The Goal of project implementation was survey of biological roles of Northern pike, Esox lucius, in decreasing of Coarse fish and other un economics organisms in carps ponds and also increasing of final crops in hectare and determination of Suitable ration of pike in ponds. This project implemented by 5 treatment with 3 replicates for every ones in 2 years. The pike density was 200, 350, 500 and 650 fish individuals per hectare for 1, 2, 3 and 4 treatment, respectively, and fifth treatment was without pike. The treatments of 1 and 3 conducted in first year and other in second year of test period. At first, about 26 brooders Caught from Anzali Lagoon, and reproduced by artificial and semi - natural methods in Sefidroud Fisheries Research Station in 12–14 °c temperature. Produced larvae reared in earthen ponds and fries reached to weight of 10 -12 g after 45 days. Mean weight, length and survival rates of fish was 12.27 and 32.5 g, 11.44 and 15.83 cm, and 40 and 21% after 45 and 60 days, respectively. The carp density in ponds was 3500 fish individuals per hectare and stocking rates were 55 % silver carp, 20 % common carp, 10 % bighead carp and 15 % grass carp. In throughout of the experiment period, physico– chemical factors measured and plankton (phyto and zoo), benthos, un wanted fish and other organisms investigated. The biomass of unwanted fishes reduced to 76/81 and 60/6 % in first and second year of experiments respectively. The results showed that Esox lucius had effect in increasing of objective fish produce about 17.9 % and 3.9 % in first and second period of project implementation respectively. The average of fish produce in pond unit (2400 m^2)was 842 kg (3508 kg/ha ), 825 kg (3439 kg/ha) and 776 kg (3232 kg/ha) in first , second and control treatments first year of test period , and also in second year was 865 kg (3603 kg/ha), 877 kg (3652 kg/ha) and 848 kg (3531 kg/ha) in second , fourth and control treatments , respectively. A significant different found in final weight mean of common carp between treatments and Control ponds (P 〈0/05), as the weight of common carp in treatments ponds was 220 % in first year and 191 % in second year more than control pond. In end of the trial, the mean weight of Esox lucius was 265 ± 74, 276 ± 104, 159 ± 33 and 265 ± 89 g in 1, 2, 3 and 4 treatment, respectively. Survival rate of Northern pike in 1 to 4 treatment was 43.8, 55.2, 40 and 35.6 %, respectively.
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