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Theragra chalcogramma:   (click for more)

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  • Gadus periscopus  Cope, 1873
  • Pollachius chalcogrammus  Jordan & Gilbert, 1881
  • Gadus minor  Doderlein, 1887
  • Pollachius chalcogrammus fucensis  Jordan & Gilbert, 1894
  • Theragra fucensis  Jordan & Evermann, 1898
  • Theragra chalcogramma chalcogramma nati  Svetovidov, 1948
    FAO Names
    En - Alaska pollock(=Walleye poll.), Fr - Lieu de l'Alaska, Sp - Colín de Alaska.
    3Alpha Code: ALK     Taxonomic Code: 1480401601
    Scientific Name with Original Description
    Gadus chalcogrammus  Pallas, 1811,Zooar..Rosso-Asiat., 3: 198.
    Diagnostic Features
    Eye 20.7 to 25.7% of head length. Predorsal length 28.1 to 29.2 °/0 total length. Caudal peduncle depth 3.0 to 3 5 of total length.  Colour: olive green to brown dorsally, often mottled or blotched; silvery on sides, pale ventrally; fins darker. 
    Geographical Distribution

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    Widely distributed in the temperate to boreal North Pacific, from Central California into the eastern Bering Sea, along the Aleutian arc, around Kamchatka, in the Okhotsk Sea and into the southern Sea of Japan.
    Habitat and Biology
    Generally demersal,from 30 to below 400 m depth, sometimes near the surface; performs diurnal vertical migrations.Reaches first maturity at 3-4 years (30 to 38 cm total length).
    Fecundity varies with age: 4 years: 520 000 eggs; 11 years: 15 million eggs for the W Bering Sea stock .Congregates in dense schools to spawn, usually at 50 to 250 m depth. The length of the spawning season varies by area, from 2 to 7 months. Spawns mostly from January to March in the Strait of Georgia and the Aleutian Basin, but spawning occurs much later to the northwest of the Pribilof Islands (extending to August) than in the southeastern Bering Sea.  Grows rapidly and lives to 14-15 years.The young feed mainly on copepods and their eggs. Adults prey upon shrimps, sand lance and herring in British Columbia, on pink, chum and coho salmon in Alaska; and on mysiids, euphausiids, silver smelt, and capelin in Asian waters.Alaska pollock is preyed upon by fur seals.
    Reaches 80 cm total length.
    Interest to Fisheries
    This species contributes the largest of all demersal fish resources; it is composed of 12 major stocks distributed in different areas of the North Pacific. The total catches have recently showed a negative trend after a peak reached in 1986 (6,758,944 t) but latest statistics shows that the trend could have been inverted. In fact, the catch recorded for 1995 in the FAO Yearbook of Fishery Statistics totalled 4 809 011 t, of which 3,330,591 mt were taken in the western North Pacific (area 61) and 1,293,939 t in the eastern North Pacific (area 67). The largest catches come from the outer shelf and slope of the eastern Bering Sea between the eastern Aleutians and the Pribilof Islands, and from waters southwest of St. Mathew Islands. Fishing depth ranges from 90 and 300 m in the Bering Sea, and from 50 to 200 m in the Gulf of Alaska (100-200 m in winter and 50 to 150 m in summer). The total catch reported for this species to FAO for 1999 was 3 362 473 t. The countries with the largest catches were Russian Federation (1 500 450 t) and USA (1 055 016 t). The Alaska pollock is caught mostly by pair trawl and stern trawl, Danish seines and longlines; gillnets and dragnets are also used in inshore areas. Trawl and longline fishing is most productive in daytime when the schools are more concentrated near the bottom.
    In the past, it was used only for animal feeds but it has now become an important food resource for humans in the form of frozen blocks (whole or fillets), roe, and salted products.
    Local Names
    CANADA : Walleye pollock .
    JAPAN : Sukeso-dara .
    USA : Alaska pollock .
    former USSR : Mintai .
    Svetovidov (1948), suggested that T. chalcogramma divides into geographical races, some of which have been named (see synonymy) Other ichthyologists recognize but a single, named species.
    Source of Information
    FAO species catalogue. Vol.10. Gadiform Fishes of the world (Order Gadiformes). An Annotated and Illustrated Catalogue of Cods, Hakes, Grenadiers and other Gadiform Fishes Known to Date.Daniel M.Cohen Tadashi Inada Tomio Iwamoto Nadia Scialabba 1990.  FAO Fisheries Synopsis. No. 125, Vol.10. Rome, FAO. 1990. 442p.
    Andriashev, (1954)
    Balykin, (1986)
    Hart, (1973)
    Niggol, (1982)
    Svetovidov, (1948)
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