Science Advisory Report 2022/051

Updated reference points and harvest options for the Giant Red Sea Cucumber (Apostichopus californicus) fishery in British Columbia using data from experimental fishing areas

Summary

• The Giant Red Sea Cucumber, Apostichopus californicus, is the subject of a commercial dive fishery (85 licences) in British Columbia, Canada (DFO 2022).
• Despite considerable research, the life history of this species is poorly understood, and many biological parameters cannot currently be estimated, preventing the use of typical fisheries models. As a result, four Experimental Fishing Areas (EFAs) were established in BC in 1998 to study the effects of harvest on sea cucumber densities.
• After 10 years, the EFA data were analyzed, a latent productivity model was developed, and recommendations were made regarding harvest rates and provisional reference points (Hand et al. 2009).
• The EFA project continued until 2015, generating another 8 years of data.
• The present document updates harvest advice based on the original latent productivity model (with some updates) and the full time series of EFA data, and also updates reference points.
• It is recommended to continue using 0.01 quantiles of the estimated sustainable harvest amounts as per Hand et al. (2009). Sustainable harvest amounts are provided in Table 1 for a variety of harvest strategies and post-harvest stock level objectives. For example, for a post-harvest stock level of 0.6 B₀ the sustainable annual harvest amount ranges from 2.0 - 8.0% of pre-harvest biomass (pre-harvest biomass is the biomass estimated from the most recent survey data). Harvest amounts for other post-harvest stock levels and harvest intervals are presented in Table 1. The upper ranges of the harvest amounts from the four EFAs may only be appropriate for areas with high productivity.
• The recommended coast wide Limit Reference Point is 0.029 sea cucumbers m^-2 on sea cucumber habitat (spatial) and the Upper Stock Reference Point is 0.038 sea cucumbers m^-2 on sea cucumber habitat (spatial). Reference points are expressed in spatial density units because this unit of measurement is independent of transect length and therefore more biologically meaningful and comparable among areas.
• The sea cucumber stock status will be assessed against the LRP and USR using a new coast wide multispecies benthic invertebrate survey that has been recently developed in a separate Canadian Science Advisory Secretariat (CSAS) process.
• It is recommended that future research consider the drivers of variable productivity, source/sink dynamics, Sea Otter (Enhydra lutris) impacts and whether coast wide reference points are appropriate. Future work comparing the recommended empirical reference points to B_MSY- or B₀-based reference points developed through data-rich methods could also be explored.

This Science Advisory Report is from the April 5-6, 2022 regional peer review on the Update to reference points and harvest advice for the commercial Sea Cucumber (Apostichopus californicus) Fishery in British Columbia. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2022/051 (PDF, 689 KB)

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