Occurrence of large numbers of carcasses of the large,grazing copepod Calanus cristatus from the Japan Sea |
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Authors: | M Terazaki M Wada |
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Institution: | (1) Ocean Research Institute, University of Tokyo, Minamidai, Nakano, 164 Tokyo, Japan |
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Abstract: | Carcasses of Calanus cristatus were discovered in plankton samples collected from the Japan Sea throughout the year from 1970 to 1985. Many carcasses of copepodite Stages IV and V occurred in the layer between 15 and 300 m below a distinct thermocline. The number of copepodite Stage V carcasses also peaked in the layer between 1 500 and 2 000 m. The highest density of copepodite Stages IV and V carcasses was 169 individuals per 1 000 m3 and 1 573 individuals per 1 000 m3, respectively. Carcasses of adults occurred at depths below 500 m and numbers of males and females per 1 000 m3 were 1 to 16 and 1 to 42, respectively. Living males were larger in catch number than living females, but the relationship for carcasses was the opposite. Weight of carcasses was 15 to 25% of living C. cristatus. Carcasses contained about 51% carbon and 8% nitrogen by weight. Carcasses may have been drifting for more than one year in the epipelagic layer under the thermocline because of their slow decomposition rate. |
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