The sea lamprey is a primitive, eel-like fish native to the coastal regions of the Atlantic Ocean. Sea lamprey entered the Great Lakes via man-made canal systems in the 1830s and was established in all the Great Lakes by 1938. Since 1956, the governments of the United States and Canada, working jointly through the Great Lakes Fishery Commission, have implemented a successful sea lamprey control program.

Characteristics

The sea lamprey is very primitive fish resembling fossil records that are over 340 million years old. Unlike most fish, a sea lamprey's body is cylindrical and has cartilage instead of bones. Sea lampreys have no scales, no lateral line, no paired fins and no swim bladder. They have two dorsal fins that are unattached and towards the rear of the body. An ocean lamprey can grow to 1m (3 feet) long and females can weigh up to 2.2 kg (5 lbs) with the males weighing a kilogram lighter. In the Great Lakes they are generally half this size 

The sea lamprey is a parasite. They have a suction cup mouth ringed with sharp teeth that surround a rasping tongue. It attaches to fish with its suction mouth and sharp teeth and uses its tongue to pierce the skin of the fish, and feed on its blood and bodily fluids. An anticoagulant in the lamprey's saliva keeps the wound open for hours or weeks, until the lamprey is satisifed or the host fish dies. Sea lampreys prey on a variety of large fish including lake trout, salmon, rainbow trout, brown trout, whitefish, yellow perch, burbot, walleye, and catfish.

Adult sea lampreys swim upstream to build nests, spawn and then die. Fertilized eggs hatch into small, wormlike larvae which burrow into stream bottoms where they feed on debris and small plant life (algae) for an average of 3 to 6 years before they transform into the parasitic adult. The adults migrate into the Great Lakes where they spend 12-20 months feeding on fish. The complete life cycle, from egg to adult, can take an average of 5 to 8 years to complete. Understanding the sea lamprey's life cycle helps scientists develop effective control measures.

Distribution

Sea lampreys were first observed in Lake Ontario in the 1830s. They entered Lake Ontario via man-made canals and then gained access to the upper Great Lakes when the Welland Canal was constructed in 1919. By 1938, sea lampreys could be found in all of the Great Lakes. There are approximately 5,747 streams and tributaries of the Great Lakes and an estimated 433 are currently known to produce sea lampreys.

Impact

One lamprey can kill more than 18kg (40 lbs) of fish during their 12-20 month adult life stage. In the 1940's and 1950's, sea lampreys were a major factor to the collapse of fish species contributing to the Great Lakes fishery. On average, only one in five fish will survive an attack from a sea lamprey; if the attack does not kill them, the resulting wound is a pathway for disease. Before sea lampreys arrived, Canada and the United States harvested about 15 million lbs of lake trout from Lakes Huron and Superior per year. With sea lamprey numbers at their peak in the early 1960s, the catch was only about 300 000 lbs per year.

Even now, with controls in place that have greatly reduced the sea lamprey population, in some areas, such as northern Lake Huron and Michigan, they still kill enough lake trout to prevent a full recovery.

Prevention

Today, through intensive control programs, lamprey populations have been reduced by almost 90% of their peak numbers in the early 1960s. This has allowed the Great Lakes fishery to slowly rebound. The control program is administered by the Great Lakes Fishery Commission in cooperation with the Department of Fisheries and Oceans Canada, and the U.S. Fish and Wildlife Service. Initiatives include:

View video of Sea Lamprey here

1. the application of the chemical T.F.M. to selectively kill lamprey larvae in streams where the adults spawn (of the 5,747 stream and tributaries of the Great Lakes, 433 are known to produce sea lampreys and about 250 are treated on a regular cycle);
   
2. construction of barriers that allow fish to travel upstream, but prevent the migration of spawning lampreys upstream;
   
3. releasing sterilized male sea lamprey into streams to compete with spawning males and reduce the reproductive success of females.

Scientists have recently isolated a sex pheromone released by male sea lampreys that attract the females for spawning purposes. It may hold great promise as many scientists are concerned about the long term affects of chemical applications of T.F.M. and if lamprey will eventually become resistant to it.