Sea Lamprey Control

The Great Lakes are a valuable resource shared by Canada and the United States. The Great Lakes fishery generates up to $4 billion for the region annually, offering recreational angling opportunities for five million people and providing 75,000 jobs. The health of the Great Lakes fishery is under constant threat from habitat loss, pollution and non-native nuisance species, including the sea lamprey. Based at the Sea Lamprey Control Centre in Sault Ste. Marie, Ontario, Fisheries and Oceans Canada (DFO) plays a critical role in minimizing sea lamprey population levels in the Great Lakes.

(Photo credit: Great Lakes Fishery Commission)

Sea lampreys are primitive fish native to the Atlantic Ocean. Sea lampreys were first observed in the Great Lakes in the 1830's. It is widely believed that they entered and spread throughout the Great Lakes via man-made shipping canals. In the Great Lakes, they have no commercial value and other fish do not normally feed on them.

Sea lampreys are parasitic pests. They attach to fish with their suction cup mouth and teeth, and use their tongue to rasp through a fish's scales and skin so they can feed on its blood and body fluids. A single sea lamprey will destroy up to 18 kilograms of fish during its adult lifetime. Sea lampreys are so destructive that, under some conditions, only one out of every seven fish attacked will survive.

In the 1940's and 50's, sea lamprey populations exploded in the upper Great Lakes as there were no effective control methods. This contributed significantly to the collapse of valuable fish populations, such as lake trout and whitefish, which were the economic mainstay of a vibrant Great Lakes fishery.

To facilitate coordinated, binational fisheries management, the governments of Canada and the United States signed the 1954 Convention on Great Lakes Fisheries, which created the Great Lakes Fishery Commission. This bilateral agreement affirms the need for the two nations to collaborate on the protection and perpetuation of the Great Lakes fisheries resources. In Canada, DFO is the primary agent of the Great Lakes Fishery Commission. In the United States, the U.S. Fish and Wildlife Service is the primary agent of the Commission, with significant support from the U.S. Geological Survey and the U.S. Department of State. Scientists and fisheries managers from both countries meet regularly to discuss new developments in research and up-to-date stock estimates.

Understanding the sea lamprey's life cycle helps scientists develop effective control measures. Adult sea lampreys swim upstream to spawn and then die. Fertilized eggs hatch into small worm-like larvae that burrow into stream bottoms and feed on debris and algae for an average of three to six years before they transform into the parasitic adult. The adults migrate into the Great Lakes where they spend 12 to 20 months feeding on fish. The complete life cycle, from egg to adult, takes an average of five to eight years to complete.

Fisheries and Oceans Canada undertakes sea lamprey control on Canadian streams and rivers in the Great Lakes. In cooperation with the U.S. Fish and Wildlife Service, extensive work is also carried out in U.S. waterways leading to the Great Lakes. Currently, the primary method to control sea lampreys is the application of selective lampricides that kill sea lamprey larvae in their nursery streams with little or no impact on other fish or wildlife. Despite the success of lampricide treatments, it is a costly control method and DFO would prefer to reduce its use by relying more heavily on alternate control methods.

The sterile-male-release technique aims to reduce the success of sea lamprey spawning. Each year, male sea lampreys are collected and sterilized during their spawning runs. When they are released back into streams, the sterile males compete with normal males for spawning females, resulting in reduced fertilization of eggs. Since they are caught during spawning runs rather than during the parasitic phase, sterilized males do not prey on fish when they are released back into the spawning streams.

Barriers have been constructed to block the upstream migration of spawning sea lampreys, while allowing other fish to pass with minimal disruption. Various types of barriers have eliminated lampricide treatment on some streams and reduced the area of the stream requiring lampricide treatment on others.



A comprehensive assessment program allows biologists to better understand the ecology and population dynamics of the sea lamprey at all stages of its life cycle. The information gathered allows DFO to track long-term trends in lamprey populations, to monitor the effectiveness of the lampricide control program and to identify alternative ways of controlling sea lamprey populations. The ultimate purpose of collecting and analyzing the data is to develop and implement the most efficient and effective control program at the lowest cost and with the least possible negative effect on the environment.

The assessment program monitors abundance of larval sea lampreys in Great Lakes streams to determine where lampricide treatments should occur, when treatments are required and how effective past treatments were. Measuring the size and age of the larvae collected provides biologists with information about how well the populations grow and survive in each stream. New technologies, such as geographic positioning systems (GPS) and geographic information systems (GIS), are being used to map the exact distribution of larvae and to target control efforts.

Through a cooperative program, charter boats and commercial fishers provide government agencies with data on the occurrence of parasitic-phase sea lampreys in the open waters of the Great Lakes. Fisheries and Oceans Canada uses these data to predict the extent of damage caused to fish communities by sea lamprey parasitism.

(Photo credit: U.S Geological Survey)

Biologists monitor adult sea lamprey spawning migrations in spring and early summer to estimate the number of spawning sea lampreys in selected Great Lakes streams. Sea lamprey traps, often used in association with barriers, are fished to catch adult lampreys as they travel upstream to spawn. These assessment data provide an accurate measure of lakewide sea lamprey populations and are used to assess the overall success of the sea lamprey control program. Male lampreys caught in the traps are used for the sterile-male-release technique; most females are used for continuing research.

Sea lamprey control in the Great Lakes has been tremendously successful. Ongoing control efforts have resulted in a 90 percent reduction of sea lamprey populations in most areas, creating improved conditions for fish survival and spawning. Although it is impossible to completely rid the Great Lakes of sea lampreys, through continued cooperation and support, their populations can be kept at levels that lessen their impact to the fishery.

For more information on sea lamprey control in the Great Lakes, contact the Sea Lamprey Control Centre at 1 Canal Drive, Sault Ste. Marie, ON, P6A 6W4; by phone at (705) 941-3000; or visit our regional website.