River mainstem thermal regimes influence population structuring within an appalachian brook trout population

Abstract

Brook trout (Salvelinus fontinalis) often exist as highly differentiated populations, even at small spatial scales, due either to natural or anthropogenic sources of isolation and low rates of dispersal. In this study, we used molecular approaches to describe the unique population structure of brook trout inhabiting the Shavers Fork watershed, located in eastern West Virginia, and contrast it to nearby populations in tributaries of the upper Greenbrier River and North Fork South Branch Potomac Rivers. Bayesian and maximum likelihood clustering methods identified minimal population structuring among 14 collections of brook trout from throughout the mainstem and tributaries of Shavers Fork, highlighting the role of the cold-water mainstem for connectivity and high rates of effective migration among tributaries. In contrast, the Potomac and Greenbrier River collections displayed distinct levels of population differentiation among tributaries, presumably resulting from tributary isolation by warm-water mainstems. Our results highlight the importance of protecting and restoring cold-water mainstem habitats as part of region-wide brook trout conservation efforts. In addition, our results from Shavers Fork provide a contrast to previous genetic studies that characterize Appalachian brook trout as fragmented isolates rather than well-mixed populations. Additional study is needed to determine whether the existence of brook trout as genetically similar populations among tributaries is truly unique and whether connectivity among brook trout populations can potentially be restored within other central Appalachian watersheds.

Evaluating the Trade‐Offs between Invasion and Isolation for Native Brook Trout and Nonnative Brown Trout in Pennsylvania Streams

“…; Aunins et al. ). A simulation study of Brook Trout in Massachusetts streams found that populations faced extirpation rapidly when barriers to movement were installed and the fish were isolated in small tributaries (Letcher et al.…”

Genetic diversity, admixture, and hatchery influence in Brook Trout (Salvelinus fontinalis) throughout western New York State

“…With the increased fragmentation of Brook Trout populations due to habitat alterations (Timm et al, ; Torterotot et al, ; Whiteley et al, ), extirpation of nearby populations (Letcher et al, ), and thermal barriers associated with increased temperatures (Aunins et al, ), population monitoring is essential to minimize the rate of species decline. Incorporating genetic tools into population assessments can reveal previously unrecognized barriers to dispersal and identify population‐level relationships that can help inform management delineations and translocation decisions.…”

Watershed‐level brook trout genetic structuring: Evaluation and application of riverscape genetics models

“…Previous watershed‐level riverscape genetics studies on other species have indicated temperature (Dionne, Caron, Dodson, & Bernatchez, ), natural features such as slope, elevation, waterfalls, and confluences (Pilger, Gido, Propst, Whitney, & Turner, ; Salisbury, McCracken, Keefe, Perry, & Ruzzante, ), or combinations of hydrologic variables and barriers (McCracken et al., ; Raeymaekers et al., ; Roberts, Angermeier, & Hallerman, ) contribute to genetic structuring of lotic fishes. Studies of brook trout genetics at watershed levels have found contradicting results in degree of connectivity, indicating that mainstem characteristics (Aunins et al., ) or watershed positioning (Rogers & Curry, ) may be influential. The patterns documented in FR suggest that development in the watershed, paired with reductions in riparian canopy cover, increases fragmentation among populations.…”

“…Second, we assessed the genetic structuring of brook trout among headwater streams in two Connecticut watersheds. Our study is one of the most extensive evaluations of watershed‐level brook trout genetic structuring to date (but see Aunins et al., ; Kelson et al., ). We hypothesised that connectivity would be observed among headwater streams, but levels of genetic relatedness would be variable across the watersheds due to heterogeneous landscape‐level influences.…”