Research Document - 2001/160

A Phase '0' review of the biology and fisheries of the Tanner Crab (Chionoecetes bairdi)

By G.G. Krause, G. Workman and A.C. Phillips

Abstract

The Tanner crab (Chionoecetes bairdi) may present some potential as a candidate for a largely inshore developmental trap fishery in British Columbia. Significant fisheries targeting Tanner and related crabs have been carried out in Alaska, Japan and the Canadian Maritimes for some years and considerable information on their biology has been accumulated. This document comprises a review of available information on these crabs in the scientific literature. Biological data identified as relevant to the fishery development process by Perry et al. (1999) are summarized although it should be noted that these data are largely derived from fished Alaskan stocks which are likely considerably different than BC stocks. Biological and catch data for C. bairdi in BC are presented from a number of sources, including exploratory surveys and bycatch data from other fisheries.

Tanner crab fisheries appear to follow a 'typical' pattern of development as production and effort quickly rise through the exploratory phase followed by cyclic catch variation over a few decades followed by a dramatic decline in abundance. This is mediated by a number of factors, including possible environmental and natural abundance variations but, in Alaska at least, the end result has been generally characterized as serial depletion of the stocks, as the fishing effort radiates further from fishing ports onto stocks which have not been exploited as a means to maintain high catch levels. Few affected stocks have recovered once so depleted, highlighting the need for caution as the potential for a sustainable fishery is defined.

These crab are widely distributed in BC waters. The data gathered thus far suggest there are significant differences in the biological characteristics of Tanner crab in different areas of BC, supporting the hypothesis that the animals occur primarily as discrete inlet stocks with limited exchange between areas. The information available on the specific biological features of the animals in each area is, however, limited and data on local abundance(s), growth, maximum size, population structure(s), spatial reproductive scale and continuity, mortality, fecundity, spawning, migration patterns, aggregating behaviours and locations are required.

Preliminary exploratory surveys using standardized Tanner crab pots and survey methods are recommended to determine the distribution, biological characteristics, stock structure and relative abundance between areas. Tagging studies to investigate local movement(s) and growth patterns of the crab are also recommended.

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