Sea Lamprey
Scientific Name: Petromyzon marinus
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Description
The sea lamprey is an eel-shaped parasitic fish that uses its sharp rasping teeth to feed on the bodily fluids of other fish species, such as Atlantic salmon and lake trout. Its body is made up of cartilage, not bone, and it belongs to a relic group of jawless fish called Agnathans. Sea lamprey (Petromyzon marinus) are one of 31 species of lamprey found throughout the world and one of four lamprey species found in the Lake Champlain Basin. The other three lamprey species found in the Lake Champlain Basin include the northern brook lamprey and the American brook lamprey that are both non-parasitic filter feeders similar in size to sea lamprey ammocoetes, as well as the silver lamprey, a small parasitic fish. While the silver lamprey is also parasitic, it does not have the same negative impacts on the fish community as sea lamprey due to both its smaller size and population.
Identification
Juvenile parasitic sea lamprey are 6 to 24 inches in length with smooth, scaleless skin that is mottled grey/blue to black, darker on top and fading to a lighter-colored belly. Adult sea lamprey, preparing to spawn, are 14 to 24 inches in length and exhibit mottled dark brown/black pigmentation. Sea lamprey have two separated fins on their back (dorsal fins) and a suction disk mouth filled with small sharp, rasping teeth and a file-like tongue.
Life History
Life Cycle Stages
Sea lamprey are "diadromous", meaning they migrate between freshwater streams and saltwater during different stages of life. Landlocked sea lamprey that also occur in New York, migrate between streams and large open lake systems like the Great Lakes and Lake Champlain. Details about each stage of the sea lamprey's life cycle is described below.
Ammocoetes Phase
The blind, worm-like larval lamprey, known as ammocoetes [am-mah-seats], 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/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. In the Lake Champlain Basin this stage of the sea lamprey's life cycle usually lasts 3 to 4 years; in other waters lamprey spend up to 10 years in their larval form.
Transformer Phase
During their third or fourth summer, the ammocoetes undergo a dramatic change in both form and function where they look like a smaller version of an adult sea lamprey. They develop eyes and a suction disk mouth, and their kidneys change to allow them to live in saltwater. Once the ammocoetes´ change is complete, the newly transformed sea lamprey, known as a transformer, leaves its burrow and moves downstream towards the ocean or large lake.
Parasitic Juvenile Phase
Once transformed, the juvenile sea lamprey moves into deeper water and seeks host fish on which to feed. The juvenile sea lamprey uses its suction disk mouth that is filled with small sharp, rasping teeth and a file-like tongue to attach to fish, puncture the skin, and drain the fish's bodily fluids. An anticoagulant in their saliva ensures that the blood of the host fish does not clot while the sea lamprey feed. Often the host fish die from loss of blood, or infections resulting from stress. Fish that survive sea lamprey attacks may end up having decreased reproduction.
Adult Phase
After 12 to 20 months, sexually mature adult sea lamprey migrate up freshwater tributaries to spawn in the spring. They locate spawning streams by following pheromones (naturally produced chemical attractants) released by ammocoetes living in those waters. A pair of male and female sea lamprey build a nest, called a redd, in a gravel stream bottom in section of flowing water. The female lays tens of thousands of eggs and the male fertilizes them, then having completed this act, the sea lamprey die. Sea lamprey in Lake Champlain take about six years to complete this life cycle. The eggs lie in the small spaces between the gravel and get oxygen from the flowing water. Weeks later, the eggs hatch and the complex life cycle of the sea lamprey begins again.
Determining if Populations are Native or Invasive in Lake Champlain
Landlocked sea lamprey are either native to New York lakes or has been present as an invasive for a long time. Sea lamprey were first noted in moderate numbers within Lake Champlain in 1929. It is not clear if, or for how long, sea lamprey had existed in Lake Champlain prior to this time.
The lack of mention of lamprey in oral and written history is consistent with the position that sea lamprey may be a non-native invasive species. They are thought to have entered Lake Champlain during the 1800s from the Hudson River Estuary through the Hudson/Champlain Canal or possibly from the St. Lawrence River through the Richelieu River-both the Hudson and the St. Lawrence Rivers empty into the Atlantic Ocean.
However, three recent genetic studies provide evidence to support the position that sea lamprey may be native to Lake Champlain and existed in the lake for around 10,000 years. If native to Lake Champlain, sea lamprey either remained in the lake as a remnant population after the retreat of the "Champlain Sea" or migrated into the lake via the Richelieu River. Overfishing, pollution, and the damming of tributaries led to the loss of native populations of lake trout and salmon in Lake Champlain during the late 1800s. This resulted in a loss of species that perhaps would be better adapted to withstand lamprey impacts. This could be a possible reason why lamprey is having a more detrimental impact on recent populations of lake trout and salmon.
Distribution and Habitat
In New York, sea lamprey are found in the Hudson, Delaware, and lower St. Lawrence River systems. It also occurs on the periphery of Long Island. Inland, it is present in Lake Ontario, Lake Champlain, Oneida Lake, Cayuga Lake, and Seneca Lake.
Habitat preferences vary depending on the sea lamprey's life cycle. As ammocoetes and spawning adults, they prefer slow moving stretches of freshwater streams with silt/sand bottoms, whereas the transformer and juvenile parasitic stage prefer large open water habitats, like the ocean or freshwater lakes.
Impact
Sea lamprey attach to a host fish, rasp and puncture its skin, and drain its body fluids, often killing the host fish. Their preferred hosts are salmon and lake trout, however they also feed on other fish species, including lake whitefish, walleye, northern pike, burbot, and lake sturgeon. The lake sturgeon is listed as a threatened species in New York and an endangered species in Vermont and se lamprey are likely affecting their survival.
Studies on the Great Lakes show a 40 to 60 percent mortality rate for fish attacked by sea lamprey. Other studies have found that a single sea lamprey can kill 40 or more pounds of fish during its life. Even when fish survive the attacks, the fish populations will decline as the fish expend more energy on healing than on producing eggs and mating.
During periods when sea lamprey are abundant in Lake Champlain, anglers often catch salmon and trout with wounds or lamprey attached. Frequently, these fish have multiple wounds, multiple scars and/or multiple lamprey attached to them. These high wounding rates indicate that sea lamprey are having a significant impact on the lake trout and salmon populations. Angler catches of lake trout and salmon in Lake Champlain were found to be just a fraction of catches in similar lakes, despite intensive stocking efforts by fishery agencies. Sea lamprey were preventing the restoration of these native fish species to Lake Champlain.
Poor fishing has caused many anglers to seek fishing opportunities elsewhere. It has been estimated that 29.4 million dollars in economic benefits to businesses and residents of the Lake Champlain Basin are lost due to the impacts of sea lamprey.
Status
Habitat degradation, water pollution, and dams on almost every tributary in the Lake Champlain basin during the last two centuries may have kept lamprey numbers low. However, recent improvements in habitat and water quality, along with the annual stocking of their preferred hosts, may be providing lamprey with a new opportunity to prosper. Continuation of current sea lamprey control efforts, ongoing innovations in treatment strategies, and new barriers have resulted in a reduction in lamprey numbers and provided improvements in the trout and salmon fishery of Lake Champlain as well as the entire aquatic community.
Management
Lake Champlain Fish & Wildlife Management Cooperative Sea Lamprey Control Project
In 1973, the DEC, the Vermont Department of Fish and Wildlife (VTFW), and the United States Fish and Wildlife Service (USFWS) formed the Lake Champlain Fish and Wildlife Management Cooperative to establish a lake-wide salmon and lake trout restoration program. By 1985, it became clear that the goal of restoring the salmon and lake trout fishery were unattainable due to the impacts of sea lamprey. The Cooperative began an integrated control program to reduce the sea lamprey population in Lake Champlain to an acceptable level.
The sea lamprey control program is not attempting to eliminate the sea lamprey from Lake Champlain, but rather to reduce the impacts of sea lamprey on the lake's fishery and restore balance to the ecosystem. The current long-term sea lamprey control program uses chemical treatments, trapping, physical barriers, and other control methods.
Strategic Plan for Lake Champlain Fisheries
Details on the current management of sea lamprey can be found in the Cooperative's Strategic Plan for Lake Champlain Fisheries (2020) (PDF). The Strategic Plan provides a framework for implementing the Cooperative's coordinated fisheries management programs, outlines fish community goals and objectives, and describes the roles of each agency responsible for managing the fisheries within Lake Champlain.
Sea Lamprey Control Methods
Barriers
Barriers prevent sea lamprey from reaching spawning areas in the tributaries. Sea lampreys are prevented from spawning or are forced to lay their eggs in habitat less suitable or unsuitable for hatching of eggs and growth of larval sea lamprey. Where conditions are favorable, barriers are an effective means of sea lamprey control, cutting off large amounts of habitat suitable for spawning from the adult sea lamprey.
A variety of barrier types are used, with different means of preventing adult sea lamprey from proceeding upstream. Vertical-drop barriers are the most widely used. Water velocity barriers and electronic barriers are under development. In many streams, provisions are made to accommodate migratory fish passage while preventing upstream passage of sea lamprey adults.
Temporary or removable barriers, which include an integrated trap, are installed in the spring, prior to adult lamprey retuning to spawn, and removed from the stream after the spawning season. It allows the passage of non-target species upstream of the barrier while trapping lamprey below the barrier. The trapped lamprey are removed and euthanized. Removing migrating adult sea lamprey below the barrier prevents them from moving to other streams and spawning in them.
Potential barrier sites continue to be revisited to determine their suitability for a sea lamprey barrier as design technologies, site access, and landowner cooperation may change over time.
Traps
Traps are used to capture adult sea lamprey before they can spawn. Adult sea lamprey are trapped in tributaries during upstream spawning migration. Traps are strategically placed where migrating adults concentrate in the stream channel, usually along the face of a weir, dam, or waterfall. Portable traps are rigid box traps with a cone-shaped (fyke) net entrance. Sometimes wing extensions are used to block the channel and/or steer the sea lamprey to the trap. Sea lamprey that enter the trap are unable to find an exit and are removed at regular intervals.
Sea lamprey traps are particularly useful in conjunction with sea lamprey barrier structures and in constricted stream channels where adults concentrate. Trapping at barriers limits the adult sea lamprey from moving to alternative streams where they may successfully spawn. Trapping is labor-intensive, and traps must be maintained for the duration of the spawning run.
Trapping is used as a supplemental control method except where the physical stream conditions make trapping an effective primary technique or where other control techniques are not feasible. Upstream escape of a small number of adults could repopulate available nursery habitat resulting in little or no reduction of the sea lamprey produced in the stream. The smallest sea lamprey spawning streams with small numbers of spawning sea lamprey and high trap efficiency provide the most potential for control by adult trapping alone.
Traps are operated during the spring spawning season, usually from shortly after ice out to late June.
Lampricides and Treatments
The most significant and effective form of control has been the treatment of streams and deltas with lampricides-chemical compound 3-trifluoromethyl-4-nitrophenol (TFM) in tributaries and Bayluscide on deltas. The lampricides target the larval sea lamprey, killing them before they can transform into their parasitic adult form. Since the larval sea lamprey typically reside in streams or deltas for 4 years, lampricide treatments need only occur every 4 years in a specific water.
TFW Treatment Process (Applied in Streams)
A great deal of effort is undertaken before, during, and after a TFM treatment to ensure it is effective, that there are no effects on human health, and there is minimal impact to the environment. During the treatment of a stream (or river) TFM is applied in closely monitored and precisely measured amounts to target larval sea lamprey. The amount of TFM applied is based on the chemical and physical characteristics of the stream-such as flows, pH, alkalinity, etc.-at the time of the treatment so as to maintain a steady but very low concentration of TFM in the stream. The application of the TFM is monitored constantly throughout the treatment period, and adjusted as needed based on the chemical and physical characteristics of the water and the concentrations of TFM in the water which are also monitored.
Activities Before Treatment
- Assess through sampling the presence and abundance of larval sea lamprey to determine whether a treatment is warranted. (1 year before treatment)
- Notify residents and landowners along the stream to be treated about the treatment and ask if they need alternate water supplies for humans or livestock. (4-6 months before treatment)
- Notify landowners along the stream of impending treatment. (2 weeks before treatment)
- Provide fencing to keep livestock out of treatment waters and provide alternate water source if needed. (1 week before treatment)
- Activate toll free "treatment hotline" that provides updated treatment schedules and water use advisory information. This number is included in all published notifications, press releases, web pages, and radio broadcasts. (1 week before treatment)
- Walk length of stream to be sure there are no dams or other obstructions that could compromise the effectiveness of the treatment (Few days before treatment)
- Publish treatment schedule in area newspapers, DEC website, and other media (Few days before treatment)
- Begin regular testing of water chemistry and monitoring of stream flows at a variety of times and locations to obtain information to determine the amount of TFM to be applied. (Few days before treatment)
- Directly notify households that use water from the stream and provide them with bottled water. (1 day before treatment)
- Post water-use advisories at access sites to the stream and lake shore near the mouth of stream. (1 day before treatment)
- Broadcast water-use advisories on area radio stations. (1 day before treatment)
- Perform a toxicity test to refine an estimate of the treatment concentration required to conduct a safe but effective treatment. (1 day before treatment)
Activities During Treatment
- Conduct chemical concentration monitoring every half hour to hour, and adjust application rates accordingly. (Water samples are taken at a variety of locations as the treatment progresses, and the samples are brought to a mobile lab and analyzed on-site.)
- Follow chemical plume as it moves downstream to verify all lamprey habitat is being effectively treated, check for unexpected impacts on non-target species, and adjust application rates accordingly. (It should be noted that unexpected impacts on non-target species have never occurred during a treatment on Lake Champlain)
Activities After Treatment
- Assess mortality of larval sea lamprey and non-target species. (1 day after treatment)
- Monitor concentrations of TFM in streams until such time that water advisories along the stream can be lifted. Notify area radio stations and update information on treatment hotline when water advisory is lifted. Notify stream water users directly.
- Monitor lake water concentrations of dilute lampricides by taking samples from multiple locations and depths in the lake shore water advisory zone. Notify area radio stations and update information on treatment hotline when water advisory is lifted. Notify lake shore water users directly.
Decades of laboratory tests and experience from thousands of stream treatments have demonstrated that at the dose needed to control sea lampreys, TFM is nontoxic or has minimal effects on aquatic plants, other fish, and wildlife. Studies have also shown TFM to be nontoxic to humans and other mammals. TFM does not accumulate in the tissue of aquatic organisms and it breaks down in a matter of days. In the Great Lakes, long term studies have shown no traces of TFM in fish, even in cases where several treatments had been made in tributaries to the lakes in which the fish were caught.
Niclosamide Treatment with TFMA 1% solution of Niclosamide, when added to TFM, reduces the volume of TFM needed by about half. The same lethal effects to lamprey can be achieved using half of the amount of TFM. Not only does this result in substantial savings in the costs of treatments but it also means a reduction of the amount of pesticide placed into the waters of the Lake Champlain Watershed. In 2011, the Boquet River in Willsboro, NY was successfully treated with a TFM-Niclosamide combination. This was the first combination treatment done in the Lake Champlain Basin. Since then, a number of tributaries have been treated using the combination of the two lampricides.
Bayluscide Treatment Process (Applied in Deltas)
Bayluscide is a granular material that is applied through a mechanical spreader mounted on a platform on the back of a boat. The boat moves back and forth on the waters above the delta using a grid of buoys to ensure that the Bayluscide is applied evenly across all areas to be treated. Bayluscide is applied at a certain number of pounds per acre of area treated.
Just as with the TFM stream treatments, precautions are undertaken before, during, and after the delta treatments to ensure it is effective, prevents impacts on human health, and minimizes environmental impacts.
Lampricide Treatment Schedule
USFWS Current Season Treatment and Advisory Schedule
Integrated Sea Lamprey Control
Scientists and fish managers have considered, and continue to consider, other methods to reduce sea lamprey impacts. These include improvements in survey methods, the use of barriers, and the stocking of lamprey resistant strains of fish.
The Cooperative will continue to use an integrated approach to control sea lamprey because no single technique can provide maximum effectiveness throughout the Lake Champlain watershed. Ecological, social, political, and financial concerns all factor into sea lamprey control; the more techniques available, the better the ability to adapt and effectively address various conditions of specific situations. The Cooperative will also continue to explore new means for effectively controlling sea lamprey. The use of a variety of methods provides the means to reduce the reliance on chemical pesticides-but likely will not eliminate it.
Sea Lamprey Population Assessments
Fish sampling programs, salmon returns to fish ladders, angler surveys, and sampling of larval sea lamprey are used to measure the effectiveness of the control program. The control program may be expanded to other streams and delta areas if significant sea lamprey populations develop in them.
Assessments of sea lamprey populations are made before any control measures are undertaken and afterwards to assist in determining the effectiveness of the controls. Field staff, using a variety of capture methods, sample both adult and larval sea lamprey from streams and deltas to determine the presence, density, and stage of sea lamprey populations.
This information is used to determine which streams or deltas are in need of control measures, if and when a stream or delta needs to be treated and which control measure will be used. Also assessment of larval sea lamprey populations in deltas allows managers to determine where to focus treatments, providing the most effective treatment while expending less effort and money.
Results of Sea Lamprey Management
Improved Fisheries
Evaluation of the eight-year experimental sea lamprey control program that took place in Lake Champlain in the 1990s documented significant benefits for fish and anglers. These benefits included decreased wounding and scarring rates, and increased survival rates of lake trout and landlocked salmon. Angler creel surveys showed that more and substantially bigger trout and salmon are being caught.
Increased Economic Benefits
Sea lamprey control generates a favorable economic benefit/cost ratio as angling opportunities increase. According to Benefit Cost Analysis of the Eight-year Experimental Sea Lamprey Control Program on Lake Champlain, a study conducted by Alphonse H. Gilbert, a researcher from the University of Vermont, sea lamprey control generated benefits of approximately $29.4 million with costs of about $8.4 million, a benefit-to-cost ratio of 3.5 to 1. These benefits were the result of the increased number of boaters and anglers spending longer periods of time in the Lake Champlain area.
Decreased Wounding Rates in Fish
Annually collected data show that the number of sea lamprey wounds on lake trout and landlocked Atlantic salmon began declining 2007. Sampling in the fall of 2011 found wounding rates have continued to remain low and near management targets. Despite not reaching the targeted goal yet, the sustained suppression of wounding rates in recent years has yielded a positive response in size and number of both species in the lake.
