Publication Abstract

Marked genetic structuring in localised spawning populations of cod within the North Sea and adjoining waters, as revealed by microsatellites

Marked genetic structuring in localised spawning populations of cod within the North Sea and adjoining waters, as revealed by microsatellites

W.F. Hutchinson, G.R. Carvalho and S.I. Rogers

Previous studies of cod population structure in European continental waters using molecular genetic markers have indi-cated high dispersal and limited structuring, in contrast to many tagging studies. More sensitive genetic techniques, in the form of microsatellite analysis, were used to reanalyse the population structure through the specific targeting of mature fish on spawning grounds. Significantly greater levels of differentiation were found than in previous studies supporting the presence of four genetically distinct populations within the North Sea: Bergen Bank, Moray Firth, Flam-borough Head, and Southern Bight. Gene flow between the southern North Sea and eastern English Channel is largely restricted to populations within the Southern Bight (southern North Sea) and Beachy Head (eastern English Channel). The spawning stock in the central English Channel (Start Point) remains distinct from those in the southern North Sea, Celtic Sea, and Irish Sea. No evidence of sub-structuring within the Irish and Celtic Seas was found, in contrast to pre-vious genetic studies, although they remained divergent from the Outer Hebrides. All European populations were sig-nificantly divergent from Canadian Scotian Shelf and Barents Sea (Bear Island) populations. The study indicates that the current fishery monitoring systems may need to be reassessed, particularly with respect to the North Sea, and high-lights the value of using microsatellites combined with the targeting of spawning stocks to investigate subtle population structuring.

Reference:

W.F. Hutchinson, G.R. Carvalho and S.I. Rogers, 2001. Marked genetic structuring in localised spawning populations of cod within the North Sea and adjoining waters, as revealed by microsatelites. ICES CM 2001/L:06 13pp.

W.F. Hutchinson, G.R. Carvalho and S.I. Rogers*

ICES CM 2001/L:06: 13pp