Recreational disturbance of a desert stream fish community: Detecting ecological effects of environmental impact
Fish assemblages in 22 pools were sampled over the summer of 1997 in the North Fork of the Virgin River, Zion National Park, Utah, to assess effects of recreational activities on native fish communities. Pools experiencing high levels of wading and float tubing contained altered population distributions and altered community structure as compared to pools generally lacking recreational activities. In addition, pools disturbed by recreation had lower abundance of desert sucker (Catostomus clarki) and lower community diversity than pools without recreation. Food availability measured as algal biomass and macroinvertebrate drift density was similar among all pools, but abundance of larval fish was lower in pools experiencing recreational disturbance. Flash floods at the end of the summer appeared to "reset" the system, redistributing fish in the river and resulting in similar communities throughout the study area. Results suggest that recreational activities do disturb native fish communities and that the greatest threat may be to larval fish.
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