Title Seasonal succession of plankton community structure in fish and pearl oyster farms of Gokasho Bay, Mie Prefecture, Japan
Authers Kazumasa HIRAKAWA, Tomoko SAKAMI, Katsuyuki ABO, Kazufumi TAKAYANAGI and Atsushi TANIMURA
Keywords Aquaculture ground, Plankton community, Karenia(=Gymnodiniummikimotoi, Oithona davisae, Microbial food chain
Citation Bull. Fish. Res. Agen. supplement No. 17, 37-55, 2006
Seasonal succession in the plankton community was studied based on samples collected monthly from May 2000 to March or April 2001 in the pearl oyster farm(Stn.A)and fish farm(Stn.B)sites of Gokasho Bay, a typical aquaculture ground in central Japan. Chlorophyll a in the water-column reached its annual maximum in summer(July)at both stations, but the average value was ca. three times higher at Stn.B(21.4µg/L) than that (7.7µg/L)at Stn.A. The marked summer increase of chl. a at Stn.B was due to exclusive predominance of a red tide alga, Karenia(=Gymnodiniummikimotoi. As a whole, microzooplankton (ciliates)abundance showed its annual maximum in winter(January-February) when mesozooplankton abundance decreased. Copepods were the most abundant mesozooplankton and showed numerically three seasonal peaks at both stations; spring(March- April), summer(June)and autumn(September-October). Major copepod constituents were Acartia omorii, Oithona davisae and Paracalanus crassirostris at both stations. From seasonal changes of biomasses and prey-predator relationships among components of the plankton community, it is assumed that the microbial food chain plays an important role in increasing the O. davisae population in the aquaculture ground, especially fish farm site during the stratified summer season.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull17/hirakawa.pdf