Zoological Studies

Vol. 56, 2017

(update: 2017.5.2)

Length-weight Relationships and Chemical Composition of the Dominant
esozooplankton Taxa/species in the Subarctic Pacific, with Special Reference to the
ffect of Lipid Accumulation in Copepoda

Asami Nakamura1,4, Kohei Matsuno2,5, Yoshiyuki Abe1, Hiroshi Shimada3, and Atsushi Yamaguchi1,*

1Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato-cho, Hakodate, Hokkaido, 041-8611, Japan. E-mail: s02129083x@eis.hokudai.ac.jp(Nakamura); y.abe@fish.hokudai.ac.jp(Abe)
2National Institute of Polar Research, 10-3, Midori-cho, Tachikawa, Tokyo, 190-8518, Japan. E-mail: k.matsuno@fish.hokudai.ac.jp
3Hokkaido Research Organization, Central Fisheries Research Institute, 238 Hamanaka-cho, Yoichi, Hokkaido 046-8555, Japan. E-mail: shimada-hiroshi@hro.or.jp
4Present address: You Story Co. Ltd., 355-14, Oiwake, Karuizawa, Kita-Saku-Gun, Nagano, 389-0115, Japan
5Present address: Australian Antarctic Division, Kingston, Tasmania 7050, Australia

(Received 6 July 2016; Accepted 28 April 2017; Communicated by Ryuji Machida)

Asami Nakamura, Kohei Matsuno, Yoshiyuki Abe, Hiroshi Shimada, and Atsushi Yamaguchi (2017) While length-weight (L-W) regressions for warm-water zooplankton taxa from the waters neighbouring Japan already exist, they are still missing for comparable cold-water species. In this study, the L-W regressions of 41 species belonging to 12 taxa that are dominant in the Oyashio region were reported. The body length and volume of zooplankton were measured with an image-analysis system, and the effects of lipid accumulation in Copepoda on their mass and chemical composition were quantified. The L-W regressions had a high coefficient of determination (mean r2 = 0.886). For the chemical composition, the water composition ranged from 69.8 to 95.2% wet mass (WM), carbon (C) composition from 3.8 to 60.8% dry mass (DM) and nitrogen (N) composition from 1.0 to 10.1% DM. Taxon-specific differences in the chemical composition were marked for the gelatinous taxa (Appendicularia, Cnidaria, Salpida), which also had high water and low C composition. Because C is an index of lipids, high water compositions together with low lipid compositions are considered to be characteristics of the gelatinous taxa. The most significant effects of lipid accumulation in the Copepoda are changes in DM and C. Within the same developmental stage, the DM and C compositions of the full lipid-containing specimens showed 495% and 741% increases, respectively, over those of the low lipid-containing specimens. These differences exceeded the changes after moulting (78.1%) for general copepod species. Thus, lipid accumulation should be evaluated for the accurate mass estimation of boreal Copepoda by image analysis.

Key words: Mass, L-W equation, Zooplankton, C/N, Lipids, Oil sac volume, Image analysis.

*Correspondence: E-mail: a-yama@fish.hokudai.ac.jp