MULTIVARIATE-ANALYSIS OF FEEDING RELATIONSHIPS OF FISHES IN BLACKWATER STREAMS

The autumnal diets of 23 fish species in 9 families from South Carolin a blackwater streams were characterized by rank order statistics and a nalyzed by detrended correspondence analysis (DCA). DCA ordinations of fishes and their food items indicate two primary gradients. The first axis contrasts fine particle feeders and omnivores (Catostomidae, som e cyprinids) eating algae, detritus, microcrustacea and bivalves, with predators (Anguilla, Esox, large Ameiurus) on decapods and vertebrate s. The second is a gradient from benthic feeders (percid darters, Notu rus catfishes) with varied invertebrate diets. to taxa (Gambusia, some cyprinids and centrarchids) feeding at the surface. With increasing s ize, fishes shift to larger prey and increased surface feeding. Much o f the trophic differentiation within the assemblage reflects diversifi cation at generic and family levels. DCA is an effective method for su mmarizing trophic relations in diverse assemblages.