Virus Killing Great Lakes Giants

  • Fishing guide Rich Clarke of Clayton, NY, is famous for muskie hunts. He's worried so many adult muskies are falling victim to VHS. (Photo courtesy of Rich Clarke)

Fall is when avid anglers flock to the Great Lakes for one of the most
challenging freshwater catches: the muskellunge, or muskie. Some call it
“the fish of 10,000 casts.” This year’s muskie season is clouded by bad news
of a new fish disease and invasive species crowding muskie habitat. David
Sommerstein reports scientists are watching this top-of-the-food-chain
species carefully:

Transcript

Fall is when avid anglers flock to the Great Lakes for one of the most
challenging freshwater catches: the muskellunge, or muskie. Some call it
“the fish of 10,000 casts.” This year’s muskie season is clouded by bad news
of a new fish disease and invasive species crowding muskie habitat. David
Sommerstein reports scientists are watching this top-of-the-food-chain
species carefully:




It’s a cool afternoon as fishing guide Rich Clarke fillets the day’s catch:


“Went out, caught some northerns, a few bass, some jack perch. Had a
pretty good morning.”


Clarke’s specialty is hunting for muskies, 60 pound fish with a lot of fight:


“I mean, the rod screams, they yank, yank, and yank. It doesn’t come all that
often, but when it comes, it’s one of the most exciting things you’ll see when
you fish in fresh water.”


Clarke worries that magical hit might become even more rare. Since 2005,
several hundred of those prized muskies were found belly-up dead, victims
of viral hemorrhagic septicimia, or VHS.


(Sound of hose)


Clarke washes down his fillet table. He mutters VHS is just another non-
native organism threatening the muskie. There are already more than 180
invasive species in the Great Lakes-St. Lawrence River system:


“Everything from the goby to the , y’know, and weed species and all
sorts of stuff, spiny water fleas, you name it, all sorts of stuff that are not native to this
waterway that we have to deal with, and it changes the whole ecology.”


A new invasive species is found every six to nine months. Scientists can
barely keep up in understanding the impact on the native environment.




In a nearby bay of the St. Lawrence River in northern New York State,
Roger Klindt, John Farrell, and a crew drag a huge net through the water:


“We’ve got two people pulling it slowly through the vegetation just trying
to basically corral fish.”


This is called seining, getting a sample of all the fish that live here. Klindt
and Farrell have been doing this in the same marshy shallows for more than
20 years. And Farrell says what they’ve found this year is disturbing:


“Muskellunge numbers in the index are at their lowest levels on record since
we’ve been collecting data.”


Down from almost 50 in the spring spawning run of 2003 to just 4 this year.
Farrell’s a researcher with the State University of New York Environmental
Science and Forestry. He says this could be the result of VHS killing so
many adult muskies in their reproductive prime.




Yet another invasive species is also troubling, the round goby. It’s an ugly
little fish from Eastern Europe that breeds like crazy. Farrell and Klindt
count minnows flipping and fluttering in the seining net:


“15 black gins, 8 blunt nose, 5 spot tail.”


“I didn’t actually count things, I was just picking gobies.”


Farrell says they’ve found more round gobies in these marshes than ever
before:


“Which is a bit of a surprise to us.”


Now the muskie young have to compete with round gobies for food:


“How these species are going to respond to the presence of gobies is
unknown at this time, but they have high predation rates, they’re very
prolific, becoming extremely abundant, so the food web in this system is
shifting.”


This is what frustrates people who study invasive species. Once researchers
train their focus on one, like the fish disease VHS, another emerges to
confound the equation. Roger Klindt is with New York’s Department of
Environmental Conservation
:


“Change happens, y’know, nothing stays the same forever. But when we
have invasive species and exotic species come in, the change is often so
rapid that native species can’t adapt to it.”


That talk makes anglers nervous. Peter Emerson’s been fishing around here
for years. In fact, he participated in a catch and release program that brought
muskie populations back to health in the 1980s:


“There was a real bonanza, til this virus showed up. I’m hopeful they don’t
go extinct.”


Biologists expect adult muskies that survived VHS will develop resistance to
the disease. But they fear the next generation won’t inherit the immunity,
causing more die-offs of one of America’s most prized freshwater fish.


For The Environment Report, I’m David Sommerstein.

Related Links

Is Goby Die Off Good News?

Officials say a disease might be killing an invasive species of fish in Lake Ontario and the St. Lawrence River. The GLRC’s David Sommerstein reports:

Transcript

Officials say a disease might be killing an invasive species of fish in Lake
Ontario and the St. Lawrence River. The GLRC’s David Sommerstein
reports.

Where the lake and the river meet, people have been finding dead round
gobies.

“Dozens in some cases, hundreds of dead gobies that have been washing up on shores.”

Steve Litwiler is with New York’s Department of Environmental
Conservation. He says a change in water temperature or a poison could
cause the die-off, but initial sampling suggests some kind of disease.

“Is it a disease that could potentially affect other fish? Fortunately right
now the only fish that are dying appear to be the round gobies.”

If only the round gobies die, this could be a good news story. Round gobies
hitched a ride from Europe in the ballast of foreign freighters. They’ve
displaced native species across the Great Lakes by breeding faster and eating
other fishes’ eggs and young.

For the GLRC, I’m David Sommerstein.

Related Links

Ten Threats: Botulism Kills Beach Birds

  • Interns for Presque Isle State Park in Erie, Pennsylvania walk along a Lake Erie beach picking up dead birds. (Photo by Lester Graham)

Researchers are beginning to understand what’s killing thousands of
Great Lakes shorebirds. It might be part of a larger problem indirectly
caused by humans. The Great Lakes Radio Consortium’s Lester Graham
reports:

Transcript

We’ve been bringing you reports from the series, ‘Ten Threats to the Great Lakes’ which is now looking at the threat to beaches. Our guide through the series is Lester Graham. He reports that scientists are beginning to understand what’s killing thousands of Great Lakes shorebirds. It might be part of a larger problem indirectly caused by humans.


Researchers are beginning to understand what’s killing thousands of
Great Lakes shorebirds. It might be part of a larger problem indirectly
caused by humans. The Great Lakes Radio Consortium’s Lester Graham
reports:


Along parts of Lake Erie, Lake Ontario, and Lake Huron, large numbers
of dead birds and fish are washing up on shore. If they’re left there, the
disease that killed them can be passed on to other wildlife. That’s why
park officials such as Mike Mumau at Presque Isle State Park at Erie,
Pennsylvania ask their staff to watch out for the dead carcasses.


“Our interns do a great job. They’re the eyes of the staff that are out. So,
there’s probably three to four days a week that they’re out on the
beaches, checking to see if they have anything.”


Since 1998, untold numbers of fish and sometimes hundreds of dead
birds a year have washed up on just these eight miles of Lake Erie beach.


Eventually, researchers figured out the problem: type “E” botulism. It
slowly paralyzes the birds until the respiratory system shuts down. Most
of them don’t make it that long. They get so weak they can’t hold their
heads up out of the water and they drown.


(Sounds of walking and shovel)


Leslie Jones and her fellow interns are headed out to an area to pick up
some dead seagulls on the beach.


“When we’re out here doing migratory bird studies, we might see some
and then we pick them up as soon as possible. A lot of times, we get
radioed from different people like lifeguards and they have us come out
and pick them up so that the disease doesn’t spread throughout the rest of
the ecosystem.”


They find five dead birds rotting on the beach. They bury the maggots
because they could carry the botulism toxin and other birds might eat the
maggots. They shovel the bird carcass into a black plastic garbage bag.


“If they’re very fresh, this one, obviously not very fresh, but, if we get a
fresh one, we actually freeze them and they’re sent off to be tested
botulism, but, something like this we’ll just bag up until we can get them
incinerated to get rid of all the disease.”


The fresh carcasses are shipped to the National Wildlife Health Center in
Madison, Wisconsin.


There, Grace McLaughlin is among the researchers who are beginning to
put the puzzle together.

Here’s what they think is happening. The invasive species zebra mussels
and quagga mussels create huge mussel beds that begin a complicated
biological phenomenon. Organic matter collects there, and then decays. It
lowers the oxygen level in the immediate area of the mussel beds. Type
“E” botulism spores occur naturally, but when the oxygen level goes
down, they begin reproducing like crazy. The waste they produce is the
toxin.


“That toxin will accumulate in the organic matter as well as in the water
in the immediate vicinity of the mussel beds. As the mussels do their
filter feeding, they will accumulate the toxin in their tissue. They are not
susceptible to the toxin. However, when the fish start coming down
there and eating the mussels, they become intoxicated, lose their ability
to swim properly and become easy prey for the birds that come in.”


The fish that feeds on the mussels the most is another invasive species,
the round goby. Researchers made the connection when they noticed the
botulism started being a problem shortly after round gobies arrived in big
numbers.


The type “E” botulism toxin has killed tens-of-thousands of birds such as
cormorants, terns, loons, ducks, and seagulls.


Back at Presque Isle State Park, Mike Mumau says it’s terrible to see so
many birds die.


“We just do our best on our end to stop the botulism cycle. When we
can, provide samples, and also, keep it a positive recreational experience
for all our visitors. They don’t want to see birds decomposing and
rotting out on the beaches, so we’re pretty diligent with that.”


Researchers say that’s about the best that can be done. Since ocean-
going vessels brought zebra mussels, quagga mussels, and round gobies
to the Great Lakes, all three of the invasive species have flourished. It
will likely be a long time before we’ll ever begin to understand the full
extent of the damage to the native wildlife of the lakes.


For the GLRC, this is Lester Graham.

Related Links

The Great Lakes’ Nine Most Wanted

We hear all the time about invasive species in the Great Lakes region. But many people have no idea what Eurasian Ruffe, Round Goby, or European Frogbit look like and even less of an idea about what to do about the problem. But environmental education groups are trying to change that. The Great Lakes Radio Consortium’s Tamar Charney reports:

Transcript

We hear all the time about invasive species in the Great Lakes region. But many people have no
idea what Eurasian ruffe, Round Goby, or European frogbit look like and even less of an idea
about what to do about the problem. But environmental education groups are trying to change
that. The Great Lakes Radio Consortium’s Tamar Charney reports:


Doug Jensen runs the Aquatic Invasive Species Information Center for the University of
Minnesota Sea Grant Program. He’s created a series of nine cards to help people identify exotic
species that are causing problems in the lakes.


“The front cover of the card is high quality photo of the aquatic plant, fish or invertebrate species
and it folds open and the inside of card has text which describes what the problem is how the
species is spreading and what people can do to take action and prevent the spread.”


Jenson hopes people will keep the ID cards in their tackle boxes, glove compartments, and aboard
their boats. Over 3.2 million of them have been printed including a French language version for
Quebec. They’ll be distributed through bait shops, marinas, environmental education
organizations, and resource management offices throughout the Great Lakes
region.


For the Great Lakes Radio Consortium, I’m Tamar Charney.

Tubenose Goby Extends Its Reach

An exotic fish species called the tubenose goby made its way into the St. Clair River after it was flushed from a ship’s ballast water 11 years ago. The tubenose hasn’t spread as fast as its cousin, the round goby, but researchers were recently surprised to find the tubenose spreading further into Lake Erie. The Great Lakes Radio Consortium’s Karen Schaefer reports:

Transcript

An exotic fish species called the tubenose goby made its way into the St. Clair River after it was flushed from a ship’s ballast water 11 years ago. The tubenose hasn’t spread as fast as its cousin, the round goby, but researchers were recently surprised to find the tubenose spreading further into Lake Erie. The Great Lakes Radio Consortium’s Karen Schaefer reports:


The invader was captured this July. The tubenose is related to the round goby, whose population explosion across the Great Lakes has scientists concerned. Round gobies eat contaminant-laden zebra mussels, and then pass those toxins on to sport fish favored by humans. But Jeff Ruetter, director of Stone Lab, says the tubenose goby actually first appeared in the Great Lakes two years before its cousin and so far, isn’t widespread.


“And the concern will be with its competition with other species in the ecosystem. Is it going to force them out?”


Ruetter says the appearance of the new invader underscores the need for tighter controls on exotic species. For the Great Lakes Radio Consortium, I’m Karen Schaefer.

Native Lake Species Fighting Back

  • Alewives washed up on Lake Michigan shores after the invaders' populations exploded, then crashed. Researchers have a difficult time predicting how invasive species will affect the balance of nature in the Great Lakes.

Ever since the Great Lakes were opened to shipping, exotic species of aquatic animals have invaded the lakes. Nearly always it’s been bad news for the region’s native fish and wildlife. The Great Lakes Radio Consortium’s Lester Graham reports on the latest effects of the invaders:

Transcript

Ever since the Great Lakes were opened to shipping, exotic species of aquatic animals have invaded the lakes. Nearly always it’s been bad news for the region’s native fish and wildlife. The Great Lakes Radio Consortium’s Lester Graham reports on the latest effects of the invaders.


Some of the exotic species that have caused major problems in the Great
Lakes have been around since the 1940’s and ’50s. For example, the sea lamprey found its way into the lakes through manmade channels. It’s a parasite that attacks lake trout and other large game fish. It devastated the lake trout fisheries. Only recently have efforts gotten the lamprey under control. It’s still out there, but it’s not decimating the lake trout population as it once was.


More recently, a big concern has been the zebra mussel. It hitchhiked its way to the Great Lakes in the ballast water of cargo ships. In the last couple of decades the zebra mussel has caused major changes in all the lakes except for Superior where it seems limited to the shallow and warmer bays.


David Jude is a researcher with the University of Michigan’s Center for
Great Lakes and Aquatic Sciences. He says the huge numbers of zebra mussels siphon through lake water like a giant network of filters. There are so many of them that water in the lakes is actually clearer.


“I think people tend to hear about the water clarity increases. ‘Ah, the water’s clearer,’ you know, ‘That’s great!’ But it’s not great, because there’s a lot of things going on in the water column.”


Things such as, algae converting the sun’s energy into more phytoplankton.
Small fish and tiny invertebrate animals called zooplankton eat the phytoplankton and then they become food for fish. But, the zebra mussels filter out a lot of the phytoplankton, stealing food from the native zooplankton.


David Jude says a couple of other invaders are also causing havoc at the base of the food chain in the Great Lakes. Instead of eating just the green phytoplankton, zooplankton invaders from the Black and Caspian Seas also eat their North American cousins.


“These are predators. And they feed on the zooplankton, our native zooplankton that is out there already. So, not only do we have the impact of zebra mussels removing algae which is a food for these zooplankton, now we’ve got two predators that have been introduced and both of those will eat zooplankton which would have been food for fish to eat.”


Besides the zooplankton floating around in the water column, a major food source for fish is in the sediment at the bottom of the lakes, and it’s disappearing. James Kitchell is with the University of Wisconsin – Madison. He says many different kinds of fish depend on a little creature called diaporeia, which have become scarce in many areas.


“It appears to correlate in general with an increases in zebra mussels. So, there’s the prospect that diaporeia is literally starving to death as a consequence of zebra mussels eating the available food, but when you look at the diaporeia, they appear to be healthy. They’re not skinny and look to be starving. So that doesn’t explain it.”


It’s a big concern because a lot of fish that anglers like, such as yellow perch, depend on diaporeia for food.


Besides the zebra mussels and the two zooplankton predators, a fourth invader is causing problems. Populations of the round goby, an ugly, aggressive feeding little fish from Eastern Europe, have exploded in the Great Lakes. The round goby scours the bottom, eating the eggs and larvae of native fish. The University of Michigan’s David Jude says as big of a problem as the invasive fish has been over the last several years. The round goby’s future might soon be curtailed a bit.


“We did SCUBA dives in Lake Erie, for example, we’d turn over rocks. Round gobys would tear out from under the rocks and we’d have small mouth bass following us around and they would ignore the round gobys. They didn’t know how to catch a round goby. But, because there’s so many round gobys now, they had to learn how to eat them or die. So, the predators are definitely learning how to eat round gobys.”


Other native fish are beginning to eat the exotics. The silver chub, which once nearly disappeared from the Great Lakes, is making a bit of a comeback feasting on zebra mussels. With each invader, the lakes ecosystems go through upheaval, and then find a new balance. But make no mistake. It’s a different balance. Nicholas Mandrak is a researcher at Youngstown State University. He says exotic species invading the Great Lakes will mean continued changes, and for people who fish the lakes, not many of the changes will be good.


“You’re not going to be able to catch as many species that you’re used to catching. You know, the native species are going to decline. The walleye are going to decline. So, I think the bottom line is the recreational and commercial fisheries are going to change in a manner that is negative to most people.”


Researchers, though, have learned to be careful about predicting how invasive species will affect the lakes. They’re often surprised by the intricacies of the food web and the ecosystems that support it. Throwing an exotic invader into the mix makes it that much more unpredictable, and it will likely get worse. Mandrak says they’ve been studying how global warming might affect the lakes. One scenario suggests 30 to 40 new exotic species from the South will make their way through manmade canals as temperatures rise. For the biologists, it’s a worrisome concept. For the Great Lakes Radio Consortium, this is Lester Graham.

NATIVE LAKE SPECIES FIGHTING BACK (Short Version)

It appears that fish native to the Great Lakes are beginning to prey on some of the alien species that have invaded the lakes. The Great Lakes Radio Consortium’s Lester Graham reports:

Transcript

It appears that fish native to the Great Lakes are beginning to prey on some of the alien species that have invaded the lakes. The Great Lakes Radio Consortium’s Lester Graham reports.


Aquatic Species from Europe and elsewhere have hitchhiked to the Great Lakes in the ballasts of cargo ships for many years. A lot of them have upset the natural ecosystems of the lakes. Lately, though, some native fish are taking advantage of the invaders. Nicholas Mandrak is a researcher at Youngstown State University. He says a Great Lakes minnow that was once thought to have died out has recently re-emerged.


“And they’re eating zebra mussels. So, it looks like the increase
in silver chub is related to zebra mussels, so we finally found a native
fish that is benefiting from the zebra mussel.”


Other researchers say small mouth bass are beginning to prey on another invasive species, the round goby, which eats the eggs and larvae of fish native to the Great Lakes. The researchers say the benefits don’t outweigh the negative affects on native species. But it evens the score a little. For the Great Lakes Radio Consortium, this is Lester Graham.