Studies on the Availability of Heterotrophic Flagellates and Ciliates as Prey Organisms for Reared Fish Larvae

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04806026
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: General fisheries
• Research Institution: Kochi University
• Principal Investigator: FUKAMI Kimio Kochi University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (30181241)
• Co-Investigator(Kenkyū-buntansha): YAMAOKA Kosaku Kochi Univ.Facl.Agricul., Associate Professor, 農学部, 助教授 (20200587) ; NISHIJIMA Toshitaka Kochi Univ.Facl.Agricul., Professor, 農学部, 教授 (60036738)
• Project Period (FY): 1992 – 1993
• Keywords: FIRST FEED / LARVAE / SEED PRODUCTION / FLAGELLATE / CILIATE / PROTOZOAN MICROZOOPLANKTON / DIGESTIVE TRACTS

Research Abstract

The S-type rotifers, Brachionus plicatilis rotundiformis, widely used as prey organisms for fish larvae in aquaculture are often too large for a gape size of some fish species to take up, resulting in the high mortality in early stages. This study aimed the availability of protozoan microzooplankton of flagellates and ciliates for an alternative food of fish larvae.
Preliminarily, gut contents of natural fish larvae were observed by using microbiological method. Digestive tracts of larvae were removed, stained by fluorescein dye, FITC and DAPI, and were observed under epifluorescence microscopy. It was clarified that some 20 genus, out of 47 among 319 individuals, apparently foraged many protozoan organisms with a size of 10 to 40 mum.
A couple of stains of flagellate and ciliate were fed on young larvae of Pagrus major, Paralichthys olivaceus, Plecoglossus altivelis, and Epinephelus akaara. Results obtained showed that larvae of E.akaara of 2 day-old and P.major of 6 day-old consumed ciliates.
These results indicate that protozoan microzooplankton such as ciliates are promising food for fish larvae with relatively small mouth in aquaculture.