Privately-operated fish hatchery on Au Sable River inspected for invasive species

Last week, the Michigan departments of Natural Resources, Environmental Quality and Agriculture and Rural Development jointly inspected the Grayling Fish Hatchery located on the East Branch of the Au Sable River in Crawford County.The inspection was conducted following the discovery in June of New Zealand mudsnails immediately upstream and New Zealand mudsnails downstream of the privately-operated hatchery. New Zealand mudsnails compete with native snails and other macroinvertebrates that trout may eat.
Inspection of the Grayling Hatchery followed a letter from the hatchery’s operator, which invited the three state agencies into the facility to conduct an inspection, and to review procedures the hatchery has instituted to reduce the risk of spreading the invasive snails.
In July, the DNR required risk reduction procedures to the hatchery owner in order for him to be able to stock fish in public waters. The owner independently also implemented additional risk reduction practices, including use of well water for fish transport. The inspection last week confirmed a source of well water is available to the hatchery for use in trucks transporting fish. Use of this specific source of well water ensures invasive snails are not leaving the property in river water.
With well water being used for fish transport, the remaining required practice to implement – which aligns with industry standard – is to hold fish for no more than 36 hours without food before transporting them. The 36-hour maximum no feed period is designed to minimize the possibility fish will feed on snails and move them elsewhere, even though snails are not a preferred food source for trout.
The on-site inspection also included surveys for New Zealand mudsnails within the facility. A small number of specimens presumed to be New Zealand mudsnails were collected from the walls of the hatchery’s raceways, where trout are reared for the purposes of stocking in other waters and harvesting for market.
Results of genetic testing are expected by the end of this week to confirm if those specimens are indeed New Zealand mudsnails. Read more











