River Impoundment and Sunfish Growth

Impoundment of rivers by dams is widespread and one of the most devastating anthropogenic impacts to freshwater environments. Linking theoretical and applied research on river impoundment requires an improved capacity for predicting how varying degrees of impoundment affects a range of species. Here, growth of 14 North American sunfish species resilient to river impoundment was compared in rivers versus impoundments. Growth response to river impoundment varied widely, but consistently among taxa: five species (shadow bass, rock bass, flier, redbreast sunfish and green sunfish) showed significantly higher growth in riverine ecosystems, four species (largemouth bass, smallmouth bass, spotted bass and longear sunfish) showed significantly higher growth in impounded ecosystems, and five species (bluegill, black crappie, white crappie, redear sunfish and warmouth) displayed no difference in growth between rivers and impoundments. Furthermore, significant linear models were developed for predicting growth of two species (largemouth bass, R1⁄4 0.75 and warmouth, R1⁄4 0.44) based on a physiographically specific index of reservoir retention time. For another species (white crappie), growth could not be predicted by the retention time index in Central Lowlands rivers (R1⁄4 0.001), but was strongly predicted by this factor in southeastern Coastal Plain rivers (R1⁄4 0.76) showing how impacts of impoundment, and prediction of its consequences, can vary across river landscape types. Further analysis of fish growth in response to river impoundment, regulation and fragmentation could greatly enhance conservation biology, restoration ecology and basic land use decisions in riverine landscapes. Copyright # 2010 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this paper. key words: Centrarchidae; climate; dams; fisheries management; natural flow regime; production; restoration; reservoir retention time Received 20 March 2009; Revised 6 October 2009; Accepted 26 January 2010