European Rudd

Diet and feeding

The FishTraits compilation records these diet categories for this species: aquatic or other vascular plants; invertebrates or larval fish. These are broad categories, not a claim that every individual consumes every example in a category.

Habitat preferences

Reported habitat associations include medium to large rivers, streams and small rivers, creeks, still-water habitats.

The source records associations with muck, clay or silt, sand, vegetation, organic debris. An association indicates reported use, rather than an exclusive requirement.

The species is classified as tolerant of a broad range of salinities. This flag does not specify a salinity range for aquarium care.

Reproduction and parental care

The compilation reports a representative maturity age of 2 years. Its maturity field summarizes mean, median, or modal estimates, usually for females; male estimates can be used when female data are unavailable. It is not a fixed age at which every fish first breeds.

Batch or serial spawning has been reported somewhere in the species’ range. This does not establish the same spawning pattern for every population.

Recorded spawning months are May, Jun for the source’s reporting region (Russia). This is a regional calendar, not a range-wide schedule.

The reproductive-guild classification includes spawning on open substrates without guarding the brood.

Size and recorded longevity

FishTraits reports a maximum total length of 51 centimetres. Some entries use an estimated asymptotic length; this value should not be treated as a certified record catch.

Recorded longevity in the compilation is 19 years. Wild observations were preferred, but captive records were accepted where wild records were unavailable, and unspecified records were assumed wild. The value is not a guaranteed wild lifespan or an aquarium life expectancy.

Spawning movements

The compilation records significant spawning-related movement. Its combined migration flag covers movements within fresh water as well as between rivers and the sea; this flag alone does not establish which migration pattern applies.

Identification and appearance

Rudd can be distinguished from all native North American minnows (Cyprinidae) by the presense of a scaled keel along the belly between the pelvic and anal fins, along with a deep compressed body. Rudd is superficially similar to the native Golden Shiner (Notemigonus crysoleucas), and can be distinguished by the following characters (Howells 1990; Page and Burr 2011)

Native range

Western Europe to the Caspian and Aral sea basins (Berg 1949; Robins et al. 1991).

Habitat and ecology

Rudd is a benthic cyprinid fish that prefers water up to 3 meters deep and temperatures between 2 and 22°C (Gerstmeier and Romig 1998; Glinska-Lewczuk et al. 2016; Juza et al. 2018). Abundance decreases with depth, and Rudd populations benefit from artificial and natural coastal refuges that help them avoid predation (Lemmens et al. 2016; Virbickas and Stakenas 2016). Rudd were previously described as a littoral species that prefers lentic habitats (Johansson 1987; Lake et al. 2002), however, recent studies of Rudd populations in the Niagara River found higher abundance, growth, and reproductive success in lotic versus lentic habitats (Kapuscinski et al. 2012a). Rudd has omnivorous feeding habits that can change with temperature and season. Generally, their diet includes macrophytes, bryophytes, and filamentous algae along with fish and some other animal material and detritus (Nurmien et al. 2003; Guinan et al. 2015). Rudd in Lake Banyoles, an oligotrophic, karstic lake was more zooplanktivorous in spring and autumn and less in summer and showed a size-dependent diet shift from microcrustaceans while small, to macroinvertebrates at larger sizes (Garcia-Berthou and Moreno-Amich 2000). Guinan et al. (2015) showed Rudd in the upper Niagara River exhibited a diet switch from piscivory in early spring towards herbivory in summer/fall coinciding with increased macrophyte abundance and warmer water temperatures. The shift from piscivory to herbivory typically occurs once temperatures exceeded ~16°C, allowing Rudd to avoid competition with other fishes or to avoid predation by piscivorous fishes (Johansson 1987; Eklöv and Hamrin 1989; Kapuscinksi et al. 2012a). Another reason for a shift in diet at higher temperatures is that cellulase efficacy was reduced at temperatures greater than 15°C (Vejrikova et al. 2016). Feeding intensity of Rudd was also positively correlated with water temperature (Kapuscinski et al. 2012a) Reproduction occurs from April to August, typically beginning once water temperatures exceed 16°C (Domagala et al. 2020). Adhesive eggs are laid among submerged vegetation in warmer, calmer, waters near shore. Fecundity ranges from 3,500–232,000 eggs. In the upper Niagara River, the presence of age-0 Rudd was greater in lotic sites and poorer in ones without measurable flow, suggesting reproduction can be successful in lotic habitats (Kapuscinski et al. 2012a). Maturation occurs at 2 to 3 years when the fish is 90 to 150 mm in total length. Maximum life span can reach 17 years (Pfleiger 1997). Rudd are consumed by various predatory fish, including Pike (Esox lucius), Pike-Perch (Sander lucoperca), and Wels Catfish (Silurus glanis) (Gurbik et al. 2015; Djait et al. 2019). Rudd have similar energy density to other Great Lakes fishes and may be a useful food source (Forzono et al. 2017).

Introduction history

Bait bucket release seems to be the primary mechanism by which Rudd have gained access into open waters. However, the history of its introduction is complex and only partly known. The species apparently entered the United States during two widely separated periods of introduction. It was initially brought to this country either in the late 1800s or early 1900s. A second period of introduction presumably began in the late 1960s or early 1970s. The first verifiable U.S. record dates to 1916. In that year, some 300 specimens were obtained from the New York aquarium by B. O. Webster, the Wisconsin superintendent of fisheries, were transplanted to Lake Oconomowoc, Wisconsin (Cahn 1927; Greene 1935). Myers (1925) reported on a population in Central Park Lake in New York City. The Central Park population, now extirpated, may have originated from Copake Lake, Roeliff-Jansen Kill system, which also supported a population in 1916 and possibly earlier (M. N. Feinberg, personal communication to Burkhead). The origin of the very first New York fish is not known; however, because Rudd is popular in Europe as a food and game species, it may have been introduced for both purposes. The Central Park population also may have been the source for the transplant to a New Jersey park just across the Hudson (Myers 1925; Greeley 1935). The early 1950s capture of Rudd by C. R. Robins in Cascadilla Creek, Tompkins County, New York, appears to be the only and last known record from the creek (Courtenay et al. 1984; Smith 1985). The origin of this population is not documented, but the relatively close Roeliff-Jansen Kill population is a logical possibility. The earliest of the more recent records is a 1973 capture of Rudd from Cobbosseecontee Lake in Maine. Neither year nor origin of the Maine introduction is known. At about the same time, a bait dealer in Suffolk, Virginia, began rearing Rudd for bait. The source of the Suffolk, Virginia fish farmer's stock is uncertain. The interest in bait culture of Rudd dramatically intensified in the early 1980s. The central Arkansas region of Lonoke and Prairie counties, an area known for its active fish farming industry, apparently became the largest producer of Rudd in the United States. It appears that the greatest dispersal of Rudd has been through interstate traffic rather than direct European import. In fact, much of its recent culture and spread can be attributed to its popularity as a bait among Striped Bass Morone saxatilis anglers. As a result, Rudd have been widely introduced through a combination of bait bucket releases, escapes from aquaculture facilities and farm ponds, and, presumably, by dispersal from various points of introduction (e.g., Burkhead and Williams 1991). Although many Rudd introductions are considered accidental, it is likely that Rudd also have been intentionally released into public waters during the past few decades.

Ecological impacts

Largely unknown. In a laboratory setting, Burkhead and Williams (1991) demonstrated that rudd readily hybridize with native golden shiner, Notemigonus crysoleucas, a primary forage species of many native game fishes. As such, the probability exists that rudd introduced to open waters will hybridize with golden shiner, with unknown consequences to wild populations of the native species. First generation hybrids offspring should show heterosis (or hybrid vigor), but the "genetic pollution" in subsequent generations could prove detrimental due to a variety of factors, for instance spawning behavior and recruitment success, and general loss of fitness (Burkhead and Williams 1991; Courtenay and Williams 1992). Nevertheless, the interactions of the two species in nature are not known (Burkhead, personal communication). Cadwallader (1977) reviewed the potential impacts of the rudd in waters of the North Island of New Zealand. He concluded, in part, that rudd can be expected to compete for invertebrate food sources with native fishes. In addition, being omnivorous, the rudd can shift its diet to plants, unlike most native fishes. Because rudd are fairly hardy, Cadwallader also indicated that the fish will fare better than many native fishes in waters that are eutrophic or polluted.