Fish assemblage changes in an Ozark river after impoundment: A long-term perspective

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survey, monitoring, trout, habitat, species richness, impact of dams, dams

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Transactions of the American Fisheries Society


We conducted an intensive fish survey in the tailwater reach of a large Ozark river 30years after its impoundment and compared the recent fish assemblage with those prior toimpoundment and shortly (4 years) after impoundment. Our primary objective was to assesswhether relatively short-term monitoring following dam construction can adequately quantify thelong-term effects of impoundment on downstream riverine fishes. The preimpoundment survey(19621963) described a fish assemblage composed of warmwater fish species, predominantlyCyprinidae, Ictaluridae, Centrarchidae, and Percidae. Yoke darter (Etheostoma juliae) (34%),central stoneroller (Campostoma anomalum) (24%), and Ozark madtom (Noturus albater) (7%)were the most abundant species. The postimpoundment surveys of 19651966 and 1968documented immediate changes in the fish assemblage. No Ozark madtoms and only four yokedarters were collected shortly after impoundment. Central stonerollers accounted for 4550% ofthe fish collected, and both short-term postimpoundment surveys collected five species of darters(Percidae) that ac- counted for 4142% of the fish collected. Thirty years after impoundment, wefound that the tailwater fish assemblage was composed almost entirely of coldwater species.Ozark sculpin (Cottus hypselurus) and four species of introduced trout (Salmonidae) accountedfor 98% of the fish assemblage by number during the 19951997 surveys. The rank abundance ofspecies was negatively correlated between our survey and the preimpoundment survey but notbetween our survey and the short-term postimpoundment surveys. Many species that wecollected (54%) are habitat generalists, and we did not collect 77% of the fluvial-specialist speciesthat were present in historical collections. All postimpoundment surveys documented dramaticallyreduced species richness and diversity. We conclude that short-term monitoring followingimpoundment is inadequate to determine the impact of dams on lotic fish assemblages andsuggest long-term postimpoundment monitoring to determine when a fish assemblage hasstabilized.





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