Comparison of innovated rotifer culturing systems from the viewpoint of reduction of environmental road in the wastewater from seedling productions

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17580154
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: General fisheries
• Research Institution: The University of Tokyo
• Principal Investigator: HINO Akinori The University of Tokyo, Graduate School of Agricultural and Life Sciences, Professor, 大学院農学生命科学研究科, 教授 (90012012)
• Co-Investigator(Kenkyū-buntansha): OKAMOTO Ken The University of Tokyo, Graduate School of Agricultural and Life Sciences, Associate Professor, 大学院農学生命科学研究科, 助教授 (20160715) ; AOKI Shigeru The University of Tokyo, Graduate School of Agricultural and Life Sciences, Assistant, 大学院農学生命科学研究科, 助手 (50270898)
• Project Period (FY): 2005 – 2006
• Keywords: Chemostat System / Marine rotifer / Freshwater rotifer / Continuous culture system / Inherent growth rhythm / Wastewater control

Research Abstract

Waste waters from hatcheries are out of control in the eye of the law at present. "Zero-emission" should be imposed, however, from the viewpoint of "Exist together Ecosystems" in the near future. Although many advanced systems appeared in resent years, the luck of fundamentals of rotifer physiology/ecology makes us feel difficult to choice the adequate system for reducing environmental road in wastewaters.
In this study, we tried to detect the inherent "growth rhythm" which may exist in every strain from every 8 or 12 hours' observations on population size and food left over, which first realized by the use of a Chemostat system. And, discussed important items which should be considered before the choice of a culture system. Next, regarding the present states of rotifer-mass-culture in Japan that newly invented "Extensive Chemostat " is prevailing among hatcheries, the possibility of application to freshwater-rotifer culture was studied.
As a result, we succeeded in detecting the "inherent growth rhythm" in the marine rotifer Brachionus plicatilis, which occurred even under the continuous and stable food provision. On the contrary, periodical growth rhythm could not be detected in B.rotundiformis which is commonly used for marine fish production same as B.phcatilis. In most of hatcheries, those rotifers are managed in the same manner, which is thought to be the cause of unstable propagation often observed in many rotifer cultures. Meanwhile in the application of "Extensive Chemostat" for the freshwater rotifer B.calycitlorus, the rotifer was revealed to have less tolerance to both ammonia and hypoxia than marine rotifers. We had produced new management scheme for the application of "Extensive Chemostat" to the freshwater rotifer, which proved to be adequate in the real seedling production in Shiga Prefectural Fisheries Station.