Genetic Analysis of Brook Trout Populations (Salvelinus fontinalis) in the Adirondack Region: NY Stocking Impact Assessment

Abstract

Brook trout, Salvelinusflontinalis, is an extensively harvested fish because of its popularity as a game fish among anglers in the US. One of the primary management tools for sustaining adequate population sizes under intense fishing pressure is to stock hatchery-produced fish. The genetic consequences, however, of mixing the hatchery-produced fish with wild fish is still unknown. In our study, stocking impact was assessed in brook trout samples from multiple stocked ponds in the Adirondack Region, Upstate New York. The wild populations (the stock pond-caught brook trout samples that did not have tag on their intact adipose fins), some having a history of trout stocking and others suspected of being genetically "pure", were compared with the Temescamie strain (the stock pond-caught brook trout samples with tags on their adipose fins), a hatchery-produced hybrid strain. The genetic variation within and among the wild brook trout populations was characterized using microsatellite DNA markers. We hypothesized that that completely introgressed fish populations would show no difference from the allele frequencies in the Temescamie strain. In contrast, individual fish or fish populations with no introgression history would have alleles, allele frequencies and allelic diversity uncharacteristic of the Temescamie strain. Microsatellite data revealed genetic difference between Temescamie population and unmarked populations that rejects the complete introgression model for stocked Adirondack ponds. Within the unmarked group, five relatively non-admixed populations were found, and they showed lower genetic diversity than the hybrid Temescamie strain, in addition to allele frequency differences. Insight on the genetic variation of wild brook trout gained through this study will prove useful in shaping management strategies to ensure the long-term viability of wild brook trout populations in New York and elsewhere in their native range.