Thursday, June 4, 2015

Lamprey Eels in Canada and the Great Lakes

The so-called “vampire of the lakes” has been found for the first time in a creek west of London, Canada.
Sea lamprey are a blood-sucking scourge that once threatened to ruin the multibillion-dollar fish industry in the Great Lakes.
Now, with a $22-million annual program to monitor lakes and treat tributaries for lamprey and their larvae, they number “about 10% of what they (once) were,” says Brian Stephens, who heads the sea lamprey control program for the federal Department of Fisheries and Oceans. “They almost decimated the populations of lake trout in the upper Great Lakes in the 1950s.”
But lamprey larvae keep popping up in new places. And the newest location to be treated with a lampricide will be a tiny tributary of the Thames River, in Komoka Creek west of London.
“This is the first time Komoka Creek is scheduled for treatment,” Stevens said.
Adult lamprey swim from lakes to spawn in clean, gravelly tributaries. The adults then die but their larvae stay in the stream-bed for about five years until they’re large enough to float downstream to the lakes.
There, they attach themselves to native fish and literally suck the life out of them.
The Komoka Creek larvae were found during survey efforts in 2013.
The population estimate is there are 730 larvae longer than 100 millimetres, or the width of a human hand.
At that stage, they’re ideal for chemical treatment to prevent them from growing into adults.
In the oceans, sea lamprey are parasites that live off large saltwater fish.
But as an invasive species in fresh water here, they threaten a $7-billion fishing industry.
“Unfortunately, in the Great Lakes, the fish aren’t as big as the host they feed on and they kill the host,” Stephens said.
Before the U.S. and Canada began a joint program in the mid-1950s to monitor, trap and apply lampricide, commercial fish populations had plummeted to just 2% of their previous average.
The lamprey larvae have low levels of an enzyme that would allow their systems to break down the species-specific lampricide, Stephens said. Fish have higher levels of that enzyme and are not harmed in the treatment.
A trout hatchery set up on the creek by Thames River Anglers Association wouldn’t be harmed by the lampricide.
Monitoring takes place continuously through the Great Lakes basin.
In the London region, Big Creek and Big Otter Creek — which feed into Lake Erie — have also been treated with lampricide in past years. This week, a team has also been treating creeks near Oshawa.
Komoka Creek was originally to have been treated this spring, but heavy rains have tentatively postponed that to August. 

Read more about invasive species in The Dynamic Great Lakes: available on a Kindle reader and also in paperback.