Multi-scale assessment of habitats and stressors influencing stream fish assemblages in the Lake Pontchartrain Basin, USA
Alford, J. B.  2014.  Hydrobiologia, 738:129-136.

This study assessed the relative influence of habitats and stressors at reach, subwatershed and watershed spatial scales on fish assemblages within the Lake Pontchartrain Basin (USA). Reach-scale habitat had the strongest association with the assemblage, after removing potential interactions among spatial structure and environmental variation from subwatershed and watershed variables (Partial redundancy analysis [pRDA]; 13.5% variation explained). Mean wetted width, mean depth, percent cover of aquatic vegetation and human debris, habitat assessment score, and large woody debris volume were the most important reach-scale variables. At subwatershed (pRDA; 9.2%) and watershed scales (pRDA; 12.8%), natural characteristics were important, including elevation, gradient, watershed area, wetland cover and stream density. Stressors included road, dam and oil/gas well densities. Cumulative fit statistics from the pRDA revealed that 16 species were influenced primarily by reach-scale habitats, including two rare species (Fundulus euryzonus and Pteronotropis signipinnis), while six species showed greater variation with watershed-scale factors, including the rare Percina suttkusi. Species exhibiting greater variation with a particular spatial scale tended to have similar life history characteristics. For example, species associated with watershed attributes had life spans < four years, egg diameters < 2 mm, spawning periods > three months, and were foraging generalists (i.e., more r-selected).