By Mark Constance
LANSING – The state has finally acknowledged a rare invasive species of snail was found in the former Grayling Fish Hatchery.
The Michigan Departments of Natural Resources (DNR), Environmental Quality (DEQ) 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 DNR said the inspection was conducted following the discovery in June of what appeared to be New Zealand mud snails immediately upstream and downstream of the privately-operated hatchery by biologists. New Zealand mud snails compete with native snails and other macro invertebrates that trout may eat.
Inspection of the Grayling Hatchery followed a Sept. 6 letter from Anglers of the AuSable President Tom Baird to Gov. Rick Snyder requesting an inspection of the hatchery.
However, an Oct. 4 release by the DNR indicated it inspected the facility immediately following a July letter from the contracted operator of the hatchery, Dan Vogler of Harrietta Farms.
‘Our experts (Mark Luttinton of Grand Valley State University said) the hatchery may have been the source of the invasive New Zealand Mud Snail now in the river – and may spread the snail into other waters as the hatchery operator distributes fish around the state,’ Baird’s letter said.
When Angler’s biologists conducted routine baseline testing near the hatchery in June, snails were located in the East Branch of the AuSable, just downstream from the hatchery, according to Josh Greenburg of Gates AuSable Lodge.
‘We reported it to the DNR and DEQ in Mid June as soon as identification was verified,’ Greenberg said.
‘But by waiting so long to look, you lose the opportunity to find the start point of the snails and ability to treat them. Now they have spread.’
DNR spokesperson Ed Golder could not be reached for comment.
The on-site inspection also included surveys for New Zealand mud snails within the facility. A small number of specimens presumed to be New Zealand mud snails were collected from the walls of the hatchery’ 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 mud snails. Some 60 fish were dissected to look for the presence of New Zealand mud snails in their digestive tracts. No invasive snails were discovered in the dissected fish.
In July, the DNR required risk reduction procedures at the hatchery owner in order for Harrietta Farms to be able to stock fish in public waters. The release indicated Harrietta Farms independently implemented additional risk reduction practices, including use of well water for fish transport. An inspection at the hatchery confirmed a source of well water is available to the hatchery for use in trucks transporting fish.
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 three state agencies will continue to work with the Grayling Hatchery – and with those who fish and float on the Au Sable River – to guard against additional spread of New Zealand mud snails.
‘We know these snails are easily transferred on the waders of anglers,’ Schist said. ‘We encourage all those who are concerned about the health of Michigan’ waterways to thoroughly clean their waders, boats and other fishing equipment before moving to another water body.
‘The state takes very seriously the finding of invasive species in any water body. That is why we have invested significantly in programs to prevent, control and eradicate invasive species in Michigan, Eisch said.
New Zealand mud snails are no more than an eighth of an inch in length and are present in other Great Lakes states, the western U.S. and Chesapeake Bay.
Prior to their discovery in the Au Sable, the snails had been found in Michigan in the Pere Marquette and the Boardman rivers.
