Genetic analysis of Arctic grayling from the upper Pembina watershed showed the presence of two well-differentiated groups. One group corresponded to samples collected from Rat Creek, while the other corresponded to samples collected from Dismal Creek. Most samples collected from the Pembina River were highly assigned to the Dismal Creek cluster. However, individuals with ancestry from both clusters, i.e. hybrids, were found in all three waterbodies.
There are several genetic metrics that could be used to evaluate changes in populations from the upper Pembina watershed following angling closure in 2016.
Genetic admixture refers to the process that occurs when genetic groups come into contact and interbreed or hybridize. The resulting novel allelic combinations in the hybrids may enhance population fitness and adaptive potential under certain conditions. If the closure of angling allowed increased movement of individuals among locations, it may be detected by an increased proportion of hybrids post-closure. The proportion of admixed individuals increased post-closure in all three water bodies, suggesting increased movement and interbreeding.
Estimates of genetic diversity and average relatedness did not differ between time points among waterbodies.
Ne (Effective Population Size) is a way for scientists to estimate the number of individuals that actually pass on their genes to the next generation. If the effective population size gets too small, the group can run into trouble. They might start inbreeding, which can make the animals sick or less likely to survive environmental changes. Ne values between time points in Rat Creek remained stable. In contrast, in Dismal Creek, the estimate of Ne post-closure was significantly larger than that from pre-closure, suggesting that the population has become more genetically robust following closure. Genetic robustness is a biological system’s capacity to maintain stable, functional, and consistent phenotypes (observable physical, biochemical, and behavioral traits of an organism) despite genetic mutations, environmental fluctuations, or molecular noise.
Similar analyses of mountain whitefish yielded slightly contrasting results. No genetic structure was detected, though this result may be expected given that all the samples originated from the Pembina River. Within this location, the species showed high genetic diversity in both time periods and no change in average relatedness. In addition, the estimates of Ne were very large, including an upper bound of ‘infinite’ population size. While this upper estimate is, of course, not true, it does suggest a larger, more genetically robust population of this species than Arctic grayling.
Future analyses could apply similar methods to locations outside the Pembina watershed. Comparison of genetic metrics between Pembina populations and those not subject to the angling closure could highlight the effects/consequences of this management action.
This study was financially supported by the Alberta Conservation Association and Northern Lights Fly Fishers.