Effects of tide level,culture density and season on growth and survival of wrinkled clam,Meretrix lyrata,juveniles

Effects of tide level,culture density and season on the growth and survival of wrinkled dam(Meretrix lyrata) juveniles were studied.The experiments were conducted at the beach of Beiyue village of Zhanjiang,Guangdong province from August,2010 to May,2011.The results were:(1) The beach was mainly composed of rough sand(graint size 0.200mm and above),fine sand(0.200~0.050mm) and silt(0.050mm or less),which accounting for 64.7%~87.5%,11.0%~32.2% and 1.5%~7.9%,respectively.The content of rough sand and silt showed increasing and decreasing trend,respectively from high to low tide.The beach was suitable for the growth and survival of Meretrix lyrata.(2) Tide level significantly(P 0.05) affected the growth rate of juvenile,the juvenile cultured in low tidal level gained the highest growth rate.So the middle and lower mid tide zone was most suitable for the growth of the rib wrinkled clam juvenile.(3) Density had a significant effect on the growth and the survival of juvenile,low density permit a faster growth and a higher survival rates,the density of 7000~12000 particle /m2 being the most appropriate for juvenile.4) The growth rate of the juvenile significantly(P 0.05) was related to Season.The growth rate of juvenile was higher in summer and autumn when the water temperature was high(24.5~31.3℃),the growth of juvenile stopped in spring when the water temperature was low(15.1~18.1 ℃) and the growth rate increased with the increasing of water temperature in spring(22.5~26.8 ℃).During spring and autumn,the growth curves of shell length,shell height and shell weight trend were S shaped.5) Significant differences of juvenile survival were detected among different seasons(autumn,summer and winter),which may related to the difference of water temperature.From summer and autumn to winter,the survival rate showed decreasing trend,though the difference were not significant between autumn and summer.Summer and autumn were suggested as the best juvenile breeding seasons in production practice.The present results provide data for future aquaculture of rib wrinkled clam.