Is an alewife just an alewife? Genetic relatedness of river herring from the Gulf of Maine

The alewife (Alosa pseudoharengus) was listed as a species of concern by the National Marine Fisheries Service in 2008. Populations in the species native range showed serious signs of decline, most evident in low adult returns during the late 1990s and early 2000s. Restoration stocking of alewife has proven very effective in reestablishing populations and augmenting existing runs in most locations. However, the effect of restoration stocking on meta-population structure only recently has been raised as a potential concern. We collected river herring (alewife and blueback herring (A. aestivalis)) from eight major river systems and a number of smaller coastal rivers between Massachusetts and New Brunswick for microsatellite DNA analysis. Alewife and blueback herring populations were significantly different in all locations. Fst values identified a southern Gulf of Maine strain of alewife and a midcoast strain, with finer scale meta-population structure evident around rivers in the eastern Gulf of Maine. In midcoast Maine, an area that has been subject to frequent restoration stocking in the recent past, Fst values were not significant for alewife but were significant for blueback herring. Blueback herring metapopulation structure in the midcoast may be an indicator of historic alewife metapopulation structure prior to restoration stocking.