Genetic Sibship Reconstruction Confirms In-Stream Brook Trout Movement Following Culvert Replacement

Improperly designed road-stream crossings can adversely affect the viability of stream fish populations by preventing or impeding movement, resulting in fragmentation. Given the high cost and effort involved in stream restoration, it is important to validate projects designed to improve population connectivity. We used a novel sibship reconstruction approach to detect brook trout (Salvelinus fontinalis) movement on an ecological time scale following the removal of a culvert/dam structure in the Huron-Manistee National Forest, Michigan. Brook trout were collected above and below the dam in July 2011, prior to its removal in August, and again downstream in November. Full-sibling families were reconstructed using microsatellite data (L = 8, A = 7.1, H_e = 0.683) from 112 young-of-the-year brook trout, resulting in 37 families ranging in size from 1 to 18 (mean = 3.0). Prior to dam removal, all individuals within a family were found entirely upstream or downstream of the barrier. Following dam removal, individuals from seven different upstream families were found in the downstream reach. This demonstrates that downstream connectivity has been restored in this stream for brook trout. Our sibship-based genetic approach could be widely applicable for the detection of movement on ecological time scales, and we will discuss under what conditions this approach would be most useful.