付着珪藻Ｎａｖｉｃｕｌａ ｒａｍｏｓｉｓｓｉｍａのアカウニ稚ウニ期生産餌料としての効果

Abstract

In order to improve the technique for artificial seed mass production of the young seaurchin Pseudocentrotus depressus, nine species of attaching diatoms (Achnanthes, two; Navicula, three; Nitzschia, three; Amphora, two) isolated from mass production tank, were tested as a food source for the culture of the young sea urchin during the early growth stage, after meta-morphosis to 5mm in test diameter. The early stage was divided into three experimental periods. For each period, twenty or thirty individuals of young sea urchin were cultured in plastic experimental tanks (20l) each containing a diatom species which had been cultured under uni-algal state. Navicula ramosissima supported the best growth and highest survival rate througout the three experimental periods. Mass culture of young sea urchin was practically conducted with cultured N. ramosissima in acutual mass production tanks (15m3) through water flowing system. Larval sea urchin just before metamorphosis were introduced into the tanks wherein N. ramosissima had been propagated under uni-algal state in batch culture condition. After metamorphosis, they grew feeding on N. ramosissima as a main food source. The growth and survival rate showed remarkably higher values than those by usual production method of culturing them with naturally attaching diatoms. Hereby, an improved technique, more stable and more efficient than in usual method was established by utilizing the culture diatom, N. ramosissima as a food soufce.