Impact of Predation by Backswimmers in Golden Shiner,Notemigonus crysoleucas,Production Ponds

Laboratory and field studies were conducted to determine the population dynamics and potential for predation on golden shiner, Notemigonus crysoleucas, fry by the backswimmers, Notonecta indica and Buenoa scimitra. Both species were found to be highly effective predators under laboratory conditions. N. indica invaded newly flooded ponds within 2 weeks of putting spawning mats with eggs into the ponds and were thus present when fry were vulnerable to predation. B. scimitra invaded ponds at a slower pace and would not be as likely to cause extensive predation. N. indica had significantly lower (P = 0.05) population levels in ponds that had been established for one year. The potential loss from backswimmer predation could easily exceed 2.3 kg per 100 m of shoreline, assuming 40% of the fry lost to predation would survive to harvest. Diesel fuel treatment of backswimmer populations in 0.05-ha ponds resulted in about a 50% control of N. indica, mostly during the first 24 hours. B. scimitra were not as susceptible to the diesel fuel treatment. Several classes of insecticides were evaluated in the laboratory as potential control agents; Curacron, an organophosphate, and Cymbush a, synthetic pyrethoid, produced 100% mortality of N. indica at a concentration of 0.01 ppm. B. scimitra was even more sensitive to these compounds.