Fun Ruffe Facts For Kids

Arpitha Rajendra
Oct 20, 2022 By Arpitha Rajendra
Originally Published on Aug 06, 2021
Edited by Luca Demetriou
Read some amazing ruffe facts here on Kidadl

Ruffe (Gymnocephalus cernua), also called Eurasian ruffe or pope, is a freshwater fish that occupies temperate areas. The origin of the name ruffe is unclear.

They grow up to 5-6 in (12.7-15.2 cm) in length. However, it probably refers to the Gymnocephalus genus as it is native to Eurasia or refers to a local member.

These species were introduced into the North American Great Lakes and Lake Superior through the ballast water discharged from the ships, where they are considered invasive due to their fast reproductive cycle. They might have also spread in lake Michigan and Huron through ballast water.

So, the population of ruffe spread across the Great lakes is under surveillance. This fish species is found in olive-brown to a golden-brown color. The ruffe fish species were found in 1982 in Loch Lomond in Scotland, which were mostly introduced by pike anglers using them as live bait.

As their population in the Loch is increasing, they harm the endemic fish Coregonus lavaretus, powan as they feed on powan's eggs. This genus consists of five recognized species.

Marcus Elieser Bloch, naturalist, and German physician, introduced Gymnocephalus. It has two Greek elements: 'gymno' translates to 'naked' and 'kephalos' which means 'head.'

If these facts about ruffe fish are interesting, then do read these salmon facts and electric eel facts for more. 

Ruffe Interesting Facts

What type of animal is ruffe?

Eurasian ruffe (Gymnocephalus cernuus) is a freshwater fish of the order Perciformes and Phylum Chordata. Ruffe can survive natural predators due to their behavioral adaptations. These fish are native species of Europe and Asia. Ruffe is aggressive by nature.

Ruffe in the great lakes prey on fish eggs, so they are considered a threat to the North American fisheries. They adapt well to new environmental conditions with varying nutrients. They are related to the yellow perch. These fish are actively fed at night.

What class of animal does ruffe belong to?

Eurasian ruffe (Gymnocephalus cernuus) belongs to Actinopteriigy class of animals.

How many ruffes are there in the world?

The current population of Eurasian ruffe (Gymnocephalus cernuus) is not known. However, in 1991 the estimated population of this fishes in Duluth Harbor, Minnesota, was two million adult ruffes.

Where does ruffe live?

Ruffe (Gymnocephalus cernuus) has a wide range of natural habitat regions in Europe and Asia. They also occupy North America, where they were previously introduced.

Their habitat range involves the basins of the Black, Baltic, North, and Aral sea. Their habitat range also extends to regions of Scandinavia, Great Britain, and some parts of the Arctic Ocean basin eastward through the Kolyma drainage.

The species were introduced to Greece, Western Europe, and the Great Lakes of North America. These fish are considered an invasive distribution in the St. Louis river basin, Lake Michigan, Lake Huron, and Lake Superior.

What is a ruffe's habitat?

Eurasian ruffe is a bottom feeder in rivers. Their habitat range also includes fresh and brackish waters.

Who does ruffe live with?

Eurasian ruffe live on their own or in schools.

How long does a ruffe live?

Eurasian ruffe life expectancy does not exceed more than 7-11 years of age.

How do they reproduce?

Eurasian ruffe has a high reproductivity rate. The average age of sexual maturity for a ruffe is two to three years.

However, they can mature early, in the first year of their life, in warmer environmental conditions. They leave their natural habitat, dark and deep waters, and migrate to shallow and warm waters for spawning.

The spawning season of ruffe is from mid-April to June. The female lays around 130,000-200,000 eggs. The diameter of these eggs is 0.0013-0.05 in (0.34-1.3 mm).

If the female lays the second batch of eggs in the same season, the eggs produced will be smaller than the eggs of the first batch, their growth rate increases in clear, brackish waters.

A study was done on reproduction and early life history of the ruffe and the fishery managers determined that the reproduction takes place in a water temperature of 53.6-57.2 F (12-14 C).

What is their conservation status?

The conservation status of Eurasian ruffe is Least Concern. Since their reproduction rate is high, fish eggs are food to these fishes and are hazardous to the North American fisheries.

They are also highly adaptable to every environmental condition. To control the populations of ruffe, studies done on their reproduction helps the fishery managers for better management.

The transportation of these aquatic species can be decreased with better ballast water management. Also, the harvesters of the bait minnows have been restricted from the Michigan, Minnesota, and Wisconsin water bodies of Lake Superior.

Ruffe Fun Facts

What does ruffe look like?

Ruffe species favorable temperature is around 70-90 F (21-32 C)

*Please note that this is an image of a Walleye, a predator of the ruffe. If you have an image of a ruffe, please let us know at

Eurasian ruffe has identical markings and coloration as the walleye fish. Ruffe has an oval-shaped body.

They have olive-brown to golden-brown color and yellowish-white underparts. Even though they grow up to 10 in (25.4 cm), they are usually half the size measuring around six in (15 cm).

The dorsal fin is large and fused. They use this spiny dorsal fin to drive away their natural predators.

They have two fins on the top of their body, soft spines on the back fin that are called rays, and hard, sharp spines on the front fin. The distinct feature of ruffe is their downturned mouth and continuously large dorsal fin. There are 11-16 rays and 12-19 spines that define the dorsal fin.

There are 16-17 rays on the caudal fin and 13-17 rays on the pectoral fins. There are black spots on the caudal and dorsal fins.

There were morphological differences found between the Eurasian and North American ruffe fish. The variation was the number of their soft rays on the dorsal fins, the length of the caudal peduncle and anal fins, and the number of preopercular spines.

There were deep and shallow-bodied species found that were spread across the Dnieper river. The sexual dimorphism is not distinct, and females can be differentiated by their enlarged bellies only during the spawning season.

How cute are they?

Eurasian ruffe is a slimy native fish of Northern Europe and Asia. They are not considered cute.

How do they communicate?

Eurasian ruffe, like other aquatic creatures, communicate through motion, smell, color, and sound. They use neuromasts, sensory organ systems to detect water vibrations. This organ allows them to find food and avoid predators.

How big is a ruffe?

Eurasian ruffe can reach up to 10 in (25 cm). However, it is very rare, and the typical length of these species is around 5-6 in (12.7-15.24 cm).

How fast can a ruffe swim?

The exact speed of the Eurasian ruffe fish is not yet known.

How much does a ruffe weigh?

The Eurasian ruffe weighs around 0.6-0.13 lb (30-60 g).

What are the male and female names of the species?

There is no specific name given to the female and male Eurasian ruffe fish.

What would you call a baby ruffe?

There is no specific name given to the baby ruffe fish.

What do they eat?

Their diet consists of small aquatic larvae and bugs and zoobenthos like Chironomidae. Eurasian ruffe competes with other benthivorous fish species for food with native fish species like trout perch, yellow perch, and other species.

So, if the population of this species increases, there will be less food for other native species. Their predation on other fish eggs negatively impacts other fish populations. The adult's diet includes mayflies, caddisflies, and midges.

Are they dangerous?

No, they are neither dangerous or poisonous. The many spines on their dorsal fins can pierce your skin if they are not handled the right way.

Would they make a good pet?

No, ruffe species would not make a good pet. They are spread across several rivers, ponds, and lake habitats. They do well in shallow, dark, and deep waters of up to 250 ft (76.2 m) depth.

Did you know...

It was in 1987 that the distribution of this species was observed in the Great Lakes in Lake superior. They not only invade the space of other fishes but also compete for food in the lake regions.

Due to this, other fishes have less food to feed on. They also have a relatively high reproductive and growth rate. They can live in any habitat and also escape predators.

To control ruffe in the great lakes, scientists increased the natural predators like yellow perch, northern pike, and walleye populations in lake and river regions. Predation on ruffes also occurs by great cormorant, gray heron, lake trout, and kingfishers.

The neuromast organs on the ruffe become even more sensitive and advanced as they mature when compared to the neuromast of a perch fish which becomes weaker as they mature.

The control through predation of ruffe was unsuccessful. The pike-perch introduced into the Netherland water had similar outcomes. However, predation of eel and pike-perch population in Russian lakes did reduce the ruffe catches in Estonian lakes.

Why are ruffe invasive species?

Ruffe fish are considered invasive because they are damaging the ecology of Lake Superior. Even though yellow perch and ruffe are related, they have constantly been competing against each other over food.

Also, the ruffe is continuing to win against the perch. The first species declared as invasive by the Non-indigenous Aquatic Nuisance Prevention and Control Program is ruffe. They were not only the most populous in the St. Louis river basin but also disruptive to the ecosystem.

The DNR first recorded the invasion in the '80s. They suggested that the ruffe fish were dumped by the ballast water from anchored freight ships into Duluth, Minnesota.

Where is the ruffe native to?

The ruffe is a native species of Europe and Asia, which is why they are also called the Eurasian ruffe.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other fishes from our butterflyfish facts and Nile perch facts pages.

You can even occupy yourself at home by coloring on one of our free printable fish coloring pages.

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Written by Arpitha Rajendra

Bachelor of Engineering specializing in Aeronautical/Aerospace Technology, Master of Business Administration specializing in Management

Arpitha Rajendra picture

Arpitha RajendraBachelor of Engineering specializing in Aeronautical/Aerospace Technology, Master of Business Administration specializing in Management

With a background in Aeronautical Engineering and practical experience in various technical areas, Arpitha is a valuable member of the Kidadl content writing team. She did her Bachelor's degree in Engineering, specializing in Aeronautical Engineering, at Nitte Meenakshi Institute of Technology in 2020. Arpitha has honed her skills through her work with leading companies in Bangalore, where she contributed to several noteworthy projects, including the development of high-performance aircraft using morphing technology and the analysis of crack propagation using Abaqus XFEM.

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