Research Document - 2013/137
Analytical assessment of Atlantic mackerel (Scomber scombrus L.) in NAFO Subareas 3 and 4 in 2011
By F. Grégoire, L. Girard, and J.-L. Beaulieu
Abstract
A sequential population analysis (SPA) was performed on the Atlantic mackerel (Scomber scombrus L.) component that spawns in the southern Gulf of St. Lawrence. The input parameters to this analysis were the data from the commercial fishery from the 1968–2011 period and the index of the spawning biomass from the egg surveys conducted since 1996. Despite high CV for some of the estimated parameters, the SPA presented no major retrospective pattern. The SPA revealed that the last two year-classes of high level of recruitment were those of 1999 and 2003 and that the year-classes that appeared over the last years were of medium and low level. Following a stability period (1968–1992), fishing mortalities reached very high values during the years 2000 and in particular for the older fish with exploitation rates varying between 50 and 80%. Total and spawning biomasses are decreasing since the mid-2000s and the last years values are near the minimum historic reached in 1999. Reference points were calculated from the SPA results and the biological data from the commercial sampling. Their evolution over the years indicates that there were overfishing since 2003. Given the average sustainable exploitation level of the 1968–1992 period, spawning biomasses projections for 2012, 2013, and 2014 would be of 62,218 t, 64,462 t, and 64,181 t., respectively, and projected catches for 2012 and 2013 would reached 8,785 t and 8,636 t. Given that stock abundance should not increase in the short term (absence of strong recruitment according to the SPA), the fishing mortality rates over the next few years should be lower compared to that of 2011. Therefore, in order to bring back fishing mortality to the average sustainable exploitation level of the 1968–1992 period, catches in 2012 and 2013 should not exceed 9,000 t.
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