Research Document - 2009/012

Estimation of the exploitation rate of the northern Gulf of St. Lawrence (3Pn,4RS) Atlantic Cod (Gadus morhua) stock, based on tagging data

By A. Le Bris, A. Fréchet and J-C. Brêthes

Abstract

Even with the introduction of two moratoriums, from 1994 to 1996 and in 2003, the Atlantic cod stock biomass in the Northern Gulf of St. Lawrence (Areas 3Pn and 4RS) remains low. Biologists in charge of assessing stock status consider the current low quotas as still too high. Therefore, it is important to properly measure the exploitation rate. The rate is usually estimated using a sequential population analysis. The study’s objective is to evaluate the exploitation rate using an independent method based on the analysis of tagging data. Results between the tagging data and the sequential population analysis are consistent. In 2007, the stock’s exploitation rate reached upwards of 30%, a value that was higher than the targeted 18% required for recovery. It seems that subdivision 3Pn is more exploited than subdivision 4RS. Repeating this study along with increased analysis appears to be necessary in order to better estimate the exploitation rate and other population parameters such as survival.

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