Effectiveness of Two Commercial Fish Toxicants on the Eradication of Northern Crayfish Orconectes virilis
October 2011 to December 2013
Northern crayfish are non-native to Arizona, and are considered a pest in many streams and lakes; however, effective control measures remain elusive. To remove Northern crayfish from water bodies, wildlife managers have primarily relied on trapping methods; yet rotenone treatment of has also been considered. We tested effects of two toxicants containing rotenone (Chemfish Regular™ and CFT Legumine™) in 32 75-L tanks. Our first experiment tested effects of maximum labeled concentrations of both compounds; further experiments tested different dosages of the most effective of the two formulations. Chemfish Regular™ was show to have a higher toxicity (12.5%) than CFT Legumine™ (0%) over a 120 hr period. Next we tested for effective dosages of Chemfish Regular™. After 5 d the following mortalities were recorded: 8% , 10 ppm; 12%, 15ppm; 76%, 20ppm; 68%, 25ppm; 76%, 35ppm; 100%, 50ppm. We found 10 times the maximum labeled dosage of Chemfish Regular™ was necessary for it to be 100% effective against crayfish. As total eradication of invasive Northern Crayfish is almost always the goal, neither rotenone formulation appeared effective for northern crayfish control. A final report is being prepared for this project.