (bottom) dense bottom water Marine Mammal Sea lions and Sea lions and seals all Sea lions and activity seals all year. year. seals all year. Blue whales Blue whales (Nov-May) Blue whales (Nov-May) (Nov-May) Right whales calve (May-Nov) Fishing Vessel minimal May- minimal May-Nov. minimal May-Nov. activity Nov. (sig. KI-Eyre (sig. Robe) Peninsula) Surface waves 2-3m height / 10- 2-3m height / 10-13 s 2-3m height / 10- 13 s period period 13 s period

Table S.1. Key indicators for SONAR testing by zone.

Additional Data Requirements – West zone, spring Additional data may be needed for T&E in the western zone in spring. The analysis below shows that there are only 125 CTD casts for the region in spring as compared to 1064 for summer. The glider data indicates the (unsuspected) possibility of upwelling in the region during early November. Thus, there is a need to refine our understanding of the vertical and spatial variability of sound speed for the region, through further glider missions and CTD survey work. These could be designed to complement those undertaken by SAIMOS which runs 8 five-day field surveys each year including one each in October and November. Three SAIMOS glider missions are run each year between Kangaroo Island and the Eyre Peninsula. In addition, in collaboration with SAIMOS, additional marine mammals could be tagged with CTDs to increase data coverage off the Eyre Peninsula (see Fig. 5.2).

14 In addition, further data is required to fully determine the temporal variability of sound speed. The SAIMOS mooring data suggests that there is almost no variability at time scales shorter than 24 hours. However, this is based on data from only one or two CTDs at fixed depths that might not resolve variations in the surface and/or bottom layers. We suggest the deployment of strings of temperature loggers on fixed moorings that include the shelf (100 m) and shelf slope (300 m), for at least 6 months to 1 year. These could be deployed in a complementary fashion to the 100 loggers that are being deployed by SAIMOS.

The above might also be complemented by direct estimates of sound speed propagation, through the installation of acoustic transmitters and receivers. Design of such a system is beyond our expertise.

In addition, it is imperative that the above field surveys, glider missions and moorings be maintained through out the T&E of the SONAR system. As we have noted and show below, there may be unexpected spatial and temporal variations in sound speed that arise from anomalous oceanographic events (e.g., the November 2009 upwelling found for the western zone – section 2.4 below). Again, T&E in October-November can lever off the SAIMOS data streams and field cruises which will continue to at least June 2013 and most likely beyond.

Finally, we note that it will also be possible to use SARDI’s ocean model to incorporate the data collected and hind-cast for the period of T&E. Further developments of the model are undertaken each year and are most promising. Thus, if sufficient effort is injected into improving the model, especially for temperature, the model output could be coupled with an acoustic model to improve the understanding of sound propagation during the T&E sonar trials.

15 1 Methodology A review has been made of relevant databases and information about the underwater oceanographic environment within the region 34°S to 40°S and 135°E to 140°E (Fig. S.2). This includes temperature and sound speed profiles, acoustic ducts (both seasonal to hourly variations) as well as other oceanographic processes that may be important to sound speed.

Data type Public Web site domain

CARS CTD y http://www.marine.csiro.au/~dunn/cars2009/ (casts, XBT)

Argo float y http://imos.org.au CTD

SAIMOS y http://imos.org.au CTD surveys

ANFOG y http://imos.org.au IMOS glider data SAIMOS y http://imos.org.au Mooring data

Marine n http://www.smru.st- mammal andrews.ac.uk/Instrumentation/pageset.aspx?psr=288 data SST data y http://www.marine.csiro.au/remotesensing/oceancurrents/index.htm

NOAA/NCEP y http://polar.ncep.noaa.gov/waves/download.shtml wave data Fishing n SARDI data vessel activity

Table 1.1. Summary of data types, public access and web sites for download and/or description. Data that is not public domain is either private research data or commercial in confidence.

The relevant data bases were identified through our long experience in oceanographic research of Australia’s southern shelves. In addition A/Professor John Middleton leads both the Oceanography Program at SARDI and also SAIMOS which is made up of marine observing platforms that include ship-based CTD surveys, moorings, ocean gliders and tagged marine mammals.

The data sources used in this report are listed in Table 1.1 along with a statement on public access and web sites where the data can be downloaded and/or is described.

16 The data is all quality controlled as required by CSIRO and IMOS. Only the marine mammal and fishing vessel data are not public domain: the latter through commercial in confidence.

In addition, many of the comments on the physical oceanography are based on our knowledge of the region summarised in the review paper Middleton and Bye 2007 (hereafter MB) and with appropriate references to the environmental reports supplied by DSTO: SAXA (2004) and URS (2010).

In order to analyse these data, three zones were chosen to group results: west (Eyre Peninsula), central (Kangaroo Is.) and east (Robe) as shown in Fig. S.2. Within each zone we define three regions by depth (Fig 1.1.): a) Region 1 – shelf depths (70 to 300 m) b) Region 2a – water depths 0 to 300 m above region 2b c) Region 2b - shelf depths (300 to 5000 m)

NOTE: for the eastern zone, region 1 is defined to be shelf depths from 20 m to 300 m as requested by DSTO.

Fig. 1.1. The three regions used during analysis (figure is not to scale).

We were also advised by DSTO that regions that would be most suitable for T&E would include: a) minimal spatial and temporal sound speed variability of sound speed and over a 30 km area. b) that the sea floor variability be minimal over this region.

17 c) that there is a focus on the shelf depths 70 (20) to 300 m.

In section 2, temperature and sound speed data are presented for these zones and regions and at seasonal time scales. Snapshots of satellite SST data are presented along with Slocum glider data.

In section 3, we present two years of SAIMOS mooring data to illustrate the monthly to hourly variability of sound speed. In section 4, seasonal data for surface waves is given and the topography and slope of the region discussed.

In sections 5 and 6, marine mammal and marine vessel activity and distributions are discussed. These data will assist in determining the locations and times of T&E of the SONAR systems.

2. Sound Speeds

2.1 CTD Cast Data All available temperature and salinity data was collated for the regions and up until June 2010. This includes around 676 XBT profiles, 1,313 CTD casts (including ARGO float data) and 4,790 CTD casts made by SARDI including 4,032 casts from seal-based CTDs: the non-SARDI data was supplied by CSIRO Marine and Atmospheric Research. The total of over 6,700 casts provide excellent coverage of the three zones and greatly exceeds that presented in the SAXA (2004) report (p64-68).

Indeed, this is the largest data set assembled for this region. Both the SARDI and CSIRO supplied data have been quality checked and temperature is accurate to within 0.05 oC. CTD data from three Slocum glider missions were not included here due to time constraints.

The sound speed was calculated using the UNESCO standard (Fofonoff and Millard 1983) that comes with the MATLAB analysis package. The formula is quite complicated, but in summary, sound speed is only weakly dependent on salinity and so for the XBT data, a value of salinity of 35 ppt was adopted. Sound speed increases by about 3 m/s for every degree increase in temperature and by about 1.1 m/s for every 100 m increase in depth (pressure).

We begin by first examining the number of casts made for each zone and by region and season (Table 2.1). Region 2a (0 to 300 m) overlies region 2b (300 to 5000m) and the number of casts in each is generally equal since both mostly result from the same CTD surveys. The total of regions 1 and 2 is given. By far, the most casts are made in autumn and then summer: the latter a reflection of the general scientific interest in summer upwelling. The central zone is the most sampled (an important upwelling area), although the number of casts in each zone exceeds 2000 most casts come from region 1. For the eastern zone, most casts are from the shelf slope (shelf depths > 70 m) as indicated by the cast location maps in Figures 2.1 to 2.12. That is, relatively few casts (~ 30) were taken on the shelf proper and for water depths 20 to 70 m.

Based on the cast numbers one might conclude that the sound speed results below would be more accurate in summer and autumn. However, as discussed below, the water column tends to be well mixed during winter and autumn so that the natural variability is smaller than in summer and autumn.

zone region winter spring summer autumn west 1 100 119 1064 504 2a 31 6 113 103 2b 31 6 112 103 Total (1+2) 131 125 1177 607 central 1 142 48 462 1834 2a 21 14 31 39 2b 21 14 31 39 Total (1+2) 163 62 493 1873 east 1 57 25 351 1352 2a 68 57 168 72 2b 68 57 166 72 Total (1+2) 125 82 517 1424 Table 2.1. Number casts for each zone and by region and season. Region 2a overlies region 2b and the number of casts is generally equal. The total cast numbers of regions 1 and 2 is given.

Plotted in Figures 2.1 to 2.12, are the sound speed C and its vertical gradient (positive values indicate C increases with depth) and for winter, spring, summer and autumn.. The number of casts is indicated in the bottom left of the lower panels. The locations of the casts are indicated in the upper left panel along with the data source XBT, CTD (CARS/CSIRO) and CTD (SARDI). The solid and dashed black lines in the profiles indicate the mean and mean ±2 standard deviations. In some figures the sound speed gradient appears quite “spikey”. This is due to a lack of data rather than errors in the data itself. To assist in determining the sign of the sound speed gradient, the zero line is plotted in dark grey.

Results - region 1 Now consider the sound speed data for region 1: 70 to 300 m shelf depths for the west and central zones and 20 to 300 m for the east zone.

The winter data (Fig. 2.1) indicate the least variability in C and dC/dz which may be expected given winter time winds mix the water to 300 m or so through downwelling and cooling (MB). For sound speed, 2 standard deviations is about 10 m/s. The sound speed itself is around 1510 m/s for each of the three zones: see also SAXA (2004). Between depths of 10 to 100 m, the (mean) sound speed increases with depth for all zones. This may result from the increase in C that is expected to arise from increasing pressure (depth) and where temperature is uniform due to mixing. Thus, on average a duct may be expected over the top 100 m. The scatter in both C and its gradient indicates that this will not always be the case. At depths below 100m, the sound speed decreases. 20

An additional feature of the results for winter, and indeed all seasons, is that there is an abrupt increase in mean speed between the surface and depths of 5 -10 m. During winter, this may be due to atmospheric cooling and results in a narrow surface duct.

For spring (Fig. 2.2), the western and central zone data indicates that C decreases over most depths and most rapidly over depths of 10 to 30 m. This results from an equivalent decrease in temperature with depth where the surface is warmed by the springtime increase in atmospheric heating. At depths of 70 to 300 m, little variability is found although not a lot of data is available. At depths 50 to 110 m, the data for the sound speed gradient indicates it can often be positive so that a duct can exist at these depths.

During summer, cold upwelled water is found at depths of 50 to 300 m in all three zones (MB). For the western and central zones the water remains largely sub-surface and is overlain by very warm water 20 oC that results from summertime heating. For the eastern zone, the cold water extends to the surface as a plume from Portland to the NW of Robe (Fig. 2.13 below).

The impact on sound speed is similar for all three zones (Fig. 2.3). For both the central and western zones, mean surface values of temperature and thus C are larger than for winter and spring. In addition, the colder upwelled water leads to a significant decrease in sound speed over depths of 30 to 50 m: the depth of the surface mixed layer corresponds to the minima in dC/dz at about 40 m. While there is some scatter in dC/dz, the mean gradient is strongly negative over the top 100 m indicating that a surface duct is not common. We note that there is again a notable increase in C with depth and within 5 -10 m of the surface. Temperature also increases in a similar way and this might result from evaporation due to generally low humidity and windy conditions expected during summer. These results would suggest the existence of 5 – 10 m surface duct.

Finally, we consider the results for autumn (Fig. 2.4) that are qualitatively similar to those for summer. After the upwelling and surface heating of summer, the winds and cooling act to mix the warmer surface and colder upwelled waters. This occurs through the progression of individual storms leading to a larger scatter in C and dC/dz than found in summer (or winter and spring).

The large scatter in summer and autumn suggests that winter or spring might be better months for T&E.

Fig. 2.1. Winter sound speed profiles for region 1 and the three zones: West (red), Central (green) and East (blue). The region is shown schematically in the top right panel. The number of casts is indicated in the bottom left of the lower panels. The location of the casts is indicated in the upper left panel along with the data source XBT, CTD (CARS/CSIRO) and CTD (SARDI). The solid and dashed black lines denote the mean and mean ±2 standard deviations. The thick grey line in the mid-panels denotes zero sound speed gradient.

Fig. 2.2. As in Fig 2.1 but for Spring.

Fig. 2.3. As in Fig 2.1 but for Summer.

Fig. 2.4. As in Fig 2.1 but for Autumn.

Results - region 2a Now consider the data for region 2a defined for water depths 0 to 300 m with seafloor depths of 300 m to 5000 m. This region is offshore and to the south of region 1 discussed above. Indeed, the 25 winter and spring results for sound speed (Figures 2.5 and 2.6) show again that there is relatively little variability in sound speed. Notably, less cast data is available (Table 2.1), although the surface duct found at depths 10 – 100 m is less pronounced than for region 1. For spring the rapid decrease in C over the top 20 m found for region 1 is not found here: presumably surface heating here is smaller than for the more northward, region 1.

For summer and autumn (Figures 2.7 and 2.8), the effects of surface heating are also evident in the rapid decrease in sound speed C (and temperature) at the base of the surface mixed layer (depth 50 m).

Unlike region 1, a surface duct within 5 – 10 m of the surface is not found.

Results - region 2b Finally, we consider the deep water data for region 2b (300 to 5000 m) and which lies below region 2a (Figures 2.9 to 2.12). As is evident, there is little variability within and between seasons and zones. All data indicate a well defined deep sound channel with axis at about 1100 m. The strong linear increase in C at greater depths results from the increase in pressure. The lack of variability is expected at such depths where atmospheric forcing of temperature and C is minimal.

The surface sound speeds for each zone is close to 1510 m/s. From Figures 2.9 to 2.12, this would imply a critical depth of about 3200 m for convergence zone propagation.

With the exception of winter, the overlying waters (region 2a) have sound speeds that increase towards the surface. Near surface SONAR emissions will therefore be focused down into the deep sound channel.

Fig. 2.5. Winter sound speed profiles for region 2a (70 to 300 m) and the three zones West (red), Central (green) and East (blue). The number of casts is indicated in the bottom left of the lower panels. The location of the casts is indicated in the upper left panel along with the data source XBT, CTD (CARS/CSIRO) and CTD (SARDI). The solid and dashed black lines denote the mean and mean ±2 standard deviations. The thick grey line in the mid-panels denotes zero sound speed gradient.

Fig. 2.6. As in Fig 2.5 but for Spring.

Fig. 2.7. As in Fig 2.5 but for Summer.

Fig. 2.8. As in Fig 2.5 but for Autumn.

Fig. 2.9. Winter sound speed profiles for region 2b (300 to 5000 m) and the three zones: West (red), Central (green) and East (blue). The number of casts is indicated in the bottom left of the lower panels. The location of the casts is indicated in the upper left panel along with the data source XBT, CTD (CARS/CSIRO) and CTD (SARDI). The thick grey line in the mid-panels denotes zero sound speed gradient.

Fig. 2.10. As in Fig 2.9 but for Spring.

Fig. 2.11. As in Fig 2.9 but for Summer.

Fig. 2.12. As in Fig 2.9 but for Autumn.

2.2 Sea Surface Temperature (SST) data

34 To augment the above we consider several SST images that illustrate some large scale processes that are considered important to sound speed variability. In Fig. 2.13 SST data for strong summer upwelling illustrates an intense surface plume of very cold (13 oC) water that is upwelled off the Bonney Coast (eastern zone) and off Coffin Bay (western zone; 15 oC). Cold water is also found along the 100 m isobath for all three zones. The horizontal temperature changes will also affect sound speed with rays bending into the cold water plumes and away from the warmer gulf waters,

Fig. 2.13. A SST image illustrating very strong upwelling during Summer.

A second image (Fig. 2.14) is typical of winter and illustrates the flow of relatively warm Leeuwin Current water from the west and into the region.

Fig. 2.14. A SST image illustrating the relatively warm Leeuwin Current inflow during Winter

A third image illustrates the SST in October after the Leeuwin Current has ceased and before the onset of summer upwelling. The uniformity of temperature in the western and central zones is strong and suggests, along with the CTD casts, that spring may provide the most uniform sound speed conditions.

The above SST image (Fig. 2.13) highlights the strong spatial variability in surface temperatures expected during summer. This variability is smoothed out in the monthly averages presented by SAXA (2004; p61) and in any climatological data base.

Fig. 2.15. SST image illustrating the relatively uniform temperatures during October (Spring).

It is also worth noting that eddy activity for the region is relatively weak compared to regions such as the Leeuwin and East Australian Currents. The white lines in the SST images denote altimetric sea level height (0.1 m contour) while the arrows denote currents. These show that while cyclonic and anticyclonic eddies do exist at the shelf edge, the speeds are typically less then 20 cm/s.

37 2.3 Ocean Model Results The above data may be augmented by results from SARDI’s S.A. Regional Ocean Model. The model has a 5 km grid resolution and has been partly validated (Middleton et al 2010) against the data streams from the Southern Australian Integrated Marine Observing System (SAIMOS; imos.org.au). The results were determined using forcing by a climatological meteorological data (monthly means) of surface fluxes of momentum, heat and freshwater (Teixeira 2010). The model was spun up over 2 years so as to reach a quasi-steady state. No forcing for the open boundaries was used. Model results are for summer (February 25th) and are presented in Fig. 2.16. In the top left and right panels are bottom temperature and salinity. In the bottom left panel are the depth averaged (oceanic) velocities with magnitudes indicated by the colour bar (m/s). In the bottom right panel are the atmospheric forcing functions: net heat flux (into the ocean; watts/m2), evaporation less precipitation (mm/d) and wind stress magnitude (Pa). The wind direction (WD) is indicated on the bottom left panel.

Fig. 2.16. Output from the SARDI’s numerical ocean model (Teixeira 2010) obtained using forcing by a monthly atmospheric climatology and for Summer (February 25th).

38 Between January and 3rd March, the winds are from the S.E. and upwell cold (14-15 oC) fresh water off the shelf near Kangaroo Island as illustrated by the model results in Fig. 2.16. The upwelled water forms a plume along the 100 m isobath that appears to block the exchange of water with Spencer Gulf. Water in the gulfs is hot (22 oC) and salty (38 ppt) and is formed as a plume that migrates south from the head of Spencer Gulf. Upwelling can occur 4-5 times during summer (MB) and is perhaps not “rare” as described in SAXA (2004). The climatological model results here indicate that in an average sense, upwelling occurs between December and early March (see also MB).

Fig. 2.17. Output from the SARDI’s numerical ocean model (Teixeira 2010) obtained using forcing by a monthly atmospheric climatology and for Autumn (April 20th).

After February, there is a net heat loss from the ocean and the shallow gulf waters get progressively cooler. In addition, by the 20th April (Fig. 2.17), the winds are to the NE. The upwelling is shut down and the dense gulf waters explode onto the shelf as a sequence of Speddies (Spencer Gulf eddies; Teixeira 2010). These dense salty eddies are mostly confined to the immediate east of longitude 136o (the central zone). These eddies flow out past Kangaroo Island and to depths of 250 m or so (MB) and between April and August (Fig. 2.18). In addition, SAIMOS data we have collected for the region indicates the dense saline outflows to be confined largely to the bottom 20 - 30 m or so.

39 After August, the atmosphere begins to re-heat the ocean and by 11th October temperatures in the western zone are largely uniform (15 oC) and well mixed in the vertical. The upwelling favourable winds return in November.

Fig. 2.18. Output from the SARDI’s numerical ocean model (Teixeira 2010) obtained using forcing by a monthly atmospheric climatology and for Winter (July 13th).

The above would suggest that temperature and sound speed is generally uniform in the western region during spring which corresponds to the transition period between summertime upwelling and the wintertime outflows from the gulf.

Fig. 2.19. Output from the SARDI’s numerical ocean model (Teixeira 2010) obtained using forcing by a monthly atmospheric climatology and for Spring (October 11th).

2.4 Ocean Glider Data The spatial variability (or otherwise) of water temperature (and sound speed) is illustrated by data from two (SAIMOS) Slocum Glider profiles below. These gliders are programmed via satellite to move towards preset way points of latitude and longitude, move up and down the water column as they do so and collect CTD information along the way. Typically the gliders travel at speeds of about 25-40 cm/s and surface every 4 hours. A typical 25 day mission can provide 3000 vertical profiles of CTD data with a sample rate of order 4 seconds. Typically, this implies a vertical resolution of order 1 m and horizontal resolution of 200 m. The first set of temperature data comes from four days of the 2010 February mission with a path (in red) shown in Fig. 2.20. The period was one of intense upwelling. The temperature data is shown in the 3-dimensional plot Fig. 2.21 with coldest water (11.7 oC) in the bottom 20 m, and in the central zone off Kangaroo Island. A well defined surface mixed layer (SML) of warm water (19 oC) is found above. The depth of the SML appears to vary along the glider path and over a scale of 10 km or so. However, this may be the result of cross shelf variations in temperature. An analysis of the data is outside the scope of this report. In either case such variability may be important to sound speed propagation and it is recommended that additional glider missions be undertaken for the SONAR testing zone.

Fig. 2.20. The Slocum glider path for 4 days in February 2010. The glider profile began off Kangaroo Island on February 14th.

Fig. 2.21. A 3-D plot of temperature data for the glider path shown in Fig. 2.20. The horizontal axes are latitude and longitude and the vertical axis is depth (m). The temperature is indicated by the colour bar.

Six days of data from a spring, (November 2009, 4th-10th) mission are shown below. The path again begins near Kangaroo Island (Fig. 2.22). Bottom temperatures are typically 13.5 to 14.5 oC (Fig. 2.23), and 2 to 3 oC warmer than that found 3 months later (Fig. 2.21) and after the onset of summertime upwelling. While vertical variations in temperature are smaller during November (3 oC), horizontal variations are comparable with those in summer and water within 20 m of the 42 bottom is 2 oC cooler in the west. The summer data (Fig. 2.21) shows near bottom water to be cooler in the east due to upwelling.

The origin of the colder near bottom water in November and in the western zone may be localised upwelling. A plot of the salinity data for the November mission (Fig. 2.24) shows the near-bottom water in the west to be cold and fresh: a property of upwelling. In the east, the water is “warm” and salty suggesting it to be residual dense water formed in Spencer Gulf during winter. The apparent upwelling in the west during November is unexpected and not apparent in other data, the ocean model output or in any previous studies (MB). It indicates that more data needs to be obtained for the region and in particular the spring period when all other information would indicate it to be the best time for T&E of the SONAR system.

Fig. 2.22. The Slocum glider path for 10 days in November 2009. The glider began off Kangaroo Island on November 4th.

Fig. 2.23. A 3-D plot of temperature data for the glider path shown in Fig. 2.22. The horizontal axes are latitude and longitude and the vertical axis is depth (m). The temperature is indicated by the colour bar.

Fig. 2.24. A 3-D plot of salinity data for the glider path shown in Fig. 2.22. The horizontal axes are latitude and longitude and the vertical axis is depth (m). The salinity (psu) is indicated by the colour bar. 3 Monthly, weekly, hourly Sound Speed Variability

44 3.1 Month to Weekly Variability Almost 2 years of ADCP and CTD data is available from moorings off Kangaroo Is (Reference Station) and Coffin Bay (Fig. 1.1). The temperature and salinity data has been low pass filtered (35 hr cut-off) and the results for sound speed and temperature at the upper and lower CTDs at the Kangaroo Island Reference Station are shown in Fig. 3.1. The upper and lower CTDs are 40 m and 100 m from the surface. At Coffin Bay, data is only available from a lower level CTD (100 m from the surface). The highest sound speeds and temperatures are found nearest the surface. During winter, the water is well mixed and sound speeds are typically 1510 m/s. During summer, the cold, upwelled water at the lower CTD lowers the sound speed to 1500 m/s. There is variability on a 10-20 day scale of 3-10 m/s due to storms, mixing and heat exchange with the atmosphere.

Fig. 3.1 Time series of temperature and sound speed at the Reference Station, low pass-filtered with a cut-off period of 35 hours. Data in the upper pair of figures is from the upper level CTD (40 m from surface) and data in the lower pair of figures is from the lower level CTD (100 m from the surface).

Fig. 3.2 Time series of temperature and sound speed at Coffin Bay, low pass-filtered with a cut-off period of 35 hours.

The largest variability is clearly in the seasonal band. A similar result is found for the Coffin Bay mooring (100 m depth) as shown in Fig. 3.2 above.

3.2 Tidal band variability The data were then filtered with 10 and 26 hr period cut-offs so as to examine the variability in the tidal band. The results for the lower CTD at Kangaroo Island (central zone) is shown in Fig. 3.3 and the variability in temperature and sound speed is typically less than 0.01 oC and 0.01 m/s respectively.

Fig. 3.3. Time series of temperature and sound speed at the Reference Station, band pass-filtered with cut-off periods of 10-26 hours (tidal band).

The results at Coffin Bay (western zone) are shown below in Fig. 3.4 and are very similar to those at the Reference Station.

Fig. 3.4. Time series of temperature and sound speed at Coffin Bay, band pass-filtered with cut-off periods of 10-26 hours (tidal band).

3.3 Hourly Variability The CTD data was finally high pass filtered with a cut-off of 4 hours. The CTD data was obtained every 15 minutes. The results for the reference station are shown below (lower CTD). The variability in temperature and sound speed is typically less than 2 X 10 –5 oC and 3 X 10 –5 m/s respectively. This variability is due to noise since the CTD accuracy for temperature is 0.005 oC. There is no evidence of significant internal waves activity as suggested by the SAXA (2004; p60) although we agree that more data is needed to confirm this or otherwise.

Fig. 3.5 Time series of temperature and sound speed at the Reference Station high pass-filtered with a cut-off period of 4 hours.

The data at other sites (Coffin Bay) showed similar results.

47 4 Other factors – Topography and Waves

4.1 Bottom Topography Plots of bottom slope and contours of depths are shown in Figures 4.1 to 4.3 for the western, central and eastern zones respectively. The bottom slope for a depth h(x,y) is computed as 1000* |grad(h)| with units meters/kilometre. The data source is the Australian Bathymetry and Topographic Grid (June 2009, Geosciences Australia). As shown, the western zone has an extensive region (~50 km) between the 70 m and 300 m isobaths that has slopes less than 50 m/km (0.05)

Fig. 4.1 Topographic gradient in the western zone as computed from 1000* |grad(h)| with units meters/kilometre. The depth contours 50, 70, 100, 200, 500 and 1000 m are shown.

Fig. 4.2 Topographic gradient in the central zone as computed from 1000* |grad(h)| with units meters/kilometre. The depth contours 50, 70, 100, 200, 500 and 1000 m are shown.

The slope for the central region (Fig 4.2) between the coast and 200 m isobath is generally 50 m/km: near the 200 to 300 m isobaths it can be up to 350 m/km. In addition the region seaward of the 70 m isobath that is uniform is smaller than that in the western zone. The seafloor in the immediate vicinity of the head of du Couedic canyon (Fig S.1) (depths 100 m) appears to be covered with meter high sponges that may absorb sound transmission (Currie and Sorokin 2011). Based on one bottom grab, the sponge biomass was estimated at around 1 tonne per hectare which is much higher than found elsewhere for comparable water depths in the Great Australian Bight and off the Bonney Coast. Currie and Sorokin (2011) speculate that the high biomass may be related to enhanced organic material associated with the wintertime dense water outflows from Spencer Gulf.

The slope for the eastern zone is also small (Fig. 4.3), and the region bounded by the 20 to 300 m isobaths is at least 50 km across and adequate for SONAR testing.

Fig. 4.3 Topographic gradient in the eastern zone as computed from 1000* |grad(h)| with units meters/kilometre. The depth contours 50, 70, 100, 200, 500 and 1000 m are shown.

4.2 Surface Wave Climatology. The significant wave height and period for summer and winter were obtained from the NOAA/NCEP wave climatology data with a resolution of 1 o latitude and 1.25 o longitude. For summer the typical wave heights are 2.5 m for the central and western zone and 1.5 to 2.5 m for the eastern zone (Fig. 4.4). The wave periods are 10-11 seconds (Fig. 4.5).

For winter wave heights are 2.5-3.5 m (Fig. 4.6) with wave periods 11 to 13 seconds (Fig. 4.7). These results are augmented by the observations that were obtained south of Portland, Victoria (Fig S.1) (water depth 1395 m) by Wood and Terray (2005) and for the April–September period of 2004. They found the waves to have a significant wave height of 3.7 m, period 13 s and to be directed from the south-west. Wave heights exceeded 8 m for 1.3% of the time and 5 m for 17% of the time.

Sig. Wave Height: Summer 35oS 5

100 4.5 500

o 36 S 50 4 50

3.5

o 37 S 3 2 00 50 1 0 0 0 1 2.5 00 metres

o 38 S 2

1.5

39oS 1

0.5

o 40 S o o o o o o 0 135 E 136 E 137 E 138 E 139 E 140 E Fig. 4.4 Significant Wave Height in summer.

35oS 15

100 14.5 500

o 36 S 50 14 50

13.5

o 37 S 13 2 00 50 1 0 0 0 1 12.5 00 seconds o 38 S 12

11.5

39oS 11

10.5

o 40 S o o o o o o 10 135 E 136 E 137 E 138 E 139 E 140 E Fig.4.5 Significant Wave period in summer.

51 Sig. Wave Height: Winter 35oS 5

100 4.5 500

o 36 S 50 4 50

3.5

o 37 S 3 2 00 50 1 0 0 0 1 2.5 00

o 38 S 2

1.5

o 39 S 1

0.5

40oS 0 135oE 136oE 137oE 138oE 139oE 140oE Fig. 4.6 Significant Wave Height in winter.

35oS 13

100

500 12.5 o 36 S 50 50

37oS 2 00 50 1 0 0 0 1 11.5 00 seconds 38oS

o 39 S 10.5

o 40 S o o o o o o 10 135 E 136 E 137 E 138 E 139 E 140 E Fig. 4.7 Mean summer wave period in winter.

The spring and autumn results (not presented) lie between those for summer and winter and again the significant wave heights and periods are around 2 -3.5 m and 11-12 seconds respectively. In addition, SAXA (2004) provides plots of the monthly averaged combined sea and swell heights and swell and wind-wave directions. The latter show the swell to be from the S.W. for most of the year. The wind-waves come from the S.E. during summer and from the west during winter. The former makes for a cork-screw motion of small vessels that during summer can make mooring deployments and field surveys difficult (source: SAIMOS).

52 5 Other factors - Marine Mammal distributions Two main groups of marine mammals occur in the DSTO study area, cetaceans (whales and dolphins) and pinnipeds (seals). All marine mammals are protected species under the Australian Government’s Environment Protection and Biodiversity Conservation Act 1999 (Cth) (EPBC Act), and some species are listed as threatened. A recent publication has indicated that 23 species of cetacean have been recorded from Gulf St Vincent, Investigator Strait* and Backstairs Passage*, 14 from live strandings; and five pinniped species (Kemper et al. 2008). Of all these marine mammal species, only four are addressed here in detail; two resident (breeding) pinnipeds, the Australian sea lion and the New Zealand fur seal and two large whale species, the blue and southern right whale. These species are the only marine mammal species in South Australian waters where there is some information on distribution and/or abundance, for at least for part of the year.

5.1 Australian sea lions Australian sea lions (ASL) (Neophoca cinerea) are listed as Threatened under the Environment Protection and Biodiversity Conservation Act 1999 (Cth) (EPBC Act), as vulnerable under the National Parks and Wildlife Act 1972 (SA), and as Endangered under the International Union for the Conservation of Nature (IUCN) Red List.

The Australian sea lion is Australia’s only endemic seal species and its least numerous. It is unique among pinnipeds in having a non-annual breeding cycle of 17 to 18 months (Gales et al. 1994). Furthermore, breeding is temporally asynchronous across its range (Gales & Costa 1997; Gales et al. 1994). There are 76 known locations where Australian sea lion pups have been recorded, 48 of them in South Australia (Fig 5.2) where the species is most numerous (~86% of estimated pup production), with the remainder (28 sites) in Western Australia (Goldsworthy et al. 2009). In South Australia, pup production is estimated to be 3,119 per breeding cycle, leading to a population estimate of 12,726 sea lions (Shaughnessy et al. in press).

53 Models describing the spatial distribution of at-sea densities of ASL in South Australia have been based on extensive satellite tracking data sets from 210 individual deployments (157 adult females from 17 colonies, 31 adult males from 9 colonies and 22 juveniles from 4 colonies) (Goldsworthy et al. 2010).

* Investigator Strait and Backstairs Passage lie at the western and eastern ends of Kangaroo Island and the mainland.

Fig. 5.1. Breeding and haul-out areas for Australian sea lions and N.Z. fur seals (URS 2010). The blue circles denote sea lion haul out areas. The red and orange circles denote sea lion and NZ fur seal breeding areas respectively. The red dashed line denotes Australian fur seal breeding areas.

Telemetry data were derived from ARGOS linked platform transmitting terminals (PTTs), and from fully archival or archival/ARGOS-linked GPS tags resulting in 100,934 satellite derived at-sea locations (Goldsworthy et al. 2010). Some of these are presented in Fig. 5.2a. Statistical models using data distributions were used to estimate the spatial distribution of foraging effort throughout South Australia, following the methods outlined in Goldsworthy et al. (2010). The foraging depths of adult females and males rarely exceed 120 m and 140 m, respectively (Goldsworthy et al. 2010).

Australian sea lions are resident and present year round in continental shelf waters. Tracking data from individuals tracked over many months indicate animals have a high fidelity to foraging grounds and that there is little seasonal variation in foraging locations. As such the density plot presented in Figure 5.2b provides an indication of year-round distribution of foraging effort/distribution.

54 5.2 New Zealand fur seals Breeding areas for N.Z. fur seals are illustrated in Fig. 5.1. Estimates for the abundance of New Zealand fur seals (Arctocephalus forsteri) (NZFS) in South Australia have been based on pup production (Shaughnessy et al. 1994). Pup production estimates at most Kangaroo Island breeding sites have been monitored annually since 1988, and other South Australian colonies less frequently (Shaughnessy 2004; 2005; Shaughnessy & Dennis 1999; Shaughnessy & Dennis 2001; Shaughnessy & Dennis 2003; Shaughnessy et al. 1994; Shaughnessy & Goldsworthy 2007; Shaughnessy & McKeown 2002). Total annual pup production in South Australia has been estimated to be 17,622, with most pups born at the Neptune and Liguanea Islands of the lower Eyre Peninsula (~10,500 pups) and two southernmost headlands on Kangaroo Island (Cape du Couedic and Cape Gantheaume, ~7,000 pups) (Goldsworthy et al. 2007; Goldsworthy & Page 2007). The total South Australian NZFS population is estimated to number ~83,860 seals (Goldsworthy et al. 2007; Goldsworthy & Page 2007). Telemetry data on NZFS were derived from ARGOS-linked platform transmitting terminals (PTTs) deployed on 64 seals (137 foraging trips) from four colonies (Cape Gantheaume and Cape du Couedic [Kangaroo Is], North Neptune and Liguanea Island) (Baylis et al. 2008a; 2008b; Baylis et al. 2005; Page et al. 2006). Some of these data (those restricted to continental shelf waters) are presented in Figure 5.2c. Statistical models using data distributions were used to estimate the spatial distribution of foraging effort throughout SA, following the methods outlined in Goldsworthy et al. (in review; 2010). NZFS undergo a marked transition in foraging behaviour as they mature. As pups, foraging activity is localised to near-colony waters (Baylis et al. 2005), then shifts to oceanic (off-shelf) waters as juveniles, and then contracts to mid-outer shelf waters in adult females and to slope waters in adult males (Page et al. 2006) (Figures 5.2c,d). Given that most of the SA NZFS population occurs in four main regions; Cape Gantheaume and Cape du Couedic (Kangaroo Island), the Neptune and Liguanea Islands, there is a marked concentration of foraging effort in near-colony waters and adjacent shelf and slope waters between south-east Kangaroo Island and south-west of the Eyre Peninsula (Figure 5.2d). However, given the size of the South Australia NZFS population and based on the foraging effort models developed, some degree of foraging effort occurs in all shelf, slope and oceanic waters off SA. NZFS are resident in South Australia and animals forage in shelf, slope and oceanic waters year-round, hence Figure 5.2c provides an indication of the density of animals in shelf and slope waters year-round.

a. b.

c. d.

56 Fig. 5.2. (above) Examples of raw satellite derived at-sea positions and modeled densities at sea for Australian sea lions (a, b) and New Zealand fur seals (c, d). Only data from the coast to the 5000 m isobath have been included for New Zealand fur seal tracking data. The at-sea data and right-side density plots are derived from 17 sea lion colonies (where tagging has been done) while there are 48 colonies in the state. The known mammal numbers from untagged colonies are used to correct the density plots and the red (light blue) colours indicates areas from highest (lowest) density (no units). Green dots indicate the location of breeding colonies for each species. Bathymetry lines in bold represent 70, 1000, 2000, 3000 and 4000 m, DSTO areas of interest (west, central and east) are also presented. All data derived from Goldsworthy et al. (in review; 2010), and are indicative of year-round distribution and density.

5.3 Blue whales The blue whale (Balaenoptera musculus) is listed as endangered species under the Australian Government’s EPBC Act. Blue whales, thought to be pygmy blue whales (Balaenoptera musculus brevicauda) aggregate to feed in a regional meso-scale seasonal cold water upwelling system between the Great Australian Bight (GAB) and Bass Strait each year between November and May (Gill 2002). Here, blue whales feed on patchy aggregations of krill (Nyctiphanes australis). Gill et al. (2011) present data on the distributions of blue whales based on aerial surveys conducted over six consecutive season between 2002 and 2007, in slope and shelf waters between south-west of Kangaroo Island through to eastern Bass Strait. The timing of when blue whales reach their feeding grounds, the duration and location of their foraging effort and timing of departure vary markedly between seasons as a function of physical and biological oceanographic factors (Gill et al. 2011). The locations of blue whale sightings within the DSTO study area from Gill et al.’s (2011) study, are presented in Fig. 5.3a. Most of the survey effort south and south-west of Kangaroo Island occurred during the 2003–04, 2004–05, and 2005–06 seasons, with most (65%) occurring in 2003–04 (Gill et al. 2011). The earliest sightings of blue whales in any seasons monitored by Gill et al. (2011) was 13 November 2003 and 8 November 2004, each about one week after upwelling onset. Most whales have departed the feeding grounds by late April (Gill et al. 2011).

Most (93%) of blue whale sightings in the eastern part of Gill et al.’s (2011) study area occurred in depths ≤200 m. However, blue whales foraged in deeper water south and south-west of Kangaroo Island. The mean depth of sighting south of Kangaroo Island was 150 m (±67 SD), significantly shallower than west of Kangaroo Island (mean depth 389 m, ±299 SD) (Gill et al. 2011). It is thought that some of the changes in the distributions of blue whales from east to west are a result of physical oceanographic differences that affect the depth and distance from shore of nutrient-rich water which underpins the distribution of krill. Gill et al. (2011) acknowledge that most of their survey effort south and west of Kangaroo Island were concentrated on the outer shelf so they may have missed whales in depths <50 m. More survey effort was expended west of Kangaroo Island, where the 100 and 200 m isobaths diverge widely and the outer shelf has a gentler depth gradient. Here, blue whales were found either side of the shelf break, some in very deep water. South of Kangaroo Island where the outer shelf is steeper due to the proximity of the 100 and 200 m

57 isobaths, Gill et al. (2011) found blue whale density (when accounting for survey effort) was higher than west of Kangaroo Island.

5.4 Southern right whales The southern right whale (Eubalaena australis) is listed as endangered under the Australian Government’s EPBC Act. Right whale numbers were critically low world-wide at the beginning of the 20th century following hundreds of years of hunting in the northern hemisphere and a briefer but very intensive period of hunting in the southern hemisphere from the early 19th century. Hunting pressure on right whales was intense because whalers considered the species were the "right" whales to kill – the whales swam slowly, often hugged the shoreline, provided a great quantity of oil, and floated when dead. In 1931, right whales were granted international protection under a League of Nations convention intended to take effect in 1935, and then protected under the International Whaling Commission (IWC) from its inception in 1946. However, commercial and illegal, unreported and unregulated whaling continued up to the 1970’s, hindering recovery of the species. The IWC imposed a moratorium on all commercial whaling from the 1985-86 season. Population levels prior to exploitation are difficult to estimate but it has been suggested that for right whales in the southern hemisphere the population was approximately 60,000 (DEH 2005). Southern right whales inhabit sub-Antarctic waters where the main summer feeding grounds are thought to be between 40° and 55° S, but have been documented in latitudes south of 60° S. The species generally spends winters in warmer waters, with current strongholds off eastern South America, South Africa, southern Australia, and in the vicinity of oceanic islands at Tristan da Cunha and Auckland Island, New Zealand (DEH 2005).

Australian Southern Right Whales migrate seasonally between higher latitudes and mid latitudes. They are regularly present on the Australian coast from about mid-May to mid-November. The general timing of migratory arrivals and departures varies slightly on an inter-annual basis; although exact migratory pathways are not well known (no satellite tracking has been undertaken in southern coastal Australian waters). It is thought that right whales follow a circular, anticlockwise migration pattern south of the Australian continent, which is supported by the majority of within year coastal movements being in a westerly direction and between year coastal movements being in an easterly direction (Burnell 2001). Within such an overall pattern it is likely that the majority of individual whales make direct approaches to the coast as the relative infrequency of sightings outside major calving areas is not consistent with a widely used near- shore migratory pathway.

58 Calving areas for right whales tend to be very close to the shore. The main calving areas in South Australia are the Head of the Bight, Fowlers Bay, and Encounter Bay. Sleaford Bay near Port Lincoln is also a regular aggregation and calving area. Two of these calving areas occur adjacent to the DSTO study are, Encounter Bay and Sleaford Bay (Fig. 5.3b). Aerial surveys of right whales between Western Australia and Ceduna (South Australia) have been undertaken by John Bannister (Western Australian Museum) between 1993 and 2008. In August 2008, 702 animals were surveyed, including 236 cow/calf pairs, the highest number reported for the region (Bannister 2008). The annual rate of increase is 6.4% (6.7% for cow/calf pairs). The Australian population estimate of southern right whales is 2,400 (Bannister 2008).

59 a.

Fig. 5.3. Distribution of blue whale sighting between 2002-2007 in the DSTO areas of interest (a), raw data from Gill et al. (2011). Locations of southern right calving areas adjacent to the DSTO areas of interest (from DEH 2005). Blue whales distribution is indicative of the periods from November to May; southern right calving grounds indicative of use between mid-May to mid- November. 5.5 Other

60 URS(2010) provides further, albeit limited information, on other relatively rare species in SA waters. Pygmy, dwarf Sperm whales, Sperm whales and Beaked whales are all found in the region and notably along the continental slope (200 m isobath) as illustrated in Fig. 5.4 below. Little other information is presented.

Fig. 5.4. Feeding areas (pale green) of Beaked, Sperm and other whales (URS 2010).

SAXA (2004; p91) provides an Australian-wide qualitative map of whale distribution that adds little to the discussion above.

61 6 Other factors – Marine Vessel Activity SARDI has routinely collected statistics on fishing vessel activity. For scalefish and lobster fishing, this data consists of the number of boat days for each month and for the one degree by one degree squares shown in Fig 6.1. Boat days are defined by the number of boats multiplied by the number of days spent at sea. Thus, 40 boat days could be one boat fishing for 40 days or four boats, each fishing for 10 days. It is thus a good measure of vessel activity.

Fig. 6.1. The number of boat days for the scalefish and lobster fisheries for the “summer” (November to April) and “winter” (May to October) periods and for the one degree squares shown. Boat days are the number of boats times the number of days each spends at sea in the regions shown. Winter boat days are in brackets.

To increase reliability, we have averaged the number of boat days into a “summer” period (November to April) and a “winter” period (May to October) and the boat days for these periods are indicated in Fig. 6.1. The data is provided by the fishing industry to SARDI as part of their license requirements and for the period November 2003 to October 2009 inclusive. The winter boat days are in brackets and are clearly much less than for summer where the largest vessel activity occurs off Robe (east zone), between Kangaroo Island and the Eyre Peninsula (mostly the central zone) and inshore of the 70 m isobath and then the region to the south of Kangaroo Island (central zone). Minimal vessel activity is found during winter for the west zone and offshore of the 70 m isobath with a total of 19 boat days.

Now consider similar data for the sardine fishery. The data supplied to SARDI is boat trips by individual vessels each month. Data on the number of days at sea is not provided, but typically might be 3-5 days per trip. The number of boat trips shown in Fig. 6.2 is for the summer and winter periods defined above and again obtained for the period November 2003 to October 2009 inclusive. One degree squares that have no entries indicate no trips for these periods. Clearly, most of the sardine vessel activity is confined to the region between Kangaroo Island and the Eyre Peninsula with little activity in the west zone and none in the east zone.

Fig. 6.2. The number of boat trips for the sardine fishery for the “summer” (November to April) and “winter” (May to October) periods and for the one degree squares shown.

While the above data give “seasonal” variability, it is also worth noting that the fishing for scalefish is least in winter (July and August) and fishing for sardines is least in August and September. The Rock Lobster fisheries opens in October and activity maximal from then until May. This fishery closes from June 1st. Data on the lobster fishery is commercial in confidence and unavailable. These state based fisheries results are augmented by information regarding both state and commonwealth fisheries from the Australian Fisheries Management Authority (SAXA 2004; p74- 76). The species, number of fishing permits and methods are listed. The spatial extent of those listed is given in a qualitative form that illustrates that all of the three zones discussed here are subject to fishing of the listed species.

63 Shipping routes are also described in SAXA (2004; p76). We quote: International shipping is relatively limited in the Great Australian Bight. The Adelaide Port Authority estimates 35 merchant ships per month enter St Vincent’s Gulf to visit Port Adelaide, Port Stanvac and Ardrossan. Vessel numbers approaching from the west are equal to the number approaching from the east. Vessels from the west pass through Investigator Strait on the north side of Kangaroo Island, while those approaching from the east almost always enter through Backstairs Passage on the east side of Kangaroo Island. About 10 vessels per month cross SAXA to the south of Kangaroo Island on route from Newcastle, Sydney, Port Kembla and Melbourne to ports in Spencer Gulf. These vessels carry ore, metals, wheat, oil, sheep and general cargo.

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