What is the impact of sea
on trout and salmon?

The impact of sea lamprey on trout and salmon populations in Lake Champlain has diminished in the last ten years. The sea lamprey control program has effectively reduced sea lamprey wounding of Atlantic salmon to near target levels consistently since 2010.

landlocked salmon

Photo: U.S. Fish and Wildlife Service

sea lamprey wounding rates in Lake Champlain

Figure 16 | Sea lamprey wounding rates in Lake Champlain

Fishery biologists continue to try to determine whether parasitic sea lamprey are a native nuisance or invasive nuisance species but, in either case, overall management of sea lamprey is not likely to change. There is strong evidence and broad agreement that the parasitic sea lamprey has had a significant negative impact on salmon and trout. Fortunately, sea lamprey management has been very effective (Figure 16).

In its parasitic phase, the sea lamprey attaches its mouth to its prey and feeds on the blood and body fluids of its host. However, before it reaches this phase in its life cycle, the sea lamprey lives in streams as a larval filter feeder for about four years. It is in this earlier phase of its life cycle that sea lamprey are most vulnerable to control measures.

The sea lamprey control program on Lake Champlain uses several strategies to reduce the number of larval sea lamprey in streams. Methods to control and reduce sea lamprey populations in the Lake’s tributaries include the use of barriers to spawning habitat, spawning traps, and pesticides applied at strategic times and places. Highly specialized pesticides (“lampricides”) have been used to control larval sea lamprey before they transform into their parasitic phase and migrate to the Lake to prey on trout and salmon.

A partnership among the US FWS, the Province of Québec, and local residents developed an innovative new method for controlling sea lamprey. In 2014, a seasonal spawning barrier was constructed on Morpion Stream, a tributary to the Pike River in the Missisquoi River basin in Québec, with funds provided by the US FWS and the Great Lakes Fishery Commission. The temporary barrier is installed early each spring and removed in early summer, to prevent sea lamprey from migrating up the Morpion Stream to spawning habitat. The design allows other fishes to continue their migration, and eliminates the need for chemical control of this tributary for sea lamprey.

As with most pesticides, there are non-target impacts from the use of lampricides. Some endangered or threatened species, including lake sturgeon, channel and Eastern sand darters, stonecats, mudpuppies, mussels, and a native lamprey species also are susceptible to lampricide treatments. The US FWS is required to ensure that there will be a minimal effect on populations of non-target species, particularly for those that are threatened or endangered. Human health risks also are minimized as much as possible. Residents within the treatment areas are notified before lampricide treatments occur and are provided with drinking water when necessary. Recreation advisories are posted in the affected areas for the duration of potential effect on water supplies.

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