Research Document 1998/86

Assessment of the Area A crab (Cancer magister) fishery in British Columbia

By J.A. Boutillier, T.H. Butler, J. Bond, I. Winther, and A. Phillips

Abstract

This paper is an assessment of the crab (Cancer magister) populations for British Columbia Crab Fishing Area A and adjacent offshore areas in Hecate Straits. The paper conducted three types of analyses: (1) a review of the various fishery dependant abundance indices and biological data. (2) biomass dynamic modeling of the various abundance indices and (3) a yield per recruit analysis of the theoretical growth, natural mortality and value data. There were a number of findings indicated that were quite different trends depending on the abundance index used and that care must be taken to determine the most appropriate index. In general however there were some findings which were consistent throughout. These included:

1. That the fisheries in McIntyre Bay and Hecate Strait have quite different dynamic behaviour.
2. That present effort levels are higher than E_opt in both the biomass dynamic models and the yield per recruit models.

As a result of the various findings the following recommendations were made:

1. Improve the logbook data and fish slip data with respect to reporting of area, soak time and gear used. This should be done in consultation with the industry to determine ways of improving reporting.
2. Consider the implications of managing McIntyre Bay and Hecate Strait together. Be aware that McIntyre Bay crab populations do not go through the same degree of fluctuations as Hecate Strait crab populations. Also be aware that even analyses which are considered to overestimate E_opt , indicate that effort in both areas already exceeds E_opt.
3. There is a need to develop a fishery independent assessment program that will provide checks as to the most appropriate fishery dependent index and allow us to gather information on the population that is not targeted on e.g. females and juveniles.
4. There is a need to collect biological data from fishery dependent and independent sources that are more consistent in frequency and cover critical biological periods (minimum spring and fall i.e. pre- and post-moulting) and more detailed with respect to the biological information gathered (an objective shell condition criteria must be developed).
5. Industry should be discouraged from leaving gear soak for excessive periods of time as the impact in terms of mortality of crabs is probably significant.

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