Habitat and the conservation of riffle inhabiting fishes: population and assemblage responses to temporal and spatial habitat change

Stephen T. Ross¹, Martin T. O' Connell¹, William T. Slack¹, and David M. Patrick^2
1 Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS 39406-5018; 601 266-4928; fax: 601 266-5797; stephen.ross@usm.edu. Current address (WTS) Curator of Fishes, Mississippi Museum of Natural Science, 111 North Jefferson Street, Jackson, MS 39202.
² Department of Geology, University of Southern Mississippi, Hattiesburg, MS 39406-5044

Habitat forms the template upon which the biological processes of organisms, populations, and communities occur, and spatial and temporal fragmentation affects the suitability of this template. We examined effects of habitat fragmentation on bayou darters and other riffle inhabiting fishes in Bayou Pierre, MS. We then evaluated simple predictions of metapopulation and source-sink models, relative to bayou darter populations. Bayou Pierre is undergoing extensive erosion which has been moving upstream 124-750 m/year. This erosion has decreased sinuosity, increased channel width, eliminated certain downstream riffle habitats, and created new riffle habitats upstream. From 1986-1994, the riffle fish assemblage (15 most abundant species), was stable. Total fish densities and densities of bayou darters did not vary among years or between Bayou Pierre and Foster Creek (a major tributary), and there was not a significant interaction among years and water bodies. Density of riffle fishes did not vary among the different degrees of recent erosion, but showed a significant interaction effect with individual streams. Bayou darters may comprise a metapopulation with local populations inhabiting riffles separated by intervening pools. Larval drift of bayou darters allows for replenishment of downstream riffles from those upstream; however, characteristics of downstream adult populations were not consistent with predictions of source-sink models.