Research Document - 2006/100
Assessment of the Atlantic mackerel (Scomber scombrus L.) spawning stock biomass from the 2003, 2004, and 2005 egg surveys
By Grégoire, F., C. Lévesque, J.-L. Beaulieu and J. Hudon
Abstract
The data that was collected during egg surveys conducted in the southern Gulf of St. Lawrence indicate a significant drop in mackerel spawning biomass since 2003. This drop could be caused above all by particular environmental conditions. In fact, for the surveys conducted since 2003, the most significant egg concentrations were found in only one small region located in the south-western part of the sampled area. This particular egg distribution pattern has never before been observed and would be associated with the presence of cold waters that covered an important portion of the Gulf of St. Lawrence during these surveys. These cold waters could also be the cause for recent changes in migration routes and the unusual and very abundant occurrence of mackerel on the east coast of Newfoundland. We recommend that the egg survey be extended outside the Gulf of St. Lawrence in order to improve the assessment of mackerel abundance. In addition, because of the recent increase in American and Canadian landings, we recommend an international egg survey between the Unites-States and Canada. This survey could be conducted periodically and cover the species’ two principal spawning grounds in the northwest Atlantic.
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