Effectiveness of Two Commercial Rotenone Formulations in the Eradication of Virile Crayfish Orconectes virilis

Abstract

The virile or northern crayfish Orconectes virilis is an invasive species throughout much of the USA, damaging aquatic communities where it is introduced. Therefore, identification of effective methods for its eradication from areas in which it is unwanted is important. We studied the effectiveness of two commercial formulations of rotenone, Chem Fish Regular and CFT Legumine, for virile crayfish control. Although both formulations were effective for fish eradication, earlier observations by fisheries managers suggested that the relative effectiveness of the two formulations differs for crayfish. The only noteworthy difference between the formulations is that the former contains a synergist. In our first experiment, we tested each toxicant at the maximum labeled dosage (5 ppm) and found CFT Legumine to be 100% ineffective (0% mortality), while the Chem Fish Regular treatment resulted in 12.5% mortality. After we deemed Chem Fish Regular to be the only toxicant with any effectiveness against virile crayfish, we tested concentrations from 5 to 50 ppm and found 10 times the maximum labeled dosage (50 ppm rotenone) was needed to kill all virile crayfish. Because crayfish burrow and can leave water, and because 100% eradication is usually desired, rotenone applied at the labeled rates will not be effective for crayfish control. However, treating a body of water with CFT Legumine to eradicate invasive fish while leaving desirable crayfish unharmed is possible.

An Assessment of the Effect of Rotenone on Selected Non-Target Aquatic Fauna

“…sidneyi , no deaths were observed at experimental concentrations which were as high as 100 μg L −1 . These observations are similar to field [ 11 , 17 , 25 , 40 , 41 ] and laboratory observations reported in the literature [ 27 , 42 , 43 , 44 ]. In acute toxicity tests, Chandler and Marking [ 42 ] for example, demonstrated that the tolerance of Dragonfly niaid Macromia sp., gastropods including Physa pomilia and the freshwater prawn Palaemonetes kadiakensis far exceeded the tolerances of the water flea D .…”

“…Similarly, Recsetar and Bonar [ 44 ] observed 0% mortality in crayfish at recommended rotenone dosages and Wujtewicz et al [ 43 ] demonstrated that rotenone concentrations required to kill crayfish Procambrus acutus (4 mg L −1 ) were > 20× higher than those resulting in 100% mortality in white perch Morone americana (0.15 mg L −1 ). The absence of any mortality in crabs (observed in this study) and crayfish [ 43 , 44 ] can likely be attributed to the open circulatory system in Decapods [ 10 , 44 ]. Öberg [ 10 ] highlighted that rotenone cause’s death at a cellular level and not at the water–blood interface.…”

“…Recent literature e.g. [ 9 , 11 , 44 , 49 – 55 ] have reported short-term extirpation of zooplankton after rotenone application, followed by a relatively rapid recovery of zooplankton communities. Examples include two lakes in Jasper National Park, Canada [ 47 ], Upper Karori Reservoir, New Zealand [ 46 ], Fern [ 52 ] and Diamond [ 55 ] Lakes in the USA, and Lakes Salmo and Alm in Sweden [ 53 ].…”

Detection and Control of Invasive Freshwater Crayfish: From Traditional to Innovative Methods

“…The target organism may be impacted by the use of chemicals to alter the surrounding environment, for instance, by an increase or decrease in pH or oxygen concentrations [105]. Pesticides and substances such as rotenone, a naturally occurring ketone, have been used to control crayfish such as F. virilis [106]. However, rotenone is toxic to fish and amphibians at levels lower than those needed to kill crustaceans [107,108].…”