Resource Partitioning Within the Centrarchid Assemblage of the Atchafalaya River Floodway System, Louisiana, Based On Stomach Content and Stable Isotope Analyses

The Atchafalaya River Basin, 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. We conducted an extensive feeding ecology study to determine the influence of these macrohabitats on foraging activity through stomach content and stable isotope analyses. We collected 2,036 centrarchids with electrofishing efforts in the summers of 2011 and 2012. Multivariate analyses of stable isotopes and principal component analysis of food items with subsequent general linear model analyses determined that species diet and trophic relationships were not significantly different among macrohabitats. However, the analyses revealed evidence of resource partitioning within the assemblage, as suggested by limited dietary overlap and significant differences in δ¹³C and δ¹⁵N values (p=0.0007). 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.