Lamprey are target of DNR crews
Written by Daily Press   
Tuesday, 30 May 2006 03:08

The Bays de Noc and Lake Michigan fisheries are thriving and U.S. Fish and Wildlife Service crews are doing their part to keep it that way.

The FWS personnel recently treated the Whitefish and Rapid Rivers and some of the tributaries with chemicals to kill sea lampreys.

FWS Fisheries Biologist Dorance Brege said the goal of the program is to target juvenile lamprey, which aren’t harmful to fish, before they reach maturity and head into the lake.

“The premise is get the young ones before they go out and do the damage,” Brege said. “If we could treat them before they get into the lake, we can prevent damage in Bay de Noc and Lake Michigan.”

Lamprey live in streams as juveniles until they reach maturity at around four years, Brege said.

Brege said streams which have good food sources for many different organisms are more likely to have lamprey. “Any river that is productive to life can produce lamprey,” he said. “They mature faster where there’s more food.”

Sea lamprey control begins when biologists go into streams to assess which ones have lamprey larvae. “Last year we were searching the rivers for lamprey,” Brege said. “We find them by electrofishing.”

Once a river is determined to hold significant lamprey numbers, a state permit is applied for to treat the stream.

The chemicals used to treat the river, TFM and Bayluscide, had studies performed on them by the Environmental Protection Agency commissioned to determine their safety, Brege said.

The main chemical used, TFM, is lethal to lamprey at approximately two parts per million in water. The numbers are arrived at from previous studies, Brege said. Each site’s water chemistry is different and variables like pH levels and alkalinity can affect the treatment’s effectiveness, Brege said.

To account for the differences, FWS personnel are aiming for a concentration of 3.5 parts per million. At the desired level, the chemicals are lethal to lamprey in 7-10 hours.

The chemicals normally aren’t harmful fish at this concentration. By comparison it takes a level of between eight and nine parts per million to be lethal to brown trout, Brege said. “Fish can process the chemicals and get rid of it,” he Brege.

Brege said fish taken from the river are safe to eat if prepared by normal methods. “The chemicals end up in the liver,” he said. “If you clean and fillet the fish it doesn’t stay in the flesh.” Brege added if anglers wait a day after treatment, fish lose 90 percent of the chemical.

The work crews take constant water samples to monitor the chemical concentrations, Brege said.

Brege said the Whitefish River presents challenges because of its two large branches. “We’re trying to match the West Branch with the East Branch and make one block of chemical,” he said.

Brege estimated the chemicals will take 24 hours to reach the mouth of the Whitefish from treatment sites beginning upstream near Trenary.

Brege said the Whitefish was treated in 2004 but water levels were so low the chemicals’ effectiveness was lessened. “We only killed 90 percent of the lamprey. WIth the water so low it’s hard to do a good job,” he said. We’re trying to get rid of the ones left.” In 2004 Brege estimated the chemical took 110 hours to travel to the mouth.

Most major lamprey producing streams like the Whitefish have to be treated every four years, Brege said. “Hopefully, we won’t have to be back until then,” he said.

There were 19 workers applying treatment and taking water samples at the various sites over the last couple of weeks, Brege said. The crews are based out of the Marquette office.

Next week the crews will be doing the same job on the Nemadji River in Minnesota.

The project is a joint venture with the Department of Fisheries and Oceans Canada to control lamprey on the Great Lakes.

“We have a good fishery in Bay de Noc,” Brege said. “That’s the benefit of this program.”

 
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