اثرات ماهيان كاراس و سوف بر بازماندگي و برخي شاخص هاي رشد ماهي كپور معمولي

The effects of carass and pikeperch on survival and some growth indices of common carp (Cyprinus carpio Linneaus 1758)

In this research that was carried out for 8 months in Dikjeh area of Gonbad, the effects of carass and pikeperch on survival and growth indices of common carp (Cyprinus carpio) in carp polyculture (300 carps, 44.15 gr) were studied. Therefore, 8 ponds were chosen, each of them 3/h, and they were divided to four treatments: A- obliterating carass without stocking (introducing) pikeperch B~ obliterating carass alongwith stocking (introducing) pikeperch (200 perchs, 2 gr) C- without obliterating carass and without stocking (introducing) pikeperch D- without obliterating carass and alongwith stocking (introducing) pikeperch. Preparation process of ponds(to empty of water, to dry, to spray lime and to fertilize) were performed in all treatments. To make sure of obliterating carasses in treatments A and B, the ponds were sprayed with poison (Andosulfan with 0.2 ppm) and the water entrances were fixed with net. Physicochemical factors of water were measured twice a month, and sampling of natural food, and also sampling of fish in order to biometery and determining growth indices were performed once a month. At the end of period, individual average weight, specific growth rate and final biomass of common carp in treatment B were more than the other groups and statistically there was significant difference (P<0.01) among them. But condition factor and survival percent had no significant difference. Regarding the results mentioned, Obliterating carass with introducing pikeperch is suggested to increase production output of common carp.