Lansing – As a precaution to not spread viral hemorrhagic
septicemia into Michigan inland waters, the DNR said it will
continue to limit production of walleye fry in 2009, but forge
ahead with full production of muskies.
Gary Whelan, the DNR’s fish-production manager, said because the
state does not have all the information it needs on VHS, it would
take a “cautious” approach to battling the disease.
“The cold-water program will be limited this year for fish like
trout and salmon, but the cool-water program for muskies will go on
full-time,” Whelan told Michigan Outdoors News. “We have a lot to
control over those cool-water fish because we can keep them longer
to ensure they are not infected.”
The main issue surrounding the battle against VHS is whether or
not the disinfection used by the DNR will kill the virus in walleye
eggs. Results could be determined as early as this spring.
“We don’t know for sure if the disinfection for cool-water eggs
will work,” Whelan said. “We can’t guarantee it right now. One
issue is, we don’t know for sure if de-clumping agents will
inactivate the iodine used for disinfection. Another issue is we
are not sure if the virus is in the eggs. We think there’s a high
probability that’s true – it’s in the eggs.”
The DNR will conduct a similar program like last year, albeit a
20-percent larger production than last year.
“The good news is many experiments will produce success,” Whelan
said. “They should provide the information we need since
disinfection experiments are ongoing. There’s a new testing
technique that will provide help in screening adult fish.”
There is no proven method for disinfecting walleye eggs,
although adult brood stock will be tested for VHS, as will samples
of walleye fry and fingerlings before they are stocked.
“There are also tests to see if fish are exposed to the virus
called QELISA, which is the same tool as BKD (bacterial kidney
disease),” Whelan said. “We hope this can be used as a screening
tool for adults. It does not test for the live virus, but a
conservative way to screen and tell whether fish have been exposed.
That will help us, because it detects the antigen (a chemical from
the antibodies). We also have much more detailed lab experiments to
take a look at and see if the effectiveness of iodine kills VHS
associated with walleye or cool-water eggs.”
The DNR must wait weeks for results of the ongoing experiment,
but another problem is the state can test eggs only once a year
when walleye eggs are available.
“If tests don’t work, you have to wait another year with
cool-water eggs,” Whelan said. “This year we are in a lot better
shape and cautiously optimistic in dealing with the virus.”
Since VHS was discovered in the Great Lakes and connecting
waters in 2003, the state has been quick to respond since the best
walleye brood stock sources are located in those waterways. Whelan
said the DNR will instead take eggs from walleyes in the Muskegon
River and Little Bay de Noc. He said the Saginaw Bay and
Tittabawassee strain will not be used in 2009, and that only the
Thompson State Fish Hatchery will be used to incubate eggs, as it
maintains a separate facility that will prevent the spread of
potential VHS into steelhead-rearing facilities, should infection
Whelan, who also manages the state’s Tribal Coordination Unit,
said the state would evaluate the feasibility of rearing additional
walleyes at private and tribal facilities.
“Right now our fisheries in Michigan are about as good as
they’ve been,” Whelan said. “There are an awful lot of bright
spots. Look at it as a whole: Lake trout are doing very well;
smallmouth and largemouth are doing well; muskies are doing very
well. It’s a good product.”
To enhance Michigan’s fisheries this year despite the VHS
outbreak, Whelan said walleye egg take will be spaced out over
several weeks to maximize production, which will remain limited to
6 million fry if the outside facilities are not used.
According to the DNR, fry spend only 3 to 5 days at the hatchery
before being transferred to off-site rearing ponds. Many external
walleye rearing ponds exist throughout the state, but only those
that are non-drainable will be used for rearing in 2009.
“Incubation, fryer-produced fish will go to ponds that are
non-drainable,” Whelan said. “We only use these fish in closed
areas or where they came from. Only stocking them in enclosed
basins or back in the Great Lakes minimizes exposure to new
Of note, Whelan said the DNR will not stock Lake Superior with
walleye fingerlings this season.
“We are testing all our brood stock and actively looking for
VHS,” Whelan said. “We are not raising northern pike. We have a
limited ability to test pike because we don’t hold them in
facilities very long. You have to wait 28 days for negative
results; positive results come much quicker.”
Furthermore, Whelan said the DNR would test fry after they hatch
and test fingerlings prior to distribution into ponds.
Regarding muskies, Whelan said they are easier to test because
the state can hold them longer in a defined space.
“Muskie is easier to handle for VHS surveillance,” he said,
noting that Thornapple Lake in Barry County and Lake Hudson in
Lenawee County are where muskies are reared.
“Muskie has the ability to be tested multiple times. We sample
fluid, milk, sperm, and can test fry and fingerlings multiple
times,” Whelan said
Whelan said VHS was not detected in 70 inland lakes last
“That’s good news,” he said. “But the virus was found in Lake
Michigan near Milwaukee in round gobies and perch.”
Still, Whelan said the DNR has not seen population decreases in
Michigan waters of fish species because of the VHS virus.
“We have seen some decline in the St. Lawrence Seaway area,” he
said. “Mortality can occur in this disease, and it could show
effects over time, but nothing right now. We don’t know the
long-term effects. We’ll spend the next decade learning more about
it and how to mange around it. We will have VHS forever, but how we
manage it will be key.”
VHS is a virus causing death of the circulator cells. Whelan
said blood leaks out and typically the kidneys fail first.
“It’s why fish get hemorrhagic spots on either side,” he