Genetic Characterization of Tennessee Brook Trout Populations and Associated Management Implications

Abstract

Previous research has indicated that native southern Appalachian brook trout Salvelinus fotinalis are genetically distinct from hatchery stocks derived from northeastern populations. Six diagnostic allozyme loci identified in earlier research were used to assess the genetic origin of 38 Tennessee brook trout populations outside of Great Smoky Mountains National Park. Twenty‐two of these populations (58%) were putatively native, eight (21%) were derived from hatchery stocks, and eight (21 %) were hybrids. Significant genetic differences among the 22 native populations were observed, and genetic structure among these populations was high (genetic variance index FST = 0.622). Thirty‐two percent of the genetic variation among native populations was attributable to differences within watersheds, whereas 29% was attributable to variation among the five major watersheds containing brook trout. Populations located north (19) and south (3) of the French Broad River clustered separately, based on a genetic distance index. Knowledge of the genetic characteristics of brook trout populations will enable fisheries managers to make more informed decisions about this resource in Tennessee and elsewhere in the southern Appalachians. Given that maintaining the genetic integrity of native southern Appalachian brook trout is an important goal, our findings will help managers to design strategies that require stocking or stock transfers to create or expand populations.

Genetic Characteristics of Southern and Northern Brook Trout (Salvelinus fontinalis) Populations at the Zone of Contact

“…Allele frequencies at the other markers were compared to those observed in northern and SABT populations characterized in previous studies [7][8][9][10][11][12][13][14][15][16]. Individual heterozygosity and polymorphism were calculated across five loci to assess levels of genetic diversity within each population [32].…”

“…The Grassy Branch population was characterized as southern Appalachian, and the Henshew Branch population was characterized as pure northern. Results from earlier genetic studies [8,11,14] and its geographic location suggest that the Holston River historically contained the southern Appalachian lineage, so the presence of the northern allele is likely due to stocking.…”

“…Genetic differences between the two lineages may be large enough to justify distinction at the subspecies level [7,8]. In addition, screening of allozyme [7][8][9][10][11][12][13][14][15][16], mitochondrial DNA [17][18][19], and microsatellite nuclear DNA [20,21] markers has uncovered smaller scale genetic variation throughout the geographic range of brook trout. Differentiation at smaller geographic scales may reflect different colonization histories, as well as differential effects of selective and non-selective population genetic processes.…”

“…Comparison of external microbial assemblages suggested that SABT exhibit greater ability to inhibit microbial growth in their epidermal mucus than do northern brook trout of hatchery ancestry [26]. Demonstration that SABT are genetically distinct from northern-origin hatchery stocks led management agencies to assess the heritage of populations within their jurisdiction, for example, in the Great Smoky Mountains National Park [8,13], Tennessee [11], North Carolina [12,16,27], and Georgia [10]. Molecular and adaptive differentiation may warrant management of brook trout populations or groups of populations as evolutionary significant units [28], although some of their population genetic differentiation may reflect stocking history.…”

Biological Consequences of the Coaster Brook Trout Restoration Stocking Program in Lake Superior Tributaries within Pictured Rocks National Lakeshore

“…Previous research suggests that hatchery stocks of Brook Trout have founded new populations when introduced into new areas (Wright and Atherton 1970;Perkins et al 1993;Kriegler et al 1995;Hayes et al 1996). However, when Brook Trout are stocked sympatrically with native populations, as was the case in PRNL, introgression rates are consistently low (Krueger and Menzel 1979;McCracken et al 1993;Danzmann and Ihssen 1995;Kriegler et al 1995).…”