Date: 12/3/08
Contact: C. Doug Nielsen
Phone: (702) 486-5127, ext. 3500

NDOW TARGETS NON-NATIVE AQUATIC SPECIES FOR REMOVAL

Visitors can often see a variety of wildlife in Nevada’s warm springs, but not every species one sees in those springs is welcome there. In fact, many species don’t belong in the springs at all. These are non-native aquatic species, and the Nevada Department of Wildlife (NDOW) is clearing out the unwanted visitors.

The removal of exotic aquatic animals from warm spring areas is part of the recovery plan for spring fish species. Exotic species end up in the warm springs because these waters are a favorite site for people to dump unwanted aquarium fish, or even rear them for sale.

“These exotic species survive well in the warm water, and become a threat to the native fish species by outcompeting them for limited resources,“ said Brian Hobbs, native fish and amphibian biologist for NDOW.

Indiscriminate spawning is another competitive advantage that exotic species possess. Mollies and mosquito fish have the additional advantage of bearing live young, which start competing with native fishes right away. The convict cichlid is another aquarium fish whose males guard the nest, so that 100-200 eggs will hatch successfully without being preyed upon.

Other non-native fish species that have shown up in warm springs include largemouth bass and tilapia. Both of these are predators that feed on other fish and also consume the algae that feeds those fish. Bullfrogs are another aquatic species that have invaded Nevada’s waters. These large frogs eat native fish, frogs, and even small land animals that wander into their aquatic territory. The bullfrog tadpoles feed voraciously on native fish eggs.

One of the biggest problems native fish species face are crayfish, Hobbs said. “Crayfish can decimate a native fish population by 90 percent. Crayfish are bottom-feeders and prey on fish when they drop their metabolism (either at night or when it is hot) and sink to lower depths.” The crayfish are being removed by the use of crab traps, which allow the native fish to swim right through.

Though the recovery plan calls for the removal to be done on an as-needed basis, vigilance is critical to the plan’s success. And that means Jeff Goldstein, a seasonal biologist, has plenty to do. The exotic species are physically removed by catching them in traps that look like inverted funnels on each end, allowing the fish to get in but not out. Some native fish will also be caught with this method, but the traps are not lethal. Any native species caught in the traps are immediately separated out and released.

Aquatic pesticides are not an option in most cases as they can kill native species as well as the exotics. Some of the native fish benefiting from the removal of exotics include the White River Spring fish, the Hiko White River Spring fish, and the Railroad Valley Spring fish.

Hobbs stated that about 14,000 convict cichlids, 39,000 mollies, almost 10,000 crayfish and over 7,500 bullfrogs have been removed recently from springs in Southern Nevada. At Duckwater Reservoir, 10,000 mollies were removed in just two days and that is estimated to be only 10 percent of the molly population. An additional 4,000 mollies were removed from Hiko Springs.

The Nevada Department of Wildlife (NDOW) protects, restores and manages fish and wildlife, promotes fishing, hunting, and boating safety. NDOW’s wildlife and habitat conservation efforts are primarily funded by sportsmen’s license and conservation fees and a Federal surcharge on hunting and fishing gear. Support wildlife and habitat conservation in Nevada by purchasing a hunting, fishing, or combination license. For more information, visit www.ndow.org.