Recovery of a lowland fish assemblage following large-scale rotenone application in eastern Arkansas

During spring 2009, the Arkansas Game and Fish Commission and the United States Fish and Wildlife Service attempted to eradicate northern snakehead, Channa argus, from the Big Piney watershed by applying rotenone to approximately 640 km of stream. To examine long-term recovery of native fishes, we collected pre-disturbance community data at 45 sites during the eradication, 19 of which were re-sampled during fall 2009. Although most species had returned to the drainage by fall, other community characteristics, including evenness, were different. Fish densities were significantly higher in fall (9.4 fish/m²) compared to eradication samples (0.5 fish/m²; t-test, P=0.026), though some species declined or were not detected.  Fall samples were dominated numerically by tolerant, generalist species such as Dorosoma cepedianum, Ictiobus sp., Gambusia affinis, and Lepomis cyanellus. Length-frequency histograms indicated population changes for several species.  Early-colonizing fishes possessed life history traits conducive to rapid repopulation including mobile adults, high fecundity, and/or early reproduction. Collection of pre-disturbance data provides the unique opportunity to further quantify patterns of recovery.  Future samples, including spring 2010 and fall 2010, will give insight into long-term recovery characteristics after severe disturbance, assisting managers in balancing benefits versus collateral damage when considering invasive species eradication.