Analysis Of Food Source Of Mud Crab (Scylla Paramamosain) In Beibu Gulf And Effect Of Different Baits On Its Growth

Mud crab(Scylla paramamosain),an important marine economic crab,is mainly distributed in the estuaries or mangrove areas along the southeast coast of China.The increase in market demand has promoted rapid development of crab enhancement and aquaculture.Nevertheless,there are still some undissoloved problems in the industries.First,there are few studies on food composition and nutrient sources of wild mud crab,which leads to the lack of reference for the selection of enhancement area.Second,the utilization efficiency of bait used for mud carb aquaculture is low,which easily causes pollution to waters and mud crab disease.Growth and survival are closely related to energy distribution of mud crab,but relevant research is few.To solve these problems,the present work conducted a one-year field investigation on potential baits of mud crab in three mangrove areas in Hepu,Qinzhou and Dongxing,Guangxi Province,respectively.Based on stable isotope technique,the food sources of mud crab were determined.Moreover,the responses of mud crab growth and energy budget to bait were studied through laboratory experiments.The main results showed:(1)Food source of wild mud crabThere was no seasonal variation in δ13C and δ15N of mud crab and its potential baits.Mud crab fed by Callionymus richardsoni,Penaeus latisulcatus,Ruditapes philippinarum and Perinereis aibuhitensis had positive enrichment effects on carbon and nitrogen stable isotopes.The diet of mud crab was omnivorous,and food composition of mud crab was different among the three sampling regions(p<0.05).From the results of food source analysis,food was not the limiting factor for the enhancemet of mud crab.(2)Growth and energy budget of mud crabUnder sufficient feeding,there were differences in body mass growth rate,specific growth rate,food conversion efficiency,food intake and molting frequency among mud crabs fed on four kinds of diets(p<0.05).There were also differences in the energy distribution(p<0.05).Considering growth rate,feed conversion efficiency and energy distribution,P.aibuhitensis was the best baits for mud crab cultivation.Aquaculture of mud crab can be fed mainly by P.aibuhitensis.