M. effects of land use and habitat on stream fish assemblages in tributaries of the lower Bogue Chitto watershed, Washington Parish, Louisiana

My research focused on how fish communities are responding to watershed land use and instream habitat in tributaries of the Lower Bogue Chitto River. To address this question I electrofished and seined 10 sites in four tributaries of the Bogue Chitto River a total of 4 times each over the course of 15 months in 2007 and 2008. I characterized habitat by measuring water flow, water depth, substrate size, woody debris, temperature, and dissolved oxygen, and quantified heterotrophic plate counts, nutrients, and chlorophyll a concentrations at the end of the sampling period each year. Watershed land cover was measured with 2001 USGS Land use/Land cover data, and my analysis focused on cultivated cropland and pasture land, as well as forested and herbaceous wetlands. Many of the most common fishes responded positively to differences in stream characteristics, particularly increased nitrate and agricultural development, and decreased wetlands, which are typically characteristic of anthropogenic stream impacts. Other fishes responded to increased flow and substrate size, which appeared to characterize less disturbed stream conditions. Overall, fish diversity was negatively associated with distance from the mainstem Bogue Chitto River. These results suggest that in nutrient limited systems, some fishes respond positively to anthropogenic alterations, and that watershedbased characteristics are more important than local habitat variables in predicting fish assemblage composition and abundance in these streams.