Reducing uncertainty in fisheries stock status James Larcombe, Rocio Noriega and Ilona Stobutzki (editors) Research by the Australian Bureau of Agricultural and Resource Economics and Sciences Publication series September 2015 © Commonwealth of Australia 2015 Ownership of intellectual property rights Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this publication is owned by the Commonwealth of Australia (referred to as the Commonwealth). Creative Commons licence All material in this publication is licensed under a Creative Commons Attribution 3.0 Australia Licence, save for content supplied by third parties, logos and the Commonwealth Coat of Arms. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided you attribute the work. A summary of the licence terms is available from creativecommons.org/licenses/by/3.0/au/deed.en. The full licence terms are available from creativecommons.org/licenses/by/3.0/au/legalcode. Cataloguing data ABARES 2015, Reducing uncertainty in fisheries stock status, ABARES research report, Canberra, August. CC BY 3.0. ISBN 978-1-74323-254-5 ABARES project 25679 Internet Reducing uncertainty in fisheries stock status is available at agriculture.gov.au/abares/publications. Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) Postal address GPO Box 858 Canberra ACT 2601 Switchboard +61 2 6272 2010 Facsimile +61 2 6272 2001 Email [email protected] Web agriculture.gov.au/abares Inquiries about the licence and any use of this document should be sent to [email protected]. The Australian Government acting through the Department of Agriculture, represented by the Australian Bureau of Agricultural and Resource Economics and Sciences, has exercised due care and skill in preparing and compiling the information and data in this publication. Notwithstanding, the Department of Agriculture, ABARES, its employees and advisers disclaim all liability, including for negligence and for any loss, damage, injury, expense or cost incurred by any person as a result of accessing, using or relying upon information or data in this publication to the maximum extent permitted by law. Acknowledgements The Reducing Uncertainty in Stock Status (RUSS) research team at ABARES comprised: Belinda Barnes, Veronica Boero, Mark Chambers, James Larcombe, Adam Leatherbarrow, Rocia Noriega, Kevin McLoughlin, Heather Patterson, Lindsay Penrose, Ilona Stobutzki, Peter Ward and James Woodhams. The research team at CSIRO comprised: Natalie Dowling, Malcolm Haddon, Neil Klaer, Eva Plagányi, Tim Skewes and Sally Wayte. The project was funded by the (then) Department of Agriculture, Fisheries and Forestry. Reducing uncertainty in stock status ABARES Contents 1 Overview 1 Stocks and biological status 1 Reducing uncertainty in stock status 3 Reducing uncertainty in stock status assessments and papers 3 Discussion and conclusions 8 Management strategy evaluation 9 References 12 2 Coral Sea Fishery: Aquarium Sector assessments 14 Summary 14 Introduction 15 Data and information 16 Methods 18 Results 20 Discussion 25 Appendix A: Key commercial families collected 26 References 26 3 Assessing Coral Sea Fishery sea cucumber stocks using spatial methods 28 Summary 28 Introduction 29 Background 30 Methods 34 Results 40 Discussion 51 Appendix B 54 References 56 4 Coral Sea Fishery Line and Trap Sector: preliminary stock assessments 58 Summary 58 Introduction 59 Catch and effort statistics 60 Assessment approaches 70 Part 1: Habitat assessment 71 Part 2: The deep scalefish assemblage 73 Part 3: The reef scalefish assemblage 79 Part 4: The shark assemblage 88 Appendix C 91 References 97 iii Reducing uncertainty in stock status ABARES 5 Status determination for trochus and tropical rock lobster stocks in the Coral Sea Fishery Hand Collection Sector 100 Summary 100 Introduction 100 Tropical rock lobster 102 Trochus 106 References 106 6 Status determination for the deepwater prawn stock in the North West Slope Trawl Fishery 108 Summary 108 Introduction 108 Background information 110 Analysis 111 Discussion 125 Appendix D 126 References 127 7 North West Slope Trawl Fishery Scampi assessment 130 Summary 130 Introduction 130 Catch and effort 133 Methods 135 Results 138 Discussion and status 142 Appendix E 144 References 146 8 Elephant fish catch rate standardisation and Tier 4 assessment, 2009 148 Summary 148 Introduction 148 Data preparation 150 Catch per unit effort standardisation 151 Tier 4 assessment 154 Appendix F 157 References 161 9 Sawshark catch rate standardisation and Tier 4 assessment, 2009 162 Summary 162 Introduction 162 Data preparation 164 Catch per unit effort standardisation 165 Tier 4 assessment 168 Conclusion 170 iv Reducing uncertainty in stock status ABARES Appendix G 171 References 175 10 Depletion analyses of Gould’s squid in the Bass Strait 176 Summary 176 Introduction 176 Data and methods 178 Results 183 Discussion 192 Conclusion 193 Appendix H 194 References 197 11 Stock status determination: weight-of-evidence decision-making framework 199 Summary 199 Introduction 199 Methods 200 Weighing evidence 213 Reporting of stock status 216 Appendix I 216 References 219 Tables Table 2.1 Area (km²) of suitable habitat classes for aquarium fish in the Coral Sea Fishery 16 Table 2.2 The scoring system to assess the vulnerability of marine aquarium species in the Coral Sea Fishery Aquarium Sector 19 Table 2.3 Scoring system to assess the susceptibility of the marine aquarium species captured in the Coral Sea Fishery Aquarium Sector applied to species with medium or high vulnerability 20 Table 2.4 Estimates of maximum footprint for the sector 20 Table 2.5 Summary of observed minimum and maximum densities, estimated suitable habitat area, standing stock and annual extraction rates based on 2008–09 catch data 22 Table 2.6 Vulnerability risk scores for species within the Aquarium Sector of the Coral Sea Fishery 23 Table 2.7 Susceptibility risk scores for species within the Aquarium Sector of the Coral Sea Fishery 24 Table 3.1 Catch statistics by reef for hand collection operations in the CSF 32 v Reducing uncertainty in stock status ABARES Table 3.2 Natural mortality estimates used by Skewes et al. (2004) for the Torres Strait and those used in these analyses 39 Table 3.3 Parameters (per hectare) used to estimate population size 41 Table 3.4 Habitat areas (in hectares) of the five habitat classes of interest 43 Table 3.5 Average animal weight for the four key commercial sea cucumber species in the Coral Sea Fishery 43 Table 3.6 Black teatfish population (numbers), biomass (kg) and maximum sustainable yield (kg) estimates by reef 45 Table 3.7 White teatfish population (numbers) biomass (kg) and maximum sustainable yield (kg) estimates by reef 46 Table 3.8 Prickly redfish population (numbers) biomass (kg) and maximum sustainable yield (kg) estimates by reef 47 Table 3.9 Surf redfish population (numbers), biomass (kg) and maximum sustainable yield (kg) estimates by reef 48 Table 3.10 Proportion of biomass remaining, 20th percentile starting biomass, Schaefer model and Pella–Tomlinson model 49 Table 3.11 Proportion of biomass remaining, median starting biomass, Schaefer model 50 Table 3.12 Proportion of biomass remaining, median starting biomass, Pella– Tomlinson model 51 Table 4.1 Coral Sea Fishery line sector annual financial year catch (kg) by species/species group 62 Table 4.2 Coral Sea Fishery trap sector annual financial year catch (kg) by species/species group 68 Table 4.3 Yield scenarios for the Coral Sea Fishery deep scalefish assemblage 77 Table 4.4 Yield calculations for the Coral Sea Fishery reef scalefish assemblage based on low and medium biomass scenarios (exploitation constant x=0.3, x=0.5 and x=0.7) 85 Table 7.1 Standing stock of scampi in North West Slope Trawl Fishery by Davis and Ward (1984) 132 Table 7.2 Biological parameters and model settings for North West Slope Trawl Fishery combined scampi used in stock reduction analysis 132 Table 7.3 A Stock Production Model Incorporating Covariates production model runs for North West Slope Trawl Fishery scampi 138 Table 7.4 Summary results of production model runs for North West Slope Trawl Fishery scampi 140 Table 8.1 Elephant fish 2009 Tier 4 methodology results (all areas) for two candidate reference periods 155 Table 9.1 Sawshark 2009 Tier 4 methodology results (base case, all areas) 170 Table 10.1 Results of the depletion analysis that used a natural mortality rate of 0.05 190 vi Reducing uncertainty in stock status ABARES Table 11.1 The criteria for status based on the biomass and fishing mortality, in line with HSP 201 Table 11.2 Catch trends and potential implications for status 206 Table 11.3 Size structure and potential implications for status 207 Table 11.4 Age structure and potential implications for status 208 Table 11.5 Effort trends and potential implications for status 209 Table 11.6 Spatial trends in the fishery area and potential implications for status 209 Table 11.7 Spatial closures and potential implications for status 210 Table 11.8 Catch per unit effort trends and potential implications for status 211 Table 11.9 Surveys and potential implications for status 211 Table 11.10 Risk assessments and potential implications for status 212 Table B1 Area of all habitat types in the Coral Sea Fishery 54 Table C1 Proportions of species catch in the Coral Sea Fishery 91 Table C2