Spatial and Temporal Dynamics in Brook Trout Density: Implications for Population Monitoring
T.Wagner et al., Abstract
Many potential stressors to aquatic environments operate over large spatial scales, prompting the need to assess and
monitor both site-specific and regional dynamics of fish populations. We used hierarchical Bayesian models to evaluate
the spatial and temporal variability in density and capture probability of age-1 and older Brook Trout Salvelinus
fontinalis from three-pass removal data collected at 291 sites over a 37-year time period (1975–2011) in Pennsylvania
streams. There was high between-year variability in density, with annual posterior means ranging from 2.1 to 10.2
fish/100 m2
; however, there was no significant long-term linear trend. Brook Trout density was positively correlated
with elevation and negatively correlated with percent developed land use in the network catchment. Probability
of capture did not vary substantially across sites or years but was negatively correlated with mean stream width.
Because of the low spatiotemporal variation in capture probability and a strong correlation between first-pass CPUE
(catch/min) and three-pass removal density estimates, the use of an abundance index based on first-pass CPUE could
represent a cost-effective alternative to conducting multiple-pass removal sampling for some Brook Trout monitoring
and assessment objectives. Single-pass indices may be particularly relevant for monitoring objectives that do not
require precise site-specific estimates, such as regional monitoring programs that are designed to detect long-term
linear trends in density.
Publication Date: 2014
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