Seasonal abundance, population structure, sex ratio and gonad maturation of Metridia okhotensis Brodsky, 1950 in the Okhotsk Sea: analysis of samples collected by pumping up from deep water

in Crustaceana
Restricted Access
Get Access to Full Text
Rent on DeepDyve

Have an Access Token?

Enter your access token to activate and access content online.

Please login and go to your personal user account to enter your access token.


Have Institutional Access?

Access content through your institution. Any other coaching guidance?


In the Okhotsk Sea, the calanoid copepod Metridia okhotensis Brodsky, 1950 is the dominant component of zooplankton, accounting for 61% of the annual mean total pelagic copepods. Although this organism is important, little ecological information is available for M. okhotensis in the Okhotsk Sea because of the ice cover during winter, which prevents the collection of seasonal samples in this region. Here, we report the seasonal changes in the population structure, sex ratio and female gonad maturation of M. okhotensis. The data are from samples collected using water pumped from a depth of 350 m off Rausu Harbour in the Okhotsk Sea at 2-week intervals over a 2.5-year period. Due to the mesh size of the strainer (420 μm), M. okhotensis was collected from C3 to adults. The sex ratio of C5 (female : male) was approximately 1 : 1 throughout the year. In contrast, the sex ratio of C6 (adult) showed a clear seasonality, with males (C6M) occurring only from December to May and females (C6F) dominating during the other seasons. The gonad maturation of C6F was scored using five categories, and their composition also showed clear seasonality. From January to April, gonads developed rapidly from stage I (immature) to V (spawning). During the other seasons, the majority of C6F had immature gonads. Based on these data, we conclude that this species likely has a diapause phase for C6F, with immature gonads, and C5M from June to November. Moulting from C5M to C6M began in December. Accompanying the occurrence of C6M, C6F were fertilized from December to January. C6F underwent gonad maturation from January to April and performed primary reproduction from April to May. Thereafter, M. okhotensis entered diapause from June to November.


International Journal of Crustacean Research



ArimaD.MatsunoK.YamaguchiA.NobetsuT.ImaiI., 2015. Seasonal and inter-species comparison of asymmetry in the genital system of some species of the oceanic copepod genus Metridia (Copepoda, Calanoida). Crustaceana, 88: 1307-1321.

ArimaD.YamaguchiA.NobetsuT.ImaiI., 2016. Usefulness of deep-ocean water pumping for the seasonal monitoring of mesozooplankton. Reg. Stud. Mar. Sci., 3: 18-24.

AsamiH.ShimadaH.SawadaM.MiyakoshiY.AndoD.FujiwaraM.NagataM., 2009. Spatial and seasonal distributions of copepods from spring to summer in the Okhotsk Sea off eastern Hokkaido, Japan. PICES Sci. Rep., 36: 233-239.

GrønvikS.HopkinsC. C. E., 1984. Ecological investigations of the zooplankton community of Balsfjorden, northern Norway: generation cycle, seasonal vertical distribution, and seasonal variations in body weight and carbon and nitrogen content of the copepod Metridia longa (Lubbock). J. Exp. Mar. Biol. Ecol., 80: 93-107.

HirakawaK.ImamuraA., 1993. Seasonal abundance and life history of Metridia pacifica (Copepoda: Calanoida) in Toyama Bay, southern Japan Sea. Bull. Plankton Soc. Japan, 40: 41-54.

MauchlineJ., 1998. The biology of calanoid copepods. Adv. Mar. Biol., 33: 1-710.

PadmavatiG.IkedaT.YamaguchiA., 2004. Life cycle, population structure and vertical distribution of Metridia spp. (Copepoda: Calanoida) in the Oyashio region (NW Pacific Ocean). Mar. Ecol. Prog. Ser., 270: 181-198.

ShimadaH.SakaguchiK.MoriY.WatanobeM.ItayaK.AsamiH., 2012. Seasonal and annual changes in zooplankton biomass and species structure in four areas around Hokkaido (Doto and Donan areas of the north Pacific, the northern Japan Sea and the southern Okhotsk Sea). Bull. Plankton Soc. Japan, 59: 63-81.

TakahashiK.KuwataA.SugisakiH.UchikawaK.SaitoH., 2009. Downward carbon transport by diel vertical migration of the copepods Metridia pacifica and Metridia okhotensis in the Oyashio region of the western subarctic Pacific Ocean. Deep-Sea Res. I, 56: 1777-1791.

TakahashiM.KawabataT.YamaishiH.ChiayaA.YamauchiS.YamashitaK.NaganoA., 2014. Consistent use of cold clean deep ocean water (DOW) assures clean and sanitary fish port in Rausu, Hokkaido. Deep Ocean Water Res., 15: 1-10.

TakahashiM.YamashitaK., 2005. Clean and safe supply of fish and shellfish to clear the HACCP regulation by use of clean and cold deep ocean water in Rausu, Hokkaido, Japan. J. Ocean Univ. China, 4: 219-223.

TandeS.GrønvikS., 1983. Ecological investigations on the zooplankton community of Balsfjorden, northern Norway: sex ratio and gonad maturation cycle in the copepod Metridia longa (Lubbock). J. Exp. Mar. Biol. Ecol., 71: 43-54.

YamaguchiA., 2009. Characteristics of the zooplankton community in the Okhotsk Sea in autumn: a comparison with the Oyashio region. PICES Sci. Rep., 36: 240-242.

YamaguchiA.OnishiY.OmataA.KawaiM.KanedaM.IkedaT., 2010. Population structure, egg production and gut content pigment of large grazing copepods during the spring phytoplankton bloom in the Oyashio region. Deep-Sea Res. II, 57: 1679-1690.

YamaguchiA.WatanabeY.IshidaH.HarimotoT.FuruyamaK.SuzukiS.IshizakaJ.IkedaT.TakahashiM. M., 2002. Community and trophic structures of pelagic copepods down to greater depths in the western subarctic Pacific (WEST-COSMIC). Deep-Sea Res. I, 49: 1007-1025.


  • A, Location of Rausu, eastern Hokkaido; and B, schema of Rausu Deep-Ocean Water sampling site. This figure is published in colour in the online edition of this journal, which can be accessed via

    View in gallery
  • A, Seasonal changes in temperature and zooplankton abundance (copepods and others) at 350 m and B, copepod abundance and species composition (Metridia okhotensis Brodsky, 1950, Metridia pacifica Brodsky, 1950 and other copepods) observed in the Rausu deep-ocean water from June 2007 to November 2009.

    View in gallery
  • A, Seasonal changes in abundance; B, stage composition; C, sex ratio of C5 and C6; and D, gonad maturation of C6F of Metridia okhotensis Brodsky, 1950 in the Rausu deep-ocean water from June 2007 to November 2009.

    View in gallery
  • Seasonal changes in sea surface temperature, chlorophyll a and ice coverage (shown as white bars) around the Rausu Harbour from 1 January 2007 to 26 December 2009 determined using satellite images (MODIS-Aqua).

    View in gallery


Content Metrics

Content Metrics

All Time Past Year Past 30 Days
Abstract Views 8 8 5
Full Text Views 5 5 5
PDF Downloads 0 0 0
EPUB Downloads 0 0 0