an Experimental Evaluation of Low-Concentration Rotenone Applications on Aquatic Benthic Invertebrates

Rotenone is a commonly used piscicide to restore aquatic ecosystems that have become dominated by invasive or undesirable fish species (e.g., common carp Cyprinus carpio, gizzard shad Dorosoma cepedianum).  However, little research is available the on the effects on rotenone on other aquatic organisms.  Therefore, the objective of our study was to evaluate the effects of low-concentration rotenone applications on benthic macroinvertebrates.  The effects of rotenone concentration were evaluated through use of mesocosm experiments in fall 2011.  Mesocosms were inoculated with approximately 19 L of littoral sediment from a nearby impoundment to provide invertebrates.  Additionally, 12 individuals of a common lentic freshwater mussel species (i.e., giant floater Anodonta grandis) were stocked into each mesocosm.  Experimental treatments included five targeted concentrations (i.e., 0, 3, 6, 9, and 12 µg/L) of rotenone applications.  Water samples were taken at 1, 24, 72, and 120 hours post application to monitor rotenone concentrations and decay through time.  No acute effects of rotenone on giant floater or non-unionid benthic macroinvertebrates were observed after 5 days.  As such, results of our study suggested limited non-target loss of aquatic organisms when using low-concentration rotenone to selectively eradicate undesirable species.