Research Document - 2000/150

Effects of soak time on catch per unit effort using longline and gill nets of the Northern Gulf of St. Lawrence Cod Stock.

By M. Bérubé, H. Bourdages, and A. Fréchet

Abstract

In the case of Northern Gulf cod, the catch per unit effort (CPUE) values for gillnets and longlines under the Sentinel Fisheries Program are used as a complementary index to the abundance assessment. The aim of this study was to determine the effect of soak time on the CPUE for these gear types. The data used came from the results of the Sentinel Fisheries Program between 1995 and 1999, and from 'Index Fishermen's Program for the 1990 -1993 period.. We have endeavoured to provide a more current picture of a potential significant link between the soak time and the catch per unit effort by drawing a trend curve, and by performing non-linear regressions on aggregated data. Subsequently, by using a multiplicative model of variance, we tested the integration of the soak time in the model and the effect of data suppression on the model. We concluded that, since none of these methods showed that soak time is a significant factor, the CPUE values do not have to be adjusted, nor does this variable need to be included in the models to correct for differences in soak time.

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