Validation of Morphological Characteristics Used for Field Identification of Bull Trout × Brook Trout Hybrids

Abstract

Bull trout Salvelinus confluentus are of conservation concern throughout much of their range, in part because of displacement by and hybridization with nonnative brook trout S. fontinalis. Hybridization between these species can complicate efforts to control brook trout because hybrids are often difficult to distinguish from parental species. Here, we assess the reliability of five morphological characteristics that were used to identify bull trout × brook trout hybrids among 106 fish collected from Quirk Creek, Alberta. Genetic analysis of up to three microsatellite loci suggested that hybrids were correctly identified 95% of the time and that no bull trout were mistaken for hybrids. Visual inspection of photographs of hybrids suggested that dorsal fin markings were the most reliable morphological characteristic for identifying hybrids. Based on these results, we recommend that field identification of bull trout × brook trout hybrids be based solely on dorsal fin markings.

Received November 20, 2010; accepted March 21, 2011

ACKNOWLEDGMENTS

We are grateful to Dean Baayens, Greg Eisler, Kevin Lake, Brian Meagher, Marc Plamondon, Matt Richard, Jeff Smith, and numerous Trout Unlimited Canada volunteers for field assistance. We also thank members of E.B.T.'s laboratory and Mark Wolansky for laboratory assistance. In-kind support was from Alberta Sustainable Resource Development, Golder Associates, Trout Unlimited Canada, and the University of Alberta. Margaret Bradley was instrumental in developing Figure 1. Jessica Ward provided insightful comments on the manuscript. Funding was provided by the Alberta Sport, Recreation, Parks, and Wildlife Foundation; the Alberta Conservation Association; the City of Calgary; Fisheries and Oceans Canada; Mountain Equipment Cooperative; and Trout Unlimited Canada. Additional support was provided by a Discovery Grant to E.B.T. from the Natural Sciences and Engineering Research Council of Canada.