Morphologically inferred niche differentiation in stream fishes [North Carolina]

General statements about the ecological significance of morphological features in freshwater fishes were used to predict differences in resource use among 10 pairs of similar sympatric species. Results of gut content analyses supported inferred differences between species in prey size and type or in foraging site in 90% of the cases. Inferred differences between species in habitat were supported by collection records and/or field observations in all cases except for two pairs in which no differences in resource use were identified. Overall, then, the use of morphological inference to identify ecological differences between quite similar species pairs works for freshwater fishes. All 10 species pairs discussed showed differences in morphology related to both the habitat and food dimensions; and, for all species combined, differences in these two major dimensions occurred with equal relative frequency This last result contrasts with theoretical predictions for competitively structured communities (i.e., niche compression hypothesis) but agrees with some earlier empirical results for aquatic animals.