A Survey on the shrimp culture condition at Delvar site

Abstract

A survey on shrimp culture situation in Delvar site was studied in this research. Lack of comprehensive investigation on shrimp culture in Delvar site, undesirable growth and low productivity in compare with standards and study of chemico-physical factors effect on shrimp culture, are some evidence for designing and performance of this project. The field operation was carried out from May to December 2001 in 5 private shrimp farms. Delvar shrimp culture complex is located 35km far from Bushehr. This site has 2 sections, Delvar 14 and Delvar 18. All of the farms belong to cooperative and private companies. There are 2 hatchery centers in this site. Cultured areas were 396.2 hectare and total productivity was 706 ton in 2001. Mean production per hectare was 1782 kg, equal to 0/022.6 of total production of all shrimp culture sites in Bushehr province. We select 2 farms from Delvar 14, 3 farms from Delvar 18 and 2 pounds from each of them. Total stocking density in these ponds, 12 hectare, were 3265750 post larvae (PL -12), duration of culture was at least 145 and maximum 193 days. The highest FCR was 2.2 and the lowest was 1.2, maximum productivity was 3600 kg and minimum of it was 1900kg, maximum stocking density was 33 post larvae per m and minimum of it was 18. Origin of shrimp larvae was from wild sea shrimps. Maximum of shrimp means weight was 13. 44g and the minimum of it was log, the highest survival rate was 86% and the lowest of it was 0/050. Structure of pond beds was made from lum and Stum (mud and slum) 86% and sand 20%. Organic matters of sediment has shown declining rate in culture period. Some of ponds had mortality, about 48 ton, because of sudden changes in weather condition and decreasing of temperature. Total productivity of 10 ponds was 26986.3kg and mean productivity per hectare was 2248kg. We measured and recorded some environmental parameters such as Salinity, D.O, temperature, pH and transparency two times a day, (before sunrise and at 3 p.m.). Some factors such as Chlorophyll-a, organic nitrogen, ammonia, T.D.S. and. T.S.S were measured twice per month (in water phase), and also we measured pH, total nitrogen and organic matter once a month (in Sediment). Water deficiency and insufficient pumping are two of the most important problems. These problems cause increasing of salinity and have effect on shrimp growth. Because of high salinity, shrimp growth in Delvar site is lower than Shrimp growth standards. This Condition needs to take suitable methods in stocking and water management (salinity, transparency, pH, DO. and temperature) during culture period. Range of salinity was 44•66 p pt in pohds and farmers maintain salinity at about 50 ppt with difficulty. In low tide, because of the high evaporation and salt gathering in water supply canal' s bed, Salinity of farms at the end of canals rising so much. According to these results range of salinity and duration of culture were over range in contrast to the natural Shrimp growth ranges. Ponds with low stocking density (18 and 19 post larvae per m2) had better FCR, survival rate, and growth and produce value. In spite of the water and soil protection principles, farmers rarely follow scientifically culture rules. Results of gathered data about culture condition, productivity and effect of chemico physical factors donating that suitable executive management is efficient factor in good productivity and reaching to favorite survival.