Economical study of the grey mullet (Mugil cephalus) culture in the Golestan province

Striped grey mullet (Mugil cephalus) is a marine fish with high commercial value and widespread distribution. The grey mullet and some other mullets can be found in saltwater, brackish and fershwater habitats at tropical, subtropical and also temporal climates.This species is suitable for aquaculture worldwide due to living in wide ranges of water temperatures and salinities, acceptable growth rate, suitable food conversion ratio, marketability, suitable species for polyculture with shrimps, marine fish and even with freshwater carps. The grey mullet is farming in different countries such as Italy, Northern Africa countries ( Egypt), occupied Palestine, India, Pakistan, Japan, Hong Kong, Taiwan, Vietnam, Indonesia, coastal countries of southern pacific ocean and Hawaii. Ten thousands of fries of this species (average weight and length of 280 mg and 28.3 mm respectively) imported in March 2008 from Egypt. The wild fries colleted from surrounding natural waters of Alexandria. After finishing the quarantine steps, they stocked in four earthern ponds (each with 2500 m2) located at the Gomishan shrimp educational centre at late march in 2008. At the first year of culture the densities were 5000 and 10000 individuals per hectar and each treatment with two replicates. At second years densities changed with 2000 and 2500 ind./hec. and each of traetments divided fishes with average primary weights of 80 and 115 grames. The fries and fish feeding begins in April when the water temperature rise above 18 °C and it cut in fall when the temperature goes under 20°C. They fed twice a day at 8 AM and 2 PM and the amount was 5-7 percents of the fish existent biomass in each ponds. They fed with dry formulated feed made of Mahdaneh Karadj Company (Danso dry feed) both the first and second years of farming. The feed prepared for carps feeding and containded 23±2% crude protein, 10±2% crude lipid, about 7% crude fiber, 15 % ash, 40±2% carbohydrates and with energy content of 4000±200 kcal/kg. After seven months culture period the average weight and length of fish in treatment 5000 ind/hec. were 113.7gr and 21.1cm respectively and in treatment 10000 ind./hec. the average weight and length were 86.6 gr and 19.6 cm respectively. At first year the average survival rate in different treatments was 77 percent. The average FCR in treatments 5000 and 10000 ind./hec. were 3.4 and 3.9 respectively. At second years after six months culture the average weights in pond no. 9 (with primary weight 115 gr and density 2000 ind./hec), pond no. 10 (with primary weight 80 gr and density 2000 ind./hec), pond no. 11 (with primary weight 115 gr and density 2500 ind./hec) and pond no. 12 (with primary weight 80 gr and density 2500 ind./hec) calculated as 476.6, 338.1, 366.5 and 440 gr respectively. The average survival rate and FCR were 93 % and 3.1 respectively. Ponds no. 9 and 11 (fish stocked with primary weight 115 gr in densities both 2000 and 2500 ind./hec) selected as the best economic efficient treatments