Persistence of Stream Fish Assemblages: Effects of Environmental Change

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Abstract
Knowledge of temporal stability and persistence of ecological communities is critical to an understanding of the importance of biotic interactions in the maintenance of community structure. Temporal stability and persistance of 2 fish assemblages, one in Brier Creek, a harsh prairie stream in southern Oklahoma [USA], and the other in Piney Creek, a more benign stream in the Arkansas Ozarkis are examined. Persistence, as indicated by presence data, was high for both stream assemblages over .apprx. 1 decade. Assemblage stability, as determined from measures of abundance, indicated greater change in the overall fish fauna of Brier Creek than that of Piney Creek. Southeastern Oklahoma had a severe summer drought in 1980 resulting in heat death of fishes in Brier Creek. Although some species were transiently affected, the harsh summer did not have a lasting effect on the Brier Creek fish assemblage overall. Upstream stations subjected to regular summer drying showed greater variability in numerical species ranks within a characteristic suite of upstream species, compared with downstream stations. Station-level changes in both Piney and Brier creeks were significant in several cases, even though the overall fauna of the former did not change significantly in species-abundance ranks. Thus, geographic scale may have had a major effect on the assessment of assemblage stability and persistence. In the absence of detailed knowledge of home ranges of component species, an assessment of assemblage stability should be based on at least several localities within a watershed.