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Brief Summary

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Ruffe is a freshwater fish commonly found in the IJsselmeer and other large open waters and canals in the Netherlands. It can grow up to 25 centimeters in length. During the day, it hunts in the water column for freshwater plankton, such as insect larvae and water fleas. It rests on the bottom at night. During spawning season from around April till June, ruffes form large schools. They spawn in shallow water. Together with roach, ruffe is the most important food source for cormorants in the IJsselmeer region.
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Diagnostic Description

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Distinguished uniquely from its congeners by its body depth 24-27% SL. Differs further from other members of the genus by the combination of having a flank yellowish with numerous, small, irregular, dark blotches and having 11-16 dorsal spines (Ref. 59043). Caudal fin with 16 to 17 rays (Ref. 40476). Dorsal fins are fused. Color brownish with dark spots (Ref. 35388).
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Recorder
Pascualita Sa-a
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Life Cycle

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Eggs turn adhesive on contact with water and stick to stones or plants. Females lay eggs in two or more portions, usually separated by about 30 days in summer. First portion of eggs is larger the second portion. Larvae without or with only a brief, pelagic larval stage, switching early to benthic life, secretive and solitary, not forming schools. Larval survival is poor below 10°C and above 20°C (Ref. 59043).
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Armi G. Torres
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Migration

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Potamodromous. Migrating within streams, migratory in rivers, e.g. Saliminus, Moxostoma, Labeo. Migrations should be cyclical and predictable and cover more than 100 km.
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Crispina B. Binohlan
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Morphology

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Dorsal spines (total): 11 - 19; Dorsal soft rays (total): 11 - 16; Analspines: 2; Analsoft rays: 5 - 6; Vertebrae: 35 - 36
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Threats

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Least Concern (LC)
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Trophic Strategy

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Inhabits lakes, quiet pools and margins of streams. Prefers deep water with deposits of sand and gravel (Ref. 9696). The membranous external walls of the head canals of this species provide high directional sensitivity; can feed at night in the dark using the lateral line system; feeds on zooplankton, chironomids, oligochaetes and amphipods (Ref. 10999).
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Biology

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Inhabits eutrophic lakes, lowland and piedmont rivers. Most abundant in estuaries of large rivers, brackish lakes with salinities up to 10-12 ppt and reservoirs. In general, its abundance increases with increased eutrophication (Ref. 59043). Reported to prefer still or slow-flowing water with soft bottom and without vegetation (Ref. 59043) and deep water with deposits of sand and gravel (Ref. 9696). Can tolerate some degradation of the environment (Ref. 30578). Can co-exist in deep lakes with Perca fluviatilis. Both species partly occur at different depths with Gymnocephalus cernua being more abundant in deeper layers (Ref. 59043). The membranous external walls of the head canals of this species provide high directional sensitivity; can feed at night in the dark using the lateral line system; feeds on zooplankton, chironomids, oligochaetes and amphipods (Ref. 10999). Pelagic in coastal lakes and tidal estuaries, preying on zooplankton and fish. Spawns on a variety of substrates at depths of about 3 m or less (Ref. 59043). White to yellow eggs in sticky strands are found on rocks and weed in shallow water (Ref. 41678). Used as bait for pike (Ref. 6258). Females live up to 10 year while males up to 7 years (Ref. 59043).
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Importance

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fisheries: minor commercial; gamefish: yes; bait: usually
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Ruffe

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The Eurasian ruffe (Gymnocephalus cernua), also known as ruffe or pope, is a freshwater fish found in temperate regions of Europe and northern Asia.[2] It has been introduced into the Great Lakes of North America, reportedly with unfortunate results, as it is invasive and is reproducing faster than other species. Its common names are ambiguous – "ruffe" may refer to any local member of its genus Gymnocephalus, which as a whole is native to Eurasia.[3]

Description

The ruffe's colors and markings are similar to those of the walleye, an olive-brown to golden-brown color on its back, paler on the sides with yellowish white undersides. The ruffe can reach up to 25 cm (9.8 in) in length, but is usually around half that size.[2] It is a very aggressive fish for its size. The ruffe also has a large, spiny dorsal fin which is 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.

Distribution

The species occurs in the basins of the Caspian, Black, Aral, Baltic and North Sea, and is also found in Great Britain, parts of Scandinavia and some regions of the Arctic Ocean basin eastward to the drainage of the Kolyma. It has been introduced to parts of Western Europe (France, northern Italy) and Greece, as well as to the North American Great Lakes.[1]

Diet

In Eurasia, the ruffe diet mainly consists of zoobenthos: chironomids,[4] small aquatic bugs and larvae, which are all found in the benthic zone of the water column. As far as researchers have been able to learn, it has kept the same diet in its transfer to the Great Lakes.

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 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 diameter, 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 of 10–15 °C (50–59 °F). The next stage in life is the embryonic/juvenile stage. Embryos that are freshly hatched are between 3.5 and 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.

Presence in the Great Lakes area

Ecological effects

The introduction of the ruffe seems to be causing much damage to Lake Superior. This fish's invasion of the lake has not only caused problems with space, but competing with other fish for food supply. The ruffe has similar eating habits, but an accelerated reproduction rate compared to other similar 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 success despite such factors as climate change or other biological changes. The ruffe also has an exceptional ability to detect water vibrations through organs called neuromasts. This trait both aids the ruffe in finding food and gives the ruffe an edge in avoiding predators. These develop into more advanced and sensitive organs as the fish matures; of note, the perch's neuromasts weaken as it matures. The ruffe has the potential to overtake many other fish species, and consequently damage the Great Lakes' ecosystem. Without concerted intervention, the ruffe have the potential to ruin Lake Superior.[5]

The ruffe is the first invasive species to have been classified as a nuisance by the Non-indigenous Aquatic Nuisance Prevention and Control Program. Along with it being the most populous 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, Minnesota, harbor by anchored freight ships. Ever since the ruffe were detected, studies have shown that the ruffe and the yellow perch are closely related and 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.

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 Walleye and Northern Pike populations, because they are natural predators of the ruffe.

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 survive, however, they will rapidly reproduce. Chemicals can be targeted to act on specific species of fish. The chemical lampricide TFM kills ruffe, but leaves other fish unharmed.

As long as a couple of the fish survive, they can move and repopulate. The problem will increase if the ruffe invade southern river systems. The use of pheromones is being investigated as a control. After extensive studies, 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.

Scientists have concluded three things:

  • The pheromone repels the ruffe (it was unclear if it would in the beginning).
  • The pheromone is species specific, so it would only repel the ruffe, none of the other fish.
  • The pheromone is resilient to freezing, so could be used even during Minnesota's long winter season; the ruffe could still be controlled. By using this method, scientists could block ruffe from natural mating spots and produce a population decline; their goal is to kill the species in the Great Lakes.

Other invasive situations

Ruffe were first discovered in Loch Lomond, Scotland, in 1982, probably having been introduced as live bait by pike anglers. It is now abundant throughout the Loch, concern was raised about the effect of the huge ruffe population on the endemic whitefish population known as powan Coregonus lavaretus as ruffe prey on their eggs. Ruffe became the principal food item for the three main fish predators found in the area, the great cormorant, grey heron and northern pike.[6]

References

  1. ^ a b J. Freyhof & M. Kottelat (2008). "Gymnocephalus cernua". IUCN Red List of Threatened Species. IUCN. 2008: e.T9568A13002898. doi:10.2305/IUCN.UK.2008.RLTS.T9568A13002898.en.
  2. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2016). "Gymnocephalus cernua" in FishBase. August 2016 version.
  3. ^ Center, National Invasive Species Information. "Invasive Species: Aquatic Species - Eurasian Ruffe (Gymnocephalus cernuus)". www.invasivespeciesinfo.gov. Retrieved 2016-02-11.
  4. ^ M. Tarvainen; K. Vuorio & J. Sarvala (2008). "The diet of ruffe Gymnocephalus cernuus (L.) in northern lakes: new insights from stable isotope analyses". Journal of Fish Biology. 72 (7): 1720–1735. doi:10.1111/j.1095-8649.2008.01847.x.
  5. ^ "Ruffe (Gymnocephalus cernua) - FactSheet". nas.er.usgs.gov. Retrieved 2016-01-28.
  6. ^ Colin E. Adams; Peter S. Maitland (1998). "The Ruffe Population of Loch Lomond, Scotland: Its Introduction, Population Expansion, and Interaction with Native Species (abstract)". Journal of Great Lakes Research. 24 (2): 249–262. doi:10.1016/s0380-1330(98)70817-2.
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Ruffe: Brief Summary

provided by wikipedia EN

The Eurasian ruffe (Gymnocephalus cernua), also known as ruffe or pope, 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, as it is invasive and is reproducing faster than other species. Its common names are ambiguous – "ruffe" may refer to any local member of its genus Gymnocephalus, which as a whole is native to Eurasia.

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