Lake Invaders Stress EUP Commercial Fishery
Local Fishery Now Brings in $2.2 Million, Down From $7.65 Million in Early 1990s
By Ellen Paquin

These half-inch-long, shrimp-like diporeia are the staple food for whitefish. Zebra and quagga mussels are consuming vast quantities of plankton, diporeia's food source, making diporeia scarce. They are already gone from Lake Erie, and declining at alarming rates from lakes Michigan, Ontario, and Huron, the National Oceanic and Atmospheric Administration reports. (Photograph from National Oceanic and Atmospheric Administration)

Zebra mussels were bad enough. Now, another and more destructive Great Lakes invader, the quagga mussel, is spreading across ever deeper and colder sections of the Lake Michigan and Lake Huron floor, changing forever the ecology of the lakes and sucking nutrients out of the water.

These mussels filter the water and alter the food chain at the very bottom, which affects the fish populations at the very top. Chinook salmon are disappearing from Lakes Huron and Michigan, and now whitefish are feeling the stress.

The lifeblood of the local commercial fishery is threatened, and fisheries researchers and state transportation experts are beginning to question whether the vitality of commercial and sport fish species is being sacrificed to appease the politically powerful saltwater shipping industry, and whether the risks of opening the Great Lakes to the world may outweigh the benefits.

At right: Three whitefish in various levels of poor condition. None are as plump as whitefish used to be, said fisheries researcher Jim Johnson. (Photographs courtesy of Jim Johnson, Alpena Fishery Research Station)

A new study by researchers at Grand Valley State University estimated that halting ocean shipping on the Great Lakes would cost about $55 million each year to U.S. and Canadian shippers. The study compared that to the amount of money that invasive species in the Great Lakes cost now, roughly estimated to be at least four times that much, between $200 million to $500 million a year, possibly ranging as high as $5 billion a year. The study was released in November 2005 by transportation expert Dr. John Taylor at the university. It explored the costs of other options open to shippers, and concluded that the economic benefit of using the Great Lakes for ocean-going vessels is not as critical as is widely believed in the industry.

Fisherman Tom Spaulding (right), aboard his ship Viking in Thunder Bay in 2001, sorts whitefish, releasing those below the 19-inch minimum size limit. With him is fisherman Wayne Wertenberger.

Meanwhile invasive species, including zebra mussels, the more recently arriving quagga mussels, and fish called round gobies, are entering the Great Lakes in the ballast water of ocean-going ships at a rate of about one new species every eight months, fisheries researcher Jim Johnson told The St. Ignace News. Mr. Johnson works at the Department of Natural Resources (DNR) Alpena Fishery Research Station.

The invaders are quickly decimating the food supply of many native fish, including whitefish, essential to the Straits area commercial fishery. With a drastically declining food supply, body condition of the whitefish is poor, driving down market prices paid to commercial fishermen. Poor market conditions have discouraged some commercial fishermen from continuing in the business.

The value of the local fishery in 2005 was conservatively estimated at $2.2 million in the areas of St. Ignace, north and east to the Les Cheneaux Islands and DeTour, and west to Seul Choix Point near Manistique, according to the Intertribal Fisheries and Assessment Program. When whitefish conditions were at their peak in the early 1990s, the local fishery brought an estimated $7.65 million into the community's economy.

"Why do we allow these exotic species in the Great Lakes?" Mr. Johnson asks. "To me, the big picture is, why don't we treat ballast water as pollution? The Clean Water Act of the 1960s would have set goals and let big industry figure out how to get us there. But it is not being followed. The mussels have torpedoed the Lake Huron chinook salmon fishery, and threaten Lake Michigan's chinooks, worth a billion dollars to the state each year, while the salt water shipping industry doesn't bring in nearly that much. We have sacrificed to the salt water shipping industry."

Salmon started "dropping out entirely" in the area in 2005, yielding a harvest only about oneseventh as large as normal, Mr. Johnson said, owing to a crash of their staple food source, alewives, brought about in part by zebra and quagga mussel infestation.

Chinook salmon were originally stocked in the lakes to reduce burgeoning populations of alewives, small ocean fish that entered the Great Lakes via the St. Lawrence Seaway. After the alewives' main predator, lake trout, was nearly wiped out by invasive sea lamprey in the late 1960s, wildlife managers introduced salmon to control the alewives population.

Since 2000, researchers have been marking all salmon they stocked, to determine if the population is reproducing on their own, Mr. Johnson said. Hatchery fish are fed an antibiotic agent in their food that causes their bones to flouresce under light, helping researchers identify hatchery fish from wild salmon.

Salmon run in the lakes seasonally in the fall.

"What we've learned is the wild fish are coming mostly from Ontario, where there are large rivers teeming with wild salmon," Mr. Johnson explained. "We've learned that our stocking efforts are being dwarfed by these wild fish. In the future, we will try to somewhat support the salmon population in the lakes, but we'll only be stocking at half of our usual rate for the next five years. We'll see where it goes from there. With the salmon collapse, we may find that populations of alewives and smelt may begin to recover. Right now, there are lots of smelt out there, but they are small. We may see a partial recovery, but we won't be seeing smelt come roaring back in full recovery to the days when people would go to places like the Carp River and enjoy huge runs of smelt."

"A big chunk of the lake is now a mussel factory."

The proliferation of quagga mussels exploded five years ago, Mr. Johnson said. The new invader can spread into much deeper and colder water than zebra mussels can.

"They have taken over Lake Huron from about 50-foot depth to 250 feet. Inside the 50-foot line, it's zebra and quagga mussels all the way to the beach. A big chunk of the lake is now a mussel factory."

Because of mussels and other invaders, Mr. Johnson said, "the food web has changed from the bottom up. We don't know the exact mechanism, but quagga mussels and zebra mussels are trapping the nutrients" needed by whitefish and others that feed in the "water column" rising from the floor of the lake.

"All of a sudden, the whitefish are coping with the disappearance of their staple food," Mr. Johnson said. "We have noted severe setbacks in the whitefish populations from St. Ignace to Cheboygan. Whitefish are also struggling with decreased reproduction and poor body condition. I mean, these fish are skinny.

"We are not sure yet how this will play out. The whitefish have managed to eat some zebra mussels, but they are not as nutritious. Whitefish have been our most important commercial species for many years," Mr. Johnson said.

Whitefish numbers remain fairly robust near Alpena, but are shrinking near Cheboygan, and possibly to the north."

Whitefish Numbers Tanking Near Cheboygan.

Whitefish eat two tiny organisms in the shrimp family, called diporeia and mysis. The diporeia are finding their food source, plankton, overtaken by the mussels now covering the lake bottom.

"We have been monitoring whitefish for a long time, since the 1960s when they collapsed due to high sea lamprey numbers," Mr. Johnson said. "We have better information on whitefish than many other species. But it could be that their recent recovery may have overshot sustainable levels. Five or six years ago, there were high whitefish harvests. But now the whitefish harvest at Cheboygan is about half of what it used to be. The question is, is this still a sustainable fishery? We're looking at what happened in the waters at Cheboygan and saying, is that headed our way, an indication of things to come?"

Researchers have recently been finding a lot of bacterial kidney disease in whitefish near Cheboygan, Mr. Johnson said, which is an opportunistic illness that attacks the fish when they are already weakened, such as by starvation. He said fishermen will not necessarily be able to tell if a fish has kidney disease by sight, but if it does, it will be too emaciated to market.

"If a fisherman pulls in a fish that's ready to die from bacterial kidney disease, it will be filled with fluid. Its kidney line along its backbone may carry calcium deposits that look like cottage cheese," Mr. Johnson explained. "There would be nothing wrong with eating them, but you wouldn't be able to get a fillet from them. There would not be enough to be marketed."

Researchers are beginning to see more kidney disease in whitefish around Alpena as well, Mr. Johnson said.

Another invasive species, the round gobie, may prove to be a more positive force in the lake, as it eats zebra and quagga mussels, Mr. Johnson said. It may provide a food source for burbot, walleye, and lake trout. On the other hand, round gobies are voracious egg predators that are eating the eggs of those same fish.

Water "clear to the bottom:" Straits, Les Cheneaux fishermen battle slime that is clogging nets.

Near St. Ignace and the Les Cheneaux Islands, commercial fishermen are seeing some recent improvement in whitefish condition, and numbers are abundant, said tribal fisheries researcher Tom Gorenflo, but fishermen are plagued with another effect of mussel infestation: copious slime in fishing nets.

"Whitefish went through some bad times, and in Lake Huron they still are, but I think they are doing a little better in northern Lake Michigan," Mr. Gorenflo said.

He tallies tribal fishing harvests, which fishermen are required to submit monthly, and is now conducting a whitefish mortality study as the program director for Intertribal Fisheries and Assessment Program. The program is a collaboration among five Michigan Indian tribes with treaty fishing rights, including Sault Ste. Marie Tribe of Chippewa Indians. All commercial fishing in the Straits area, and almost all in the state, is tribalbased, Mr. Gorenflo said. Among all five tribes, the fishery supports hundreds of families through 133 licensed fishing operations, each of which may employ several people. In the Straits area, 28 operations are harvesting fish this year. Area fish markets, smokers, and restaurants are part of the network touched by the commercial fishery.

Seventy percent of the local commercial harvest is whitefish, with the balance in perch, deep water chubs, walleye, and menominee, and a seasonal salmon run in August and September.

"The tribes harvest a variety of fish, but if there is no whitefish, there is no fishery," Mr. Gorenflo said.

"Zebra and quagga mussels have changed the whole lake ecology," he added. "Admittedly, it is hard to directly prove the linkage. When zebra mussels moved in, it caused a snowball chain of events."

"Now we have this slime, which is brown or green gunk caught in nets, made up of vast amounts of algae, both dead and alive," he explained. "The slime used to be a seasonal or occasional problem for fishermen, but in the last two years, it's always there. Be careful where you set nets, or you will get a netful of junk, and no fish. Sometimes the fishermen have to throw the nets away because they are too damaged to clean them. It is costly. It all corresponds to zebra mussels. They consume vast quantities of plankton and clear out the water column. It allows sunlight to penetrate deeper and changes the plant ecology of the lake. People have been saying the water is so clear, they can see all the way to the bottom. That's not a good thing. From sunlight to plants to animals, the whole system has been disrupted."

Mr. Gorenflo noted these changes have not been seen in nearby Lake Superior, where zebra and quagga mussels do not thrive because of the depth and cold temperatures. Whitefish populations, he said, are looking okay there.

"We don't know how it's all going to shake out yet," Mr. Gorenflo said of the fishery. "Will whitefish continue to suffer? At any rate, it's not good. It's a bad thing. Whitefish numbers will be worse than they historically were. These invasive species are permanent and they are the number one threat to our fishery by far."

He said lake herring numbers may be on the upswing, noting, "If this continues, we may be able to build a market for herring" in the future.

"The snowball effect of an invasive species is often underestimated."

"A lot of research is going on right now to find out how the mussels wipe out the diporeia," Mr. Gorenflo said. "We do bottom sampling that takes in one square yard of sand from the bottom, where the diporeia live. We used to find 10,000 diporeia in a sample, and we're finding samples with zero now."

"The snowball effect of an invasive species is often underestimated. The economic damages of the zebra mussels will get into inland lakes as well, sooner or later, and the slime will start messing up people's waterfront properties," Mr. Gorenflo pointed out. "The effects are not always related to fish, and they're not always someone else's problem."