Petromyzon marinus Linnaeus, 1758

Common Name: Sea Lamprey

Synonyms and Other Names:

Copyright Info

Identification: The sea lamprey is a jawless cartilaginous fish that is somewhat eel-like in appearance. This species has two closely-spaced but separate dorsal fins, no paired fins, seven gill openings on each side of its head, and a large round sucker-like mouth ringed with small, sharp teeth that act as a rasp along with a file-like tongue. Juvenile parasitic sea lamprey are 6 to 24 inches in length with smooth, scaleless skin that is mottled gray-blue to black, darker on top and fading to a lighter colored belly. Adult sea lamprey are 14 to 24 inches in length and exhibit mottled dark brown/black pigmentation. Several keys to the ammocetes of lampreys found in the Great Lakes region are available from Becker (1983); Page and Burr (1991); Jenkins and Burkhead (1994); and Vladykov and Kott (1980). For further identification resources, see Page and Burr 1991; Jenkins and Burkhead 1994.

Size: 120 cm anadromous; 64 cm landlocked

Native Range: Generally marine but ascends freshwater rivers to spawn. Atlantic Coast from the Gulf of St. Lawrence to the St. Johns River, Florida; Atlantic Coast of Europe and Mediterranean Sea (Page and Burr 2011).

Great Lakes Nonindigenous Occurrences: Lamprey was first discovered in Lake Ontario in 1835, Lake Erie in 1921, Lake Michigan in 1936, Lake Huron in 1937, and Lake Superior in 1946 (Applegate 1950; Lawrie 1970; Smith 1979; Smith and Tibbles 1980; Smith 1985). Its distribution in all five Great Lakes and selected tributaries includes the states Illinois (Smith 1979; Emery 1985); Indiana (Gerking 1955; Emery 1985); Michigan (Applegate 1950; Smith 1979; Cudmore-Vokey and Crossman 2000); Minnesota (Eddy and Underhill 1974; Phillips et al. 1982; Emery 1985); New York (Smith 1985); Ohio (Trautman 1981; Emery 1985; USFWS 2005); Pennsylvania (Emery 1985); and Wisconsin (Becker 1983; Emery 1985). This species is also present in Apostle Islands National Lakeshore, Wisconsin; Indiana Dunes National Lakeshore, Indiana; Isle Royale National Park, Pictured Rocks National Lakeshore, and Sleeping Bear Dunes National Lakeshore, Michigan (Tilmant 1999); and Walnut Creek, Pennsylvania (Phillips et al. 2003).

This species was formerly believed to be introduced into the Finger Lakes and Lake Champlain in  New York and Vermont (Lee et al. 1980 et seq.). Recent genetic evidence shows it is native to these areas (Bryan et al. 2005), but this is refuted by Eshenroder (2014).

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Petromyzon marinus are found here.

Full list of USGS occurrences

State/ProvinceFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
IL193619981Lake Michigan
IN194920143Lake Michigan; Little Calumet-Galien; St. Joseph
MI1934202134Au Gres-Rifle; Bad-Montreal; Betsie-Platte; Betsy-Chocolay; Black-Macatawa; Black-Presque Isle; Boardman-Charlevoix; Carp-Pine; Dead-Kelsey; Fishdam-Sturgeon; Kalamazoo; Keweenaw Peninsula; Lake Huron; Lake Michigan; Lake St. Clair; Lake Superior; Little Calumet-Galien; Lone Lake-Ocqueoc; Lower Grand; Manistee; Manistique River; Maple; Millecoquins Lake-Brevoort River; Muskegon; Ontonagon; Pere Marquette-White; St. Clair; St. Joseph; St. Marys; Sturgeon; Tacoosh-Whitefish; Tahquamenon; Thunder Bay; Waiska
MN194620012Beartrap-Nemadji; Lake Superior
NY1863201418Ausable River; Black; Buffalo-Eighteenmile; Cattaraugus; Grass; Irondequoit-Ninemile; Lake Champlain; Lake Erie; Lake Ontario; Mettawee River; Niagara River; Oneida; Raisin River-St. Lawrence River; Raquette; Salmon; Salmon-Sandy; Seneca; St. Regis
OH192720104Ashtabula-Chagrin; Chautauqua-Conneaut; Grand; Lake Erie
PA198520002Chautauqua-Conneaut; Lake Erie
WI195820148Bad-Montreal; Beartrap-Nemadji; Door-Kewaunee; Lake Michigan; Lake Superior; Lower Fox; Manitowoc-Sheboygan; Oconto

Table last updated 5/27/2024

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Ecology: Sea lampreys are an ancient species that have retained their primitive ancestral characteristics from millions of years ago. This species is diadromous, spending the early stages of their life in streams and rivers and the middle stage of their life in the ocean or, in the case of the Great Lakes populations, in a large freshwater lake. They then return as breeding adults to spawn in the freshwater streams and rivers, and die shortly after spawning. The blind, worm-like larval lamprey, known as ammocoetes, can grow up to 5 inches long. They hatch from eggs in gravel nests in tributaries and drift downstream with the current. When they locate suitable habitat -- usually silt or sand stream bottoms and banks in slower-moving stretches of water -- they burrow in and take up residence, filter-feeding on algae, detritus and microscopic organisms and materials (Lake Champlain Sea Lamprey Control, 2020). Lampreys may stay in this larval form from 3-17 years. Nutrition levels in larval habitat may influence sex assignment in this fish, with larvae that consume more nutrients being more likely to develop as female (Bircenau 2017).

As they mature, the larval lampreys grow eyes and a sucker-like mouth. Once the ammocoetes’ transformation is complete, the sea lamprey leaves its burrow and moves downstream to open water. The sea lamprey is then ready to begin the next stage in its life as a parasite of fish: the juvenile sea lampreys move into deeper water and begin to seek host fish on which to feed over the course of 12-20 months. In the spring, adult  sea lamprey migrate up tributaries to sexually mature and spawn. Spawning streams are located by following pheromones released by ammocoetes living in those waters. Once they reach a suitable spawning site, usually rocky riffle areas that are shallow with fairly swift current, male and female sea lampreys build a nest, often called a redd. The female lays tens of thousands of eggs and the male fertilizes them, after which both adults die. Weeks later, the eggs hatch and the life cycle of the sea lamprey begins again (Lake Champlain Sea Lamprey Control, 2020).

Means of Introduction: Controversy exists as to whether the sea lamprey is native to Lake Ontario. Several believe it is native (e.g., Lawrie 1970; Smith 1985), suggesting that sea lamprey found in Lake Ontario and its tributaries, the Finger Lakes, and Lake Champlain represent relict populations from the last Pleistocene glaciation. Those contending that it is not native believe that this species, unknown in Lake Ontario prior to the 1830s, had most likely entered the inland lake from Atlantic coastal drainages via the artificially created Erie Canal (e.g., Emery 1985). 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 sea lamprey was previously prevented from spreading into Lake Erie and the rest of the Great Lakes basin by Niagara Falls. The Welland Canal, opened in 1829, bypassed Niagara Falls providing a route to Lake Erie from Lake Ontario (Aron and Smith 1971). From the opening of the Welland Canal (1829) to the discovery of sea lamprey in Lake Erie (1921), there is almost a century difference. Yet sea lamprey was found throughout the Great Lakes to the farthest Great Lake, Lake Superior, within twenty-five years of their arrival to Lake Erie. The improvements done to the Welland Canal in 1919 are likely the change that facilitated sea lamprey immigration into Lake Erie (1921) (Great Lakes Fishery Commission, 2019).

Status: Widespread populations overwinter and reproduce in tributaries throughout the Great Lakes basin. This species was common in Lakes Michigan and Huron by the 1930s and in eastern Lake Superior by the 1940s; abundance was initially low in Lake Ontario (Applegate 1950; Emery 1985) and Lake Erie (Smith 1985), but has fluctuated ever since. As an example: abundance in Lake Erie was historically low, increased substantially after 2004, and is currently dropping -- estimated to be around 20,000 individuals (Status of Sea Lamprey, 2019).

Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...


Petromyzon marinus has a high environmental impact in the Great Lakes.

Attack and parasitic feeding on other fishes by adult sea lamprey often result in death of the prey, either directly from the loss of fluids and tissues or indirectly from secondary infection of the wound (Phillips et al. 1982). Of the fish that survived attacks by sea lamprey, 85% of various species had been attacked up to five times (Scott and Crossman 1973). The species' introduction to the Great Lakes and its later abundance, combined with water pollution and overfishing, resulted in the decline of several large native species, including several ciscoes (Coregonus spp.), lake trout (Salvelinus namaycush), and walleye (Sander vitreus), among others. Sea lamprey is also known to attack white sucker (Catostomus commersoni), longnose sucker (Catostomus catostomus), redhorses (Moxostoma spp.), yellow perch (Perca flavescens), rainbow trout (Oncorhynchus mykiss), burbot (Lota lota), channel catfish (Ictalurus punctatus), northern pike (Esox lucius), common carp (Cyprinus carpio), and Pacific salmonids (Nepszy 1988, Scott and Crossman 1973, Swink 2003). During the late 1940s, the alewife (Alosa pseudoharengus) invaded the Great Lakes from the Atlantic Ocean. Because the sea lamprey had greatly reduced the population of large predators, alewife populations exploded and were followed by tremendous die-offs, resulting in additional changes to fish species composition in the lakes (Smith and Tibbles 1980). Indirect impacts may be more difficult to attribute to sea lamprey, but changes in fish species composition spurred by sea lamprey introduction (especially the proliferation of alewife) have likely had far-reaching indirect effects on other biotic and abiotic components of the Great Lakes ecosystems, including plankton communities (J. Gunderson, MN Sea Grant, pers. comm. 2010).

Although the number of sea lamprey in the Great Lakes has been reduced, this species still wounds or kills substantial numbers of lake trout in some areas and, thus, is impeding the rebuilding of established populations (Adair and Young 2007, Madenjian et al. 2008, Schneider et al. 1996 and references therein). For example, a recent study in northern Lake Michigan found that sea lamprey wounding rates in this region have increased from 1990-1999 to 2000-2008 despite continued management of sea lamprey populations (Madenjian and Desorcie 2010). In Lake Huron, the probability of lake trout and lake whitefish (Coregonus clupeaformis) wounding also increased from 2000–2009 at three of five monitored sites, despite large scale treatment efforts in St. Marys River (McLeod et al. 2011). Other native species continue to be affected as well. A recent survey of lake sturgeon (Acipenser fulvescens) in the Green Bay Basin of Lake Michigan in 2003 found sea lamprey wounds on 34% of sturgeon captured from open water and 53% of sturgeon captured from spawning runs (Elliot and Gunderman 2008); research suggests that such wounds may lead to mortality in a significant percentage of small sturgeon (< 650 mm fork length) (Patrick et al. 2009). In Lake Ontario, sea lamprey exhibited a strong preference for lake trout when host abundance was ≥ 32% lake trout, but sea lamprey preference switched to Chinook salmon when host abundance was ≤ 13% lake trout (Adams and Jones 2020).

In combination with other factors (e.g., overfishing and hybridization with more common cisco species), sea lamprey predation led to the extinction of the deepwater cisco (Coregonus johannae) and shortnose cisco (C. reighardi), and the dramatic decline of the blackfin cisco (C. nigripinnis), all endemic to the Great Lakes (Jelks et al. 2008, World Conservation Monitoring Centre 1996).

If control of sea lamprey ceased, it is believed that this parasite would once again have an extreme negative effect on the ecosystem similar to that of the mid 20th century depletion of top predators (Jones 2007) and, in turn, a negative economic impact on the eight US states, provinces of Ontario and Québec, and multiple tribal and First Nations around the multinational Great Lakes Basin -- especially those directly connected to the Great Lakes fishery to make a living, for subsistence, for recreation, and spiritually (Brant 2019).

Petromyzon marinus has a high socio-economic impact in the Great Lakes.

The introduction of sea lamprey caused a collapse in the commercial fisheries during the 1940s and 1950s in many parts of the Great Lakes, particularly in lakes Huron and Michigan, and in eastern Lake Superior (e.g., Becker 1983, Christie 1974, Courtenay 1993, Emery 1985, Lawrie 1970, Scott and Crossman 1973, Smith and Tibbles 1980). Lake trout (Salvelinus namaycush) catch in Lake Huron fell from 3.4 million pounds in 1937 to virtual failure in 1947. In Lake Michigan, total catch fell from 5.5 million pounds in 1946 to 402 pounds in 1953. In Lake Superior, total catch dropped from an average of 4.5 million pounds to 368 thousand pounds in 1961 (Scott and Crossman 1973). Furthermore, the cascading impact of sea lamprey introduction, beginning with the decline of native commercially fished species and resulting in the explosion of introduced forage fishes and Pacific salmonid stocking, was the major force resulting in the transition of the Great Lakes fisheries from being primarily commercial-based to primarily recreation-based (J. Gunderson, MN Sea Grant, pers. comm. 2010). However, sea lamprey also took a toll on the introduced salmons in the Great Lakes, much to the dismay of anglers and state fish agencies (Scott and Crossman 1973). Following the collapse of fish stocks in the mid 20th century, sea lamprey was reportedly the best-publicized cause of the problem (Francis et al. 1979).

Between 1958 and 1979, an estimated $54.5 million was spent on sea lamprey control in the Great Lakes (Fetterolf 1980). This effort continues today, with an estimated $14 million/year spent on control, monitoring, and research (Jones 2007). Overall, current sea lamprey abundance in the Great Lakes is reportedly less than 10% of the peak abundance of the mid-20th century (Siefkes 2009). However, control efforts evidently fell to insufficient levels in Lake Erie, which resulted in a return of pre-control sea lamprey abundance in 2005; this was accompanied by a noticeable increase in lake trout wounding in Lake Erie, and control efforts have subsequently increased (Siefkes 2009).

It is commonly stated that sea lamprey control helps protect an estimated $7 billion/year fishery and over 75,000 jobs (GLFC, 2019). It has been estimated that if control efforts of sea lamprey were to cease, losses exceeding $500 million/year could be incurred in the great Lakes (OTA 1993).

There is little or no evidence to support that Petromyzon marinus has significant beneficial effects in the Great Lakes.

Although sea lamprey is consumed as a delicacy in some parts of the world, muscle tissue samples of Great Lakes sea lamprey revealed levels of toxaphene, PCBs, and mercury which exceeded health advisory limits for human consumption (MacEachen et al. 2000).


Regulations (pertaining to the Great Lakes region)

In Minnesota, sea lamprey is a prohibited species and therefore it is unlawful to possess, import, purchase, transport, or introduce this species except under a permit for disposal, control, research, or education (MDNR 2012).  In Ohio it is illegal to possess, import or sell live lamprey (OAC Chapter 1501:31-19). In New York, the sale, import, purchase, transport or introduction of sea lamprey is prohibited under NYS Part 575 and (NY ECL 11-1315, 6a) prohibits the use of lamprey larvae as bait. Restricted in Wisconsin under Wis. Admin. Code § NR 40. The import, possession, transport, and release of live sea lamprey in Manitoba is prohibited under articles 6 to 10 of the Canadian Fisheries Act SOR/2015-121

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.


Since the bi-national Sea Lamprey Control program (managed by the Great Lakes Fishery Commission) was started in the 1950s, populations have been reduced by 90%, and fish survival and spawning have increased (Page and Laird 1993, Smith 1985). It is impossible to completely eradicate sea lamprey from the Great Lakes; however, continuous control efforts can minimize their impacts on the ecosystem and fisheries (FOC 2009).

An effective bio-control of sea lamprey is the implementation of the sterile-male-release program. Male sea lamprey are captured during spawning runs, sterilized using bisazir, and released to compete with  fertile males for mating; thus reducing egg fertilization. Released males are sterilized past their parasitic phase and do not return to the lake. (FOC 2009, GLFHC 2000a). It is important to note that the sterile male release technique (field-tested from 1991-1995 and then used for 15 years in the St. Marys River) is not currently being deployed, but is still considered a viable control option when populations are at low densities in certain streams (Siefkes 2017). A potential alternative to bisazir is a lamprey GnRH antagonist. However, further research of this alternative sterilizing agent is necessary (Bergstadt and Twohey 2007).

Barriers and traps have been effective controls of sea lamprey since the 1950s. Barrier options include mechanical weirs, electrical barriers, low-head barriers, adjustable crest barriers, and velocity barriers (GLFHC 2000, Scott and Crossman 1973, Smith and Tibbles 1980). Traps are often used in association with barriers to capture sea lamprey while allowing desired species to continue upstream (FOC 2009, GLFHC 2000b, Sherburne and Reinhardt 2016, Zielinski and Freiburger 2020). Barriers have reduced the need for lampricide applications (GLFC 2012). Once captured, sea lamprey are killed, used for research, or used in sterile-male-release programs (Zielenski et al 2019).

Beginning in the late 1950s, sea lampreys began to be successfully controlled by use of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM), a chemical agent that kills larval lampreys in their stream habitats (Smith and Tibbles 1980). The lampricide has reduced the population by over 90% of the 1961 peak (Scott and Crossman 1973). However, continued use of TFM is required to keep populations under control (Becker 1983, Scott and Crossman 1973). TFM is sometimes harmful to other fish (e.g., walleye) as well as to the larvae of nonparasitic native lamprey species (Becker 1983).  Bayluscide (granular niclosamide) treatments in deltas are also a widely used and effective control of sea lamprey larvae (NYSDEC 2012). Recent research has investigated the use of alarm cues, such as conspecific alarm pheromones and predator cues (including human saliva), to drive lampreys into traps and away from areas such as fish ladders (Byford 2016, Imre et al 2016, Johnson et al 2020, Rocco et al 2016).


A recent study showed that CO2 applied to water results in behavioral agitation for both adult and transformer sea lampreys, and will eventually result in equilibrium loss. More importantly, both adult and transformer sea lampreys will avoid water with CO2 concentrations of 85 and 160 mg/L, respectively (Dennis et al. 2016).

To increase the efficacy of lampricide treatments, streams and rivers are frequently assessed for larvae density to help determine the application sites (FOC 2009, GLFC 2012).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

For more information on Sea lamprey management in the Great Lakes region, please visit the Great Lakes Fishery Commission.


Remarks: Early methods to control this species included mechanical weirs and electrical barriers (Scott and Crossman 1973; Smith and Tibbles 1980). Beginning in the late 1950s, sea lampreys began to be successfully controlled by use of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM), a chemical agent that kills larval lampreys in their stream habitats (Smith and Tibbles 1980). The lampricide has reduced the population by over 90% of the 1961 peak (Scott and Crossman 1973). As a result, commercial fisheries reportedly have shown some recovery (Smith 1985; Page and Laird 1993) and the sea lamprey's impact on native fishes has been reduced (Page and Laird 1993). However, continued use of TFM is apparently required to keep sea lamprey populations under control (Scott and Crossman 1973; Becker 1983). TFM is sometimes harmful to other fish (e.g., walleye) (Becker 1983), as well as to the larvae of nonparasitic lamprey species.

Results of an international symposium on the sea lamprey were published in the Canadian Journal of Fisheries and Aquatic Sciences in 1980. The demise of lake trout led to development of the splake, a hybrid between lake trout and brook trout. It was hoped that the hybrid would better avoid lampreys and mature faster, hence spawn at least once before becoming parasitized (Scott and Crossman 1973).

As of 1991, it was estimated that the U.S. and Canada were spending $8 million per year on lamprey control and another $12 million per year on lake trout restoration (Newman 1991). The sea lamprey is one of the most important invasive species in the Great Lakes. Although perhaps the first invader to the Great Lakes, having migrated out of Lake Ontario in the 1830s and into the other Great Lakes through the Welland Canal, it was not until the 1950s that impacts on fisheries were so great as to prompt serious management efforts. It was then that the Great Lakes Fisheries Investigations, the progenitor of the present day USGS Great Lakes Science Center in Ann Arbor was charged with discovering a lampricide targeting the larval stage. The Great Lakes Fisheries Commission was also formed at this time, an organization primarily concerned with sea lamprey management. Successful application of lampricide ensued, reducing the lamprey population dramatically. However, decimation by sea lamprey of predatory fish representing the top trophic levels of the Great Lakes food web had already caused another invader, the alewife, to proliferate. The alewife population exploded, causing fish kills that washed up on shore. Thus the sea lamprey created the need to control alewife. Due also tothe decimation of native predatory fish populations by sea lamprey, a Great Lakes sport fishery was created with the stocking of Chinook salmon in the 1960s.

There is currently a debate as to whether the sea lamprey are indigenous to Lake Ontario.  Randy L. Eshenroder summarized the argument for and against this belief (Eshenroder, 2009, 2014).  Analysis of mitochondrial DNA by Waldman et al. (2004, 2006) seem to show that sea lamprey is native to Lake Ontario and Lake Champlain. This hypothesis is contrary to the commonly held belief by Smith (1971) that the sea lamprey entered the lake by hitchhiking under boats after the construction of the Erie Canal in the 1820's. Smith proposes that the sea lampreys entered the Hudson River, went through the Erie Canal, entered the Oneida Lake, then entered the finger lakes and Lake Ontario.  Waldman disagrees with Smith and maintains that the reason the sea lamprey was not seen before the canal was built is that it was rare due to cold water and lack of suitable habitat. He suggests that the population boomed after the canal was built because the environmental degradation associated with human settlement created a more hospitable habitat for the sea lamprey. There is much debate about the many haplotype differences seen between the Atlantic and Lake Ontario populations.  Waldman believes that the presence of unique haplotypes in the lake (haplotypes B amd P) could not have developed in the short time between the opening of the Erie Canal and present time supporting the argument for nativity.  Others suggest that the unique haplotypes observed could have simply gone extinct in the Atlantic or that more sampling needs to be done to find them. It is also possible that the sea lamprey could have invaded the lake more than once. 

Waldman et al. (2009) wrote a comment in response to the issues raised above by Eshenroder (2009).  Waldman did further genetic analysis on the Atlantic populations of sea lampreys and still maintains that the unique alleles found in Lake Ontario, but absent in the Atlantic coast collections, would have taken between 15,000 and 31,000 year to develop.  He also refutes the hitchhiking under boats hypothesis by citing the difficult path the migrating lampreys would have had to follow including shallow pools, stagnant water, and complicated canal locks.  Waldman also raises the issue that the "hitchhiking" behavior is actually a feeding behavior which is not exhibited in migrating lampreys - such as those entering the Hudson River.  The lampreys would also be migrating in response to pheromonal signals sent from conspecifics upstream.  These pheromones would be lacking in the Hudson River unless there was a population of sea lamprey already in the area.  Eshenroder (2014) argues that P. marinus first entered Lake Ontario during a watershed breach between the Susquehanna River (in which lamprey are native) and Lake Ontario in 1863.  The debate is yet unresolved.

References (click for full reference list)

Author: Fuller, P., L. Nico, E. Maynard, J. Larson, A. Fusaro, and A.K. Bogdanoff

Contributing Agencies:

Revision Date: 12/18/2020

Peer Review Date: 8/25/2015

Citation for this information:
Fuller, P., L. Nico, E. Maynard, J. Larson, A. Fusaro, and A.K. Bogdanoff, 2024, Petromyzon marinus Linnaeus, 1758: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 12/18/2020, Peer Review Date: 8/25/2015, Access Date: 5/27/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.