Research Document - 2014/031

Environmental conditions in the southern Gulf of St. Lawrence relevant to lobster

By J. Chassé, N. Lambert, M. Comeau, P.S. Galbraith, P. Larouche, and R.G. Pettipas

Abstract

Environmental conditions in the southern Gulf of St. Lawrence (sGSL) were examined in relation to lobster (Homarus americanus). Data analysis show that recent annual mean air temperatures over the sGSL have been above normal, with 2010 having the highest temperature on record surpassing 1999, 2006 and 2012. Furthermore, maximum ice volumes of years 2010 to 2012 were among the lowest values since 1969. This is in agreement with the volume of the Cold Intermediate Layer that shows a decrease in recent years. Sea Surface Temperature, based on satellite imaging, has been generally increasing between 1986 and 1999, and relatively stable since in each Lobster Fishing Area (LFA). The ocean surface degree-days accumulation over 4°C was variable but for all LFAs, the rate was the fastest in 2006 and the slowest in 2011. Small increases in bottom water temperatures were observed since the mid 1990’s in several LFAs. Frequency distribution calculations show that 95% of the lobsters were found in bottom water temperatures between 0.1 and 13.3°C in June while they were found in temperatures between 2.5 and 18.2 °C in September. Based on bottom water temperatures, the habitat index of lobster shows significant variability and it has been increasing in June during the 1999-2012 time period. In September, an increase of the habitat index of lobster is also observed during the same period but to a lesser extent.

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