Battle against lamprey on Beaver and Big Head Rivers

[Spiel]

Battle against lamprey on Beaver and Big Head Rivers

 

 

May 21, 2008

Doug Edgar / theenterprisebulletin.com

 

 

Canada's sea lamprey busters plan to treat a section of the Sauble River during the first week of June.

 

They are also monitoring lamprey runs on the Beaver River, which enters Georgian Bay at Thornbury, and on the Bighead, which enters the bay at Meaford.

 

Also, a metal plate will be added to the top of Denny's Dam as added insurance that the parasitic jawless fish - although they're often called eels, technically they're not - don't get into the vast Saugeen system, which has extensive areas suitable for lamprey spawning.

 

The drive to reproduce is so strong that lampreys will attach themselves to a dam or other obstacle and work their way over the top if the drop is small enough, said Paul Sullivan, section head, control, with the Department of Fisheries and Oceans Sea Lamprey Control Centre in Sault Ste. Marie.

 

"It's remarkable the tenacity they have," he said.

 

The drop at Denny's Dam is great enough to stop them, but the plate, which will form a horizontal lip over the crest of the dam, will make the structure better.

 

"It's just an added safety measure," Sullivan said.

 

The Saugeen was treated with lampricide once, in 1970, when Denny's Dam was put to use as a barrier, Sullivan said. It was the most expensive treatment to that point and would cost $700,000 to do today.

 

The local work is part of efforts on both sides of the border to control sea lampreys, an invasive species that is believed to have entered the upper Great Lakes through the Welland Canal in the early 20th century. They helped decimate lake trout and other large predatory fish.

 

The Sauble River will be treated from the Jewel Bridge Road downstream, Sullivan said. That area, a short distance east of Bruce Road 13, which is the main north-south route along the Huron shore, is as far upstream as larval sea lampreys have been found.

 

The Sauble has been periodically treated with lampricide since 1970, Sullivan said. The chemical, which kills the larval stage of the lamprey but doesn't affect other aquatic organisms under normal conditions when used in the correct concentration, will be pumped into the river for 12 to 14 hours.

 

A trap at the fish ladder in the Beaver River is also regularly checked during the lamprey spawning run, which lasts from early April through the end of June.

 

The Bighead River was treated last year and it will be checked this year to see how effective those efforts have been, said Sullivan.

 

The Bighead has no barrier to stop sea lampreys from reaching spawning areas, he said. The river is treated with lampricide every four years, since that's the minimum time it takes the larvae in the river to reach the point they change into adults and head for the lake.

 

Larval lampreys are filter feeders that live in the bottom of the stream before they enter their parasitic stage, while adult sea lampreys have a ring of sharp teeth that they use to scrape a hole in a fish. They then suck out the fish's blood and bodily juices.

 

Sullivan said there is evidence that adult lampreys find their way to spawning sites - gravel areas with clean, well oxygenated water, roughly what is suitable for rainbow trout - because they are attracted by pheromones produced by the larvae. To complicate the matter, there is also evidence that sea lampreys are attracted to pheromones produced by the larvae of native lampreys that live in some local river systems, including the Saugeen. That means that even if sea lampreys aren't present in a watershed, adults could be drawn to spawn.

 

The native lampreys include the non-parasitic northern brook lamprey, which is under consideration for partial protection under the federal Species at Risk Act.

 

Once sea lampreys reach a suitable spawning area, they make crescent shaped nests by moving gravel around with their mouths. They die after spawning.

 

Officials are also evaluating a program in which sterilized male lampreys are released in the St. Marys River. The idea is that they spawn with females and produce non-viable eggs. The DFO control centre will help the U.S. Fish and Wildlife Service release 25,000 such lampreys this year.