Bay‐scale population structure in coastal Atlantic cod in Labrador and Newfoundland, Canada

Abstract

Polymorphisms at five microsatellite DNA loci provide evidence that Atlantic cod Gadus morhua inhabiting Gilbert Bay, Labrador are genetically distinguishable from offshore cod on the north-east Newfoundland shelf and from inshore cod in Trinity Bay, Newfoundland. Antifreeze activity in the blood suggests that Gilbert Bay cod overwinter within the Bay. Gilbert Bay cod are also smaller (weight and length) for their age and consequently less fecund for their age, than cod elsewhere within the northern cod complex. The productivity and recruitment potential of coastal cod off Labrador may thus be much lower than that of offshore northern cod or of inshore cod farther south, implying that a more conservative management strategy may be required for cod from coastal Labrador than traditionally practised for northern cod inhabiting less harsh environments. Relatively high F ST and R ST measures of population structure suggest that important barriers to gene flow exist among five components that include two inshore (Gilbert and Trinity Bay) and three offshore cod aggregations on the north-east Newfoundland Shelf and the Grand Bank. D A and D SW estimates of genetic distance that involve Gilbert Bay cod are approximately three-and 10-fold larger, respectively, than estimates not involving Gilbert Bay cod. The differences between inshore cod from Gilbert Bay and Trinity Bay raise the possibility that other genetically distinguishable coastal populations may exist, or may have existed prior to the northern cod fishery collapse.Harvesting strategies for northern cod should recognize the existence of genetic diversity between inshore and offshore components as well as among coastal components. 2000 The Fisheries Society of the British Isles

Sub-populations of coastal cod with different behaviour and life-history strategies

“…This phenomenon has also been reported recently for cod in Canadian waters (Robichaud & Rose 2001). Genetically distinct sub-populations in bays, inlets and fjords have been identified in Canada (Ruzzante et al 1996a(Ruzzante et al , 1997(Ruzzante et al , 2000 and Iceland (Jonsdottir et al 2002), and among local spawning populations in the North Sea (Hutchinson et al 2001). Tag-release-recapture experiments have shown that the juvenile and adult coastal cod in Norwegian waters tend to remain in their local areas (Salvanes & Ulltang 1992, Jakobsen 1987, Nordeide & Pettersen 1998, Svåsand et al 2000.…”

The fish fauna of Gilbert Bay, Labrador: a marine protected area in the Canadian subarctic coastal zone

“…The year-round residency of the Gadus morhua population in Gilbert Bay is well documented (Ruzzante et al, 2000;Green & Wroblewski, 2000;Morris & Green, 2002). We collected both juvenile and adult G. morhua, as would be expected for a self-sustaining, local population (Wroblewski et al, 2005).…”

“…These cod have a reddish or golden-brown colour due to their carotenoid-rich diet of invertebrates (Gosse & Wroblewski, 2004;Wroblewski et al, 2005). The Gilbert Bay cod population is genetically distinguishable from coastal cod of eastern Newfoundland and from offshore cod of the Grand Banks (Ruzzante et al, 2000;Beachem et al, 2002). Gilbert Bay cod are a subpopulation of the northern cod metapopulation (Smedbol & Wroblewski, 2002).…”

Extent of mitochondrial DNA sequence variation in Atlantic cod from the Faroe Islands: a resolution of gene genealogy

“…Part of the difficulty is that different signals seem to emanate from the various genetic systems used. There is an apparent disagreement among workers about the utility of the various molecular markers for population studies (eg, Frydenberg et al, 1965;Jamieson and Jones, 1967;Mork et al, 1985;Carr et al, 1995;Á rnason et al, 2000;Ruzzante et al, 2000;Jó nsdó ttir et al, 2002).…”