Toxicity of Rotenone to Giant River Freshwater Prawn Macrobrachium rosenbergii

Abstract

Aquaculturists have often suffered predation losses in the production of freshwater giant river prawn Macrobrachium rosenbergii due to the presence of wild fish species in culture ponds. The piscicide rotenone is widely used to remove undesirable fish species from ponds. Although evidence in the technical literature suggests that crustaceans generally have a higher tolerance to rotenone than fish, there are currently no data on the acute or chronic toxicity of rotenone to juvenile freshwater prawns. In this study, two static acute-toxicity bioassays (96 h) were conducted using Prentox Prenfish (5% active ingredient) rotenone to determine the median lethal concentration (LC50) for juvenile freshwater prawns (average weight = 0.55 g, SD = 0.25; length = 41.43 mm, SD = 6.45). In bioassay 1, prawns were exposed to rotenone concentrations of 1.0, 3.0, 5.0, and 10.0 mg/L. In bioassay 2, prawns were exposed to rotenone concentrations of 2.2, 3.6, 6.0, 10.0, and 16.7 mg/L. All rotenone concentrations used in the study were based on the total product of the commercial rotenone formulation. The LC50 calculated in bioassay 1 was 6.2 mg/L, and the LC50 calculated in bioassay 2 was 7.5 mg/L. Freshwater prawns were able to tolerate 3.0 to 3.6 mg/L of rotenone with no mortality or apparent adverse effects during the study. Prawns held at the end of each bioassay for 5 d showed no signs of delayed effects from rotenone exposure. Data from this study indicate that juvenile prawns should be able to tolerate the concentrations of rotenone required to eradicate certain problematic wild fish species.

Received April 29, 2010; accepted October 1, 2010

ACKNOWLEDGMENTS

This work was financially supported by Kentucky State University's Aquaculture Research Center. We would like to thank Michael Goss at the Division of Environmental Services in Frankfort, Kentucky, for analyzing the dilution water used in the study. Additional thanks to Linda Metts for her assistance with the experiment. Reference to trade names does not imply endorsement by the U.S. Government.