Updated Reference Points and Harvest Options for the Giant Red Sea Cucumber (Apostichopus californicus) Fishery in British Columbia using data from Experimental Fishing Areas

Abstract

The Giant Red Sea Cucumber, Apostichopus californicus, is the subject of a lucrative commercial dive fishery in British Columbia (BC), Canada. Despite considerable research, the life history of this species is poorly understood and many biological parameters cannot 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, 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 EFAs continued until 2015, generating another 8 years of data. This document updates harvest advice based on the original latent productivity model (with some updates) and the full time series of EFA data. Maximum sustainable harvests are presented for various harvest strategies, combining harvest intervals of 1 to 5 years with different minimum equilibrium stock level thresholds (minimum observed, 0.50 B0, 0.60 B0, and 0.80 B0) and estimates of either current or virgin biomass. Recommendations include implementing harvests that do not exceed the range of the lower 0.01 quantile for equilibrium stock outcomes above 0.60 B0. For example, for annual harvest rates, the range not to be exceeded is 2.0 to 8.0% of estimated pre-harvest biomass, whereas for triennial harvest it is 5.7 to 18.8% of estimated pre harvest biomass, with the caveat that the upper ranges may only be appropriate for highly productive areas. Furthermore, the adoption of empirical reference points is recommended: a conservative Limit Reference Point of 0.029 sea cucumbers m-2 on sea cucumber habitat, and an Upper Stock Reference Point of 0.038 sea cucumbers m-2 on sea cucumber habitat.