Population Dynamics and Reproductive Ecology of the Southern Calamary in Tasmania
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FRDC FINAL REPORT POPULATION DYNAMICS AND REPRODUCTIVE ECOLOGY OF THE SOUTHERN CALAMARY (SEPIOTEUTHIS AUSTRALIS) IN TASMANIA Natalie Moltschaniwskyj, Gretta Pecl, Jeremy Lyle, Malcolm Haddon, & Michael Steer June 2003 FRDC Project No. 2000/121 National Library of Australia Cataloguing-in-Publication Entry Moltschaniwskyj, Natalie Ann, 1965- Population dynamics and reproductive ecology of the southern calamary (Sepioteuthis australis) in Tasmania. ISBN 1 86295 104 7 1. Squid fisheries - Tasmania. 2. Squids - Reproduction - Tasmania. I. Moltschaniwskyj, N. II. Tasmanian Aquaculture and Fisheries Institute. 639.485809946 Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Private Bag 49, Hobart, Tasmania 7001. E-mail: [email protected]. Ph. (03) 6227 7277 Fax (03) 6227 8035 The opinions expressed in this report are those of the author/s and are not necessarily those of the Tasmanian Aquaculture and Fisheries Institute. Tasmanian Aquaculture and Fisheries Institute, University of Tasmania 2003. Copyright protects this publication. Except for purposes permitted by the Copyright Act, reproduction by whatever means is prohibited without the prior written permission of the Tasmanian Aquaculture and Fisheries Institute. Table of Contents Table of Contents 2 List of Figures 4 List of Tables 9 Non-Technical Summary 12 Acknowledgements 16 Background 17 Need 18 Objectives 19 General Introduction 20 Chapter 1: Small-scale spatial and temporal patterns of egg production by the temperate loliginid squid Sepioteuthis australis 22 Introduction .................................................................................................................22 Materials and Methods................................................................................................23 Results.........................................................................................................................27 Discussion ...................................................................................................................32 Chapter 2: An assessment of the use of short-term closures to protect spawning southern calamary aggregations from fishing pressure in Tasmania, Australia 34 Introduction .................................................................................................................34 Materials and Methods................................................................................................35 Results.........................................................................................................................37 Discussion ...................................................................................................................44 Chapter 3: Temporal variability in embryonic development and mortality in the southern calamary Sepioteuthis australis: a field assessment 48 Introduction .................................................................................................................48 Materials and Methods................................................................................................50 Results.........................................................................................................................52 Discussion ...................................................................................................................57 Chapter 4: Spawning aggregations of squid (Sepioteuthis australis) populations: fisheries management of a continuum of ‘micro-cohorts’ 60 Introduction .................................................................................................................60 Methods and Materials................................................................................................61 Results.........................................................................................................................63 Discussion ...................................................................................................................73 Chapter 5: Interannual variation in the spawning aggregations 76 Introduction .................................................................................................................76 Materials and Methods................................................................................................78 Results.........................................................................................................................80 Discussion ...................................................................................................................92 Chapter 6: Large scale temporal and spatial patterns of adult populations and spawning activities 96 Introduction .................................................................................................................96 FRDC Final Report 2000/121, Page 2 Material and Methods..................................................................................................97 Results.......................................................................................................................100 Discussion .................................................................................................................114 Chapter 7: Description and assessment of the Tasmanian southern calamary fishery 117 Background ...............................................................................................................117 Management context .................................................................................................117 Data sources ..............................................................................................................119 Catch, effort and catch rates......................................................................................120 Modelling the southern calamary fishery..................................................................129 Management Implications.........................................................................................141 Benefits and Beneficiaries 143 Further Developments 143 Planned Outcomes 145 Conclusions 146 Literature Cited 149 Appendix 1: Intellectual Property 159 Appendix 2: Staff Involved 159 FRDC Final Report 2000/121, Page 3 List of Figures Figure 1.1: Map of Tasmania and Great Oyster Bay showing the two locations surveyed. ............................................................................................................... 23 Figure 1.2: An egg mass made up of a number of egg strands (A). Each egg strand contains between three and nine eggs (B)............................................................. 25 Figure 1.3: The average density of newly laid egg strands at each of the two locations during the thirteen months of monitoring. - = no data. Hazard Bay n=60, Coles Bay n=48. Letters above the means are results of the post-hoc test; means sharing the same letter are not significantly different. (from Moltschaniwskyj & Pecl 2002) ..................................................................................................................... 27 Figure 1.4: The number of Stage I eggs produced in the sites monitored in each of the two locations in 1999 (solid bars) and 2000 (cross-hatched bars). Note different scale for each location. - = no data. (from Moltschaniwskyj & Pecl 2002)........ 28 Figure 1.5: The average density of Amphibolis plants and the average height of the plants across the two locations in summers of 1999 and 2000. (from Moltschaniwskyj & Pecl 2002)............................................................................. 30 Figure 1.6: Differences in the average density of egg masses deposited at two sites in Hazards Bay between two consecutive survey dates approximately two weeks apart. If the confidence limits do not encompass zero then the average difference in the density of egg masses is significantly different from zero. (from Moltschaniwskyj & Pecl 2002)............................................................................. 31 Figure 1.7: The wind speed (km/hr) and atmospheric pressure (HPa) during the spring/early summer of 1999 and 2000. The arrows indicate the days on which surveys of the eggs masses were conducted. The asterisks indicated times at which egg mass loss had been detected. (from Moltschaniwskyj & Pecl 2002) . 31 Figure 2.1: Map of Tasmania and Great Oyster Bay showing the location of the study area. ....................................................................................................................... 35 Figure 2.2: The mean number of egg strands.m-2 (± standard error), in Hazards Bay (solid line) and Coles Bay (dashed line). Means with different letters are significantly different from one another based on post-hoc Tukeys HSD test among the ten means. In 2000 the letters refer to means at each time across locations. ............................................................................................................... 38 Figure 2.3: The mean gonosomatic index for females and males for the open and closure periods in 1999 and 2000 for the two locations combined. The sample size is indicated above each mean......................................................................... 39 Figure 2.4: The total body weight for females and males for the four occasions during the study across the two locations. The sample size is indicated above each mean. Females caught during Open 2 were not included in the analysis because only three were caught. ................................................................................................