Distribution of Benthic Stream Fishes and Crayfish in the Sam Houston National Forest

Healy, B. D. and F. P. Gelwick, Department of Wildlife and Fisheries Sciences, Texas A&M University

Benthic stream invertivores are sensitive to environmental disturbances such as siltation and drought that reduce available habitat and food resources. The distribution and abundance of crayfish and benthic stream fishes are a focus of conservation efforts because their numbers have been declining and they are likely sensitive to such environmental disturbances. However, differences in their sensitivity to various types of environmental disturbances could influence their relative distribution and abundance. In addition, some studies indicate that crayfish may negatively influence distribution and abundance of benthic stream fish via competition for food resources and predator-free space. In habitats where resources are scarce due to environmental disturbance, such interactions are likely to be stronger. To evaluate the distribution and possible interactions among members of this benthic invertivore guild, we surveyed 35 discrete mesohabitat units (pools or runs) in 6 streams within the San Jacinto and Trinity River drainages in East Texas using block nets and back-pack electrofishing. For initial samples in fall 1999, percent similarity was 40% for crayfish and benthic fish occurrence across sampled mesohabitats. Within mesohabitats, the abundance of both crayfish and benthic fish increased with habitat area except in the largest runs, in which small crayfish (40.2 mm mean length, rostrum to tail) were abundant, but few benthic fishes (46.8 mm mean SL) were collected. Because ontogenetic niche shifts for both crayfish and benthic fishes may occur, our continued sampling during January through April will document temporal change in distribution and abundance of these taxa by size class.

Copyright © 1999
Texas Chapter of the American Fisheries Society
Last modified: 01/07/09 06:45:17 AM