تركيب و فراواني ماكروبنتوزها در استخرهاي پرورش ميگوي سفيد هندي در منطقه دكوار-استان بوشهر

Composition and abundance of macrobenthos in shrimp (Penaeus indicus)culture ponds in Delvar - Bushehr province

This study was conducted to determine composition and abundance of macrobenthos in marine shrimp culture ponds. Two salt water ponds with an area of 1.2ha each and water depth 1.8m were used in this study during 3 months of summer in 2002. Sediment was sampled using by an Ekman grab covering a surface area of 225Cm2 monthly from entrance,central and out let sections and in each area 3 times. Samples were immediately preserved with 10% formalin.ln the laboratory; each sample was seived through a 500 micron mesh screen to retain macrobenthos. With a binocular microscope, all organisms were counted and identified according to major taxonomic groups. Water quality parameters such as temperature, pH and salinity were measured weekly. For determining alkanity and percent of total organic matter (TOM %) monthly and grain size totally, sediment were sampled distinctly. Sediment analysis for composition and abundance of macrobenthos revealed the presence of 3 groups namely; Arthropoda (crustacea, insecta), Mollusca (gastropoda, bivalvia) and Annelida (polychaeta) that mollusca group was dominant in 1 and 2 ponds with 87% and 71.4% abundance respectively.In this group,gastropoda was dominant with 90% in each ponds. The composition and abundance of macrobenthos differed in different months in each pond. Soil alkanity did not significantly differ between two ponds and in first pond in different months, but it significantly differed in secound pond. Also the percent of total organic matter did not significantly differ in two ponds, but it significantly differs in different months. Grain size consisted of coars and medium sand, silt and mud that quantity of them differed in two ponds and different locations, too. The range of temperature, pH and salinity were30.67-36.3°c, 8.23-8.77 and 42.67-56 ppt in first pond and were 31.67-36c, 8.37-8.8 and 41.67-56ppt in secound pond respectively.