Science Advisory Report  2010/078

Updated framework for the pink and spiny scallop (Chlamys rubida and C. hastata) dive fishery in British Columbia

Summary

• A revised assessment framework for the pink and spiny scallop dive fishery was presented in 2010 describing new survey methodology and providing revised and new estimates of pink and spiny scallop density and biomass, along with updated estimates of population parameters and a new look at harvest rates.
• Pink and spiny scallop density and biomass at survey locations in 2008–2009 was found to be 25–35% lower than the same locations in 2001–2002 but it is unknown whether the differences in density and biomass represent a declining trend, a change in distribution, or a natural fluctuation in population size.
• A cautious approach to harvest is recommended in response to the unexplained drop in density and biomass estimates that appears to have occurred between the 2001-2002 and 2008-2009 sampling events in PFMA 18-1 and PFMA 29-5.
• As there are only two areas (Mayne Island – PFMA 18-1, Valdes Island – PFMA 29-5) with any time series of biomass surveys, continuation of annual or biannual biomass assessment surveys and collection of biological data from these two areas is recommended.
• Given the continuing paucity of time series for biomass assessment surveys and biological data, the current harvest rate of 4% of legal-sized biomass is recommended for the areas to be fished. However, planning of future fishing opportunities in PFMA 18-1 (Mayne Island) and PFMA 29-5 (Valdes Island) requires particular caution, given the large decrease in densities observed between 2001-2002 and 2008-2009.
• Should harvest from unexploited areas be considered, the collection of biological samples from these areas is required to confirm maximum size and age for pink and spiny scallops, and delineation of bed areas is recommended.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat Pacific Regional Advisory meeting of November 30 – December 2, 2010 on Pink and Spiny Scallop, Sea Cucumber, Central Coast Manila Clam, Geoduck Clam Aquaculture, and Shrimp Trawl. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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