Long-term trends in the Bogue Chitto River fish assemblage: A 27 year perspective

We conducted a thorough survey of the Bogue Chitto River fish assemblage from February 1996 to January 1997 to examine long-term trends in the assemblage by comparing our findings to surveys conducted in 1971-1974 and 1987-1988. The 1971-1974 survey described an assemblage dominated by Cyprinidae (50%), Percidae (9%), and Ictaluridae (8%). Numerically abundant species included Notropis longirostris (19%), Cyprinella venusta (13%), and Percina sciera (10%). The 1987-1988 survey described an assemblage dominated by Cyprinidae (74%), Percidae (9%), and Centrarchidae (9%). The numerically dominant species were C. venusta (36%) and N. longirostris (16%). Our survey described an assemblage dominated by Cyprinidae (75%), Percidae (8%), Centrarchidae (6%), and Poeciliidae (6%). We identified a decline in the relative abundance or possible extirpation of over twenty species during the 27-year period and the numerically dominant species was C. venusta (57%). Using Morisita's Index of Similarity, we found relatively low faunal similarity between the 1970-1974 survey and our study, but relatively high similarity between the 1987-1988 survey and our survey. In addition, assemblage evenness and heterogeneity decreased over time, indicating a change in the system's fish fauna from one with relatively high species evenness and diversity to a fauna dominated by a few, abundant species. We speculate that increased siltation has contributed to changes in the Bogue Chitto River fish assemblage because many of the declining species were benthic minnows and darters, which would be adversely effected by increasing substrate loads.