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).

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

Environmental	Socioeconomic	Beneficial

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

Realized:
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).

Potential:
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.

Realized:
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).

Potential:
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.

Control

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).

Biological
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).

Physical
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).

Chemical
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).

Other

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.