More than 100 years ago, a parasitic, snake-like fish hitchhiked a ride to America’s sixth Great Lake – invading the almost 500-square-mile Lake Champlain straddling Vermont and New York. At least, that’s what some say.
|Sea lamprey. Credit: USFWS|
Other information indicates the fish—sea lamprey—may be native to the lake and even a resident since the last ice age. Either way, the sea lamprey grew in numbers and preyed on native fish. By the 1900s, native salmon and lake trout were no longer found in Lake Champlain. When sea lamprey impeded efforts to bring the fish back, concern grew about populations of this parasitic fish.
A single sea lamprey kills 40 or more pounds of fish in its life as a parasite. They attach to host fish and feed on their blood and body fluids, leaving a wound at risk for infection. The lamprey is often confused with eels because it is jawless, but its circular sucking disk helps to distinguish it from the American eel, which has a true jaw. Inland adults average 24 to 30 inches in length.
Of the 36 species of northern lampreys, only about half of them are parasites. And, even if they are parasitic, not all lampreys are invasive. There are two species of lamprey native to the Lake Champlain basin—silver lamprey (parasitic) and American brook lamprey (non-parasitic). The northern brook lamprey calls the Great Lakes region home, but isn’t parasitic either. In contrast, there are conservation efforts to restore two threatened and endangered lamprey species on the Pacific coast and California—the Pacific lamprey (parasitic) and western brook lamprey (non-parasitic).
In an effort to control the sea lamprey population in Lake Champlain, the Lake Champlain Fish and Wildlife Management Cooperative, formed by the New York State Department of Environmental Conservation, Vermont Fish and Wildlife Department and the U.S. Fish and Wildlife Service, began an integrated control program to reduce the population and restore balance to the ecosystem.
Their efforts will continue this month, as staff applies lampricides to five Lake Champlain tributaries and two deltas beginning on September 10 and continuing through October. The cooperative will use a suite of pesticides specific to lampreys and in amounts that will be closely monitored during application.
The lampricide, TFM, works by interfering with sea lamprey metabolism and glucose uptake while at their vulnerable larval stage. It will be applied in the rivers for about 12-14 hours, followed by either Bayluscide concentrate in rivers or granular Bayluscide in deltas to kill sea lamprey larvae effectively before they reach their adult parasitic stage.
|Sea lamprey control. Credit: USFWS|
In the Saranac River delta this week, treatment proved extremely successful. Bradley Young, coordinator of the sea lamprey control program at the Service’s Lake Champlain office, indicated that though he doesn’t have exact numbers of larvae deaths, hundreds of thousands were thought to have been destroyed.
In addition to lampricide treatments, other control efforts used by the NYSDEC include the use of barriers to prevent adult sea lamprey from migrating up waterways to spawn and traps to capture adult sea lamprey before they can spawn. These physical methods, however, are not as effective as lampricides.
During treatments, temporary water use advisories will be in effect to minimize human exposure to affected waters. It is recommended that during advisories, treated river and lake water be avoided for drinking, swimming, fishing, irrigation, or livestock watering activities. No municipal water supply systems will be affected.
Time has shown that use of lampricide to control sea lampreys gives positive results. Annual assessments have shown a significant decrease in the recorded average sea lamprey wounds, dropping from 99 per 100 lake trout seen in 2007 to 30 per 100 lake trout in 2011. Landlocked Atlantic salmon have also seen a significant decline in wounds dropping from 79 in 2003 to 19 in 2011 per 100 fish.
Whether the sea lamprey is native to Lake Champlain or not, it is having detrimental impacts on the Lake Champlain fisheries and ecosystem, as well as people who fish Lake Champlain, whose livelihood is directly or indirectly supported by fishing, and tourist industry. The efforts of the cooperative play a major role in taking control of sea lamprey in the Lake Champlain basin and protecting the fisheries for wildlife and people.
If any Champlain basin resident has a question about the treatment of their local waters for sea lamprey control, please call the cooperative at 1-888-596-0611.
Submitted by Denise Clay, fishery biologist at the Service's Lower Great Lakes Fish and Wildlife Conservation Office.