Great Lakes sea lamprey control is critical
If not kept in check invasive sea lamprey populations would increase quickly.
The sea lamprey is native to the Atlantic Ocean and spawns in freshwater streams. When sea lamprey entered the Great Lakes through the Welland Canal they quickly spread and by 1938 they had been observed in all of the Great Lakes. They are a parasitic fish that feeds on the blood and body fluids of their host and can grow to 20 inches in length in the Great Lakes and kill 20 to 40 pounds of fish in its lifetime. Like many invasive species, they have no natural predators in the Great Lakes. They reproduce in large numbers with each female having up to 90,000 eggs. They also have little commercial value and generally complete their life cycle in 4 to 7 years.
Michigan Sea Grant and Michigan State University Extension recently held a fisheries educational session at the Michigan Fish Producers Association Annual Conference. Scott Grunder of the U.S. Fish and Wildlife Service Sea Lamprey Control Program presented information on Sea Lamprey Control in the Great Lakes.
Sea lampreys have a very unique life cycle. The adult parasitic phase when they damage the Great Lakes fishery lasts for 12 to 18 months. The sea lamprey then spawn in rivers in the spring of the year and then die. After eggs hatch they enter a non-parasitic larval stage that lasts 3 to 6 years. When the larval stage is completed the sea lamprey transform in the spring or fall and enter the Great Lakes where they begin feeding on Great Lakes fish. Two phases of the sea lamprey life cycle are particularly vulnerable to control—when they are the larval phase and in tributaries for 3 to 6 years, and the spawning phase when they migrate up streams to spawn.
Sea lamprey control embraces the concept of integrated pest management and is often touted as the best example of aquatic invasive species management in the world. Program components include assessment, lampricide control, risk management and alternative controls.
Larval assessment determines where lampreys have recruited and their distribution in those streams. This information is used to select control actions such as barriers and lampricide treatments and to direct treatments in streams. These assessments include more than 5,000 tributaries to the Great Lakes with 511 in Michigan that had 126 recorded infestations. Spawning phase assessment involves trapping sea lampreys in Great Lakes tributaries for the purpose of estimating abundance with about 70 streams being trapped each year. These data are used in an index which is the summation of mark-recapture estimates from a sub-set of streams characterized by a consistent trapping history and large spawning run. Correction factors are developed for each lake to scale index estimates to lake-wide estimates.
The lampricides TFM and Bayluscide remain the primary means of control in most streams. Both lampricides are registered use pesticides that have been approved by the EPA. They are selectively toxic to sea lampreys in the concentrations applied and the EPA determined that there is no unreasonable risk to the public or environment. Both lampricides are non-persistent in the environment and degrade through light and microbial action. The Great Lakes Fishery Commission and its control agents, the U.S. Fish and Wildlife Service and Fisheries and Oceans Canada, implement a program to control sea lamprey in the Great Lakes. The total control program budget exceeds 20 million dollars per year with about $3 million for chemicals. Lampricides are applied through a variety of pumps and spray devices and more than 100 streams are treated annually. Regularly infested streams are treated once every 3 to 4 years.
Alternative controls are another important component of sea lamprey control. Physical barriers are used in some streams to block upstream migration of sea lamprey spawners and reduce habitat available for producing the next generation. There are about 70 program constructed barriers in the Great Lakes basin. Traps are also used near these barriers to capture adults. Trapping for control is primarily conducted in the St. Marys River, where it reduces reproductive potential of the population.
Research continues in the areas of genetic manipulation, pheromones, repellents, effects of lampricides on non-target organisms, and resistance to lampricides. All program activities are evaluated for their risk to the environment. The risk management program annually conducts a programmatic review of all activities, identifies potential impacts to protected species and recommend actions that will avoid or minimize potential impacts. This work is done in close consultation with state and federal partners.
The integrated sea lamprey control program has had great success in minimizing damage to Great Lakes fish. Spawning sea lamprey abundance across the Great Lakes has been reduced by about ninety percent since the onset of the sea lamprey control program.
Without the control program sea lamprey would increase in numbers again in the Great Lakes.
Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.