The extent of hybridization between bull trout (<i>Salvelinus confluentus</i>) and brook trout (<i>S. fontinalis</i>) across Alberta’s Eastern Slopes

Understanding the extent of hybridization with non-native species is important for the conservation of native species. Bull trout ( Salvelinus confluentus), a char native to Alberta, face population declines across their range and one risk may include hybridization with introduced brook trout ( Salvelinus fontinalis). The extent of hybridization throughout Alberta, however, is not well understood. Therefore, we aimed to quantify bull × brook trout hybridization in three ways: (1) observed hybrid presence across Alberta, (2) post-F1 hybrid proportion, and (3) hybrid proportion relative to brook trout in well-sampled watersheds. Using two sets of diagnostic single nucleotide polymorphisms (1174 bull trout loci and 1499 brook trout loci), we identified 35 F1 and 7 post-F1 hybrids ( n = 42) across 10 Hydrologic Unit Code 8 watersheds. Results show hybridization throughout bull trout’s range; however, they provide little evidence of extensive introgression. Misidentification was low (2.1%), though 20 of 42 hybrids were misidentified, suggesting a higher misidentification rate (47.6%). This work improves understanding of hybridization of at-risk bull trout and informs management decisions, such as limiting brook trout where possible.