Selective Eradication of Gizzard Shad Dorosoma Cepedianum with Low-Dose Rotenone Applications

The use of rotenone to restore aquatic ecosystems is often necessary when undesirable fish species negatively impact physiochemical conditions (e.g., bioturbation) and other fish species.  At high abundance, gizzard shad Dorosoma cepedianum can have strong ecosystem effects (e.g., alter zooplankton and phytoplankton assemblages, nutrient loading) and are commonly targeted for removal or control at low biomass.  However, the use of rotenone is costly, time consuming, and results in the temporary loss of fisheries.  The overall objective of this study was to experimentally evaluate the effects of varying low-dose rotenone concentrations (i.e., 0, 3, 6, 9, and 12 µg/L) on gizzard shad and common lentic sport fish species (i.e., bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides, walleye Sander vitreus).  Walleye were more susceptible than gizzard shad, while bluegill and largemouth bass were more tolerant.  Overall, results from this study provide knowledge on the relative influence of rotenone concentrations on gizzard shad, bluegill, largemouth bass, and walleye that can be used by managers to better target and more efficiently use resources for improving ecological integrity lakes ecosystems.