The Department of Fish and Game (DFG) will modify trout distribution following the discovery of New Zealand Mud Snails (NZMS) in Hot Creek Hatchery. However, the detection of the invasive aquatic snails in the hatchery located approximately 37 miles north of Bishop is expected to have little impact on the number of trout the DFG stocks in area waters.

"The Governor and the Legislature made a commitment to enhance angling opportunities through the passage of AB 7," said DFG Director Ryan Broddrick. "The Department, in turn, is committed to meeting its fish-stocking obligations and the detection of New Zealand Mud Snails in Hot Creek Hatchery will not deter us from carrying out that responsibility."

AB 7 added Section 13007 to the California Fish and Game Code in 2006 and requires DFG to deposit one-third of sport fishing license fees in the Hatchery and Inland Fisheries Fund (HIFF). Beginning July 1, 2006, HIFF funds may be used, upon appropriation by the Legislature, to support DFG programs related to the management, maintenance, and capital improvement of California's fish hatcheries, the Heritage and Wild Trout Program, and enforcement activities. The fund will also support other activities eligible for revenue generated by sport fishing license fees.

NZMS, which reproduce rapidly and can crowd out native insects that aquatic wildlife depend upon for survival, were found Dec. 29, 2006 in samples collected from the spring that supplies water to the primary production ponds for the hatchery. In 2004, NZMS were found in Hot Creek, 150 yards downstream from the settling ponds.

DFG will allow an estimated 515,000 fish from Hot Creek Hatchery to be planted only into waters that have been surveyed and are NZMS positive, such as the Owens River, Crowley Lake and Pleasant Valley Reservoir. As information supporting less restrictive action becomes available, DFG may allow increased distribution of fish in the area. Surveying area waters for the presence of the snail and for water conditions which may favor or restrict snail establishment is being planned by DFG officials.

"We will be able to use some fish from other hatcheries to help ensure quality recreational sport fishing opportunities in the Eastern Sierra while we carefully address the ramifications of the unfortunate presence of New Zealand Mud Snails in Hot Creek Hatchery," said William Cox, DFG Program Manager, Fish Production and Distribution. Officials are also developing strategies to improve the infrastructure and operations to contain the spread of NZMS within and outside of Hot Creek Hatchery.

NZMS are believed to be spread within North America primarily by anglers who fish an infested area, then leave the area without cleaning their waders and other fishing gear. The snails will often get stuck to debris and mud left on waders and can survive for weeks in the moist conditions. When the angler visits a new stream snails can deposit there. NZMS, which can grow as large as one-quarter inch but are often much smaller, are parthenogenic, which means that they are able to start a new population with one snail.

NZMS have the potential of extraordinary population densities ??? up to nearly one million snails per square meter and comprising up to 95 percent of the invertebrate biomass of a river. It is believed that populations in New Zealand are kept in check naturally by a native parasite. In North America, however, native stream communities can be drastically altered because there are no natural predators or parasites of the snail and the populations have flourished where they have been introduced.

NZMS colonies disrupt the base of the food chain by consuming algae in the stream and competing with native bottom-dwelling invertebrates. A population decline of invertebrates (small aquatic insects) can follow the introduction of NZMS, which reduces fish forage. With a decrease in food availability, the fish populations can decline as well.