Looking for lampreys
Tuesday, September 11, 2001
The Associated Press
RAPID RIVER (AP) -- Like rock bands that tour every so often, biologists and technicians from the Marquette Biological Station of the U.S. Fish and Wildlife Service have taken to the road this summer.
Hitting selected tributaries of rivers connected to Lake Superior and Lake Michigan, scientists are busy collecting data and treating waters shown to contain sea lamprey larvae.
Early this summer, biologists and technicians began a process to treat Haymeadow Creek, a tributary of the Whitefish River, with a chemical lampricide called TFM (3-trifluoromethyl-4-nitrophenol). This month, they will return to treat the main river. Scientists say low water conditions in the latter part of the summer can prevent treatment on small tributaries. Technicians are now taking advantage of higher stream levels caused by a rainy spring. Streams and rivers are typically treated every three to five years, after surveys prove the existence of lamprey or lamprey larvae. This timetable is partly based on the life cycle of the sea lamprey.
According to treatment supervisor Terry Morse of the U.S. Fish and Wildlife Service, Haymeadow Creek was studied to show over 70,000 growing larvae. Total larvae in the entire Whitefish System is estimated at over 300,000.
"We're treating to prevent as many potentially transformed lampreys from going out into the lake as we possibly can," said Morse. He estimates treatments will kill 90-95 percent of all larvae. "At this level, we're just managing, not completely eliminating," he said.
Lamprey numbers are 10 percent of the all-time high several decades ago, according to the Great Lakes Fishery Commission, which promotes and govern the sea lamprey control program for the entire Great Lakes region.
During treatment, according to the U.S. Fish and Wildlife Service, lampricide is carefully metered into the main stream and selected tributaries. Stream flow then carries the TFM downstream through infested areas. "Stream water is continually analyzed at predetermined sites to assure proper concentrations of TFM are maintained," said Morse. Portable laboratories and monitoring devices are set up as crews study and treat the rivers.
According to biologists, TFM is selectively toxic to sea lampreys, but a few fish and insect species are sensitive. Generally, according to biologists, most larval sea lampreys are eliminated during treatment and most non-target organisms survive. According to the Commission, studies are being conducted to further clarify the risk to certain important non-target species, like the Lake Sturgeon.
Fish stressed by disease, spawning or poor water quality may be susceptible to TFM. The U.S. Fish and Wildlife Service claims the chemical is not harmful to humans, birds or animals when diluted in stream water to the concentrations necessary to kill sea lamprey, said Morse. The Service does recommend against unnecessary exposure, i.e. don't let the dogs go roaming in the creeks.
"TFM is one of the safest chemical uses around, in regards to toxicity to organisms," said Morse. "We monitor continuously while in the water, and we're very accountable. We have some of the best people in the world (conducting the treatments)."
According to Morse, TFM mainly targets larval lamprey, which live in the sediment for up to four years before they are large enough to enter the Great Lakes. This is when the lamprey are most vulnerable to control efforts, concluded the Commission. Once in a lake, lamprey parasitically attach to large species of fish, namely lake trout, steelhead and salmon. After spending a year to a year and a half in the lakes, they return to streams to spawn and then die.
The sea lamprey is a monster parasite in that it actually kills its hosts, says Morse. Lamprey, an exotic species accidentally introduced through the Welland Canal, have been in the Great Lakes in significant numbers since the 1950s. They decimated huge numbers of large predator fish and nearly eliminated remnants of overfished lake trout stocks.
"The bottom line is if we let lamprey go uncontrolled, we may have a situation like one created in the St. Mary's River, where lamprey created havoc in the entire river -- it was then very costly to treat and much more difficult to deal with.
Current treatments in the area underscore a new lamprey concern for Lakes Michigan and Huron. The lakes essentially make up one body of water, connected by the Straits of Mackinac. According to the U.S. Fish and Wildlife Service, the St. Mary's River "contributes large numbers of parasitic-phase sea lampreys to northern Lake Huron. It is estimated that northern Lake Huron contains as many sea lampreys as the other Great Lakes combined."
According to one assessment the sea lamprey population there is largely uncontrolled "due to the large volume of water flowing through it and the presence of large lakes within the river system."
"There is a growing concern about northern Lake Michigan as well, among fish managers and user groups," says Morse. "We try to be responsive to user groups' concerns.
Part of that responsiveness has been an attempt to reduce the use of lampricide by 50 percent in an effort to reduce reliance on chemical methods, according to the Commission. Reasons include commitment to a healthier ecosystem, a need to integrate the program and cost. One researcher states the cost of TFM has tripled since 1986. Relying on one method (lampricide) is also dangerous, say researchers, like "putting all your eggs in one basket."
"Lamprey efforts have now evolved into a much more integrated management program," says Morse. "Lampricide, the use of (spawning) barriers and the sterile male program, together combine to make an integrated approach to sea lamprey management." Since 1997, the Commission has spent upward of $5 million dollars on lamprey eradication efforts. Funding remains a political football.
Morse notes that the low-head barriers on the west branch of the Whitefish River and on the Days River "are very effective at controlling lamprey populations." Barriers restrict lamprey spawning and add to efforts on more difficult to manage waterways, like the Whitefish.
Lamprey are caught in traps on the Manistique River and the male lampreys are sent downstate to be sterilized, explained Morse. Sterile males are released back into the water to essentially "trick" spawning females. This allows for mating to continue, but halts fertilization. It is more effective than just removing male lamprey.
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