| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 94 === The sand shrimp（M. ensis）is one of the most important and commercial shrimp cultured with milkfish（C. chanos）in south-west coastal zone of Taiwan. When the aquacultural environment is deteriorated and full of the pathogenic bacteria, the culture harvest is not stable. In order to promote and maintain the sand shrimp’s unit area production, we must understand the aquatic environment and the nutrient requirement of sand shrimp. Therefore, the purpose of this studies aimed at as（1）To investigate the water quality in milkfish-shrimp polyculture pond and the growth rate of sand shrimp in Tainan Prefecture.（2）To compare the growth promoting effect of four commercial feedstuffs on sand shrimp.（3）To elucidate the effect of salinity on the survival rate, oxygen consumption, ammonia excretion and osmoregulation of juvenile sand shrimp.
Our results demonstrated that the harvest of sand shrimp in three different ponds was not consistant due to the bad weather and fluctuation of pond salinity, ammonia, organic accumulation, dissolved oxygen and great pH values. High mortality juvenile and subadult sand shrimp was also noticed under the the stresses of lower dissolved oxygen and great pH variation. However, experimental ponds can have a profitable harvest, if better pond managements were paid.
For growth rate comparison, it is found that feedstuffs for seawater shrimp are better than that for milkfish to feed sand shrimp. Among four different feedstuffs, the ingredients of whiteshrimp feed were more suitable for sand shrimp. With its growth performance being the best. However, the growth rate of sand shrimp fed with four different feedsuffs is lower than those reared in polyculture system, indicating the composition of commercial shrimp feed maybe not sufficient for the requirement of sand shrimp. Lack of natural food could be another reason.
Salinity can affect the physiology of sand shrimp. Since the shrimp are osmo-comformer, it can tolerant of salinitydrop up to 7ppt/day. Even in low salinity（1∼10ppt）, the mortality was always kept the same as these in high sality. In addition, the oxygen consumption rate is positively correlated with the increasing salinity. Furthermore, the ammonia excretion rate was also slightly correlated with the external salinity(3∼33ppt) therefore, more paddlewheels in the higher salinity pond is recommanded. In low-salinity adapted group, hempolymph osmolarity of shrimp is decreased, while the whole body water content is increased. It is concluded that for growth promotion and survival increase, culture of sand shrimp shall be kept in low salinity（15-25ppt）.
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