Master of Science (MS)
Renewable Natural Resources
The Atchafalaya River Basin (ARB), Louisiana supports a diverse centrarchid assemblage, characterized by abundant populations of largemouth bass Micropterus salmoides, black crappie Pomoxis nigromaculatus, warmouth Lepomis gulosus, bluegill Lepomis macrochirus, redspotted sunfish Lepomis miniatus, longear sunfish Lepomis megalotis and redear sunfish Lepomis microlophus. This dynamic floodplain ecosystem is comprised of a mosaic of macrohabitats, including natural bayous, shallow lakes, dead-end and open pipeline canals. I conducted an extensive feeding ecology study to determine the influence of these macrohabitats on foraging activity through stomach content and stable isotope analyses. I collected 2,036 centrarchids with electrofishing efforts in the summers of 2011 and 2012. Canonical correspondence analysis of prey items revealed evidence of resource partitioning within the assemblage, as suggested by limited dietary overlap and significant separation of diets among the seven species (F = 8.6516, P = 0.01). Multivariate analysis of stable nitrogen (δ15N) isotopes revealed evidence of trophic specialization (F = 24.29, P = 0.0001) within the assemblage, despite moderate overlap in foraging habitat suggested by carbon (δ13C) signatures (F = 2.76, P = 0.0147). Results of the generalized linear mixed model (F = 1.06, P = 0.3907) and multivariate analyses of stable isotopes (P = 0.86) indicated that macrohabitat did not have an overall effect on diets or isotope values. Traditional dietary indices, such as index of relative importance values, indicated specialization in prey preference for each species, suggesting a limited degree of competition between centrarchids. In summary, despite physicochemical differences among macrohabitats, these results suggest that prey selection was species specific and independent of macrohabitat type.Condition (relative weight) was also investigated to discern the potential influence of macrohabitat and physicochemical properties. Associations were species specific, indicating disparate manners of habitat utilization that may influence niche separation, although parameters such as dissolved oxygen differential were positively associated with multiple species. Although water quality and physical habitat characteristics differed among macrohabitats, trends in centrarchid condition suggest that while habitats within the ecosystem differ regarding their overall suitability as sunfish foraging habitat, all of the centrarchid species are generally able to flourish within the permanent waterbodies of the ARB floodplain.
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Miller, Brett A., "Effects of physicochemical properties and macrohabitat on the foraging ecology and condition of the centrarchid assemblage of the Atchafalaya River Basin, Louisiana" (2013). LSU Master's Theses. 912.