Feeding ecology of three omnivorous fishes in Lake Texoma (Oklahoma-Texas)

Feeding ecology of 3 omnivorous fishes in a large southern United States re servoir was investigated to develop hypotheses on the potential functional roles of these species in this ecosystem. I examined distribution, abundanc e, and diet of smallmouth buffalo (Ictiobus bubalus), river carpsucker (Car piodes carpio), and gizzard shad (Dorosoma cepadianum) relative to the avai lability of potential resources during summer 1997 and 1998. In July and Au gust, abundance of smallmouth buffalo was significantly greater at stations with depths of 10 m than at 1 m or 3 m stations. There was no significant difference in abundance of gizzard shad or river carpsucker by depth or mon th. Relative proportions of detritus and zooplankton in the diet varied amo ng species. Smallmouth buffalo primarily ate copepods, whereas gizzard shad primarily ate detritus. The diet of river carpsucker was intermediate in r elative proportions of zooplankton and detritus to that of smallmouth buffa lo and gizzard shad. Of the 3 species examined, only gizzard shad showed a significant decline in dietary crude protein, phosphorus, and organic conte nt over the summer. This corresponded to a decline in condition of gizzard shad. Overall, benthic invertebrates had a heterogeneous distribution withi n the reservoir, and organic content of sediments was not different across sample stations. Relative importance to ecosystem functioning of these spec ies, all of which are highly abundant in southern reservoirs, likely depend s on species-specific feeding ecology and environmental conditions.