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List of Species Threatened by the Eurasian Ruffe

Emerald Shiner

Walleye

Russian Whitefish

Yellow Perch

Trout-Perch

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Characteristics of the Eurasian Ruffe



http://www.invadingspecies.com/Invaders.cfm?A=Page&PID=5

     Ruffe resemble young walleye, yellow perch, and trout perch, but can be distinguished from these by the following characteristics. Ruffe can be identified by their perch-like body shape and are generally less than 20cm (4-6 in) long. They are slimy when handled and have olive brown colouring on the back and pale sides. They have two, large dorsal fins (on top) that are joined together. The row on the first fin has hard spines (11-16 in number) with rows of dark spots and the second fin has soft rays. It has sharp spines on the dorsal and anal fins and sharp spines on its gill covers. It has glassy eyes, a small, down-turned mouth and no scales on the head.



    

     Ruffe have all the characteristics to make it a highly successful invader: it can adapt to many different environmental conditions, will eat a wide range of food, has very few predators, matures quickly and has a high rate of reproduction. The ruffe spends its days in deeper water to avoid predators and moves to the shallows to feed at night. It is found in fresh and brackish water, water with low or high nutrients, in depths of 0.25m to 85m and at a wide range of temperatures. Ruffe mainly feed on aquatic insects and other bottom-dwelling organisms and are know to eat fish eggs. Thus far, only bullheads, yellow perch and northern pike appear to feed on ruffe since their hard spines make it difficult for fish to eat. Ruffe mature young (on average at the age of 2-3) and can spawn in a variety of conditions and habitats. Females can lay between 13,000 to 200,000 eggs per season and have an average life span of 7 years.

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What You Can Do to Prevent the Spread of the Eurasian Ruffe



http://www.iisgcp.org/exoticsp/ruffe.htm

If you catch a ruffe, kill it, freeze it, and call a local DNR fishery office, or Local Sea Grant Office or Extension.   Do not throw it back alive. Always drain your livewells, bilge water, and transom wells before leaving the water access. Never empty your bait bucket into the water, always empty it on land. Never dip your bait bucket into one lake if it has water in it from another. Never dump live fish from one body of water into another.

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Eurasian Ruffe Control Strategies



http://www.seagrant.umn.edu/ais/ruffe

     -Fisheries managers in Lake Superior first tried to control ruffe by increasing the number of its predators, especially walleye and northern pike. They did this by limiting sport catches of these species, and stocking walleye and northern pike. Results of the predator-stocking program were disappointing.

     -Researchers analyzed stomach samples of the predators and found very few ruffe in walleye stomachs. Bullheads appear to be the only species that consistently eat ruffe. Research suggests that predators stocked to control ruffe may not eat them because they prefer soft-rayed shiners and small hard-rayed fish like darters and young perch.

        -Surveys of northern pike stomachs, however, suggest that ruffe may be growing in importance as a food source. Ruffe made up less than one percent of fish eaten by northern pike in 1989. By 1992, the figure had climbed to 15 percent. Poisoning ruffe in some areas was considered, but was ruled out. 

     -To keep ruffe from spreading to the other Great Lakes, the Lake Carriers Association developed best management practice guidelines for handling ballast water in Great Lakes ships.

     -Other methods that have been considered are poison and chemical control. If a large school of ruffe is found, they can be poisoned. If some of them survive, however, the problem will only continue. Chemicals, on the other hand, can be specifically made to only harm a certain kind of fish. The chemical lampricide TFM  kills ruffe, but leaves other fish untouched.

     -The major problem with this though, is that as long as a couple of the fish survive, they can move and repopulate. The problem would increase if the ruffe started to move farther down south. A new method of control is being investigated to prevent this: pheromones. After an extensive amount of tests, scientists discovered that the ruffe can be repelled by their own alarm pheromone. When injured, a ruffe will release this pheromone into the water to warn other ruffe to stay away. After doing these tests, the scientists involved concluded three significant things. One, that the pheromone does repel the ruffe (it was unclear if it would in the beginning). Second, the pheromone is species specific, so it would only repel the ruffe, none of the other fish. Finally, the scientists found that it is resilient to freezing, so even during Minnesota's long winter season; the ruffe could still be controlled. By using this method there is a chance the ruffe could be prevented to go to their natural mating spots and therefore eventually the ruffe might die out.

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Location and Impact of the European Ruffe



     http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=7

http://en.wikipedia.org/wiki/Ruffe

     The Eurasian Ruffe is a freshwater fish native to the temperate regions in Europe and Northern Asia.  It has been introduced into the Great Lakes region of the United States with many unfortunate results.  The ruffe was first collected in 1986 from the St. Louis River at the border of Minnesota and Wisconsin. It subsequently spread into Duluth Harbor in Lake Superior and several tributaries of the lake.  It is found in the Amnicon, Flag, Iron, Middle, Raspberry, and Bad Rivers, Chequamegon Bay, and Apostle Islands National Lakeshore in Wisconsin.   It was found in Saxon Harbor, Wisconsin, and in the upper peninsula of Michigan at the mouths of the Black and Ontonagon rivers.  In the lower Peninsula of Michigan along Lake Huron, the first three specimens were caught at the mouth of the Thunder Bay River in August 1995.  This species has also been collected in Michigan in Lake Michigan, Lake Superior, Torch Lake, Little Bay de Noc in Escanaba, Big Bay de Noc, Misery River, Ontonagon River, Thunder Bay, and Sturgeon River Sloughs.  The ruffe has been collected in Lake Superior at Thunder Bay Harbour, Ontario, Canada.  The ruffe was probably introduced via ship ballast water discharged from a vessel arriving from a Eurasian port, possibly as early as 1982-1983.  Recent genetic research has indicated that the origin of ruffe introduced to the Great Lakes was southern Europe, not the Baltic Sea as previously believed.  Impact:       -The ruffe has affected fish populations in other areas where introduced. In Scotland, native perch populations declined, and in Russia whitefish numbers have declined because of egg predation by ruffe.

      -Ruffe exhibit rapid growth and high reproductive output, and adapt to a wide range of habitat types therefore the species may pose a threat to native North American fish.       -Yellow perch, emerald shiners, and trout-perch have all declined since the introduction of the ruffe.       -There is much concern that ruffe may have a detrimental effect on more desirable species in Lake Superior, such as yellow perch and walleye, by feeding on the young of these species or by competing.       -Findings indicated that the species prey heavily on benthic insects thereby suggesting that ruffe compete for food with yellow perch, trout-perch, and other native benthic-feeding fishes.       -Ruffe hold an advantage over native perch in their ability to better select moving objects under relatively dim light conditions or at high turbidity.       -Ruffe have a very sensitive lateral line system and night adapted vision, and are more adapted to foraging under poor light conditions that yellow perch.       -In a study of ruffe predation by native pike, bass, bullhead, walleye, and perch found that though ruffe comprised 71-88% of prey species biomass, all five of the selected predators ate ruffe at lower proportions, preferentially selecting native fish species.

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Rusty Crayfish Control



     Many chemicals kill crayfish and some are even selective for crayfish; however, none are currently registered for crayfish control.   And, none selectively kill rusty crayfish without killing other crayfish species. Intensive harvest will not eradicate crayfish, but may help reduce adult populations and minimize some impacts. Researchers suggest that nuisance populations of rusty crayfish are the result of poor fishery management and that by restoring a healthy population of bass and sunfish, rusty crayfish would be less disruptive in some lakes.

Rusty Crayfish trap.

      A combination of intensive trapping and enhanced fish predation, through regulations that protected smallmouth bass, effectively controlled rusty crayfish in Sparkling Lake, Wisc.  This whole-lake experiment found that aquatic plants, benthic invertebrates and sunfish increased as a result of rusty crayfish population decreases. The best method of control, however, is to prevent their introduction. Educating anglers, crayfish trappers, bait dealers, and teachers about the threats posed by rusty crayfish will help reduce the risk of spreading rusty crayfish to new areas.

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List of Species Threatened by Invaders of the Rusty Crayfish Sort

Pumpkinseed Sunfish

Bluegill

Walleye

Northern Pike

Smallmouth Bass

Largemouth Bass

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Potential Impact of Rusty Crayfish in New Environments



     Rusty crayfish may cause a variety of negative environmental and economic impacts when introduced to new waters.  This aggressive species often displaces native or existing crayfish species.  Rusty crayfish displace other crayfish species through three primary mechanisms:

          1.) Crayfish to Crayfish Competition

Rusty crayfish are better able to exclude other crayfish from shelters and better able to compete for limited food resources.

     2.) Increased Fish Predation

Rusty crayfish can increase fish predation on native crayfish in a variety of ways. They force native species from the best hiding places. As the native crayfish try to swim away from a fish or rusty crayfish attack, this makes them more vulnerable to capture by fish. Rusty crayfish, on the other hand, assume a claws-up defensive posture that reduces their susceptibility to fish predation. Also, rusty crayfish are larger and have larger claws than most native species, which results in fish preying upon native species over rusty crayfish.

     3.) Hybrdization

While rusty crayfish do not hybridize with Orconectes virilis, they do hybridize with Orconectes propinquus. This hybridization results in fertile and vigorous offspring, but ultimately results in the decline of Orconectes propinquus. The competitive superiority of the hybrids helps exclude genetically pure Orconectes propinquus faster than Orconectes rusticus would without hybridization.

     The destruction of aquatic plant beds is perhaps the most serious impact. Rusty crayfish have been shown to reduce aquatic plant abundance and species diversity.   This can be especially damaging in relatively unproductive northern lakes, where beds of aquatic plants are not abundant. Submerged aquatic plants are important in these systems for:

habitat for invertebrates (which provide food for fish and ducks),

shelter for young gamefish, panfish, or forage species of fish,

nesting substrate for fish, and

erosion control (by minimizing waves)

     Although other crayfish eat aquatic plants, rusty crayfish eat even more because they have a higher metabolic rate and appetite.  They also grow larger, hide less often from predators – and therefore feed longer – attaining high population densities.      Rusty crayfish are more likely to compete with juvenile game fish and forage fish species for benthic invertebrates than are native crayfish species. Displacement of native crayfish by rusty crayfish could result in less food for fish. Crayfish are eaten by fish, but because of the higher ratio of their thick exoskeleton (shell) relative to soft tissue, their food quality is not as high as many of the invertebrates that they replace. Less food or lower food quality means slower growth, which can reduce fish survival.      Rusty crayfish can harm fish populations by eating fish eggs, reducing invertebrate prey, and through loss of habitat (aquatic plants). Male bass and sunfish protect their nests until the eggs hatch and the advanced fry swim away.  It was also found that total zoobenthos, larval midges, mayflies, dragonflies, and stoneflies decline as rusty crayfish populations increase.  Walleye reproduction dropped after a rusty crayfish invasion. Observations and circumstantial evidence gathered by Wisconsin fishery managers suggest that bluegill and northern pike populations frequently decline following the introduction of rusty crayfish.  Impacts on other fish species are not as obvious.  The cause of bluegill, bass, and northern pike declines is probably reduced abundance and diversity of aquatic plants.  Reduced food (such as mayflies, midges, and stoneflies) and egg predation may also play a role.      Cabin owners on heavily infested northern Wisconsin and Minnesota lakes have even stopped swimming because large numbers of "rustys" occupy their favorite swimming area throughout the day. They fear stepping on them and getting pinched by their large claws. Other crayfish species, even if abundant, are less conspicuous during daylight hours.

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Everything You'll Need to Know About A Rusty Crayfish's Life



http://www.seagrant.umn.edu/ais/rustycrayfish_invader

          Rusty crayfish live in lakes, streams, and ponds.  They prefer areas that offer rocks, logs, or other debris as cover. Bottom types may be clay, silt, sand, gravel, or rock.  Rusty crayfish inhabit both pools and fast water areas of streams. They generally do not dig burrows other than small pockets under rocks and debris, although there have been reports of more substantial burrows.  Rusty crayfish need permanent lakes or streams that provide suitable water quality year-round.

     A female rusty crayfish with eggs.

     Mature rusty crayfish mate in late summer, early fall, or early spring.  The male transfers sperm to the female.  She stores the sperm until her eggs are ready to fertilize, typically in the spring as the water temperature begins to increase.  Stored sperm are released as eggs are expelled and external fertilization occurs. The eggs are then attached to the swimmerets on the underside of the crayfish's abdomen ("tail section").  Rusty crayfish females can lay from 80 to 575 eggs.      Eggs hatch in three to six weeks, depending on water temperature.  Once hatched, young crayfish cling to the female's swimmerets for three to four molts.  Young crayfish may stay with the female for several weeks. She offers them protection during this vulnerable life stage. Eventually, the young leave the female. They undergo eight to ten molts before they mature, which may occur during the first year, but more likely in the following year. Rusty crayfish reach maturity at a total length of one and three-eighths inches (3.5 cm) and reach a maximum length of about four inches (10 cm), not including claws.      Growth slows considerably after crayfish attain maturity.  Males typically molt twice a year while females only molt once a year.   Females molt after the release of their young, typically in June or early July.   Because males have an additional molt each year, they are usually larger than females of the same age.  A typical rusty crayfish lives three to four years.     Crayfish are considered opportunistic feeders. Rusty crayfish feed on a variety of aquatic plants, benthic invertebrates (like aquatic worms, snails, leeches, clams, aquatic insects, and crustaceans such as side-swimmers and waterfleas), detritus (decaying plants and animals, including associated bacteria and fungi), fish eggs, and small fish. Juveniles especially feed on benthic invertebrates like mayflies, stoneflies, midges, and side-swimmers.

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The Origin and Distribution of Rusty Crayfish



http://www.seagrant.umn.edu/ais/rustycrayfish_invader

     Rusty crayfish were not found in Wisconsin in a 1932 survey, but populations have rapidly expanded throughout Wisconsin lakes and streams since their introduction around 1960.  Rusty crayfish have been observed in 430 Wisconsin lakes and streams and the occurrence of rusty crayfish in sites that support crayfish has increased from 3% in the 1970s to approximately 50% in 2007.

     The first observation of rusty crayfish in Minnesota was in 1967 at Otter Creek in southern Minnesota. Since then, their range has expanded to approximately 50 different lakes and streams spanning 13 counties.  Rusty crayfish from east central Minnesota  may have resulted from the natural dispersal of introduced populations from Wisconsin. People most likely spread rusty crayfish to the other waters of Minnesota where they are currently found.

     Presumably people can spread crayfish in several ways. Anglers using crayfish as bait are thought to be the primary means of spread. While crayfish never were a significant component of Minnesota live bait sales, they are popular in other states and may have been brought to Minnesota by non-resident anglers.  Rusty crayfish are also sold to schools by biological supply houses. Even though a warning not to release rusty crayfish into the wild accompanies these crayfish, such warnings may be forgotten, or live crayfish may be given away to students. Crayfish from schools or collected from the wild and placed in home aquariums may eventually be released.  Developing a viable commercial harvest of rusty crayfish from natural lakes could be incentive for unscrupulous trappers to plant them into other waters. In fact, this may have contributed to the spread of rusty crayfish in Wisconsin.  The harvest of rusty crayfish for food and bait may provide the only beneficial use for this exotic. Harvest for bait has been going on for over 40 years in Wisconsin. Commercial harvest for food is more recent and varies from year to year in Wisconsin and Minnesota. Regulations in both states make it illegal to introduce rusty crayfish into any waters. In Minnesota, it is illegal to sell live crayfish as bait or as aquarium pets.

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Rusty Crayfish

http://www.anstaskforce.gov/spoc/rustycrayfish.php

Rusty crayfish live in lakes, ponds and streams, preferring areas with rocks, logs and other debris in water bodies with clay, silt, sand or rocky bottoms. They typically inhabit permanent pools and fast moving streams of fresh, nutrient-rich water.

Dark “rusty” spots are usually apparent on either side of the carapace, but are not always present in all populations.

Claws are generally smooth, with grayish-green to reddish-brown coloration. Adults are opportunistic feeders, feeding upon aquatic plants, benthic invertebrates, detritus, juvenile fish and fish eggs.

The native range of the rusty crayfish includes Ohio, Tennessee, Kentucky, Indiana, Illinois and the entire Ohio river basin. However, this species may now be found in Michigan, Massachusetts, Missouri, Iowa, Minnesota, New York, New Jersey, Pennsylvania, Wisconsin, New Mexico and the entire New England state area (except Rhoda Island).

Its further spread is of great concern since the prior areas of invasion have led to severe impacts on native flora and fauna.

It is thought to have spread by means of released game fish bait and/or from aquarium release. Rusty crayfish are also raised for commercial and biological harvest.

Rusty crayfish reduce the amount and types of aquatic plants, invertebrate populations, and some fish populations--especially bluegill, smallmouth and largemouth bass, lake trout and walleye.

They deprive native fish of their prey and cover and out-compete native crayfish. Rusty crayfish will also attack the feet of swimmers.

On the positive side, rusty crayfish can be a food source for larger game fish and are commercially harvested for human consumption.

Rusty crayfish may be controlled by restoring predators like bass and sunfish populations. Preventing further introduction is important and may be accomplished by educating anglers, trappers, bait dealers and science teachers of their hazards. Use of chemical pesticides is an option, but does not target this species and will kill other aquatic organisms.

PREVENTION: Do not use rusty crayfish as bait in areas where it is not native. Never transport bait from one water body to another. Discard your bait in the trash before leaving. Never release pet crayfish (or any other organisms) into the wild.

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Control and the Prevention of the Spread of Sea Lamprey



http://www.glsc.usgs.gov/main.php?content=research_lamprey&title=Invasive%20Fish0&menu=researchinvasive

     The sea lamprey is one of the few aquatic invasive species that is being successfully controlled. In the late 1940s the State of Michigan began investigations into the biology of sea lampreys. In 1950, this became a federal program. In 1955, the Great Lakes Fishery Commission (GLFC) was created under a convention between the United States and Canada for the purpose of restoring fisheries. One of the GLFC’s primary duties was the control or eradication of sea lampreys. It currently manages sea lamprey populations across the Great Lakes to about 10% of their former levels. Control is delivered through its control agents, the U.S. Fish and Wildlife Service and the Department of Fisheries and Oceans, Canada.

     Control depends on breaking the life cycle. The first control efforts attempted to do that by blocking access to the spawning areas in streams. This was only partially successful because the weirs used to do this were impossible to maintain 100% of the time. There were attempts to use electric fields alone or in conjunction with the weirs, but that was eventually abandoned as too dangerous. A second vulnerable point in the life cycle is during the larval stage, when sea lampreys spend at least three years burrowed in the stream sediment. During the 1950s, over 6,000 chemicals were screened before finding one that was selectively toxic to sea lampreys. That chemical, TFM, has been carefully applied to infested streams, beginning in Lake Superior in 1958. Treatments quickly decreased sea lamprey numbers to 10% or less of their former numbers. Reduced lamprey numbers allowed native and stocked lake trout to survive and the lake trout populations to rebound. Recently, the restoration of lake trout in Lake Superior was declared a success and federal stocking of lake trout was stopped. Lake trout stocks in Lake Superior are once again selfsustaining.

Locations of dams preventing the spread of spawning sea lamprey.

     Treatments with TFM start with electrofishing surveys of the Great Lakes tributaries known to potentially produce sea lampreys. Based on estimates of the number of metamorphosed sea lampreys to be produced and on treatment costs, a list of streams to be treated is made each year. Because of the duration of the larval stage, streams are treated at intervals of 3 to 5 years or longer.

      Ineffective and labor-intensive screen weirs have been replaced with low-head barriers that block sea lampreys but allow jumping fish to pass.  A combined low-head and electrical barrier was constructed on the Ocqueoc River, which functions effectively as a low-head barrier but also blocks sea lampreys during high water on this flood-prone stream. This combination of proven technologies allows effective blockage of migrating sea lampreys and passage of jumping fishes under a much broader range of stream flows. Under normal flows, the low-head barrier is functional, no current flows to the electrical barrier, and jumping fish can pass. During flood conditions, when the low-head barrier is inundated, the electric barrier automatically turns on and blocks sea lampreys.

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Impact of Sea Lamprey on the Great Lakes

The Correlation Between the Number of Sea Lampreys and Lake Trout in Lake Superior



Sea Lamprey feeding on a native lake trout in Lake Superior. http://www.glsc.usgs.gov/main.php?content=research_lamprey&title=Invasive%20Fish0&menu=researchinvasive

     Sea lampreys quickly devastated the fish communities of the Great Lakes.  Sea lampreys probably entered Lake Ontario in the 1830s via manmade locks and ship canals. Improvements to the Welland Canal in 1919 allowed sea lampreys to bypass Niagara Falls and enter Lake Erie. After sea lampreys were discovered above Niagara Falls (in Lake Erie in 1921 and Lake Huron in the early 1930s), they spread throughout the upper Great Lakes by 1939. The lake trout was the main predatory species at that time and the sea lamprey’s preferred host. Although early declines in lake trout abundance in the 1940s are suspected to have been caused by overfishing, sea lampreys are believed to be responsible for the very rapid decline in the later 1940s and 1950s. Lake trout actually became extinct in Lakes Ontario, Erie, Huron (except a few inlets of Georgian Bay), and Michigan. Only remnant native stocks remained in Lake Superior. Two factors contributed to the devastating effect of sea lampreys. First, sea lampreys lacked effective predators. Second, the Great Lakes probably have as many miles of tributaries and as many acres of larval habitat as the native range of the sea lamprey along the Atlantic Coast. Host fishes in the Great Lakes are much smaller than those attacked in the Atlantic Ocean and are more likely to be killed by a sea lamprey attack. Between 40% and 60% of lake trout attacked by a sea lamprey will die from loss of blood. These attacks were a major cause of the collapse of lake trout, whitefish, and chub populations in the Great Lakes in the 1940s and 1950s. Lake trout harvests in the U. S. and Canada averaged 15 million pounds per year before the sea lamprey, but declined to record lows within 20 years of the sea lamprey’s appearance.      Other equally important secondary effects were caused by cascading changes in the fish communities. After the elimination of predators like lake trout, the populations of invasive prey species like the rainbow smelt and alewife increased rapidly in the absence of predation. Those invasive species then out competed native species or preyed on their young. Extinctions of sculpin and deepwater cisco species have been suspected of being linked to extended periods of high abundance of smelt and alewives. The massive annual die offs of alewives that fouled the beaches in Michigan during the 1950s and 1960s were due to overcrowding and poor condition and were a secondary effect of the invasion of the sea lamprey. Alewives also prey heavily on zooplankton. Because zooplankton graze on phytoplankton, the density of phytoplankton increased and the color and clarity of water were affected, particularly in the lower Great Lakes.      Human activities were affected first through the loss of sport and commercial fisheries across the Great Lakes. Following those losses, came other, equally important economic effects caused by the disappearance of fishery-related jobs and the loss of fishing tourism. With the beaches fouled with dead alewives, there were also losses of tourism associated with beach use.

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Sea Lamprey Life Cycle



     Sea Lamprey are unusual in having a complex life cycle, whereas most fish have a simple life cycle.

     1.) Sea lampreys go through an extended larval phase before metamorphosing into the bloodsucking parasitic phase. Each summer and fall there is one group of parasitic sea lampreys actively feeding in the Great Lakes.

     2.) The next spring, that group leaves the lake and migrates into tributary streams where they must build nests in clean gravel with flowing water.      3.) Each female spawns an average of 60 to 70 thousand eggs.

     4.) After hatching, the larvae drift downstream to areas with slower currents and sand/silt bottoms. There, they establish permanent burrows and enter a larval stage varying in duration from 3 to 10-or even more years.

     5.) Larvae lack eyes and the oral disc. Living concealed in their burrows, they are harmless and filter microscopic material from the water for food. When they reach lengths of 120 mm or more, some individuals begin metamorphosis in mid-summer.

     6.)  During metamorphosis they develop eyes, the oral disc, and changes in their kidneys that (in their native range) would allow them to enter the salt water of the Atlantic Ocean. That fall or the following spring, they instead enter the Great Lakes to feed parasitically on fish that summer and fall, and mature and spawn the next spring—completing their life cycle. Sea lampreys only spawn once and then die after spawning.

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What is a Sea Lamprey?



http://www.glsc.usgs.gov/main.php?content=research_lamprey&title=Invasive%20Fish0&menu=researchinvasive

     The sea lamprey is an aquatic invader from the Atlantic Ocean that entered the Great Lakes through ship canals and locks built to bypass natural obstacles like Niagara Falls.  An unintended consequence of these canals has been the introduction of invasive species like the lamprey eel.  The sea lamprey was one of the first to invade the Great Lakes.  It has been very damaging because part of its life cycle is spent feeding parasitically on the blood of host fish like the native lake trout.   Sea lampreys are a very primitive, jawless fish.   Although they are classified as a vertebrate, they lack bones and have only a cartilaginous rod or “notochord” for a spine.   The paired fins found on most fish are also absent.  The most remarkable feature of the sea lamprey is the toothstudded oral disk found at the anterior end.  During the parasitic period of their life cycle, they use the oral disc like a suction cup to attach to the side of a host fish similar to the actions of a leech.   The many teeth on the rim of the disc provide traction and make it very difficult for a fish to dislodge a sea lamprey.  Once attached, they use the teeth on the tongue in the center of the disk to rasp through the skin. An anticoagulant in their saliva maintains blood flow as they feed. Often the host dies from the blood loss. Estimates of the number of pounds of fish killed by each sea lamprey vary from about 15 to 40 pounds.

     Several characteristics of the sea lamprey made it an effective marine invader of the Great Lakes. First, the sea lamprey is an “anadromous” fish.  This means that it spawns in fresh water streams, the juvenile phase is spent in salt water in the ocean (or one of the Great Lakes as a substitute), and the adult returns to freshwater streams to spawn.  Special modifications of their kidneys allows these species to live in either fresh or salt water.  Second, sea lampreys produce large numbers of eggs.  Third, lampreys locate streams for spawning using a pheromone excreted by larvae. This pheromone identifies streams successfully producing young. Because the native lampreys also produced this pheromone, the larger, invading sea lampreys had an effective “road map” for expansion

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The Lake Erie Watersnake: A Rare Success Story Resulting from the Introduction of Round Goby



Invasive species often have rapid and far-reaching negative impacts on populations and ecological communities. These effects are most common when invasive species have few competitors or predators. Although higher level carnivores do consume invasive species, quantitative effects of new and abundant food sources on predators have rarely been documented and, as a consequence, potentially positive effects of invasive species may be under appreciated. There was an investigation on the effects of the invasive round goby on diet composition, growth rate, and body size of the Lake Erie Water Snake which is threatened in the USA and endangered in Ontario, Canada. Water Snakes have shifted their diet, and round gobies now constitute >92% of prey consumed. This shift in diet has occurred in just one or two Water Snake generations, yet has resulted in more rapid growth and attainment of larger body size in Water Snakes. These positive effects may reduce predation, speed reproductive maturity, increase offspring production, and fuel population growth of this threatened species.

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Round Goby: How it Got Into the Great Lakes and How to Keep Them from Spreading



http://www.seagrant.umn.edu/ais/roundgoby

 Habitat:

     Round goby are widespread in the Sea of Marmara and in the rivers of its basin.  They can also be found in the Black Sea and the Sea of Azov along all coasts and freshwaters of their basins.  Round gobies also inhabit the rivers of Crimea and Caucasus.  Since the year 1990, the round goby is considered to be an "introduced" or "invasive" species in the Great Lakes region of the United States and in certain regions of Europe.  Round goby were accidentally introduced to the Great Lakes via ballast water transfer in cargo ships.  They were first found in America in the St. Clair River in 1990.  Since their introduction, round gobies have had a profound impact on native ecosystems and on the economy due to their interference with the actions of sport fishing anglers. How to prevent them from spreading: -Learn to identify the round goby from the ruffle, another fish species. -Inspect and remove aquatic plants, animals, and mud from boats, motors and trailers. -Drain the water from boats, livewell, and bilge before leaving any water access point. -Dispose of unwanted bait and worms in the trash; don't dump them into the water. -Never dump live fish into any body of water. -If you catch a round goby, kill it and freeze it.