 A shad infected with viral hemorrhagic septicemia. It was taken from Lake St. Clair, which is located between lakes Huron and Erie. |
It's a disease known to infect salt water fish, but no one really knows how viral hemorrhagic septicemia came to be a highly contagious and often fatal disease for fresh water fish in the Great Lakes.
It's blamed for huge fish kills last summer in Lake Erie, where killed large numbers of fresh water drum, yellow perch, and round gobies.
"But it was the fresh water drum die off that gathered the most attention because we had dead fish floating everywhere, and actually forming wind rows on the beaches," says Fred Snyder, an extension specialist with Ohio Sea Grant.
The virus known as VHS was first identified in the lakes two years ago, but it might have been around much longer. It's not always obvious. VHS can cause a distended abdomen, or sometimes red patches on a fish's head or near its gills. The real damage is done to internal organs.
What's troubling, Snyder says, is how many kinds of fish are susceptible.
"It has been found in 37 species,"says Snyder. That does not mean that all of them have had die offs. It simply means that when they take kidney tissue samples they do find the virus."
The virus isn't believed harmful to humans. Beyond the "ick" factor on the beach, the real trouble could be to businesses that deal with live fish.
"The big concern right now is that the virus will get into fish farms - the aquaculture facilities - and potentially wipe out a chunk of the nation's aquaculture capability," Snyder says.
Already the federal government has clamped tight restrictions on anybody moving live fish to or from Great Lakes states. That could be a problem for the bait industry.
And, while it's unclear how the disease has spread, some conservationists say a likely culprit is ship ballast water.
At a press conference in Duluth's Great Lakes Aquarium, the Izaak Walton League has called for new ballast water treatment rules to take effect before the first "lakers" sail in March. Gary Glass is a former researcher at the Environmental Protection Agency's fresh water laboratory in Duluth.
Source: Minnesota Public Radio