birds, fish litter Lake Erie beaches
species blamed as fish and birds fall victim to bacteria
TORSTAR NEWS SERVICE
PORT RYERSE, Ont. — Large numbers of fish
and fish-eating waterfowl have been washing up dead
on the north shore of Lake Erie this week as botulism
bacteria make their way up the food chain through exotic
species such as zebra mussels and goby fish.
Experts warn this unnatural "die-off,"
which has plagued Lake Erie since 1999, may soon be
coming to Lake Ontario.
"There's a die-off out there like we've
never seen before, and it's crossing a lot more species,"
said John Piggott, of the Long Point Bay Anglers Association.
The extent of the phenomenon is evident
along the beach in Port Ryerse, between Port Dover and
Turkey Point, where the shoreline is littered with carcasses
of yellow perch, carp, bass, sheep's head, round goby,
gulls and cormorants.
Cottager Garth Hagey says the beach
would be unusable without regular cleanups. His parents
have been collecting and burying nearly 100 fish and
birds a day.
"It's just insane," he said.
Wildlife and health officials have so
far been unable to pinpoint the cause. The toxin produced
by type E botulism bacteria is usually found in the
dead fish and birds. But how it's entering the food
chain remains unclear.
The bacteria are common in the lake-bottom
mud but normally lie there undisturbed, causing no harm.
Scientists suspect the arrival of zebra
and quagga mussels 15 years ago, coupled with the recent
arrival of the bottom-feeding round goby, has caused
the release of the bacteria into the ecosystem. The
bacteria come to the surface when the lake waters flip
in an event known as a thermocline.
Conditions over Long Point Bay last
week were ideal for a thermocline. Steady northerly
winds pushed the warm layer of water on top south to
the U.S. side. This allowed cool water from below to
roll to the top, bringing with it type E botulism bacteria.
It's not known whether gobies are creating
the conditions for its release or simply ingesting the
toxin and poisoning other wildlife when eaten.
"There seems to be a link between these
inversions in the near-shore areas and these botulism
outbreaks we're seeing in summer," Robinson said.
If gobies prove to be the critical link,
Robinson says, people around Lake Ontario should brace
themselves for similar die-off events. Round gobies,
native to Europe, are making their way into the neighbouring
lake. Zebra and quagga mussels are already there.
Since the die-offs began in 1999, there
have been no reports of humans falling ill. Previous
die-offs in Lake Erie have lasted into December.