Methods for Including Reservoir Fishery Impacts in Reservoir Operations or Basinwide Assessments: A Case History for Black Bass in Bull Shoals Reservoir.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL LAB
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Three methods are described for relating reproductive success of fish to reservoir hydrology with an example of responses of young black bass in Bull Shoals Reservoir, Arkansas. Reproductive success was indexed by standing crops of one or two length classes of young largemouth bass Micropterus salmoides, spotted bass M. punctulatus, and smallmouth bass M. dolomieui in 34 years of August cove-rotenone samples. First, hydrologic variables were calculated based upon inflow, release, volume, mean area, change in area, or selected ratios thereof from time segments ranging from one season to 2 years before fish sampling in August. This segmented temporal approach produced 36 variables, many of which were intercorrelated. Standing crops were regressed on subsets of variables lacking intercorrelation at a 0.05. Although time-consuming, this approach usually provided the best, most easily interpreted predictive models. Second, intercorrelation problems were avoided by using principal components as independent variables in regression analyses. Four components explained 91 percent of the variation in 13 segmented-temporal hydrologic variables, but only the first two explaining 82 percent were possible to interpret and were significant in regression models. This method was foolproof, easy, and fast but did not necessarily produce the best most useful models. Third, cosine functions were fit to monthly discharge of the unregulated White River 1920-49 and to end-of-month area of Bull Shoals Reservoir 1955-93. Eight independent variables were derived related to amplitude, phase, differences in the phase of the reservoir from the preproject river, and error in fit of the harmonic function to reservoir hydrology.
- Agronomy, Horticulture and Aquiculture
- Biological Oceanography
- Hydrology, Limnology and Potamology
- Civil Engineering