Salmonidae is a family of fishes of the order Salmoniformes. Passable and freshwater fishes. They live in cold, tropical and temperate waters of the basins of the world's oceans. There is an adipose fin. The scales are cycloid. The lateral line is complete. In the fins spiny rays are absent. Includes 6 genera: Brachymystax, Hucho, Oncorhynchus, Salmo, Salvelinus, Salmothymus. Fish large and medium-sized, from 50 to 150 cm. Spawn in fresh water. After spawning, all Pacific salmonids die. A number of passerine Salmonidae form dwarf resident freshwater forms. They are of great commercial importance.

     Salmonidae have been known since the Cretaceous period (145-66 million years ago) of the Mesozoic Era.

     The family includes both anadromous and freshwater fish species. The most famous representatives are: salmon, pink salmon, chum, nelma, nyolma, nerka, kizhuch, chinook salmon, kumzha, whitefish, omul, char, grayling, taimen, and lenok. The well-known collective names of several different species are salmon and trout. Salmonidae inhabit the Atlantic and Pacific Oceans, as well as fresh waters of the Northern Hemisphere, in the middle and northern latitudes. The largest natural spawning grounds of Salmonidae are located in Kamchatka, Sakhalin and the Kurils. Most Salmonidae are valuable commercial fish. Salmonidae are actively harvested not only for their valuable red meat, but also for their red caviar. The object of cultivation and artificial breeding are salmon, Pacific salmon, and various trout species.

     Body length - from a few centimeters (whitefish) to 3 meters. Weight - up to 90 kg (salmon, chinook salmon, taimen). Life span - several years, in some species the average life span reaches 15 years. The record holders in terms of both size and longevity (over 50 years) are taimen - a fish weighing 105 kg and 250 cm long has been reported.

     Salmoniformes are close to the herring family in their structure. Moreover, the family Salmonidae was previously referred to the herring family, and only relatively recently a separate order, Salmoniformes, was singled out.

     The body is long, compressed from the sides, covered with round or scalloped edge of easily falling cycloid scales. The pelvic fins are multilobed (more than 6 rays), located in the middle part of the abdomen, the pectoral fins are low-sitting, there are no barbed rays in the fins. Dorsal fins two - the present and the next behind it, located opposite the anal fin, a small adipose fin, which is one of the characteristic features of Salmoniformes. The dorsal fin has 10 to 16 (in Salmonidae) or 17 to 24 (in grayling) rays. The adipose fin has no rays.

     The swim bladder is usually connected to the esophagus by a canal. The mouth is bordered from above by two pairs of bones - maxillary and maxillary. In females, the oviducts are rudimentary or absent, so that the maturing eggs fall out of the ovary into the body cavity. The intestine has numerous pyloric appendages. Most eyes are equipped with transparent eyelids.

     In many Salmoniformes, the skeleton is not fully ossified: the cranium is largely composed of cartilage, the lateral processes are not attached to the vertebral bodies.

     Breed only in freshwater - some species live permanently in freshwater lakes, but most come up to spawn from the ocean or lakes into rivers and streams (passage fish). In doing so, they usually return to the same places where they were born. During spawning salmon strongly change in shape and coloration (mating attire). In freedom and with artificial insemination, they easily produce mixtures, easily acclimatized (e.g., some forms of trout in Australia).

     Salmonidae are fishes that easily change their lifestyle, appearance, and coloration depending on external conditions.

     The meat of all Salmonidae is excellent in flavor, and most of them have become objects of fishing and fish breeding. Salmonidae are among the most important commercial fishes in the world, producing catches of 0.5-1 million tons per year - about 3% of the total marine fish catch (data from the 1960s-70s). In 2005, 1 million tons of artificially farmed salmon were caught in Norway alone.

     All Salmonidae spawn in fresh running water - in rivers and streams. This is quite natural, since the ancestors of Salmoniformes were freshwater and only some species evolved into passage (anadromous) fish - salmon proper: noble (Atlantic) salmon and Pacific (Far East) salmon. Passage forms of Salmonidae spend most of their lives in marine waters, gaining weight, and when the time comes (usually after 2-5 years), they return to spawn in rivers, in the same places where they were born.

     Virtually all passage salmon spawn once in their lives and die after spawning. This is especially characteristic of Pacific salmon (chum salmon, pink salmon, sockeye salmon, etc.). In contrast, not all Atlantic salmon (salmon) die and some spawn up to 4 times (the only recorded record is 5 times), although this is more the exception than the rule.

     Before spawning, the organism of passage Salmonidae undergoes significant metamorphosis - radically changes in appearance, internal changes occur - the body loses its silver coloration, acquiring bright colors, red and black spots appear, it becomes taller, males often have a hump (hence the name of one of the species - pink salmon). The jaws of salmon become hook-shaped (the upper jaw curves downward, the lower jaw curves upward), the teeth become larger. At the same time, the stomach, intestines and liver degenerate, and the meat becomes less firm and fatty and, consequently, less valuable.

     The family is divided into three subfamilies: whitefish (3 genera), salmonids proper (7 genera) and grayling (1 genus).

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