Bulgarian Journal of Agricultural Science
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I. Iliev, A. Zaikov, T. Hubenova
Abstract: Size and age at which the channel catfish reared in the conditions of a thermal power station cooling lake have reached sexual maturity were studied. The fish were reared in net cages situated in the cooling lake. The water temperature during the winter months does not fall under 10оС, which allows the fish to feed during the autumn-winter period and to generate growth. The established body weight of the one-summer old catfish is 100.5 g for males and 81.2 g for females. For the one-year old catfish, the body weight was 163.4 g for males and 133.2 g for females. Differentiation of the gonads was clearly pronounced as early as at age of one-summer. The GSI was 0.19% for the females and 0.016% for the males. By the age of one year, the ovaries doubled in size with an average weight of 0.21g, and the testes of 0.03 g. The GSI had values of 0.21% for the females and 0.04% for the males. The maturity stage of the ovary and the testis was determined as stage II. For the two-summer old catfish (16-17 months of age), an average body weight of 958.9 g for the males and 894.8 g for the females was established. The GSI was 1.68% for females and 0.15% for males. The ovary was in the III-IV stage of maturity and their predominant fraction consisted of early vitellogenic follicles. At an age of 18-19 months, the ovary was in the IV stage of maturity, and the vitellogenic follicles were the main fraction in the ovary. The spawning takes place during mid May-early June, and the fish that reached the age of two years, is with an average body weight of 1007.8 g for the males and 985.2 g for the females, and can participate successfully in the reproduction process. The values of the absolute (7 583 eggs) and relative (8700 eggs/kgbody weight) fecundity for the two-year old matured channel catfish were lower than those typical for the older sexually mature fish. The weight and diameter of the eggs were 0.0071 g and 2.12 mm, respectively.
Keywords: channel catfish; egg size; fecundity; first maturity
Date published: 2017-10-10
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