Mono - culturing of crayfish ( Astacus leptodactylus ) in different stocking rate in earthen ponds

Abstract

The research project have been formulated to find-out bio-technique for raising crayfish in soil ponds by given supplementary food . Creation new prodactive activity with potential for export , increasing job opportunity and enhancing aquatic-products were also the contemplated aim of the schem . The investigation time planed for a six months period in Gilan region ( Asstanehashraphyeh ) in the year of 1999. Culture practice have been done in two test ponds ( treatment) with four replicates ponds each with the surface of 400 m2 . The stocking rate were between 20, 30 ind crayfish /m2 (200000 ind/ ha). Crayfish seedlings collected , when they have been released from female brooders and cultivated indoor with artificial feed in a 25 days period reaching at theird stage of juvenile with mean length of 14 mm and weight of 100 mg , these crayfish stocked in earthen ponds. Of course 15 days befoore stocking the ponds natural production strengthen by manure application and live- feed reached 3-5 mg/l. The raising crayfish in addition to natural feed , supplied with cincentrated feed , rice bran, chopped and whole Kilka also provided slaughter -house residue . During culture period each 45 days the biometric data of culture crayfish were gadered , since slaughter- house waste affected water quality in ponds every month 50% of water in ponds discharged . The 15°c could be considered as a temperature which crayfish start active feeding in 30°c eating temporarily stope as the temperature get lower , again food are taken by crayfish . Aquatic _plants in the bottom and pond,s dike function as forage for crayfish also as refuge . Length and weight of the raising crayfish and survival rate at the end of culture period in different replicates are as followes : In the first and second replicate ponds , the density of stocking were 20ind/m2 mean weight 16.4 g and 15.34 g and average length 8 cm and 7.8 cm respectively. In third and fourth replicate ponds crayfish stocked 30 ind /m2 with mean weight of 11.1 g and 13.06 g with average length of 6.9 cm and 7 cm respectively . Survival rate from first until fourth replicates calculated 87.675% , 94.112% , 85.291% and 69.033% respectively . The test yield generalized per ha and calculated as followes : With the density of 20 ind/m2 in first and second replicated the production calculated 2875.74 kg and 2887.34kg respectively . With cocentratin of 30 ind /ha in third and fourth replicates the crayfish crop computed 2840kg and 2704 kg respectively .