Ruffe
Encyclopedia
The Eurasian Ruffe or simply Ruffe is a freshwater fish
found in temperate regions of Europe
and northern Asia
. It has been introduced
into the Great Lakes of North America
, reportedly with unfortunate results. Its common names are ambiguous – "ruffe" may refer to any local member of its genus
Gymnocephalus
, which as a whole is natively endemic to Eurasia
.
, an olive-brown to golden-brown color on its back, paler on the sides with yellowish white undersides. The ruffe is usually 4-6 inches (10 – 25 cm) in length and will never exceed 10 inches, but is a very aggressive fish for its size. The ruffe also has a large, spiny dorsal fin
likely distasteful to its predators. It also has two fins on top, the front fin has hard and sharp spines, the back fin has soft spines called rays. The most obvious features to recognize a ruffe are the ruffe's large, continuous dorsal fin and its slightly downturned mouth.
of the water column. As far as researchers have been able to find, it has kept the same diet in its transfer to the Great Lakes.
Ruffe eat the young of the signal crayfish
which is threatening many European water creatures.
season for the ruffe occurs from the middle of April through approximately June.
, depending on the size of the female. If the same female has a second batch in the same season, the eggs will be smaller than the first batch. The size of the second batch of eggs is about 0.36 to 0.47 mm, while the first batch of eggs goes from 0.90 to 1.21 mm in size. If the female lays twice in one season, there is usually one in late winter/early spring and one in late summer. Hatching occurs in 5–12 days in temperatures ranging from 10 to 15 degrees Celsius
.
The next stage in life is the embryonic/juvenile stage. Embryos that are freshly hatched are between 3.5 to 4.4 mm in size. These embryos are sedentary for 3–7 days, and in that time grow to about 4.5 to 5 mm in length. One week after the hatching, the young ruffe start to swim and feed actively, but they do not form schools at this age.
From here, the ruffe gradually mature until they are 2–3 years old, when they reach full maturity. At full length, the adult ruffe is usually around 20 cm, but at a maximum of 29 cm. Growth is usually occurs more when the ruffe is in clear, brackish waters. Generally, female and male ruffe do not live longer than 7 to 11 years.
inconvenience to Lake Superior
. This pesky fish's invasion on the lake has not only caused problems with space, but problems with food supply to other fish as well. The ruffe has similar eating habits, as well as having an accelerated reproduction rate compared to other like fish. Therefore, having more ruffe in the water, leads to less food for other fish. This fish is unique in its ability to adapt in many habitats and temperatures, resulting in its way of life can be maintained with little interference from climate change
or other biological changes. The ruffe also has an excepional ability to detect water vibrations through organs called neuromasts. This trait both aids the ruffe in finding food and gives the rudge an edge in avoiding predators. These will develop into more advanced and sensitive organs as the fish matures; for example, the perch
's neuromasts weaken as it matures. The ruffe has the ability to overtake many other fish species, and consequently damage the Great Lakes ecosystems. If there is no intervention taken by the public the ruffe have the potential to ruin Lake Superior.
Not only has the ruffe become an inconvenience but, it is also the first invasive species to have been labeled a nuisance by the Non-indigenous Aquatic Nuisance Prevention and Control Program. Along with it being the most populated fish in the St. Louis river basin it has disrupted ecosystems all across the Great Lakes. The invasion was first noticed in the 1980s by the DNR. They suggest that the fish was introduced to the lake via ballast water that was dumped into the Duluth harbor by anchored freight ships. Ever since the ruffe were detected, studies have not only shown that the ruffe and the yellow perch are closely related but they are quickly becoming rivals. The ruffe and perch are competing in numbers and are also competing for food; this is a match that the ruffe are winning. It shouldn't be too long for the ever so quickly reproducing ruffe to soon phase out any perch that stands in its way. Some researches believe that if a plan isn't thought of soon, this fish could be the only kind left in the Great Lakes area.
and Northern Pike
populations because they are natural predators of the ruffe. Even though this really didn't work in the beginning, it is still too early to tell because it takes a couple years for fish to switch to a new food source.
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.
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
found in temperate regions of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and northern Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. It has been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
into the Great Lakes of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, reportedly with unfortunate results. Its common names are ambiguous – "ruffe" may refer to any local member of its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Gymnocephalus
Gymnocephalus
Gymnocephalus is a ray-finned fish genus of the perch family . Its members live in western Eurasia. They are collectively called ruffes and resemble the common perches , but are usually smaller and have a different pattern....
, which as a whole is natively endemic to Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
.
Description
The ruffe's colors and markings are similar to those of the walleyeWalleye
Walleye is a freshwater perciform fish native to most of Canada and to the northern United States. It is a North American close relative of the European pikeperch...
, an olive-brown to golden-brown color on its back, paler on the sides with yellowish white undersides. The ruffe is usually 4-6 inches (10 – 25 cm) in length and will never exceed 10 inches, but is a very aggressive fish for its size. The ruffe also has a large, spiny dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
likely distasteful to its predators. It also has two fins on top, the front fin has hard and sharp spines, the back fin has soft spines called rays. The most obvious features to recognize a ruffe are the ruffe's large, continuous dorsal fin and its slightly downturned mouth.
Diet
In Eurasia, the ruffe diet mainly consists of zoobenthos: chironomids, small aquatic bugs and larvae, which are all found in the Benthic zoneBenthic zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such...
of the water column. As far as researchers have been able to find, it has kept the same diet in its transfer to the Great Lakes.
Ruffe eat the young of the signal crayfish
Signal crayfish
The signal crayfish, Pacifastacus leniusculus, is a North American species of crayfish. It was introduced to Europe in the 1960s to supplement the Scandinavian Astacus astacus fisheries, which were being damaged by crayfish plague, but the imports turned out to be a carrier of that disease...
which is threatening many European water creatures.
Reproduction
The ruffe has the capacity to reproduce at an extremely high rate. A Ruffe usually matures in two to three years, but a ruffe that lives in warmer waters has the ability to reproduce in the first year of life. A single female has the potential to lay from 130,000 to 200,000 eggs annually. Ruffe will leave the deep dark water where they prefer and journey to warmer shallow water for spawning. The primary spawningSpawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
season for the ruffe occurs from the middle of April through approximately June.
Life cycle
Life, for the Eurasian ruffe, starts as an egg, like other fish. Egg sizes typically range from 0.34 to 1.3 mm in diameterDiameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
, depending on the size of the female. If the same female has a second batch in the same season, the eggs will be smaller than the first batch. The size of the second batch of eggs is about 0.36 to 0.47 mm, while the first batch of eggs goes from 0.90 to 1.21 mm in size. If the female lays twice in one season, there is usually one in late winter/early spring and one in late summer. Hatching occurs in 5–12 days in temperatures ranging from 10 to 15 degrees Celsius
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
.
The next stage in life is the embryonic/juvenile stage. Embryos that are freshly hatched are between 3.5 to 4.4 mm in size. These embryos are sedentary for 3–7 days, and in that time grow to about 4.5 to 5 mm in length. One week after the hatching, the young ruffe start to swim and feed actively, but they do not form schools at this age.
From here, the ruffe gradually mature until they are 2–3 years old, when they reach full maturity. At full length, the adult ruffe is usually around 20 cm, but at a maximum of 29 cm. Growth is usually occurs more when the ruffe is in clear, brackish waters. Generally, female and male ruffe do not live longer than 7 to 11 years.
Ecological effects
The introduction of the ruffe seems to be causing much damage and has become a biginconvenience to Lake Superior
Lake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...
. This pesky fish's invasion on the lake has not only caused problems with space, but problems with food supply to other fish as well. The ruffe has similar eating habits, as well as having an accelerated reproduction rate compared to other like fish. Therefore, having more ruffe in the water, leads to less food for other fish. This fish is unique in its ability to adapt in many habitats and temperatures, resulting in its way of life can be maintained with little interference from climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
or other biological changes. The ruffe also has an excepional ability to detect water vibrations through organs called neuromasts. This trait both aids the ruffe in finding food and gives the rudge an edge in avoiding predators. These will develop into more advanced and sensitive organs as the fish matures; for example, the perch
Perch
Perch is a common name for fish of the genus Perca, freshwater gamefish belonging to the family Percidae. The perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning spotted, and the...
's neuromasts weaken as it matures. The ruffe has the ability to overtake many other fish species, and consequently damage the Great Lakes ecosystems. If there is no intervention taken by the public the ruffe have the potential to ruin Lake Superior.
Not only has the ruffe become an inconvenience but, it is also the first invasive species to have been labeled a nuisance by the Non-indigenous Aquatic Nuisance Prevention and Control Program. Along with it being the most populated fish in the St. Louis river basin it has disrupted ecosystems all across the Great Lakes. The invasion was first noticed in the 1980s by the DNR. They suggest that the fish was introduced to the lake via ballast water that was dumped into the Duluth harbor by anchored freight ships. Ever since the ruffe were detected, studies have not only shown that the ruffe and the yellow perch are closely related but they are quickly becoming rivals. The ruffe and perch are competing in numbers and are also competing for food; this is a match that the ruffe are winning. It shouldn't be too long for the ever so quickly reproducing ruffe to soon phase out any perch that stands in its way. Some researches believe that if a plan isn't thought of soon, this fish could be the only kind left in the Great Lakes area.
Control
Ever since the ruffe was introduced into the Great Lakes system, scientists and fishery managers have been searching for the right way to get rid of them. In the beginning, the main method of control was to increase the WalleyeWalleye
Walleye is a freshwater perciform fish native to most of Canada and to the northern United States. It is a North American close relative of the European pikeperch...
and Northern Pike
Northern Pike
The northern pike , is a species of carnivorous fish of the genus Esox...
populations because they are natural predators of the ruffe. Even though this really didn't work in the beginning, it is still too early to tell because it takes a couple years for fish to switch to a new food source.
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
Lampricide
Lampricide is a chemical which is designed to target the larvae of lampreys in river systems before their recruitment as parasitic adults. TFM is one such chemical...
TFM
TFM (piscicide)
TFM is a common piscicide, i.e., a fish poison used to combat parasitic and invasive species of fish.The substance was discovered in 1958 when researching means to combat sea lampreys and it remains the primary lampricide in the Great Lakes area.TFM is nontoxic to humans and other mammals...
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.
External links
- Fishbase entry for the Ruffe
- GLANSIS Species FactSheet
- Species Profile- Eurasian Ruffe (Gymnocephalus cernuus), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
. Lists general information and resources for Eurasian Ruffe.