Diet Partitioning in a Diverse Centrarchid Assemblage in the Atchafalaya River Basin, Louisiana

Abstract

AbstractWe examined trophic and habitat resource partitioning among seven centrarchid species inhabiting four macrohabitat types in the Atchafalaya River basin (ARB), a 900‐km2 bottomland hardwood swamp in south‐central Louisiana. Fish (n = 2,036) were collected at 24 sites by boat electrofishing, and trophic position was determined from stomach contents and tissue analysis of 15N and 13C stable isotope signatures (n = 140). Stomach content analysis (index of relative importance), Morisita's index of dietary overlap, and canonical correspondence analysis revealed little effect of ARB macrohabitat type on centrarchid trophic relationships despite significant habitat alterations in dredged canals. Analyses revealed substantial diet overlap among three predominately insectivorous species (Bluegill Lepomis macrochirus, Redspotted Sunfish L. miniatus, and Longear Sunfish L. megalotis), whereas much more distinctive trophic positions were occupied by Largemouth Bass Micropterus salmoides (dominant prey = fish), Black Crappies Pomoxis nigromaculatus (palaemonid shrimp), Redear Sunfish L. microlophus (mollusks), and Warmouths L. gulosus (crayfish). Stable isotope signatures reflected dietary differences among species and complemented stomach content analyses in assessing the feeding ecology of these centrarchids, although isotopic similarities were sometimes higher than actual similarities in diet composition. Results suggest that centrarchid functional morphology and prey selection, combined with the diversity and productivity of ARB littoral habitats, effectively reduce the potential for competition among the seven cohabiting centrarchids.