Research Document - 2006/080

An assessment of the snow crab resident on the Scotian Shelf in 2005

By Choi, J.S. and B.M. Zisserson

Abstract

For the 2005 fishing season, landings of snow crab were 562 and 6407 t for N-ENS and S-ENS, respectively. Relative to 2004 landings, this represents a decline of 61% and 24%, respectively. These declines were due to reductions in TACs, which were attained by both areas. Most landings were obtained from offshore areas. Catch rates were 30.6 kg/trap and 109.4 kg/trap for N-ENS and S-ENS, respectively. N-ENS catch rates have declined 50% relative to 2004 levels while those of S-ENS have increased marginally. However, due to the removal of sub-area lines, higher catch rates were expected, apriori. The offshore slope areas were minimally exploited. Discard rates of soft-shelled crab were high as was the exploitation of immature crab.

Mature female numbers have increased from the maturation of the leading edge of juvenile female pulses observed for the past three years. Mature male numbers have declined, resulting in increasingly more balanced sex ratios. The abundance of snow crab on the Scotian Shelf declined in 2005, continuing the downward trend observed since the peak abundances of the late 1990s and early 2000s. Fishable biomass estimates as of the winter of 2005 stands at approximately 1200 t and 20800 t, in N-ENS and S-ENS, respectively. They represent declines of 11% and 29%, respectively, even with the large TAC reductions of the 2005 season. Recruitment to the mature fishable biomass expected for 2006 was very low, whereas recruitment to the immature fraction of the fishable biomass is expected to be large. Forecasts of potential future trends indicate that soft-shell incidence will be a major issue in the 2006 season. The 2007 season should see the beginning of a recovery of the fishery.

Due to the (1) continued declines in fishable biomass, even though exploitation rates were reduced in the 2005 season; (2) the Scotian shelf snow crab entering a reproductive mode with dwindling numbers of large adult males; (3) high likelihood of soft-shell incidence in the 2006 season; and (4) the untested nature of the (optimistic) projections of future fishable biomass, a conservative approach to the fishery is recommended for the 2006 season.

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