Ecological studies on Euphausia pacifica Hansen and seasonal change of its environment off Onagawa, Miyagi prefecture [Japan], 2: Zooplankton biomass and copepod community structure
1996
Kotani, Y. (Nansei National Fisheries Research Inst., Ono, Hiroshima (Japan)) | Kuroda, K. | Taki, K.
Zooplankton biomass and copepod community structure were investigated along the 38 degrees 22 minutes N line off Onagawa in Miyagi prefecture from April 1993 to February 1994 at two monthly intervals, to provide environmental data for ecological studies on Euphausia pacifica. Zooplankton samplings were conduced using the improved Norpac net along the transact at depths of 50, 100, 150, 200, 300 and 800 m during day time. The present study shows the seasonal changes of the total zooplankton biomass and biomass by the major zooplankton groups. Total zooplankton biomass excluding gelatinous organisms was most abundant in April, rapidly decreased on June and gradually reached a minimum value in December at all of the survey areas. Copepods constituted the most dominant taxonomic group in the zooplankton community, with a total of 90 species from 38 genera, 22 families and 4 orders. The diversity (from the number of copepod species and 1 - lambda; lambda = Simpson's diversity index) and similarity (from Morishita's similarity index and number of common species between pairs of samples) of copepod communities were analyzed, in relation to the seasonal changes of zooplankton biomass and oceanographic conditions
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