North Sea herring population structure revealed by microsatellite analysis

The Atlantic herring Clupea harengus has played a pivotal role in the formulation of relating to population structuring in marine fishes, yet considerable uncertainty remains as to extent to which phenotypic and genetic differentiation coincide in such a highly mobile species. this study, we examined genetic population structure across the major herring spawning aggregations the North Sea and adjacent waters over 2 years, 2002 and 2003. We analysed 1660 spawning across 9 microsatellite loci. Data were analysed using several approaches, taking into the effect of location, year-class and sex, as well as pooling all individuals together, making assumption as to the number of populations present in the data set. The results suggest the presence a genetically homogeneous unit off Northern Scotland, and a temporally stable pattern of isolation distance determined predominantly by the divergence of the English Channel samples and, 2003, by the Norwegian spring spawners. Our data suggest that the current view of North Sea as a unit-stock might be adequate, but confirm the considerable degree of demographic of the herring populations in the English Channel. Despite major recent population, genetic data indicated no evidence of bottlenecks affecting the genetic diversity of extant Sea herring populations. Finally, despite evidence of weak population structuring, we discuss risks of underestimating population differentiation in marine fish of large population sizes, and reference to herring population history and dynamics, we attempt to reconcile the existing on herring population structure.