Analysis of population and taxonomical structure of Atlantic cod, Gadus morhua (Actinopterygii: Gadiformes: Gadidae) from the Baltic Sea with use of microsatellite DNA

Abstract

Background. Substantial declines in biomass of Atlantic cod, Gadus morhua L., one of the most valuable commercial fish species in the north Atlantic (including the Baltic Sea), has been observed in recent decades. A comprehensive understanding of the population structure contributes to proper management and conservation of genetic resources. We attempted to answer the question whether there exists differentiation among localized samples, and if so, whether this separation is large enough to warrant the recognition of distinct clades in cod as well as whether these distinct clades correspond to traditionally described regions of spawning and nursery areas or even stocks. Materials and methods. Six microsatellites were used for finding differentiation between four sampling areas of G. morhua) from the Baltic Sea (Puck Bay, Bay of Gdańsk, Pomeranian Bay, and Øresund) and two from the north-eastern Atlantic (North Sea and Barents Sea). Genetic differences among localities were estimated with FST using Weir and Cockerham’s estimator θ. Genetic distances among samples were calculated and visualized by multidimensional scaling using XLStat (Addinsoft). Results. There is a statistically supported structure pattern among sampling localities from the Baltic Sea. One of them is related to the population from the Barents Sea, second is mixing with cod migrating from the North Sea. Conclusion. The level of heterozygosity and slight heterozygote deficiency suggest that, in case of all samples, we observed an isolation processes that could be an effect of withering or weakening the migrations between separate breeding stocks. This effect is most apparent for the most eastern populations from the Puck Bay and the Gulf of Gdańsk.

Keywords

• Atlantic cod
• Gadus morhua
• microsatellites
• Balti