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July 6, 2022

The roach (Rutilus rutilus) is a species of freshwater and brackish water fish belonging to the order of carp (Cypriniformes), which is found in Western Asia and Europe, excluding the Mediterranean region. It has also been introduced to many countries outside its original range, mainly for recreational fishing. The roach is an elongated and flat-sided species with silver flanks, red eyes and red ventral fins. Roaches are schooling fish and mainly eat small animals. Roaches can affect the eutrophication of water bodies by eating zooplankton and thus promoting the reproduction of phytoplankton.

Size and appearance

A roach usually grows to a length of 10–25 centimeters and a maximum length of 30–35 centimeters and a weight of 300–500 grams. Females are often larger than males and also grow a little faster. The heaviest documented roach in Finland was caught on July 29, 2007 in Posio's Mutkalamme, and it weighed 1.24 kilograms. The often mentioned roach weighing 2.5 kilos was probably really a roach. Estonia's record roach weighed 1.05 kilograms, and Sweden's sportfished roach record is 1.7 kilograms. In other parts of the world, roaches can grow up to 3 kilograms in weight; for example, in Germany, the record catch from the Rhine has been 3.13 kilograms. The growth of the roach is quite slow, only 2.5–3 centimeters per year. Growth rate varies according to environmental conditions. A total of 779 specimens of the species were caught in 2006 in Italy's Lake Maggiore for research purposes, with a total length ranging between 5.5 and 38.8 centimeters and an average of 21 centimeters. All in all, the males were calculated to be significantly smaller than females. The body of Särje is elongated and flat on the sides. Its mouth is small and forward-facing. The front edge of the roach's ventral fins is at the same point on the body as the front edge of the dorsal fin. The roach's body height varies slightly depending on its food intake. Finnish fish species that resemble roach are seipi, sorva, säyne, toutain and turpa. The species has red eyes and red ventral fins. However, in marine areas and lush waters, the eye can be lighter. The roach's tail fin is short, and its scales are large. The roach has 42–45 scales on the lateral line, and its caudal fin has 12–14 spines, of which 9–10 are branched joint spines. The dorsal fin has three unbranched articular spines and 9–11 branched articular spines. There are 17–19 reeds in the tail. The roach has six pharyngeal teeth and they are all in one row.

Distribution and habitat

The natural distribution of the roach extends from the western parts of Asia to almost all of Europe, with the exception of the Mediterranean region. The roach has been introduced to many countries for fishing, angling, feed production or sport fishing, and is found as an alien species in Australia, Cyprus, Spain, Italy, Portugal, the Azores, Morocco, Kazakhstan, Great Britain and Ireland. In northwestern Italy and Ireland, it is classified as invasive, i.e. as a harmful alien species. The International Union for Conservation of Nature (IUCN) classifies the roach as a viable species due to its wide distribution and low threats. The species is also classified as regionally viable in Finland. In Finland, roach is common in all coastal and inland waters, except for the northernmost Lapland. Sarki is the third most common fish species in Finland after perch and pike. Pike is also common in Sweden and is among the country's six most common fish species. Barren lakes and ponds are the roach's primary habitat. Secondary habitats include rivers, streams, brooks, lush lakes and lush ponds. The roach thrives in lush water and tolerates low oxygen levels, but cannot tolerate too acidic water. Usual