Research Document - 2000/093

Origins of two recruitment pulses of 0-group Atlantic cod (Gadus morhua) in Bonavista Bay, Newfoundland during 1999, determined from genetic variation.

By Beacham, T.D., Gregory, R.S., Brattey, J.

Abstract

Recruitment of 0-group Atlantic cod (Gadus morhua) to the nearshore of coastal Newfoundland occurs in two or more pulses. The two largest of these recruitment pulses occur in August and in late September to October. We investigated the origin (parentage) of these two recruitment pulses appearing in Newman Sound (Bonavista Bay), Newfoundland using genetic variation. Variation at seven microsatellite loci (Gmo3, Gmo8, Gmo19, Gmo34, Gmo35, Gmo36, and Gmo37) and the synaptophysin locus (SypI) was examined in a sample of 200 0-group cod from each pulse collected by seine during August 16-18 and October 12-13, 1999. Genetic variation within pulses was compared with that of four offshore and five inshore populations of adult cod. For both pulses, variation was most similar to locally spawning adults from within Bonavista Bay in over 50% of 0-group cod. Of those individuals most similar to adults outside Bonavista Bay, the majority was most closely related to those collected north (i.e., "upstream") of the bay. Comparatively few 0-group were most similar to aggregations of adults sampled to the south, and then only in 0-group sampled in October. Offshore populations (primarily Funk Island Bank) were estimated to contribute 49% of the August pulse, but only 30% of the October pulse.

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