Fine-scale landscape genetic structure of brook trout in headwater stream networks in Connecticut

The spatial genetic structure was investigated for two selected brook trout populations inhabiting headwater stream networks in Connecticut. Brook trout was captured via electrofisihng from continuous stream stretches (5-7km), and eight microsatellite loci were genotyped for over 1,000 individuals in the two stream systems. Spatial patterns were observed despite the fine spatial scale, spatially continuous fish distribution and in some cases the lack of obvious movement barriers. Genetic data were useful for examining the presence of cryptic population boundaries, permeability of in-stream structures (e.g., road crossings and natural falls), asymmetry of fish movement (upstream vs. downstream direction), and reproductive success of stocked trout. Also, the influence of landscape variables (e.g., stream channel distance, gradient, and temperature) on the observed genetic patterns was examined. The information obtained from the genetic analyses was useful for better understanding population ecology of brook trout in headwater streams.