Research Document - 2012/118

Analyses of newly molted commercial-sized male crab percentages in landings in the southwestern Gulf of St. Lawrence snow crab fishery (Area 12): Why the estimated percentages were abnormally higher in the 2009 and 2010 seasons?

By M. Moriyasu, M. Biron, P. DeGrâce, and M. Hébert

Abstract

The percentage of newly molted crabs (soft and white crabs) in landings has been historically low, i.e., an average of 1.6% (not adjusted to landings) between 1992 and 2008, as these crabs are not marketable. However, a considerable increase in the estimated numbers of landed commercial-sized newly molted crabs was observed in 2009 (13.5%) and 2010 (10.5%) in the southern Gulf of St. Lawrence (sGSL) snow crab fisheries. These estimates, based on at-sea sampling data, did not concord with the observations reported by some participants from the fishing industry on the level of newly molted crabs in landings. These data were reviewed in more detail to better understand the source of the discrepancies. Results showed that there were discrepancies in the carapace condition categorization criteria between observers from Biorex Gaspé and Biorex Caraquet. This difference was due to the different criteria for carapace conditions used by DFO Québec and DFO Gulf (Moncton). A new protocol was implemented in 2009 by DFO Québec and Biorex Gaspé prior to the fishing season in the northern GSL snow crab fisheries and consequently a significant number of crabs with carapace condition 3 were classified as 2 by observers from Biorex Gaspé working in the sGSL fisheries. Hence, between 2008-2010 the percentages were significantly overestimated for vessels sampled by Biorex Gaspé compared to those sampled by Biorex Caraquet. The discrepancy was adverted for the 2011 fishing season as the situation was explained to observers from both groups during the observer training sessions and necessary adjustments were made. As a result, the percentage of white crab in landings was at a low level (1.1% in Area 12) in 2011.

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