Research Document - 2014/079

Analytical assessment of the Atlantic mackerel (Scomber scombrus L.) in NAFO Subareas 3-4 in 2013

By François Grégoire and Luc Beaudin

Abstract

A sequential population analysis (SPA) was performed on the Canadian Atlantic Mackerel (Scomber scombrus L.) component that spawns in the southern Gulf of St. Lawrence. The main input parameters for this analysis were the catches, weights, and maturities at age from 1968 to 2013 and the spawning biomass index from the egg survey conducted since 1996. The SPA revealed no major retrospective pattern. Despite some high CV for certain of the estimated parameters, no important problem of adjustment was detected. Model residuals showed no particular pattern. However, for the survey, the highest residuals were observed in 2013 which indicates a more important difference between the index – which shows an upward trend between 2012 and 2013 – and the SPA which presents an opposite trend. This difference could be explained by a catch at age that is not representative of the actual landings.

According to the SPA results, the last two year-classes with high recruitment level were those of 1999 and 2003 and that the year-classes that occurred in recent years had medium and low recruitment levels. Following a period of stability (1968–1992), fishing mortalities reached very high values in the 2000s and in particular for older fish with exploitation rates varying between 40 and 90%. Total and spawning biomasses have been decreasing since the mid-2000s and values in recent years represent the historical lows. The relationship between spawning biomass and fishing mortality indicates that the stock is in a critical situation. In addition, the trajectory of the stock indicates that the latter is overfished since 2007. According to the average level of sustainable exploitation of the period 1968–1992 (F = 0.087), catches projected for 2014 and 2015 would be 662 t and 821 t, respectively.

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