出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/18 00:32:24」(JST)
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| Rutilus rutilus | |
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Conservation status
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Least Concern (IUCN 2.3) |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Cypriniformes |
| Family: | Cyprinidae |
| Genus: | Rutilus |
| Species: | R. rutilus |
| Binomial name | |
| Rutilus rutilus (Linnaeus, 1758) |
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The roach (Rutilus rutilus), also known as the common roach, is a fresh and brackish water fish of the Cyprinidae family, native to most of Europe and western Asia. The name "roach" is not unique, but fishes called roach can be any species of the genera Rutilus and Hesperoleucus, depending on locality. The plural of the term is also roach.[1]
The roach is basically a small fish, often reaching no more than about 35cm, maximum length is 45-50cm. The body has a bluish silvery colour and becomes white at the belly. The fins are red. The number of scales along the lateral line is 39-48. The dorsal and anal fins have 12-14 rays. Young specimens have a slender build; older specimens acquire a higher and broader body shape. The roach can often be recognized by the big red spot in the iris above and beside the pupil. Colours of the eye and fins can be very pale, however, in some environments.
In Central and Northern Europe, the common roach can most easily be confused with the common rudd (Scardinius erythropthalmus), the dace (Leuciscus leuciscus), or the ide (Leuciscus idus). They can be distinguished, though, by the following characteristics:
The common roach is found throughout Europe except for the area around the Mediterranean, and its distribution reaches eastward into Siberia. Eastern Europe and Asia have several subspecies, some with an anadromous lifecycle living around the Caspian and Black Seas.[2] Around the Mediterranean and in northwestern part of Spain and Portugal, several closely related species occur with no overlap in their distribution.
It was introduced in Australia in the Murray River and coastal drainages of southern New South Wales and Victoria from Europe during the 1860s and 1880s for sport purposes.
The common roach mostly feeds in the deeper parts of water bodies, but can be found in any water body deeper than 20 cm (7.9 in) and wider than 1.5 m (4 ft 11 in), and adapts to local circumstances, although in the summer, it can be caught using surface floats and bread. It tolerates organic pollution and is one of the last species to disappear in polluted waters, but is also often the most numerous cyprinid in nutrient-poor waters. It also tolerates brackish water. The lethal temperature is around 31°C (88°F).
In most parts of its distribution, it is the most numerous fish, but it can be surpassed by the carp bream in biomass in water bodies with high turbidity and sparse vegetation. The roach is a shoaling fish and is not very migratory with the exception of the anadromous subspecies. In the cold season, they migrate to deep waters, where they form large and dense shoals (small inland harbours are a favourite).
The roach mostly inhabits waters that are somewhat vegetated, because larval and young fish are protected by the vegetation and the mature fish can use it for food. The common roach eats plant material, bottom-dwelling (benthic) invertebrates, and plankton. Young fish feed mainly on plankton, while the mature fish feed mainly on benthos. They can adapt to environments where invertebrates are scarce by slowing their growth, maintaining slender body shapes, and early maturation.
The spawning season is in April and May. Most often, spawning occurs on sunny days. Roach generally spawn at the same location each year. Large males form schools where females enter. Males trail the females and fertilize their eggs. The behaviour is rough and the fish often jump out of the water. A female can lay up to 100,000 eggs. When the pH of the water is below 5.5, the roach cannot reproduce successfully.
Fishing for roach in Britain is relatively easy because the species is found in most rivers, lakes, and ponds throughout the country. Larger specimens tend to be elusive, but smaller ones are easy to catch on relatively light line and with a bait such as maggots or worms. They also take particle baits such as sweetcorn, and can be caught on a variety of baits. The only limit is the size of the bait, because the mouth of the roach is relatively small and the pharyngeal teeth are not particularly strong. A popular bait, particularly in France and Belgium, is germinated, cooked hemp seed.
Essential for good catches is regular feeding to keep the shoal active and feeding around the bait. Mostly fixed rods and floats are used for a controlled presentation of the bait, and for larger distances and specimens, match rods and swim feeders are used. The line doesn't need to be thicker than 0.12 mm and the hook not more than a size 12. Thinner lines and smaller hooks produce more fish especially when the roach are of small size. The best catches with fixed float fishing are often made when the bait is presented just a few centimeters above the bottom.
Boilies and luncheon meat are generally avoided by roach because they are too large for roaches to swallow. It is a schooling species, and it is not unusual for an individual to be caught and released many times during a single session. Sometimes, a larger specimen can be waiting outside the shoal. Roach are infamous for their ability to throw the hook during retrieval, which perpetuates the idea that larger roach are notoriously difficult to bank. The maximum recorded weight for the species in Britain is 4 lb (1.8 kg). Any fish over a pound is regarded as a specimen individual.
Laran be made in harbours where large shoals concentrate in the winter season. Flyfishing in such places with sinking artificial flies with a gold-colored bead for a head on long leaders can produce good catches.
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| リンク元 | 「roach」「Cyprinus」「Barbus」「Cyprinidae」「carp」 |