Degrading Barriers – A Risk to the Great Lakes Fishery
Harpersfield Dam Grand River, Ohio showing signs of deterioration under normal stream flow. John Stegmeier/USFWS.
Barriers are an important component of the Sea Lamprey Control Program of the U.S. Fish and Wildlife Service. Many barriers, such as dams, were constructed around the turn of the century in tributaries of the Great Lakes. Originally many of these barriers were not built to control invasive sea lampreys or block the sea lampreys from reaching upstream spawning migration, but ultimately, they have served this purpose. Other barriers were built specifically to control sea lampreys to effectively block the sea lamprey spawning migration and limit the amount of spawning and rearing habitat available.
With time, barriers experience wear and tear. They degrade and require repair or replacement. Without attention and repair, adult sea lampreys will eventually find a route around, through or over the “leaky” barrier. Breeches of degrading barriers often result in large increases of sea lampreys as they access new spawning and rearing habitat in the tributaries. Left uncontrolled, these voracious parasites will eventually end up in the Great Lakes where they feed on and kill valuable sport and commercial fishes.
The Harpersfield Dam, located near Ashtabula, Ohio on the Grand River, currently acts as a barrier to the upstream migration of adult sea lampreys, blocking access to 462 miles of river that could contain ideal spawning and larval habitat for sea lampreys. Like many dams in the Great Lakes region, the Harpersfield Dam, built in 1913, is in poor condition. If this dam deteriorates and adult sea lampreys migrate upstream of the dam, sea lamprey production will likely increase dramatically as additional habitat will be available. Costs to replace this dam are estimated at about eight million dollars. Therefore, it is critical to understand what the habitat suitability on the Grand River is for sea lampreys upstream of the barrier. This information is necessary to accurately assess the cost-benefit of restoring the dam.
During October 2013, a team of Service biologists and technicians traveled to Ohio to conduct habitat and larval lamprey surveys in the Grand River upstream of Harpersfield Dam. The team surveyed 42 locations in the mainstem and associated tributaries. At each location they measured and classified larval and spawning habitat and conducted electrofishing surveys for native lampreys. Finding native lampreys in the river indicates that sea lampreys would survive in these locations as well. Our findings will be used to estimate the production potential of sea lampreys in portions of the Grand River located upstream of the Harpersfield Dam and will be useful in estimating the cost and benefit of repairing the Harpersfield Dam.
The Program continues to work closely with partners to control populations of sea lampreys in tributaries of the Great Lakes to protect the fishery and related economic activities in the Great Lakes basin. This is an estimated annual benefit of more than $7 billion/year to the region. The Service delivers a program of integrated sea lamprey control in U.S. waters of the Great Lakes in partnership with the Great Lakes Fishery Commission.
-- Alex Gonzalez