Publication Abstract

Temporal analysis of archived otoliths indicate a loss of genetic diversity in the declining North Sea cod.

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

Fishes have been shown to be one of the most diverse groups of all the vertebrates, displaying exceptionally high levels of allelic diversity and heterozygosity. However, nearly half of the world’s teleosts are intensively commercially exploited and fisheries are collapsing as a result of overexploitation. Evolutionary theory predicts that a loss of genetic diversity will occur where a population undergoes a significant decline. Until recently it was believed that marine fish species existed in such high numbers that declines must be extensive before a genetic impact is observed, however this assumption is now being questioned. The North Sea cod (Gadus morhua) stock has undergone a number of declines since the 1920’s, and has been slow to recover despite large quota cuts. In this study we provide the first large-scale temporal population genetic analysis of an exploited species, using archived otoliths collected from cod caught off the English east coast. Data obtained from three microsatellite loci indicates that, between 1954 and 1970, levels of allelic diversity and heterozygosity declined significantly, and then showed an increase leading up to 2000. It is proposed that the observed trend in genetic diversity and structuring within the samples might be explained by a population decline followed by a proportionally greater influx of migrants from surrounding genetically divergent populations.

Reference:

W.F. Hutchinson, C. van Oosterhout, S.I. Rogers, and G.R. Carvalho. 2004. Temporal analysis of archived otoliths indicate a loss of genetic diversity in the declining North Sea cod. Proceedings Royal Society 270: 2125-2132