View source for Ruffe

{{Short description|Species of fish}}
{{Distinguish|Ruff (disambiguation){{!}}Ruff}}
{{For|other fishes|List of organisms with the common name Ruffe}}
{{Multiple issues|
{{more citations needed|date=January 2016}}
{{lead too short|date=April 2013}}
{{More footnotes|date=April 2009}}
}}
{{EngvarB|date=June 2022}}
{{Use dmy dates|date=June 2022}}
{{Speciesbox
| image = Gymnocephalus cernuus Pärnu River Estonia 2010-01-06.jpg
| image_caption  = Ruffe in [[Pärnu (river)|Pärnu River]] (Estonia)
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn">{{cite iucn |author=Freyhof, J. |year=2024 |title=''Gymnocephalus cernua'' |volume=2024 |article-number=e.T9568A135087494 |doi=10.2305/IUCN.UK.2024-2.RLTS.T9568A135087494.en |access-date=16 March 2025}}</ref>
| taxon = Gymnocephalus cernua
| authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]])
| synonyms =
* ''Perca cernuus'' <small>Linnaeus, 1758</small>
* ''Acerina cernua'' <small>(Linnaeus, 1758)</small>
* ''Holocentrus post'' <small>Lacépède, 1802</small>
* ''Cernua fluviatilis'' <small>J. Fleming, 1828</small>
* ''Acerina vulgaris'' <small>G. Cuvier, 1829</small>
* ''Acerina fischeri'' <small>Eichwald, 1873</small>
* ''Acerina czekanowskii'' <small>Dybowski, 1874</small>
* ''Acerina cernua danubica'' <small>Vladykov, 1931</small> (ambiguous)
* ''Acerina cernua essipovi'' <small>Burmakin, 1941</small>
}}

The '''ruffe''' ('''''Gymnocephalus cernua'''''), also known as the '''Eurasian ruffe''' or '''pope''', is a freshwater [[fish]] found in temperate regions of [[Europe]] and northern [[Asia]].<ref name=fishbase/> It has been [[introduced species|introduced]] into the [[Great Lakes (North America)|Great Lakes]] of [[North America]] as an [[invasive species]] and is causing unfortunate results as it 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]].<ref>{{Cite web|title = Invasive Species: Aquatic Species – Eurasian Ruffe (''Gymnocephalus cernuus'')|url = https://www.invasivespeciesinfo.gov/aquatic/fish-and-other-vertebrates/eurasian-ruffe |website = www.invasivespeciesinfo.gov|access-date = 2016-02-11|publisher = National Invasive Species Information Center}}</ref>

==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 {{cvt|25|cm|in}} in length,<ref>{{cite web |title=Invasive Species: Eurasian Ruffe |url=https://www.michigan.gov/invasives/id-report/fish/eurasian-ruffe |website=Michigan Invasive Species |publisher=Michigan State Government |access-date=19 November 2023}}</ref> but is usually around half that size.<ref name=fishbase>{{FishBase | genus = Gymnocephalus | species = cernua  | month = August | year = 2016}}</ref> It is a very aggressive fish for its size. The ruffe also has a large, spiny [[dorsal fin]] which is likely distasteful to its [[predator]]s. 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 Sea|Caspian]], [[Black Sea|Black]], [[Aral Sea|Aral]], [[Baltic Sea|Baltic]] and [[North Sea]], and is also found in [[Great Britain]], parts of [[Scandinavia]]<ref>{{cite journal |last1=Kålås |first1=Steinar |title=The ecology of ruffe, ''Gymnocephalus cernuus'' (Pisces: Percidae) introduced to Mildevatn, western Norway |journal=Environmental Biology of Fishes |date=1 March 1995 |volume=42 |issue=3 |pages=219–232 |article-number=219 |doi=10.1007/BF00004915 |bibcode=1995EnvBF..42..219K |s2cid=20474424 |url=https://link.springer.com/article/10.1007/BF00004915 |access-date=11 February 2023 |language=en |issn=1573-5133|url-access=subscription }}</ref> 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]].<ref name="iucn" />

==Diet==
In Eurasia, the ruffe diet mainly consists of zoobenthos: [[chironomid]]s,<ref>{{cite journal |author=M. Tarvainen |author2=K. Vuorio |author3=J. Sarvala |name-list-style=amp |year=2008 |title=The diet of ruffe ''Gymnocephalus cernuus'' (L.) in northern lakes: new insights from stable isotope analyses |journal=[[Journal of Fish Biology]] |volume=72 |issue=7 |pages=1720–1735 |doi=10.1111/j.1095-8649.2008.01847.x|bibcode=2008JFBio..72.1720T }}</ref> small aquatic bugs and larvae,<ref>{{cite journal |last1=Peterson |first1=Greg S. |last2=Lietz |first2=Julie E. |title=Identification of ruffe larvae (''Gymnocephalus cernua'') in the St. Louis River, Lake Superior: Clarification and guidance regarding morphological descriptions |journal=Journal of Great Lakes Research |date=1 February 2017 |volume=43 |issue=1 |pages=205–210 |doi=10.1016/j.jglr.2016.10.005 |pmid=30364801 |pmc=6198672 |bibcode=2017JGLR...43..205P }}</ref> 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.<ref>{{cite journal |last1=Hölker |first1=Franz |last2=Thiel |first2=Ralf |title=Biology of Ruffe (''Gymnocephalus cernuus'' (L.))—A Review of Selected Aspects from European Literature |journal=Journal of Great Lakes Research |date=1 January 1998 |volume=24 |issue=2 |pages=186–204 |doi=10.1016/S0380-1330(98)70812-3 |bibcode=1998JGLR...24..186H |url=https://www.sciencedirect.com/science/article/abs/pii/S0380133098708123 |access-date=11 February 2023 |language=en |issn=0380-1330|url-access=subscription }}</ref>

==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 [[Spawn (biology)|spawning]] season for the ruffe occurs from the middle of April through approximately June.<ref name = 'life history'>{{cite journal |last1=Gutsch |first1=Michelle |last2=Hoffman |first2=Joel |title=A review of Ruffe (''Gymnocephalus cernua'') life history in its native versus non-native range |journal=Reviews in Fish Biology and Fisheries |date=1 June 2016 |volume=26 |issue=2 |pages=213–233 |doi=10.1007/s11160-016-9422-5 |bibcode=2016RFBF...26..213G |s2cid=254990236 |url=https://link.springer.com/article/10.1007/s11160-016-9422-5 |access-date=11 February 2023 |language=en |issn=1573-5184|url-access=subscription }}</ref>

==Life cycle==
Ruffe egg sizes typically range from {{cvt|0.34|to|1.3|mm}} in [[diameter]], depending on the size of the female.<ref name="life history" /> 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 {{cvt|0.36|to|0.47|mm}}, while the first batch of eggs goes from {{cvt|0.90|to|1.213|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 {{convert|10|-|15|C|F}}.
The next stage in life is the embryonic/juvenile stage. [[Embryos]] that are freshly hatched are between {{cvt|3.5|and|4.4|mm}} in size. These embryos are sedentary for 3–7 days, and in that time grow to about {{cvt|4.5|to|5.0|mm}} in length. One week after the hatching, the young ruffe start to swim and feed actively; they do not form schools at this age.<ref>{{cite journal |last1=Ogle |first1=Derek H. |title=A Synopsis of the Biology and Life History of Ruffe |journal=Journal of Great Lakes Research |date=1 January 1998 |volume=24 |issue=2 |pages=170–185 |doi=10.1016/S0380-1330(98)70811-1 |bibcode=1998JGLR...24..170O |url=https://www.sciencedirect.com/science/article/abs/pii/S0380133098708111|access-date=19 November 2023|url-access=subscription }}</ref>

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 {{cvt|20|cm}}, and a maximum of {{cvt|29|cm}} Growth 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 North American 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 [[habitat]]s and [[temperature]]s, resulting in success despite such factors as [[Climate change (general concept)|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.<ref>{{Cite web|title = Ruffe (''Gymnocephalus cernua'') – FactSheet|url = https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=7|website = nas.er.usgs.gov|access-date = 2016-01-28}}</ref>

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 (piscicide)|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 introduced as live bait by [[Esox|pike]] anglers. It is now abundant throughout the Loch. There are concerns 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]].<ref name = "Adams & Maitland">{{cite journal | author1 = Colin E. Adams  | author2 = Peter S. Maitland | year = 1998 | title = The Ruffe Population of Loch Lomond, Scotland: Its Introduction, Population Expansion, and Interaction with Native Species (abstract) | journal = Journal of Great Lakes Research | volume = 24 | issue = 2 | pages = 249–262 | doi=10.1016/s0380-1330(98)70817-2}}</ref>

==References==
{{Reflist}}

==Sources==
{{Div col}}
*{{cite thesis|author=Gangl, James Allen|year=1998|title=Effects of Eurasian Ruffe (Gymnocephalus cernuus) and Yellow Perch (Perca flavescens|degree=M.S.|publisher=University of Minnesota|location=Duluth|pages=1–5}}
*McLean, Mike. "Ruffe: A New Threat to Our Fisheries." Minnesota Sea Grant. 24 July 2007.1  Oct 2007 http://www.seagrant.umn.edu/ais/ruffe_threat
*{{cite journal |author=Peter J. Maniak |author2=Ryan D. Lossing |author3=Peter W. Sorensen |name-list-style=amp |year=2000 |title=Injured Eurasian ruffe, ''Gymnocephalus cernuus'', release an alarm pheromone that could be used to control their dispersal |journal=[[Journal of Great Lakes Research]] |volume=26 |issue=2 |pages=183–195 |doi=10.1016/S0380-1330(00)70685-X|bibcode=2000JGLR...26..183M }}
*Crosier, Danielle M., Molloy, Daniel P., Marsden, J. Ellen. "[https://web.archive.org/web/20070716161555/http://el.erdc.usace.army.mil/ansrp/gymnocephalus_cernuus.pdf Ruffe – ''Gymnocephalus cernuus'']."  New York State Museum.  University of Vermont. October 23, 2007.
{{div col end}}

==External links==
{{Commons category|Gymnocephalus cernuus}}
*[https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?SpeciesID=7&Potential=N&Type=0 GLANSIS Species FactSheet], [[United States Geological Survey]]
* [https://www.invasivespeciesinfo.gov/aquatic/fish-and-other-vertebrates/eurasian-ruffe Species Profile – Eurasian Ruffe (''Gymnocephalus cernuus'')], National Invasive Species Information Center, [[United States National Agricultural Library]]. Lists general information and resources for Eurasian Ruffe.

{{Taxonbar|from=Q187981}}

[[Category:Gymnocephalus]]
[[Category:Fish described in 1758]]
[[Category:Animal taxa named by Carl Linnaeus]]
[[Category:Freshwater fish of Europe]]
[[Category:Fish of Europe]]
[[Category:Fish of Asia]]
[[Category:Fish of Russia]]
[[Category:Fish of the Great Lakes]]