Comparative Fish Assemblage Structure of a Naturally Disturbed vs. a Tailwater Stream in Central Texas

Allison A. Anderson, Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas 77843-2258

Tailwater areas (directly downstream of a dam) of flood-control dams have a number of features that could affect assemblage composition. Discharges from these types of dams are usually hypolimnetic and cold, and reduced temperature may affect growth, egg size, and development. These areas also lack the seasonal scouring floods that provide habitat heterogeneity in a natural stream. Such disturbances play an important role in the life history strategies of fishes. This study examined the relative representation of life history strategies in assemblages of a tailwater and a natural stream in central Texas. Results from two years of sampling show that the natural stream is higher in total fish abundance but lower in total biomass. Abundances of opportunistic or ‘‘r-type’’ species (Gambusia affinis and Etheostoma spectabile) were higher in the tailwater, whereas cyprinids (periodic strategists that respond to large-scale environmental heterogeneity) were dominant in the natural stream. Relative equilibrium or ‘‘K-type’’ strategists (Lepomis spp.) had similar abundances between streams. Lepomis megalotis was dominant on both streams, however non-indigenous L. auritus dominated centrarchid biomass in the tailwater. Micropterus spp. were more numerous and had a higher relative biomass in the natural stream.

Copyright © 1999
Texas Chapter of the American Fisheries Society
Last modified: 03/03/04 04:15:38 PM