Sunday, June 16, 2013

Measures Taken To Reduce Invasive Sea Lampreys' Great Lakes Population

Since 1830, sea lampreys have been a menace to the fish populating the Great Lakes. Native to the Atlantic Ocean, they stowed away in the ballast of ocean-going ships where they found their way to Lake Ontario and eventually infested all five of the Great Lakes. Sea lampreys wreaked havoc on fish populations and in some cases nearly wiped them out.

Lakes Ontario, Michigan and Superior are holding at sea lampreys target levels -- numbers authorities believe the lake can tolerate. The target level for Lake Ontario is 40,000 to 50,000 lampreys. "We'd like it to be at zero, but the naked truth is that lampreys are in the lake to stay," Gaden said.

Using their suction like mouths, sea lampreys latch onto the sides of fish and feed off their blood. Marc Gaden, communications director of the Great Lakes Fishery Commission (GLFC), describes them as "incredibly destructive predators."

In the Great Lakes, sea lampreys prefer to feed on lake trout, steelhead, whitefish and burbot, and are believed to be impacting the populations of those popular angling species. In Lake Erie's Pennsylvania waters, sea lampreys are known to spawn in three popular Erie County steelhead streams.

Earlier this month, the GLFC announced that in New York, a sea lamprey barrier and trap was built was on Orwell Brooke, a tributary that feeds into Lake Ontario's Salmon River. The barrier is one of 70 sea lamprey barriers in all of the great lakes.

The barrier, which was placed as close to Lake Ontario as possible, stops sea lampreys before they can spawn in Orwell Brook. It is designed to allow other migratory fish to go on as normal, and has aluminum stop logs that will be removed outside of the sea lamprey's migratory period.

In its lifespan, one adult sea lamprey can kill 40 pounds of fish. A female sea lamprey can lay 100,000 eggs. Once these eggs have hatched, the larvae burrow into the bottom of stream beds where they stay for three years until they mature into full grown adults and swim into the Great Lakes to wreak their havoc.

Orwell Brook is one of the largest contributors to the sea lamprey population in Lake Ontario. It is downstream from Pekin Brook, another contributor to the sea lamprey population.
Now that the barrier is in place, hundreds of thousands of dollars in treatment will be saved and redirected to other lamprey infected areas of the Great Lakes. One effective lamprey control method is to spray the affected area with TFM, a lampricide that specifically targets lampreys while preserving other fish in the area. This treatment alone costs tens of thousands of dollars.

Orwell Brook will need to be treated one last time before it will remain lamprey free, said Gaden. The strategic location of the barrier ensures that Peking Brook also will be reclaimed from lampreys. Some 15 percent to 20 percent of suitable lamprey habitats have been taken away from the sea lampreys because of the barriers, Gaden said.

Lake Huron is the most problematic of all of the Great Lakes in regards to lampreys. At 280,000 lampreys, it is 200,000 lampreys above target.

Lake Erie also is another problem spot with 10 tributaries in which sea lampreys spawn, including Conneaut, Raccoon and Crooked creeks.

Following a dramatic spike in the number of sea lampreys in the lake, it was treated with lampricide in 2009 and 2010. The expectation that all of the lampreys would be destroyed was dashed when an assessment revealed that lamprey levels were still very high.

The puzzling thing was that no lampreys were found in the tributaries. The Great Lakes Fishery Commission concluded that the lampreys might be coming from St. Clair and Detroit rivers between Lake Huron and Lake Erie. Today lamprey levels in the Lake Erie are higher than they were before lamprey control measures were taken in the lake in the 1960s.
"We will find where they're coming from and we will get them," Gaden said. "We just have to find the source, zero in on it and verify it."

Anglers rarely see the lampreys but sense their impact in diminished quantities of game species. Ed Kissell, vice president of the S.O.N.S. of Lake Erie sportsmen's club, said his brother caught a walleye that had a 17-inch lamprey attached to it. Lamprey's generally don't go for walleyes because they have hard scales.

"There could be an increase, possibly, in the population of the lampreys," Kissell said, adding that another possibility was that a large population of walleye might have been targeted by the lampreys because they were easier to get.

In the meantime, sea lampreys are getting in the way of lake trout rehabilitation in the eastern part of Lake Erie. Lake trout usually live for 7 to 8 years and spawn late in life. Many lake trout are killed by lampreys before they have a chance to mature, dramatically reducing the lake trout population.

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