An evaluation of liquid ammonia as a new candidate piscicide

Authors: David L. Ward

Year: 2011 (xliii)

Abstract

The continued decline of native fish in the southwestern United States is largely attributed to interactions with introduced fish species. Attempts to remove nonnative fish from areas with native fish are common, but success is limited because very few tools are available for managing invasive aquatic species. Currently licensed piscicides such as Rotenone are likely to become unpopular because of recent data linking Parkinson’s disease to Rotenone use in agriculture. This creates the need to evaluate new chemicals that could be used as management tools for native fish conservation. At high concentrations, ammonia is known to be toxic to a wide variety of aquatic organisms and yet ammonia is the natural byproduct of fish metabolism and is naturally present in the environment at low levels. Natural bacteria in the environment rapidly convert ammonia to non-toxic nitrate. A suite of common nonnative fishes including smallmouth bass Micropterus dolomieu, largemouth bass Micropterus salmoides, green sunfish Lepomis cyanellus, fathead minnow Pimephales promelas, red shiner Cyprinella lutrensis, mosquitofish Gambusia affinis, black bullhead Ameiurus melas, channel catfish Ictalurus punctatus, flathead catfish Pylodictis olivaris, bullfrog tadpoles Rana catesbeiana, and crayfish Orconectes virilis were introduced into two experimental outdoor ponds located at the Rocky Mountain Research Station in Flagstaff, AZ. Each pond was treated with ammonium hydroxide (29%) at 0.5 ml of ammonia per gallon of water. Water quality was monitored for 30 days to determine how fast the natural bacteria in the environment converted the ammonia to non-toxic nitrate. After 30-days all water in both ponds were drained and no fish, crayfish or tadpoles were found to have survived the treatment, but red ear slider turtles Trachemys scripta and hatchling mud turtles kinosternon baurii remained alive and appeared unaffected.