Possible Seasonal Population Bottlenecks In Brook Trout (Salvelinus fontinalis) in Central Appalachian Headwater Streams

Abstract

Brook trout (Salvelinus fontinalis) in the Appalachian Mountains often inhabit low production streams that limit growth. Therefore, we examined seasonal changes in body composition of age-1 and older brook trout to identify critical periods of growth or depletion that may lead to mortality and determined if brook trout in headwater streams reached critical levels of resource depletion over winter. Six streams in the central Appalachian Mountains in West Virginia containing naturally reproducing brook trout were sampled from June 2003 to March 2004 to assess changes in brook trout populations and physiological status. Dry, protein, and fat weights were highest in early summer (June) and decreased through the November/ December sampling period. To better understand trout compositional changes over winter, we starved 40 brook trout in experimental tanks simulating winter conditions and estimated body composition using bioelectrical impedance analysis. We found low rates of fat and protein loss during simulated winter conditions. This, coupled with field estimates of fat and protein levels in wild fish, suggests that brook trout do not likely starve during winter or other times of the year.

Behavioural and physiological responses of brook trout Salvelinus fontinalis to midwinter flow reduction in a small ice-free mountain stream

“…Although salmonids have not always been found to deplete lipid reserves over winter (Webster & Hartman, 2007), several studies have reported declines in lipid content and increases in water content in overwintering fishes similar to those reported here (Cunjak & Power, 1986; Biro et al, 2004). Salmonid winter feeding is restricted because low water temperatures limit appetite, digestion and gastric evacuation rates (Cunjak et al , 1987; Sweka et al, 2004); consequently they primarily rely upon stored fat to meet energetic demands, and thus can lose mass during this period (Cunjak et al , 1987).…”

Is the winter period a severe bottleneck of anadromous riverine Arctic charr parr?

“…Although almost all individuals gained weight throughout the ice-covered period in our study, we cannot rule out that starvation was a significant cause of the observed overwinter mortality. However, there are indications that also other streamdwelling charrs (e.g., Salvelinus fontinalis) suffered little from starvation during the winter (Webster & Hartman 2007). Overall, we observed relatively low mortality and thus, size-dependent survival should probably not be expected to be prominent.…”

“…The overall density of charr in the experimental brook was lower compared to fish density in other subarctic rivers and streams (Gabler & Amundsen 1999;Gabler et al 2001;Jensen 2004), and generally, stream-dwelling salmonids have low antagonistic behaviour during winter with low temperatures and light intensities typically for under ice conditions (reviewed by Huusko et al 2007). However, there are indications that also other streamdwelling charrs (e.g., Salvelinus fontinalis) suffered little from starvation during the winter (Webster & Hartman 2007). Although almost all individuals gained weight throughout the ice-covered period in our study, we cannot rule out that starvation was a significant cause of the observed overwinter mortality.…”

Does Bioelectrical Impedance Analysis Accurately Estimate the Physiological Condition of Threatened and Endangered Desert Fish Species?

“…Therefore, future studies should move beyond reporting proximate composition on a TBM basis and compare percentage-based models of morphology with those including BIA metrics to gauge the actual benefit of using this tool in field operations. Many studies to date have included morphometric and BIA (or just BIA) metrics as candidate predictors in models without including a morphometric-only model by which to evaluate the added utility of BIA (Cox and Hartman 2005;Duncan 2007;Webster and Hartman 2007;Hanson et al 2010). The addition of BIA metrics to our percentage-based morphometric models only increased the proportion of explained variance marginally (as much as 4% across species), such that the effort of taking BIA measurements in addition to length and wet-mass measurements is likely not worth the gain in predictive power.…”