engleski

Controlled reproduction of European catfish (Silurus glanis L.) in small ponds without artificial nests

Controlled reproduction of European catfish in special small spawning ponds whitout artificial nests was performed by previous hypophysation of broodfish (females 1-1, 5 mg/kg, males 1, 0 mg/kg) which spawn naturally on the grass covered banks of the spawning pond. The dimension of the ponds was 12x8 m with concrete bottom and thick grass on the slopes. The depth near the outlet was 1, 50 m. Spawning started usually at the end of May or at the beginning of June, when maximal water temperatures stabilized at 23-25o C. Only 1 female and 1 male equally weighted were nested in each pond. Immediatelly after spawning of the females, yeast was added daily into ponds in doses 4x50 g per pond. Fifth day after hatching of fry trout starter was applied every two hours (daily ration: about 15 kg/ha at the start to 30kg/ha at the end of the rearning). During the period 1980-1990, removal of the fry started at the age of 17-23 days after hatching, while in 1991 removal started at the age of 10-12 days. The mean number of grown up fry per female in the above periods was 29100 and 53800 respectively. Shortening of the fry rearning period resulted in significant increase of fry reared per one female. Ichthyophiriosis was avoided and there was no mass mortality. The grown up fry were in good condition, but they were more sensitive to manipulation and transport.

Silurus glanis ; reproduction ; spawning ponds ; hypophysation ; rearing of fry

nije evidentirano