Research Document - 2005/085

A preliminary examination of spawning suppression in relation to recruitment in NAFO Subdivision 3Ps cod (Gadus morhua)

By Morgan, M.J., and R.M. Rideout

Abstract

Recruitment in 3Ps cod has been relatively weak over the last decade or more. Only 2 strong year classes have been produced from 1990-2001, even though the SSB has been relatively large since 1996. One possible factor causing low recruitment is that not all sexually mature fish may spawn in every year. Cod in 3Ps have been found to suppress spawning at frequencies as high as 46% in some years. The purpose of this study is to recalculate SSB for 3Ps cod, including only female fish that were predicted to spawn and to determine if low recruitment in some years could be related to spawning suppression. On average 84% of female cod in 3Ps were estimated to spawn each year with little variability in this estimate from year to year. However there were a few years (1980, 1985, 1986 and 2001) in which the proportion spawning was lower than 80%. There was little or no relationship between recruitment and the proportion of fish spawning. The lack of effect may be the result of a reasonably constant rate of spawning suppression. 

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