Fishery biology of the sea cucumber Parastichopus californicus (Stimpson, 1857) from the San Juan Islands, Washington Lummi Natural Resources Department 2013–2015 Sea Cucumber Study Karl W. Mueller Harvest Management Division INSIDE FRONT COVER LEFT BLANK INTENTIONALLY Fishery biology of the sea cucumber Parastichopus californicus (Stimpson, 1857) from the San Juan Islands, Washington Karl W. Mueller Harvest Management Division Lummi Natural Resources Department 2665 Kwina Road Bellingham, Washington [email protected] 360-312-2316 October 2016 Lummi Natural Resources Department 2013–2015 Sea Cucumber Study Suggested citation for report: Mueller, K. W. 2016. Fishery biology of the sea cucumber Parastichopus californicus (Stimpson, 1857) from the San Juan Islands, Washington. Harvest Management Division Technical Report, October 2016, Lummi Natural Resources Department, Bellingham, Washington. Pp. 98 including Appendices. Lummi Natural Resources Department 2013–2015 Sea Cucumber Study ABSTRACT The California (or giant red) sea cucumber Parastichopus californicus (Stimpson, 1857) (Echinodermata: Aspidochirotida: Stichopodidae) has been commercially harvested from the marine waters of Washington State for more than 40 years, but the dive fisheries (primary gear type) targeting P. californicus have only been actively managed for about 20 years following their peak production in the late 1980s and early 1990s. Today, all P. californicus dive fisheries are co-managed by the western Washington treaty tribes, including the Lummi Nation, and the state’s natural resource authority, the Washington Department of Fish and Wildlife (hereafter, “co-managers”). While the co-managers continue to collaborate on stock assessment procedures for P. californicus and to refine harvest strategies for the species, gaps in the co-managers’ understanding of the basic fishery biology of P. californicus remain an issue (as is the case for many sea cucumber fisheries across the Pacific Ocean and elsewhere). To rectify the problem, the Lummi Natural Resources Department (LNR) agreed to conduct field research that was designed to extend the published work of others and to verify management-relevant aspects of P. californicus life history. Fishery-dependent and fishery-independent data were gathered during various months from June 2013 through May 2015 at 12 sites in the San Juan Islands, Washington that were open to commercial harvest diving. Fifty P. californicus were hand- collected by diver(s) during each sampling trip (n = 18) and individually bagged to insure that any ejected coelomic contents, including gonads, were traced back to the individual sea cucumber (N = 900). In the laboratory, the whole, wet (round) weight of P. californicus was recorded then the sea cucumber was dissected to determine its sex, split-and-drained (market) weight, and gonad weight. In addition, notes on the incidence of ecto- and endofauna associated with P. californicus were recorded. Existing morphometric analyses were used to convert sea cucumber weights to estimated whole, contracted lengths and to estimate the age of P. californicus to 6+ years. Finally, a gonadosomatic index was used to evaluate reproductive maturity. This report contains useful information about the age and growth of P. californicus, and the size structure and reproductive biology of the species in the San Juan Islands, Washington. Several indicators of size-selective harvesting of P. californicus are described, including a decrease in the average market weight of individual sea cucumbers compared to market weights from past decades. The LNR study also revealed that local reproductive capacity of the sea cucumber may be impacted by size-selective harvesting and that peak spawning in P. californicus occurs several weeks earlier in Washington State compared to that which was previously published for the species. Lastly, some novel information is provided concerning the relationship between P. californicus and a commensal polychaete worm and parasitic snail. Several management considerations are discussed based on the LNR findings: 1) implementing a size restriction for P. californicus, 2) updating harvestable biomass estimates more frequently, 3) adjusting timing of the sea cucumber spawning closure, 4) expanding assessment of P. californicus inside of existing no-harvest zones, and 5) integrating the LNR findings with current sea cucumber hatchery practices. Lummi Natural Resources Department 2013–2015 Sea Cucumber Study THIS PAGE LEFT BLANK INTENTIONALLY Lummi Natural Resources Department 2013–2015 Sea Cucumber Study TABLE OF CONTENTS List of Figures iii List of Tables vi INTRODUCTION 1 MATERIALS AND METHODS 5 Data Analyses 11 RESULTS 16 Environmental Conditions 16 Age and Growth 18 Size Structure 23 Relationship between Round Weight and Market Weight 27 Reproductive Biology, Gonadosomatic Index, and Spawning Periodicity 30 Incidence of a Commensal Scale Worm and a Parasitic Snail 36 DISCUSSION 40 Impact of Global Climate Change 40 Growth of P. californicus and Lee’s Phenomenon 42 Size-Selective Harvesting 44 Genetic Change(s) in P. californicus? 45 Spawning Periodicity 45 Change in Reproductive Capacity of P. californicus? 47 Ecto– and Endofauna of P. californicus 47 MANAGEMENT CONSIDERATIONS 48 Implementing a Size Restriction for P. californicus 48 Updating Harvestable Biomass Estimates More Frequently 51 Adjusting Timing of the Sea Cucumber Spawning Closure 52 Lummi Natural Resources Department 2013–2015 Sea Cucumber Study Page i Expanding Assessment of P. californicus Inside of No-Harvest Zones 53 Integrating the LNR Findings with Current Sea Cucumber Hatchery Practices 54 CONCLUSION 55 ACKNOWLEDGEMENTS 56 REFERENCES 57 APPENDIX A Size frequency histograms derived from fishery-dependent data 69 APPENDIX B Size frequency histograms derived from fishery-independent data 71 APPENDIX C Field and laboratory data from the LNR 2013–2015 sea cucumber study 73 Lummi Natural Resources Department 2013–2015 Sea Cucumber Study Page ii LIST OF FIGURES Figure 1. Map of Parastichopus californicus management districts 2 Figure 2. Voluntary minimum size limit used by many commercial harvest divers 3 Figure 3. Trend in landings of P. californicus in Washington State, 2000–2013 4 Figure 4. Map of P. californicus sampling locations 5 Figure 5. LNR staff diver preparing to sample sea cucumbers off Vendovi Island 6 Figure 6. Determining round weight or whole, wet weight in air (WWA) 7 Figure 7. Commensal scale worm Arctonoe pulchra 8 Figure 8. Determining sex of P. californicus 8 Figure 9. Undeveloped gonad of immature sea cucumber 9 Figure 10. Parasitic snail Enteroxenos parastichopoli 9 Figure 11. Determining gonad weight 10 Figure 12. Determining market weight or split-and-drained weight in air (SWA) 10 Figure 13. Natural variation in shape and length of P. californicus 12 Figure 14. Determining body size index of Parastichopus 12 Figure 15. Monthly averages of various water quality parameters measured during study 17 Figure 16. CTD instrument used to record water quality parameters by depth 17 Figure 17. Other water quality parameters and diver depths 17 Figure 18. PAR readings at 5-m depth encountered while sampling sea cucumbers 17 Figure 19. Results of size frequency analysis of SWAs of P. californicus 19 Figure 20. Percent frequency distributions of estimated ages of P. californicus 19 Figure 21. Cumulative distribution plot of SWAs from commercial ride-along trips 21 Figure 22. Cumulative distribution plot of SWAs, fishery-independent sampling trips 21 Figure 23. Cumulative distribution plot of est. contracted lengths (WL), commercial 22 Figure 24. Cumulative distribution plot of WL from fishery-independent sampling trips 22 Lummi Natural Resources Department 2013–2015 Sea Cucumber Study Page iii Figure 25. Box-and-whisker plots of SWAs for all sampling dates 24 Figure 26. Box-and-whisker plots of SWAs, fishery-dependent vs. fishery-independent 24 Figure 27. Box-and-whisker plots of SWA by general location 25 Figure 28. Box-and-whisker plots of SWA by sampling depth 25 Figure 29. Mean (± SD) SWAs plotted for sex by sampling date vs. historic SWAs 26 Figure 30. Historical photograph analysis of WLs from two time periods 27 Figure 31. Relationship between loge WWA and loge SWA plotted by sampling period 28 Figure 32. Ratio of SWA to WWA plotted by sampling period 29 Figure 33. Ratio of WWA to SWA plotted by sampling period 30 Figure 34. Sex ratio of P. californicus plotted as proportions by sampling date 31 Figure 35. Mean (± SD) gonadosomatic index (GSI) plotted for sex by sampling date 31 Figure 36. Relationship between gonad weight and WL, ♀ P. californicus, May 2014 33 Figure 37. Relationship between gonad weight and WL of ♂ P. californicus, May 2014 33 Figure 38. Relationship between gonad weight and WL of ♀ P. californicus, Mar 2015 34 Figure 39. Relationship between gonad weight and WL of ♂ P. californicus, Mar 2015 34 Figure 40. Mean (± 95% CI) GSIs plotted for sex by sampling period 35 Figure 41. Mean (±95% CI) GSIs plotted for age by sampling period 35 Figure 42. Proportional presence of A. pulchra plotted by sampling date 37 Figure 43. Proportional presence of E. parastichopoli plotted by sampling date 37 Figure 44. Proportional presence of A. pulchra plotted by sampling location 38 Figure 45. Proportional presence of E. parastichopoli plotted by sampling location 38 Figure 46. Proportional presence of A. pulchra plotted by age of P. californicus 39 Figure 47. Proportional presence of E. parastichopoli