Arizona fish hatchery controls New Zealand mud snails while preserving fish stocks

EarthTec QZ can effectively control New Zealand mud snails while preserving trout stocks, according to a recent study by the Arizona Game and Fish Department (AGFD). Fish hatcheries have traditionally avoided copper-based molluscicides because salmonids such as trout are highly sensitive to copper. The new study suggests that low doses of liquid copper in the form of cupric ions (Cu++) are effective on New Zealand mud snails and tolerable for trout.

New Zealand mud snails invaded Arizona’s portion of the Colorado River in 1995 and recently spread to the Page Spring Hatchery (PSH) in Phoenix. PSH produces the largest stock of rainbow and brown trout in Arizona, worth almost $200 million annually to the state’s economy. Controlling the New Zealand mud snail infestation was essential, both to protect this valuable economic resource and to prevent further spread.  Shared stocking activities between hatcheries threatened to transfer this fast-producing and ecologically harmful species to municipalities and watersheds across the state.

The AGFD study examined survival rates of mud snail and trout populations while administering EarthTec® QZ at a metered dispersal of 30 ppb for a 39-day period. The mud snail population decreased below 50% within 18 days and reached total eradication on day 36. The trout population remained at normal operational levels for the duration of treatment. These results suggest that EarthTec QZ can be used to control New Zealand mud snails without significantly reducing non-target trout populations in hatchery environments. The full article is posted below.

The following article originally appeared in Management of Biological Invasions (2020) Volume 11.