Effectiveness of freshwater treatment against Lepeophtheirus simplex (Copepoda: Caligidae) and Neobenedenia sp. (Monogenea: Capsalidae), skin parasites of bullseye puffer fish, Sphoeroides annulatus reared in tanks

Concurrent infections provoked by the sea lice Lepeophtheirus simplex and the monogenean Neobenedenia sp. on bullseye puffer fish Sphoeroides annulatus, reared in tanks, have been related to skin pathology and mortality. Freshwater treatment is widely used to treat two parasite groups, but the results differ depending on the parasite species, life stage and exposure time. The present study describes the effectiveness of freshwater treatments to remove both parasites. Sea lice nauplii and free swimming copepodids, reared in the laboratory, were exposed to freshwater treatments for periods from 30 s to 16 min. Fish experimentally infected with sea lice or monogeneans were exposed to freshwater for 15 to 90 min and 10 to 60 min, respectively. All sea lice nauplii and copepodids were killed by freshwater dips at 2.5 and 14 min, respectively. For pre-adult and adult sea lice, 30 and 60 min of freshwater exposure significantly reduced up to 95 and 99% respectively. However, most freshwater exposures did not reduce chalimus stages more than 10%. Immature and adult populations of monogeneans showed a significant reduction of 95% at 20 min of exposure. These results indicate that, if used properly, freshwater baths constitute an efficient alternative to control these mixed ectoparasite infections on bullseye puffer fish reared in tanks.