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Great Lakes Article:

Botulism hits Erie
Scientists believe alien species such as zebra mussels and round goby fish spread the lethal toxins, killing thousands of the lake's sheepshead fish and gulls.

PETER GEIGEN-MILLER
London Free Press
Posted 10/10/2002

LONG POINT -- Thousands of dead fish and birds littering the Lake Erie shoreline are victims of a deadly botulism outbreak.

The botulism and the lethal toxin it produces have killed mainly freshwater drum -- a common fish species also known as sheepshead -- and gulls.

Scientists suspect Lake Erie's waters have turned deadly because the introduction of alien species such as zebra mussels has dramatically upset the lake's ecosystem.

The presence of invaders such as zebra and quagga mussels and the round goby, a pest fish, has made it easier for botulism bacteria to grow and produce the toxin, said Jeff Robinson of the Canadian Wildlife Service in London.

Scientists believe the deadly chain of events begins when botulism bacteria, which occur naturally in lake sediments, are absorbed by mussels.

Gobies, which grow to a maximum of about 20 centimetres, spread the bacteria and its toxin up the food chain when they eat the mussels and are in turn eaten by other fish or birds.

Gulls ingest the toxin and die after eating sheepshead that have gobbled toxin-tainted mussels.

The dead sheepshead along Long Point beaches came as a shock to Sandy Lovering and Craig Newman.

The two work in Saudi Arabia and return each year to wander the beaches near Long Point.

"We've never anything like this," said Lovering, sidestepping some of the dead fish.

Dave Stone, a long-time beach resident, is equally surprised by the toll of fish and gulls.

"You used to see the odd dead fish, but I've never seen it like this before," Stone said.

"They've got a serious problem here."

Robinson said sheepshead seem to be the main victims of the outbreak, but gobies are dying too.

Sheepshead float when they die, while gobies, lacking a swim bladder, sink to the bottom, he said.

A few dead gobies have been caught in currents and washed ashore, but Robinson suspects many more are on the bottom.

The outbreak is not expected to threaten the region's sheepshead population because the fish are so plentiful, Robinson said.

There's no market for sheepshead, considered a coarse fish, so there's no commercial catch to reduce their numbers.

The botulism outbreak could potentially kill loons, mergansers and other fish-eating birds that begin migrating through the area later in the fall.

The birds die after eating botulism-tainted fish.

Robinson said nothing can be done to stem botulism outbreaks since gobies, an apparent key player, are one of the most numerous species in the lake.

"There will be no opportunity to remove them from the system," he said.

BOTULISM SAFETY

- Avoid harvesting fish or birds acting abnormally, since people can ingest the botulism toxin by eating these creatures. Cooking may not destroy the toxin.

- If you must handle dead fish or birds on the beach, wear protective plastic or rubber gloves.

- Keep pets away from dead birds or fish along the shoreline to prevent them from falling ill.

- The toxin must be ingested to be harmful. There's no risk from swimming in water where botulism is present.


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