Tag: diporeia

The Invasion of the Quaggas

  • A close-up of the quagga mussel. Quaggas have spread in all of the Great Lakes except Lake Superior. (Photo courtesy of the Michigan Sea Grant Archives)

Whitefish is a main dish for everything from fish boils to fancy dinners all around the Great Lakes region. But in some areas of the Great Lakes, whitefish aren’t doing so well. Rebecca Williams reports on what’s happening to the fish many people love to eat:

Transcript

Whitefish is a main dish for everything from fish boils to fancy dinners all around the Great Lakes region. But in some areas of the Great Lakes, whitefish aren’t doing so well. Rebecca Williams reports on what’s happening to the fish many people love to eat:

(sound of knives getting sharpened and fish being filleted)

Mike Monahan sells fish from all over the world at his seafood market. But he says whitefish is a very popular seller.


“It’s been there forever, and everybody just expects it to be there, and it’s inexpensive. But really it’s a great fish, as far as a nice light delicate fish, I’d put it up against the soles and flounders.”


Monahan says he’s still getting good supplies of whitefish. So, for now, he’s happy.


But some of the people who catch whitefish are worried. Commercial fishers have been hauling in skinnier whitefish in some parts of the lakes. It’s taking whitefish longer to grow to a size worth selling. And in some cases, the fish aren’t fat enough to make a good fillet.


(sound of shorebirds)


Paul Jensen fishes for whitefish in Lake Michigan. He says lately, he’s had to move his boat to deeper waters. That’s because whitefish are hungry and they’re swimming out deeper. They aren’t finding their favorite food. It’s a little shrimp-like creature called Diporeia.


“Diporeia are probably like a Snickers bar to whitefish; they were high in fats, high in lipids and it was their main food – it was very nutritious for them and it affected their growth rate. Eating Diporeia a fish could reach maturity maybe in 18 months or 2 years. Now we’re looking at fish that may take 5 years to get there.”


Whitefish are not eating Diporeia because it’s vanishing. In some places, researchers used to find 10-thousand of the little critters in a square meter of sediment. Now there are very few, or none at all.


Tom Nalepa has been trying to figure out why. Nalepa is a biologist with the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Lab.


“It’s a real scientific puzzle as to why Diporeia is declining. It’s definitely related to the spread of quagga mussels and zebra mussels but that exact negative relationship is kind of elusive at this point in time.”


But Nalepa says he’s sure the invasive mussels are to blame. The mussels got into the Lakes in the ballast tanks of foreign ships. And they’ve spread in all the lakes except Superior.


Tom Nalepa says he’s seen populations of Diporeia crash right around the time the mussels were booming. Nalepa says now, Diporeia’s gone from large areas in most of the Lakes.


That’s bad because Diporeia is an important food source for most of the fish in the Great Lakes.


But for whitefish it’s really crucial. Back in the good old days, Diporeia made up about 80% of their diet.


Tom Nalepa says whitefish are trying to find something else to eat. He’s seeing them switch to a snack food that could make them even skinnier.


They’re starting to eat quagga mussels.


“When whitefish feed on quagga mussels they have to deal with the shell which has no energy content at all and it has to pass the shells through its digestive system so basically the fish feels full when it’s not getting any energy source.”


Nalepa says to the fish, quagga mussels must seem like good food, because there are lots of them.


He says quagga mussels are booming, because they can live in harsher conditions than zebra mussels can. So biologists are predicting quaggas will be even worse for the lakes than zebra mussels.


“Where are things ultimately going to end up? People may just have to get used to fewer fish. Because basically now we’re trading the fish community for the mussel community. The lakes are loaded with mussels instead of fish now. It may be just the way it’s gonna be.”


Some fishermen are already seeing things change. One day last season, Paul Jensen pulled in some of his nets. He was expecting fish.


“It was kind of startling because the amount of quagga mussels that came up with those nets far exceeded the catch of fish. And we hadn’t really equipped the boat with a snow shovel to shovel quagga mussels out of the boat. The impacts are startling because you begin to wonder, if our little net caught these, how many are there and what are the impacts going to be down the road?”


Jensen says he wishes the invaders had never gotten into the lakes in the first place, because there’s no way to predict what effect they’ll have next.


But some scientists worry these changes at the bottom of the food chain will lead to a major collapse of the fish stocks that many people depend on.


For the Environment Report, I’m Rebecca Williams.

Related Links

Invasives Destroying Great Lakes Food Chain

  • Biologists sorting fish. The populations of smaller fish that game fish eat have collapsed in Lake Huron. (Photo courtesy of MI DNR)

Although zebra mussels have been affecting the ecology of the Great Lakes since they were first found in 1988, researchers are continuously surprised at how much damage they’ve caused. Now, biologists are wondering if zebra mussels and the more recently arrived quagga mussels are to blame for a collapse of the fishery in one of North America’s largest lakes. Lester Graham reports the researchers are also wondering if this collapse is a preview of what will happen to all of the Great Lakes:

Transcript

Although zebra mussels have been affecting the ecology of the Great Lakes since they were first found in 1988, researchers are continuously surprised at how much damage they’ve caused. Now, biologists are wondering if zebra mussels and the more recently arrived quagga mussels are to blame for a collapse of the fishery in one of North America’s largest lakes. Lester Graham reports the researchers are also wondering if this collapse is a preview of what will happen to all of the Great Lakes:


It’s off-season for charter boat fishing and Captain Wayne Banicky asked if we could meet at a local watering hole called the Boat Bar. Captain Banicky takes people out fishing on Lake Huron. Well, he used to. The past few years he’s been charter boat fishing in Lake Michigan. He says fish started to become more scarce on Lake Huron, and he was forced to make the move.


“Economics, pure and simple. Dollars and cents. Once you start seeing a decline and being on the water every day and you see those declines in your numbers, it’s just a matter of time before financially you can’t afford to stay there. Those dock fees aren’t given up free. That’s an expensive tab to pay every year.”


Fishing for most species in Lake Huron is not good. But the story is not just a matter of not stocking enough fish or just a bad year, it’s a matter of a collapse of the bottom of the food chain. It’s not just the fish sport fishers like to catch that are down, it’s their prey: the smaller fish those big game fish eat. Prey fish stocks have collapsed, and supplies of the food those small prey fish eat, the plankton, have also collapsed.


Jim Johnson is with the Michigan Department of Natural Resources Alpena Fisheries Research Station.


“There was a huge decline in the amount of nutrients available to zooplankton and phytoplankton in the middle of Lake Huron. These are the basic nutrient bits that fish eat. And it appears now to most of us in the scientific community that a large portion of the nutrients that used enter Lake Huron are now being trapped by zebra and quagga mussels and not finding their way to alewives and other prey fish.”


Scientists from different government agencies and universities in the U.S. and Canada had been noticing changes, but things have gone seriously wrong very quickly in Lake Huron, and it might go wrong other places.


Tom Nalepa is with the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Lab. He says tiny aquatic food sources for fish, such as a shrimp-like organism called diporeia, are declining dramatically in other Great Lakes.


“All the players are in place for it to happen in these other lakes too, you know, the loss of diporeia, the expansion of quagga mussels. And maybe Lake Huron is the first to show a collapse in the prey fish. What does it mean? Well basically, you know, there’s not going to be many fish out there for the sport fisherman to catch anymore.”


And sport fishing is multi-billion dollar industry in the Great Lakes. Back at the Boat Bar, charter fishing boat captain Wayne Banicky says fishing is still good in Lake Michigan, but he worries when he thinks about what happened in Lake Huron.


“I think that the fishery as a whole in the Great Lakes is in serious jeopardy right now. Something’s got to be done.”


But the question is what? What can be done when invasive species are changing an entire ecosystem to the point the fishery collapses?


“I don’t know to be honest with you. I don’t think any one of us knows. It’s scary, that much I will admit to you. It is scary right now.”


And guys like Captain Banicky aren’t the only ones worried.


Jim Johnson at Alpena Fisheries Research Station says you can’t undo the damage that’s already done. It’s just a matter of waiting to see how nature responds to the invasive zebra and quagga mussels and other invaders. Johnson says the key is to prevent more invasive species from being introduced to the lakes.


“The best we can do right now, I think the single most effective thing we as managers can do, is to make it understood by the decision makers just how disruptive the invasive species are and try to put a stop to those.”


The source of many of these invasive species is the ballast tanks of foreign ships entering the Great Lakes. Some regulations have reduced the chance that more invasive species will hitchhike to the Great Lakes, but more are still getting in. In the meantime, agencies such as the US Environmental Protection Agency and the US Coast Guard say Congress hasn’t given them the authority to regulate foreign ships strictly enough to stop new invasive species from entering.


So, fishery managers can only watch the other Great Lakes for more signs of a collapse of the fisheries as they’ve only been able to stand by and watch happen in Lake Huron.


For the Environment Report, this is Lester Graham.

Related Links

Ten Threats: Break in the Food Chain?

  • Diporeia are disappearing from Lakes Michigan, Huron, Erie, and Ontario. The actual size of a diporeia is ½ an inch. (Courtesy of the EPA)

Some of the life in the Great Lakes has been hit hard by industry and trade. Pollution and
invasive species have hurt some of the native plants and animals important to the food
chain. While popular game fish might be the first to come to mind, it’s a little organism
at the bottom of the food chain that has biologists and fishing experts most concerned.
The Great Lakes Radio Consortium’s Lester Graham reports:

Transcript

In a survey, experts said one of the Ten Threats to the Great Lakes is a disappearing
species. Some native fish populations and organisms are declining. Our guide through
the Ten Threats series is Lester Graham.


Some of the life in the Great Lakes has been hit hard by industry and trade. Pollution and
invasive species have hurt some of the native plants and animals important to the food
chain. While popular game fish might be the first to come to mind, it’s a little organism
at the bottom of the food chain that has biologists and fishing experts most concerned.
The Great Lakes Radio Consortium’s Lester Graham reports:


(Sound of swinging doors)


Jack Donlan is taking me behind the fish counter at Donlan’s Fish House. In the
backroom he’s scaling and filleting some whitefish.


“Of the fishes caught in the Great Lakes, whitefish is one of the big volume fishes. Lake
perch, walleye bring more money per pound, but I would think from a tonnage-wise,
whitefish, it’s an extremely popular fish.”


This is a popular place to get Great Lakes fish, but Donlan’s suppliers, the commercial
fishers, are worried about the catch. At some places in the Great Lakes whitefish aren’t
doing too well.


(Sound of Lake Guardian motors)


Tom Nalepa is trying to figure out why whitefish are struggling. He’s onboard the U.S.
Environmental Protection Agency research ship, the Lake Guardian. Nalepa is a
biologist with the National Oceanic and Atmospheric Administration’s Great Lakes
Environmental Research Lab. He’s been studying Lakes Michigan and Huron, and on
this day he’s getting ready to study the bottom of Lake Erie.


He’s not studying whitefish. He’s actually looking for a tiny shrimp-like crustacean, only an
eighth to a quarter inch long, called diporeia. Eighty-percent of the whitefish diet is
made up of diporeia.


“And what we’re seeing is a dramatic drop in populations, and not only drops, but there are
large areas now in all the lakes, except Lake Superior, that no longer have diporeia. This
is real concern because diporeia is a very important fish food.”


Researchers used to find eight to 10-thousand diporeia or more in a square meter of sediment just
a few years ago. Now, there are only a dozen or so, or none at all. Diporeia is one of the
mainstays of the bottom of the food chain, and Nalepa says whitefish aren’t the only ones
that eat the tiny critters in the sediment at the bottom of the lakes.


“Just about every type of species found in the Great Lakes will feed on diporeia at some
stage in its life-cycle. Diporeia is high in calories and has a high-energy content. It’s a
very good food, nutritious food source for fish.”


Without it, fish are not getting enough to eat. Marc Gaden is with the Great Lakes
Fishery Commission. He says when diporeia disappears, commercial fishers can’t help
but notice.


“Right now we’re seeing skinnier whitefish. Whitefish that are somewhat emaciated in
some areas because they just don’t have as much of these low-end of the food web organisms
to eat, and we think it’s related to an invasive species that came in.”


That invasive species is the zebra mussel, and more recently another invader that was
likely carried to the lakes in the ballasts of ocean-going cargo ships, the quagga mussels.


Back on the Lake Guardian, Tom Nalepa says he’s seen the connection again and again.


“There’s no question that it’s related to zebra mussels and quagga mussels. In every area
that we’ve studied, regardless of the lake area, declines were happening a couple of years
after the quagga mussel or zebra mussel were first found, but that connection remains
elusive.”


Biologists thought the invasive mussels might have been filtering out all of the food the
diporeia eat, but when they find diporeia, they don’t appear to be starving. They appear
healthy. Now, scientists are wondering if there’s some kind of disease or toxin spread
by the mussels that’s wiping out the diporeia.


Even if researchers learn why the diporeia are disappearing, there might be nothing that
can be done to help. Some scientists worry that the decline of diporeia and other
organisms at the base of the food chain might ultimately lead to a massive collapse of fish
stocks in the Great Lakes.


For the GLRC, this is Lester Graham.

Related Links

Break in the Great Lakes Food Web?

A major link in the food web is disappearing from the Great Lakes. Researchers are concerned that its absence will damage fish populations. The Great Lakes Radio Consortium’s Lester Graham has more: