Relationships between Hydrology and Largemouth Bass Growth in the Ouachita River, Arkansas

We explored whether increased river flows negatively affected growth of largemouth bass (Micropterus salmoides) in the lower Ouachita River, Arkansas. To test this hypothesis, largemouth bass (n = 460) were collected during 2008-2010 from the Felsenthal Reservoir region of the river. Largemouth bass were aged and annual growth increments were calculated using standard back-calculation techniques. Growth of largemouth bass was relatively rapid in the Ouachita River, with von Bertalanffy growth model parameters determined as L = 513 mm, K = 0.324, and tο = -0.314; catch-curve analysis estimated that total annual mortality of the population averaged 48% (95% CL 42%-54%). Back-calculated growth increments of largemouth bass were compared across years classified as "high-flow," "low-flow," and "average-flow" based on analysis of historical June-October hydrology (i.e., corresponding with the largemouth bass growing season). Two-way factorial ANOVA analyses indicated that largemouth bass growth was lower during high-flow years, with the effect most pronounced for the age 2-4 cohorts. Results suggested that high-flow periods typically beneficial to fishes in large river-floodplain systems may not always result in increased growth rates in more highly regulated river systems such as the Ouachita River. Better understanding of fish growth-hydrology relationships will become increasingly important in light of predicted future effects of climate change, which include increased frequencies of hydrologic extremes.

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