POPULATION STRUCTURE IN THREE SPECIES OF CO-DISTRIBUTED SALMONID FISHES IN THE PEACE RIVER AND TRIBUTARIES NEAR A MAJOR PROPOSED HYDROELECTRIC DEVELOPMENT IN NORTHEASTERN BRITISH COLUMBIA,CANADA

摘要

Dam construction and reservoir formation represent profound anthropogenic alterations to natural riverscapes, especially in terms of connectivity in migratory fishes. The Peace River in northeastern British Columbia (BC), Canada, is the largest river system in BC, home to 39 native fishes and currently has two major hydroelectric projects, and a third one ('Site C') is proposed. Three co-distributed and migratory fishes, the bull trout (Salvelinus confluentus), Arctic grayling (Thymallus arcticus) and the mountain whitefish (Prosopium williamsoni) are key species in the Peace River ecologically and in terms of recreational fisheries. We examined microsatellite DNA variation in these species to assess genetic diversity, levels of population subdivision and connectivity to better understand potential impacts and to provide baseline information for subsequent monitoring. Expected heterozygosity and number of alleles averaged 0.65 and 7.7, 0.73 and 11.9, and 0.72 and 10.8 for bull trout (nine loci), Arctic grayling (10 loci) and mountain whitefish (10 loci), respectively. Estimates of the effective number of breeders (N_b) ranged from 35 to 255 for bull trout to over 3700 for Arctic grayling. Population subdivision (F_(ST), θ) was 0.040, 0.063 and 0.023 in bull trout, Arctic grayling and mountain whitefish, respectively (all p＜ 0.001). Temporal differences within localities for all species accounted for ＜1% of total variation in allele frequencies. An estimated 6.2% (mountain whitefish), 4.6% (bull trout) and 8.8% (Arctic grayling) of fish samples were inferred (p ＜ 0.05) to be immigrants to one locality from another locality. Our results suggest that connectivity amongst localities is important to successful completion of the life history of each species, the potential disruption of which will be a critical aspect of post-development monitoring.