Scientists say lampricide puts rare, sensitive species at risk
By TOM MITCHELL Staff Writer | August 13,2006
NORTH FERRISBURGH ó Some scientists are concerned that a chemical used to kill sea lampreys in a tributary of Lake Champlain could put endangered species at risk.
The sea lampreys are being targeted in Lewis Creek because the eel-like parasites attach to trout and landlocked Atlantic salmon. The lamprey wound and sometimes kill the cold-water fish, which tend to occupy deeper reaches of Lake Champlain.
"The lamprey go to the cool, deep water along with the trout," said Brian Chipman, a biologist with Vermont Fish and Wildlife. The lamprey also attach to other stocked fish, including walleye pike, lake sturgeon, channel catfish and lake whitefish, he said.
The parasites spawn in the most of the 24 rivers and streams that feed into Lake Champlain. All of those feeder streams are included in the state and federal long-term sea lamprey control program and most have been treated with lampricide at least once.
State environmental officials say the lampricide, trifluoromethyl or TFM, would kill most of the sea lamprey larvae in such places as Lewis Creek and should spare most of the endangered freshwater mussels, if the chemical application levels are kept within designated limits.
State and federal fish and wildlife officials have a permit to conduct the chemical application in early October over a 12-hour period, according to Bradney Young, a U.S. fisheries biologist.
But independent experts and members of two scientific committees that advise the state on endangered species say the lampricide will likely threaten the freshwater mussels and the mudpuppy, a salamander that is not on the endangered species list.that is not on the endangered species list.
Peter Wimmer, a Shoreham entomologist and authority on aquatic invertebrates, says the permitted amounts of lampricide will be close to toxic levels for the mussels.
"They (the officials) are tinkering around with animals that are living on the edge," Wimmer said. "They want to apply a rather high level (of chemical) that is getting awful close to the number that (is) known to be toxic to freshwater mussels."
State officials maintain that the pocketbook, pink heelsplitter, fluted shell and fragile papershell mussels that live in the stream where the TFM is being applied should survive if levels of the chemical stay within the permitted limit. The fifth, the giant floater mussel, is a threatened species that has been found in the river delta and it has moved up Lewis Creek because of the encroachment of zebra mussels in Lake Champlain, Wimmer said in findings earlier this year.
The threatened giant floater and all of the four endangered mussels have also already been stressed by the exotic zebra mussels that have invaded their habitat and greatly reduced their numbers in Lake Champlain.
In past studies of the giant floaters in the Mississippi River, 21 percentage have died when exposed to similar levels of TFM, according to Wimmer. The invertebrate could be vulnerable to doses applied in this proposed treatment as well, he said.
The state Department of Environmental Conservation recently approved a permit that sets an upper limit on the concentration of TFM to be applied in the creek at or near the falls in North Ferrisburgh at 1.2 times the minimum lethal concentration, the amount of the chemical that will kill the lamprey larvae based on the conditions on the day of the treatment.
On the day of treatment, Fish and Wildlife representatives will test individual lamprey in their mobile laboratory to determine how much of the lampricide is necessary to kill them based on the temperature and alkalinity of the water, Young said.
The permit requires water testing at five locations to make sure concentrations stay at or below the limit. Once treatment starts, if testing shows that the concentration of TFM exceeds the target amount, Fish and Wildlife officials would have to cut the chemical feed rate until they reach the limit.
The actual lethal dose varies with each treatment, depending on the conditions on the day of a treatment and is set in order to kill 99 percent of the lamprey, according to Bradney Young, a biologist with the U.S. Fish and Wildlife.
The dose is roughly 20 percent higher than the amount Fish and Wildlife used on the Winooski River in the fall of 2005. The plan is to treat 5.5 miles of the stream between North Ferrisburgh Falls and Lake Champlain, said Chipman.
In the 2002 treatment of Lewis Creek, 9 miles of stream was treated with 538 pounds of TFM, Young said. This time, because so much less of the stream will be treated, about half as much TFM will likely be used, he said.
A 2005 U.S. Fish and Wildlife Service survey found about 59,000 sea lamprey larvae and at least 237 swimming juveniles in the stream from its mouth to the falls in North Ferrisburgh.
Without treatment, Fish and Wildlife officials estimate almost 1,000 juveniles would enter the lake next spring, Young said.
The mussels, meanwhile, have survived during testing and should likewise survive the treatment, state officials said.
"We wouldn't issue a permit if we thought it was going to affect the mussel populations,'' said Steve Fiske, an aquatic biologist in the state Department of Environmental Conservation who has tracked the populations.
The level of TFM is high enough that it does have the potential to stress the mussels, as it has during past treatments, Fiske said.
Fiske has begun observing the pocketbook and fluted shell mussels in a limited stretch of the creek within the designated treatment areas. "The mussels are pretty rare, so it is hard to generate quantitative data."
His survey detected a couple dozen of the rare mussels in a seven-foot stretch of the stream in work that has continued this year, Fiske said. But the state doesn't have long-term population information, he said.
Jim Andrews, a Middlebury College amphibian and reptile specialist, pointed out that it may be hard to determine how many of the mussels will be killed, if any, because the surveys cover part of a stream, as little as 20 percent in the last treatment on the Winooski.
However, Ian Worley, chair of the Endangered Species Committee, which provides recommendations for treatment, said it is hard for species to make the endangered list and the low numbers of the mussels and long-term populations are not well documented.
"When they get on the (endangered) list they have to go through considerable scrutiny."
Worley said there is a need for more information on ecological impacts because the limits on chemical treatment "hangs on thin threads of statistics."
Worley and other members of the Endangered Species Committee are appointees who make recommendations to the state Agency of Natural Resources on issues involving rare species. They are considered experts in their fields, and they are independent to the extent that they are not part of state government.
The state had to seek two permits in order to treat Lewis Creek with TFM Ė an aquatic nuisance permit for killing the lamprey and an endangered species permit, which essentially allows the state to "take" the mussels in the event some of the invertebrates are killed after the application of the chemical.
Canute Delmasse, acting secretary of the agency, last week approved an endangered species permit for the 2006 TFM treatment of Lewis Creek. Based on recommendations from the Endangered Species Committee he did not approve a proposed second TFM treatment in 2010. The aquatic nuisance permit approved by DEC was also limited to one application of the chemical in 2006. Only one rare mussel was found dead in five prior treatments in three Vermont rivers, according to state officials.
"We requested two treatments in a five-year period," said Eric Palmer, direcor of fisheries in Fish and Wildlife. "We got approval for a single treatment."
Andrews, chair of the state Scientific Advisory Committee for amphibians and reptiles, is concerned that the treatments are designed to protect species of salmonid game fish (trout and salmon) that are not threatened.
"We have regularly recommended against these treatments," Andrews said. "From the ecological perspective, we should be protecting the species that are in most need of protection."
Citing a lack of information about the treatment's long-term impact, Andrews said the treatments could be a threat to the five species of mussels.
"I think they are the ones we should be careful about," he said.
Andrews, who is also a fisherman, said he doesn't think lack of a treatment would diminish the sale of fishing licenses.
For the most part, the salmon and lake trout that comprise the game fishery are stocked in the lake. During hearings, Fish and Wildlife officials received testimony from operators of charter fishing boats and sport fishing groups on the damage the lamprey does to fish species.
One sea lamprey can grow from six inches to more than 18 inches in its 12- to 20-month life as a parasite in Lake Champlain, where it can kill up to 40 pounds of fish, scientists said.
Sylvia Knight, the Charlotte Conservation Commission spokesperson, said she is concerned that state officials have not developed alternative treatments for lamprey in the stream.
Officials wrote in the permit that a barrier dam on Lewis Creek would not be an acceptable alternative control for the lamprey because it would also restrict game fish such as smallmouth bass, rainbow trout and white suckers from the stream.
As part of the lamprey control project, in the northern edge of the overall Lake Champlain watershed in Canada, the plan is to build a screened blockage structure on a tributary of the Pike River, where many lamprey originate, Chipman said.
Canadian environmental officials rejected a proposal for applying TFM, but approved building a barrier on the tributary, Chipman said. Construction of the dam, which is a joint project of the United States and Canada, will begin later this summer.
Knight also expressed concern that in the fall, when the water gets colder, the TFM will seep into the ground where the mussels burrow for winter shelter.
She said the mussels are potentially absorbing the chemical for a month or longer. The Environmental Protection Agency has acknowledged the properties of TFM allow it to linger in the water.
The Endangered Species Committee also said in its review that in colder water, TFM is absorbed by sediments and could later bleed back out into the water.
The state Department of Health, meanwhile, has expressed concern about the amount of TFM in the water staying within the permitted range. The health department wants Vermont Fish and Wildlife to identify the product and batches of TFM that will be used, including studies on what impurities of the chemical could degrade in the environment.
A check of the record of the last treatment in Lewis Creek in 2002 showed concentrations of 1.2 times the minimal lethal concentration above the Route 7 bridge were diluted to 1.1 times the minimum lethal concentration at a point near where the listed mussels live.
State officials have used levels in the last treatment as a guide that would help keep the concentrations at a non-toxic level for nontarget species.
Another cause for concern, they said, is the mudpuppy, a large salamander that lives in tributaries to Lake Champlain; 23 dead mudpuppies were found after a lampricide treatment in 1990 and 18 following a 1994 treatment, according to the permit application.
The permit recommends hiring biologists to document the presence of mudpuppies in the stream and other tributaries of Lake Champlain.
During past studies, officials with Vermont Fish and Wildlife have not been able to find the salamanders, leaving them unable to assess their populations.
In a review earlier this year, several members of the Endangered Species Committee said their concern for the mudpuppy has been so great that the committee should recommend against issuing the TFM permit.
And Wimmer, the invertebrate authority, expressed concern about a declining number of mudpuppies in Lewis Creek. Noting that the mudpuppy appears to be at risk in Vermont, good methods for finding them are needed, Wimmer said.
The permit requires state Fish and Wildlife officials to submit a plan that describes how it will develop information on numbers of mudpuppies in Lewis Creek, as well as other tributaries of Lake Champlain. In the meantime, over the past eight months or so, the technical status of the sea lamprey has changed following a discovery that it is apparently native to Lake Champlain.
Last fall, researchers from Michigan State University announced that they had determined that the Lake Champlain sea lamprey was native to the lake for thousands of years before Samuel de Champlain explored it in 1609.
In response to the finding, fishermen said the eel, even though native, is adversely affecting salmonid fishing in the lake.
Young, the U.S. Fisheries biologist, said federal and state fish and wildlife officials still need to subdue the lamprey in order to reestablish the salmon and lake trout. Scientists are now considering how lamprey coexisted with salmon and trout for thousands of years.
Contact Tom Mitchell at firstname.lastname@example.org