The effects of slurry on larviculture of Rutilus frisii kutum and chienes carp yield and determination of efficient concentration for increasing of production

Rutilus frisii kutum is one of the important fish of Caspian Sea which has significant economical role in the region .The objective of this project is a comparative study on traditional culture of fishes versus slurry. This survey were conducted on nine pound of 1.7 hec triplicate with their treatment with stocking densities of 1.7 million fish larva at Dr yousefpoor center (Affiliated of Shahid Beheshti culture and propagation) at Siakal village , 32 km far from Rasht city in North of Iran, the first treatment considered as control which practice traditionally (using concentrated food plus grinded kilka fish) .In the second treatment for 13 days the pound supplied only by slurry then followed by concentrated fish food only .The tired treatment started with slurry for 13 days and followed by slurry plus concentrated food. The physical and chemical parameters of water, plankton, biometry of fish, growth indices such as daily weight growth (DWG), daily length growth (DLG) as well as specific ratio (SGR) were monitored weekly. The result indicate that net fish production was 1.7 to 2 times higher in slurry than traditional treatment also the survival rate were 1.7 times higher in slurry treatment . The treatment of slurry follow by addition of concentrated food plus slurry showed higher yield camper to others. Slurry with several active substances is more effective and can promote the growth of zooplanktons which is the food of larval stage of rutilus frisi kutum. In second phase of this project the effect of slurry was surveyed on Chinese carp. This experiment was conducted in triplicate with two treatment (one treatment is control which use cow manure plus chemical fertilizer and second treatment was conducted with slurry) and stocked with 2375 N/hec (Silver carp 60%, Big head 15%, common carp 17% and grass carp 8%) at June. In this survey common carp and grass carp were feed with concentrate food and fresh grasses respectively. Chemical factors were measured once for each two week and density of plankton was determined when it was necessarily. Nutritional content of phosphorous, nitrogen, calcium, potassium and magnesium after anaerobic fermentation as well as protein and lipid content with 1.4and 1.9 times respectively were higher in slurry treatment than control. The results showed that survival rate and yield were higher in slurry than control. The increasing percent of yield were 13.5, 2.6, 18.4 and 85.3 in Silver carp, Big head, common carp and grass carp respectively. The survival rate of grass carp was twice higher in slurry treatment than control. Zooplankton abundant in slurry pounds was more but blue- green algae density was less than control. Protein and lipid analysis reviled no significant difference between control and slurry. In general the result indicate that the slurry with higher nutritional content is more effective on the survival and growth rate of fishes and also is more efficient in proliferation of plankton in particular zooplankton.