DNR Coolwater Fish Production Strategy for 2008 Announced

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After placing a moratorium on coolwater fish production in 2007 because of concerns related to viral hemorrhagic septicemia virus (VHSv) in the Great Lakes, the Department of Natural Resources today announced its fish production strategy for 2008.

The DNR plans to produce approximately 2 million spring fingerling walleye – about 20 percent of the normal production -and up to 50,000 fall fingerling muskellunge. Northern pike will not be produced in 2008, and lake sturgeon will be produced in very limited numbers, up to 5,000 fall fingerlings.

“Much has been learned about VHSv in the past year, including experiments on the effect of egg disinfection chemicals on the survival of coolwater eggs, a better understanding of the distribution of VHSv in our waters, and an analysis of scientific literature on similar viruses that was focused on how those viruses are managed,” said DNR Fisheries Division Chief Kelley Smith. “This new information has been incorporated into the 2008 strategy for coolwater production.”

During 2006 and 2007, VHSv was directly implicated in a number of fish kills in Michigan Great Lakes waters, including Thunder Bay in Lake Huron, the St. Clair River, Lake St. Clair, the Detroit River and Budd Lake in Clare County. Budd Lake remains the only inland lake in which VHSv has been detected.

“Although additional information is needed, particularly the effectiveness of egg disinfection in killing VHSv on coolwater eggs, sufficient information is available to allow the DNR to begin to manage the coolwater production risks surrounding VHSv,” said DNR Fish Production Manager Gary Whelan. “While not completely risk-free, the proposed coolwater production strategy will greatly minimize risks, allow the limited production of coolwater fish and allow the DNR to learn how to manage this disease issue.”

A number of measures will be taken in the DNR production system to reduce the risk of VHSv in Michigan’s waters and ensure the health of the hatchery system. They include:

  • VHSv testing of all coolwater broodstocks (all were negative in 2007);
  • VHSv testing of all coolwater fry prior to moving to rearing ponds and fingerlings prior to stocking;
  • The destruction of any hatchery fish that are shown to be positive at any stage for VHSv;
  • Disinfecting all coolwater eggs in an iodine solution (Iodophor);
  • Raising walleye in non-drainable ponds from which fish can be completely killed off if VHSv is detected in these fish.

Since muskellunge require significantly more fish culture effort and require live feeds, they will be reared in isolated drainable muskie ponds at Wolf Lake State Fish Hatchery. Muskie egg takes are conducted in Lake Hudson and Thornapple Lake, which are far removed from current VHSv-positive locations. When the egg take location is combined with intensive testing of the adults and young fish, a reasonable level of protection against VHSv spread by hatchery operations is provided, Whelan said.

“Muskies give us many more opportunities to test for VHSv as they are typically not stocked from the rearing ponds until the fall, unlike walleyes, which are stocked in early summer,” Whelan added.

“In addition to the fish production biosecurity measures, we are also going to limit the locations to which we stock walleye to further protect our state’s waters from VHSv,” Smith said. “Walleyes will only be stocked in waters from which egg takes were conducted (the Muskegon River and Little Bay de Noc); waters in which Muskegon River and Little Bay de Noc walleye broodstock normally move to; and for Muskegon River walleye only in Lake Michigan or Lake Huron inland lakes that do not have any connections to other waters. The risk is much lower and manageable for muskellunge, so they will be stocked in normal stocking locations.”

Smith said it was important to note that the 2008 strategy was not completely risk-free.

“While the measures we have put in place do reduce our ability to rear and stock coolwater fish, they will also greatly reduce the risk of inadvertently spreading VHSv. We are optimistic that the new testing methodologies and improved disinfection options will allow us to resume full coolwater production in the near future,” Smith said.

Additional details on the 2008 coolwater production program can be found at www.michigan.gov/dnrfisheries