Preliminary studies on silver hake (Merluccius bilinearis ) population identification using microsatellite DNA along the Northeastern US coast and their abundance correlated with bottom water temperatures in the Middle Atlantic Bight

Silver hake, or whiting, populations appear to be declining in the Middle Atlantic Bight off the east coast of the United States as judged from Government research vessel data, recorded landings and anecdotal evidence provided by the commercial fishing fleet. There is some evidence that this may be due to overfishing. If true, it may necessitate additional governmental regulation of this fishery. However, with a migratory species such as silver hake, an alternative interpretation of the declining landings may be that the stocks have relocated from traditional fishing areas in the Middle Atlantic Bight in response to changing environmental factors such as changes in bottom temperatures and others. Moreover, since little is known of the population structure of the silver hake stock, it is difficult to analyze if the overall stock is in decline or only certain populations. Such information will be needed to develop effective management strategies. We are currently investigating the decline of silver hake populations by reviewing National Marine Fisheries Service (NMFS) research data collected from the 1960s-1990s looking for correlations between changes in the environment and declines in catch. Such correlations may favor relocation of the stock, as opposed to overfishing, to explain the recorded declines in landings. In addition, we are collecting blood samples from the Gulf of Maine southward to the Middle Atlantic Bight in order to prepare DNA for microsatellite DNA analysis to determine the silver hake population structure. We believe that the population structure as determined by microsatellite DNA analysis, together with correlations between catch and environmental factors, will provide valuable information for the development of effective fisheries management plans for the silver hake stock. Preliminary microsatellite DNA data analyses suggest that there may be more than one silver hake population. Also, preliminary analysis of bottom water temperatures in the Middle Atlantic Bight appears to indicate an average rise in temperature over the three decades investigated