Research Document - 2006/045

Temperature Conditions in the Southern Gulf of St. Lawrence during 2005 Relevant to Snow Crab

By Chassé, J., R.G. Pettipas and W.M. Petrie

Abstract

Temperatures during 2005 are presented for the waters of Southern Gulf of St. Lawrence inhabited by snow crab. Data were available from a number of sources including snow crab and multi-species surveys. In 2005, near bottom temperatures in the southern part of the Southern Gulf, from Miscou Island to western Cape Breton and all around PEI, were significantly below normal while the deeper parts of the Magdalen Shallows, including Chaleur Bay, exhibited warmer than normal conditions (average based on 1971-2000 period). A snow crab habitat index, defined by the area of the bottom covered by waters between -1° to 3°C, was calculated for the southern Gulf region. The habitat index is now above the long-term average. However, the mean temperature within the habitat area in 2005 also significantly increased compared to 2004; this is an unusual situation as the two time series are negatively correlated. The mean temperature is above the long term mean, reaching a value similar to the ones observed during the 1999-2002 warm period and is the highest of the last 23 years. The crabs caught during the annual snow crab surveys were found in warmer waters in 2005 than in 2004, which is believed to reflect in large part the warmer temperatures as opposed to 2004 when cooler conditions were observed.

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