Research Document - 2013/035
Results of the Atlantic mackerel (Scomber scombrus L.) egg surveys conducted in the southern Gulf of St. Lawrence from 2008 to 2011
By F. Grégoire, M.-H. Gendron, J.-L. Beaulieu, and I. Lévesque
Abstract
This document presents the results of the Atlantic mackerel (Scomber scombrus L.) egg surveys conducted in the southern Gulf of St. Lawrence from 2008 to 2011. For each of these surveys, very low abundances of eggs of less than 10 eggs/m² were measured at more than 40% of the sampled stations. Abundances ranged from 0.0 to 785.1 eggs/m² for respective averages of 95.3 and 56.1 eggs/m² in 2008 and 2009 and of 20.0 and 30.0 eggs/m² in 2010 and 2011. The highest egg abundances were measured at the stations between Îles-de-la-Madeleine, baie des Chaleurs, and the northeast coast of New Brunswick. It is also at these stations that water temperatures were the highest. In 2008 and 2009, total egg productions were evaluated at 4.18 x 1012 and 1.90 x 1012 eggs and in 2010 and 2011, at 6.48 x 1011 and 9.58 x 1011 eggs. These egg productions are associated with an index of the spawning stock biomass ranging from 25,960 t to 99,631 t. This index has significantly decline from the mid-1990s and the values calculated since 2005 are among the lowest of the historical series. In order to verify if these low values were associated with a displacement of the main spawning activities outside the Gulf of St. Lawrence, an additional egg survey was conducted on the Scotian Shelf and on a portion of the southern coast of Newfoundland in 2009. The low egg abundances measured during this survey suggest that the spawning biomass was not important and that the low values measured in the southern Gulf of St. Lawrence represent a real decline in abundance. All the results presented in this document suggest a reduction of the Total Allowable Catch (TAC).
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