fish in GTA waters
Rudd illegal in Canada as baitfish
Crossbreeding could hurt native species
By Gail Swainson
Published January 26, 2006
A tiny, unwanted alien has invaded a lake in Greater
Toronto and wildlife biologists are warning there may
be more lurking in the weeds.
At least one rudd, an invasive baitfish originally from
Europe, has found its way — likely via the U.S. — into
Lake Wilcox in Richmond Hill.
Ministry of Natural Resources biologists say it is the
first time rudd, discovered in the Great Lakes in the
early '90s, has been found in an Ontario inland lake.
This black-sheep member of the minnow family competes
with native fish for food and destroys the spawning and
nursery habitats of fish like the northern pike, muskellunge
and yellow perch.
Although only a single rudd was captured alive in Lake
Wilcox in late October, wildlife biologists say there
could be more and they will resume monitoring the lake
in the spring.
Lake Wilcox is the headwaters for the Humber River, which
flows into Lake Ontario through Toronto. This means if
there is more than one rudd in Lake Wilcox, it could easily
migrate through the Humber to Toronto's shoreline.
It is suspected the fish was carelessly dumped out of
a bait bucket into Wilcox. Illegal in Canada as a baitfish,
rudd have been used for that purpose in the U.S., where
they were introduced in the 1920s.
"When these kinds of things happen, they threaten
our natural biodiversity," said Mark Heaton, a fish
and wildlife biologist with Ontario's Ministry of Natural
Rudd, which can grow to 38 centimetres and weigh up to
1.8 kilograms, inhabit warm, shallow, shoreline areas
with lots of vegetation. Rudd eat mainly aquatic vegetation
They can also crossbreed with the native golden shiner,
which could effectively wipe out that fish as a separate
species if rudd were to spread to other lakes.
Rudd isn't the first non-indigenous species to invade
The sea lamprey, which travelled on its own from the
Atlantic Ocean, wreaked havoc in Lake Erie in the early
1940s. Most recently, zebra mussels spread like wildfire
through the Great Lakes region when ships dumped their
ballast. More than 160 non-native species live in the
Great Lakes basin.
Heaton says Lake Wilcox is already in bad shape through
phosphorus overloads caused by leaking septic systems.
This has depleted the oxygen levels in deep waters, leading
to massive winter fish kills.
Large mouth bass, shiners, white suckers, carp and as
many as 200 northern pike are in Lake Wilcox. The northern
pike are especially vulnerable because they live and spawn
in the weeds, on which the rudd feed.
David Donnelly, a lawyer with Environmental Defence,
calls the growth in invasive species "one of the
greatest threats to biodiversity in Ontario waters."
Donnelly said the invaders tend to crowd out indigenous
species, leading to fluctuations in numbers.
This, in turn, causes what Donnelly calls a "species
wobble," with population decreases following on the
heels of explosions. "And the whole natural balance
gets out of whack," Donnelly adds.
Beth Brownson, senior invasive species biologist with
the ministry, said getting rid of an invasive species
can be difficult if not impossible once they take root
in another environment.
"The public needs to be really vigilant," she
Ministry officials are considering erecting signs on
Lake Wilcox asking residents and anglers to be on the
lookout for rudd and to call a hotline number if any are
The signs will also warn anglers that rudd are an illegal
baitfish in Ontario and to refrain from dumping them in
area lakes and streams.
Meanwhile, the Lake Wilcox rudd now resides, preserved,
in a specimen jar at the Royal Ontario Museum. Heaton
says it will take further study to determine its sex.
The rudd was first discovered in the St. Lawrence River
Since then, it has also been found in western Lake Ontario
and eastern Lake Erie.