BRENDAN J. ANNETT

ABSTRACT

Variation in microsatellite DNA loci was analyzed to determine the structure of genetic variation and evaluate the impacts of historic hatchery stocking in the remnant anadromous brook trout populations at the southern end of their range, along the coast of the northeastern United States. The trout were taken from four wild reproducing coastal stream populations on Cape Cod, Massachusetts, an intensively managed coastal stream population on Long Island, New York and from the hatchery broodstock that has been used to repeatedly stock the Cape Cod streams. Using F statistics, genetic distances and individual assignment tests, we found that each stream contains a genetically distinct population and that genetic differentiation is independent of geographic distance between populations. These results indicate that contemporary gene flow was low even between nearby streams, suggesting that although interstream movement has been reported, such behavior may be rare and/or straying trout generally do not successfully mate with fish from other streams. Pairwise F ST values and individual assignment tests indicated that repeated historic stocking from the Sandwich Hatchery had minimal impact on the genetic structure of the wild brook trout populations in the coastal streams of Cape Cod. Consideration of these results in decision making pertaining to management of fisheries, as well as management of the aquatic and marine habitats the fisheries depend on, could be of great value to conservation and restoration of the unique anadromous brook trout in this region.