Eurasian ruffe, blacktail, pope, redfin darter, river ruffe, Acerina cernua, Gymnocephalus cernuus

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic

Realized:
Ruffe was first discovered in the St. Louis River, a tributary to western Lake Superior, in the mid 1980s; by 1991, it was the most abundant fish in this area (Bronte 1998). The increase in ruffe was concurrent with declines in several fish species, including yellow perch (Perca flavescens), emerald shiner (Notropis atherinoides), and trout-perch (Percopsis omiscomaycus) (Bronte 1998, McLean 1993). However, there was a lack of clear causal evidence between the two events (Bronte 1998).

There has been a great deal of concern that ruffe may have a detrimental effect on more desirable species in Lake Superior, including yellow perch and walleye (Sander vitreus), by feeding on the young of these species (Raloff 1992) or by competing with them for food (McLean 1993). In Lake Superior, consumption of cisco (Coregonus artedii) eggs by ruffe has been documented at a level which could impact the population over winter months (Selegby 1998). Ogle et al. (1995) studied the diet of introduced ruffe inhabiting the St. Louis estuary. Their findings indicated that the species preys heavily on benthic insects, thereby suggesting that ruffe competes for food with yellow perch, trout-perch, and other native benthic-feeding fishes.

Potential:
Savino and Kolar (1996) conducted a laboratory study to test for food competition between ruffe and yellow perch. They found that competition could occur between the two species, but that the outcome was not always clear, as each species exhibited competitive advantages and disadvantages (Savino and Kolar 1996). Fullerton et al. (1998) also concluded that similarities in dietary preferences and feeding rates of ruffe and yellow perch suggest a strong possibility for interspecific competition.

Ruffe holds an advantage over native perch in its ability to better select moving objects under relatively dim light conditions or at high turbidity. Kolar et al. (2002) found that in a laboratory setting, ruffe exhibited higher consumption rates of benthic invertebrates in darkness over bare cobble and complex substrates than did yellow perch. With a very sensitive lateral line system and night-adapted vision, ruffe is more suited for foraging under poor light conditions than is yellow perch (Hölker et al. 1998).

Mayo et al. (1998) completed an assessment of an experimental top-down control system which sought to control ruffe populations with the stocking of five native predators (northern pike (Esox lucius), walleye, smallmouth bass (Micropterus dolomieu), brown bullhead (Ameiurus nebulosus), and yellow perch). The authors found that although predators consumed nearly half of available ruffe biomass in one year, each species preferentially selected native fish species and ruffe abundance continued to increase (Mayo et al. 1998). However, consumption of ruffe appeared to increase yearly for most native predators, suggesting that native species may learn to prey on ruffe over time (Mayo et al. 1998).

Ruffe exhibits rapid growth and high reproductive output, and adapts to a wide range of habitat types (McLean 1993); therefore the species may pose a threat to native North American fish. 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 (McLean 1993).

Current research on the socio-economic impact of Gymnocephalus cernua in the Great Lakes is inadequate to support proper assessment.

Realized:
When ruffe first invaded Lake Superior, it was thought that this species could generate a considerable cost for recreational fishing, particularly by causing a decline in yellow perch (Perca flavescens) populations (Leigh 1998). Under a moderate scenario of spread and impact, it was predicted that ruffe could generate costs in excess of $500 million by 2050 (Leigh 1998). However, these concerns have yet to be confirmed as the extent of ruffe’s contribution to declines in native fish populations remains undecided (Czypinksi et al. 2007). Ruffe abundance appeared to remain stable or decline annually in Lake Superior as late as 2001-2005 (Czypinski et al. 2007, Gorman et al. 2010).

There is little or no evidence to support that Gymnocephalus cernua has significant beneficial effects in the Great Lakes.

In Pennsylvania, it is unlawful to possess live ruffe or to import or introduce live ruffe to Pennsylvania waters under 58 PA Code § 71.6. It is unlawful to sell, purchase, offer for sale or barter for live ruffe under 58 PA Code § 63.46. Ruffe may not be transported from another state, province, or country into Pennsylvania, liberated into a Pennsylvania watershed, or transferred between Pennsylvania waters without written permission from the Pennsylvania Fish and Boat Commission under 58 PA Code § 73.1. In Ohio, it is unlawful to possess, import, or sell live individuals of ruffe except for research, education, or public display when authorized (Ohio Admin. Code § 1501:31-19-01). In Michigan, ruffe is a prohibited species under MI NREPA 451 § 324.41301. No person shall knowingly possess a live prohibited organism in Michigan except for education, research, or identification purposes as listed in MI NREPA 451 § 324.41303. It is also unlawful to introduce prohibited organisms in MI under MI NREPA 451 § 324.41305. In Michigan, a violation involving a prohibited species is a felony, and a knowing introduction violation with intent to harm is punishable with up to 5 yrs. imprisonment and a $2,000 to $1,000,000 fine (MI NREPA § 324.41309). In Indiana, ruffe is classified as an exotic fish under 312 IAC 9-6-7, meaning except as otherwise provided, no individual can import, possess, propagate, buy, sell, barter, trade, transfer, loan, or release into public or private waters live fish, recently hatched juveniles, viable eggs, or genetic material. In Illinois, ruffe is listed as an injurious species under Illinois Admin. Code 17 § 805.20. It is unlawful to possess, propagate, buy, sell, barter, or offer to be bought, sold, bartered, transported, traded, transferred, or loaned an injurious species to any person or institution unless a permit is obtained from the Illinois DNR (Illinois Admin. Code 17 § 805.30). In Wisconsin, ruffe is a restricted species as an established non-native, and therefore cannot be transported, possessed, transferred, or introduced without a permit (Wis. Admin. Code § NR 40.05). In Minnesota, ruffe is a prohibited invasive species, meaning it is unlawful (a misdemeanor) to possess, import, purchase, transport, or introduce an organism except under permit for control, research, or education (Minn. Admin. Rules § 6216.0250).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
Minnesota and Wisconsin, with advice from the U.S. Fish and Wildlife Service, implemented a top-down control program for ruffe in the St. Louis River, western Lake Superior, in 1989, using northern pike (Esox lucius), walleye (Sander vitreus), smallmouth bass (Micropterus dolomieui), brown bullhead (Ameiruus nebulosus), and yellow perch (Perca flavescens) (Mayo et al. 1998). A bioenergetics modeling evaluation of the top-down control program revealed that although predators ate as much as 47% of ruffe biomass in one year, they avoided ruffe and were selective for native prey, and were thus unable to halt the increase in ruffe abundance (Mayo et al. 1998). However, the authors noted that northern pike and walleye appeared to have potential for top-down control of ruffe due to a combination of their diets and population sizes, and due to indications that they may learn to prey more selectively on ruffe (Mayo et al. 1998).

As Mayo et al. (1998) noted, caution is advised when considering top-down biological control as a management tool because the stability properties of a system do not just depend on predation, but also on the life histories of component species and their interactions.

Physical
There are no known physical control methods for this species.

Chemical
Of the four chemical piscicides registered for use in the United States, antimycin A and rotenone are considered general piscicides, but no studies have been found of their effects on Gymnocephalus cernua (GLMRIS 2012).

Evaluation of the effects of common piscicides on ruffe revealed that the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has potential for selective control of the species (Boogaard et al. 1996). Ruffe was 3 to 6 times more sensitive to TFM than both yellow perch (Perca flavescens) and brown trout (Salmo trutta) (Boogaard et al. 1996). Toxicity tests in May and August 1992 on the Brule River, Wisconsin revealed a 12h LC99.9 (concentration at which 99.9% of organisms are killed after 12 hours) of 5.9 mg/L at normal pH levels (~8.4) and 2.80 mg/L at low pH levels (Boogaard et al. 1996). Furthermore, at low pH levels (7.7-7.9) 12h LC25’s of 7.2 mg/L and 4.6 mg/L were recorded for yellow perch and brown trout, respectively, but at normal pH levels no brown trout or yellow perch mortality was recorded at the highest tested concentration of 8.8 mg/L (Boogaard et al. 1996). A cost benefit analysis of a U.S. ruffe control program supported TFM as a promising chemical control (Leigh 1998). However, Dawson et al. (1998) suggest that TFM may have more application for treating entire bodies of water rather than localized areas because it tended to repel ruffe in preference tests, allowing them to move to untreated areas. Bottom-release formulations of bayluscide and antimycin showed promise for effectiveness in treating localized concentrations of ruffe, but more field testing is needed (Dawson et al. 1998).

Increasing CO2 concentrations, either by bubbling pressurized gas directly into water or by the addition of sodium bicarbonate (NaHCO3) has been used to sedate fish with minimal residual toxicity, and is a potential method of harvesting fish for removal, though maintaining adequate CO2 concentrations may be difficult in large/natural water bodies (Clearwater et al. 2008). CO2 is approved only for use as an anesthetic for cold, cool, and warm water fishes the US, not for use as euthanasia, and exposure to NaHCO3 concentration of 142-642 mg/L for 5 min. is sufficient to anaesthetize most fish (Clearwater et al. 2008).

It should be noted that chemical treatment will often lead to non-target kills, and so all options for management of a species should be adequately studied before a decision is made to use piscicides or other chemicals. Potential effects on non-target plants and organisms, including macroinvertebrates and other fishes, should always be deliberately evaluated and analyzed. The effects of combinations of management chemicals and other toxicants, whether intentional or unintentional, should be understood prior to chemical treatment. Boogaard et al. (2003) found that the lampricides 3-trifluoromethyl-4-nitrophenol (TFM) and 2’,5-dichloro-4’-nitrosalicylanilide (niclosamide) demonstrate additive toxicity when combined. In another study on cumulative toxicity, combinations of Bayer 73 (niclosamide) and TFM with contaminants common in the Great Lakes (pesticides, heavy metals, industrial organics, phosphorus, and sediments) were found to be mostly additive in toxicity to rainbow trout, and one combination of TFM, Delnav, and malathion was synergistic, with toxicity magnified 7.9 times (Marking and Bills 1985). This highlights the need for managers to conduct on-site toxicity testing and to give serious consideration to determining the total toxic burden to which organisms may be exposed when using chemical treatments (Marking and Bills 1985). Other non-selective alterations of water quality, such as reducing dissolved oxygen levels or altering pH, could also have a deleterious impact on native fish, invertebrates, and other fauna or flora, and their potential harmful effects should therefore be evaluated thoroughly.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

Brazner et al. (1998) found that densely vegetated shoreline wetland habitats provide a refuge from intense competition with ruffe for indigenous fish.

Since the last ITIS update and 2004 American Fisheries Society names list update, there has been a return to the original species epithet (cernua). Authorities such as Eschmeyer's Catalog of Fishes (30 Sept. 2011 update), the Peterson fish guide, have FishBase reflect this change. According to W. Eschmeyer (pers. comm.), "cernua" is a noun and so does not decline (i.e., not an adjective to match the masculine genus). The ITIS expert for this species also confirmed the valid species name is now G. cernua (W. Starnes pers. comm.), although ITIS has yet to reflect that change.