Research Document - 2004/026
Utility of Historical Catch Data in Setting Reference Points for the British Columbia Shrimp by Trawl Fishery
By Rutherford, D.T., Barton, L.L., Gillespie, G.E., Boutillier, J.A.
Abstract
The current assessment and management framework utilizes fishery independent survey methods to index shrimp biomass in selected Shrimp Management Areas (SMA's). Annual catch limits in surveyed SMA's are set based on applying a harvest rate to the estimated biomass index. Annual catch limits in the non-surveyed SMA's are set through two different methods. For some SMA's biomass is indexed through extrapolation procedures using neighbouring survey sites. For all non-indexed sites arbitrary catch ceilings are set by fish managers.
Historical catch data from the shrimp trawl fishery is not a suitable proxy for abundance. Historical catch data have poor resolution to species or current management area and lack supporting information to track stock trends over the historical time period. Even in the hypothetical event that historical catch did track past abundance, the shrimp trawl fishery is undergoing profound changes including size and species specific targeting which would invalidate the use of historical catch records in reference point models.
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