( Petromyzon marinus )
DESCRIPTION: Sea lampreys are members of an ancient family of "jawless fishes." Although lampreys resemble eels, lampreys lack jaws and possess only cartilage. Lampreys have a large sucking disk for a mouth and a well-developed sense of smell. The mouth is filled with sharp teeth that surround a file-like tongue. A lamprey’s body has smooth, scale-less skin and two dorsal fins, but has no lateral line, no vertebrae, no swim bladder, and no paired fins. They are also characterized by a feathery fin from their midsection down and under the tail. Juveniles have white undersides and uniformly colored backs, usually described as blackish blue or silver. The back of the adult lamprey can be a range of colors (olive brown, yellow brown, green, red, or blue); mottled with a darker shade of the same color; or sometimes nearly black if the dark patches are confluent. The underside is typically white or gray. Full grown, sea lampreys average 2 to 2½ feet long, up to a maximum of about 3 feet.
PATHWAYS/HISTORY: Native range of the sea lamprey is generally marine, along the Atlantic Coast from Labrador to the Gulf of Mexico, but it spawns in freshwater rivers. Some believe it is native, suggesting that sea lampreys found in Lake Ontario and its tributaries, the Finger Lakes, and Lake Champlain represent relict populations from the last Pleistocene glaciation. However, others contend that it is not native and that this species, unknown in Lake Ontario prior to the 1830s, had most likely entered the inland lake from Atlantic coastal drainages through the Erie Canal, which opened in 1825. Whether or not the sea lamprey is native to Lake Ontario, this species is not native to the other Great Lakes and tributaries where it is now readily found. The Welland Canal, which joins Lake Ontario to Lake Erie bypassing Niagara Falls, was in place for nearly nine decades before sea lampreys invaded Lake Erie. Upgrades to the Welland Canal in 1919 appear to have provided an improved avenue for lampreys to invade Lake Erie as they were found just two years after improvements were made. Once in Lake Erie, it took just 25 years to spread to the remaining Great Lakes. Now landlocked in the Great Lakes, the sea lamprey has distributed itself into the tributaries of those lakes.
RISKS/IMPACTS: Sea lampreys attach to fish with their sucking disk and sharp teeth, rasp through scales and skin, and feed on the fish’s body fluids. Adult sea lampreys often kill their prey due to their parasitic feeding, either by direct loss of blood and tissue or because of an infection in the open wound caused by the lamprey. During its life as a parasite, each sea lamprey can kill 40 or more pounds of fish. Consequently, sea lampreys have had an enormous negative impact on the Great Lakes fishery. This invasive species was a major cause of the collapse of lake trout, whitefish, and chub populations in the Great Lakes during the 1940s and 1950s. For example, before the sea lamprey’s spread, the United States and Canada harvested about 15 million pounds of lake trout in the upper Great Lakes each year. By the early 1960s, the catch was only about 300,000 pounds. Sea lamprey predation, in combination with other factors, has also led to the extinction of three endemics in the Great Lakes: the longjaw cisco (Coregonus alpenae), the deepwater cisco (C. johannae), and the blackfin cisco (C. nigripinnis). Declining abundance of native fish species allowed the alewife (Alosa pseudoharengus), another invasive species, to explode in population, followed by tremendous die-offs, resulting in additional changes to fish species composition in the lakes.
MANAGEMENT: The application of selective lampricides is the primary method used at this time to kill larval sea lamprey in the nursery streams. While lampricide treatments have been successful at reducing lamprey populations, this method is costly to implement throughout the Great Lakes. The U.S. and Canadian governments together spend up to $15 million per year on lamprey control. Therefore other management strategies are being investigated. Lamprey barriers have been installed in a number of locations to block the migration of spawning sea lampreys while allowing other fish to pass. In some streams, these barriers have been so successful that lampricide treatments are no longer necessary upstream of the barriers. Another technique being used to reduce the sea lamprey population is the sterilization of males. During spawning runs, male sea lampreys are collected, sterilized, and released back into the tributary. These sterile males compete with fertile males for spawning females. This results in reduced fertilization of the eggs. Due to the success of the various tools being used, the sea lamprey population has been reduced by 90% in most areas. While sea lampreys will never be extirpated from the Great Lakes even with the most aggressive combination of management approaches, the lamprey population can be suppressed to low levels which will lessen the impact to the sport fishery.
WHAT YOU CAN DO: Learn about sea lamprey and support your governmental agencies that are collaborating to control this nuisance species. General aquatic nuisance species prevention: Do not release aquarium pets or live food into the environment. Never dump live fish, e.g. baitbuckets, from one body of water into another body of water. Always drain water from your boat, livewell, and bilge before leaving any water access.
PROFILE CREDIT: Susan Pasko, NOAA and Anne Marie Eich, USFWS - IMAGE CREDIT: USGS