ЛИНЕЙНО-ВЕСОВЫЕ ХАРАКТЕРИСТИКИ СТЕРЛЯДИ ACIPENSER RUTHENUS (LINNAEUS, 1758) НИЖНЕГО ИРТЫША (УВАТСКИЙ РАЙОН)

Abstract

Sterlet ( Acipenser ruthenus (Linnaeus, 1758)) is a widespread, but small in number freshwater fish that lives in the waters of Europe, Siberia, the Black, Azov, Caspian, Baltic, White, Barents, and Kara Seas. In catches made for conducting forensic expertise in 2015-2017 there occurred sterlet with absolute length from 23.9 to 50 cm, total weight from 54 to 722 g, the age varied from 1 to 7 years. Juvenile stage individuals made 25%, females - 46.9%, males - 28.1%. The annual increment in the age group from 1-2 years old was 1.2 cm, at the age 2-3 years old - 4.3 cm, at the age of 3-4 years old - 6.4 cm, at the age of 4-5 years old - 2.1 cm. This sample has a feature in the presence of slow-growing fish of old age. The rate of linear growth decreases after the 4th year and makes 5.1%. The annual increase in body weight at the age of 1-2 years old was 15.8 g, at 3 years old - 71.2 g, at 4 - 196 g, at 5 - 67 g, accordingly. Weight gain at the age of 1-2 years old was 18.7%, at 2-3 - 70.8%. In categories at the age of 3-4 years old and 4-5 years old the weight gain was 114.6% and 18.3%, correspondingly. Sterlet sires with II stage of maturity of sexual products were dominating. Among the examined individuals the predominant ones had I degree of fat content; species with a given degree were met in all age groups. There was stated a large number of long-nosed individuals (97.7%) and extremely small number of short-nosed individuals (2.3%).