Roach, Rutilus rutilus (Linnaeus 1758)

Native to Europe. Introduced from Central Europe by acclimatisation societies to Tasmania between 1860 and 1870, and then to the Yarra River system in Victoria, New South Wales, and Western Australia. Roach were subsequently moved southwest of the Great Dividing Range in Victoria and are now in the Goulburn River system, north of the Great Dividing Range, and are in the Murray-Darling River system. The Roach has recently been reported from Port Stephens (New South Wales), however they are no longer found in Western Australia. They have probably been spread by anglers who use them as live bait.

 Usually inhabits still and slow-flowing rivers, lakes and ponds, especially amonsgt aquatic vegetation. The species usually lives in water temperatures of 8-25°C, but can reportedly tolerate temperatures of 0-38°C. They can have some tolerance of  brackish water.

Dorsal fin III, 9-11; Anal fin III, 9-11; Pectoral fin I, 15; Pelvic fin II, 8; Lateral line scales 40-45.

Relatively deep-bodied, laterally-compressed, back arched; caudal peduncle relatively slender; tail distinctly forked; head small; snout blunt; mouth terminal, small, gape not reaching to front of eye; barbels around mouth absent; eye small, red; small axillary scale process present at pelvic-fin bases. Scales cycloid, of moderate size and firmly attached. Single, short-based dorsal fin positioned midway on back, somewhat square edged; anal fin short based, similar in shape to dorsal fin but not as high; pectoral fins low, well forward, somewhat pointed, anterior most rays longest; pelvic fins abdominal, somewhat pointed, with a small axillary process, inserted below dorsal fin; caudal fin deeply forked.

Olive green on back, silver on sides and silvery white on belly; eyes bright red.

An omnivore and zooplanktivore often seen feeding in schools. Juveniles feed on plankton, whereas adults are mostly bottom feeders eating mainly aquatic invertebrates and plants. They will also take terrestrial insects from the water surface.

The sexes are separate, and fertilisation is external. Males mature at 1-2 years and females at 2-3 years and females are egg layers (oviparous). The breeding season is from spring to early summer, and males develop nuptial tubercles on their pectoral fins before spawning. Females spawn between 5,000 to 200,000 demersal eggs that are attached to aquatic vegetation or onto tree roots, gravel or stones on the bottom. The eggs are small (~1-1.5 mm diameter), transparent and slightly adhesive. Larvae hatch in 4-10 days (dependent on water temperature) at 5-6 mm TL, and attach themselves to aquatic vegetatin before they become free swimming. Individuals can live to 18 years of age.

Although a popular food fish in eastern Europe, the Roach is not commonly fished by recreational anglers in Australia, where it is often regarded as a nuisance. The white flesh is considered to be poor eating.

In South Australian waters, under the SA Fisheries Management Act, 2007, it is illegal to release fish species that are not native to South Australia into any SA waterway. Exotic species such as Roach out-compete native fishes for food and habitat, they may degrade water quality and may prey directly on native species.

Primary Industry and Resources, South Australia. 2011. DAM SPECIES! Are you illegally releasing fish? Available online at http://www.pir.sa.gov.au/__data/assets/pdf_file/0009/157338/Dam_Species!_brochure_August2011.pdf

"Rutilus" is from Latin, meaning reddish gold, presumably in reference to the coloration of the fins.

Cyprinus rutilus Linnaeus 1758, Systema naturae. Holmiae 10^th ed: 324. Type locality: European lakes.

Gomon, M.F. & Bray, D.J. 2015