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Seasonal occurrence of the pelagic poecilostomatoid copepods off Miho Key, Suruga Bay, Japan
Itoh, H.; Mizushima, T. (1999). Seasonal occurrence of the pelagic poecilostomatoid copepods off Miho Key, Suruga Bay, Japan. Bull. Inst. Oceanic Res. & Develop., Tokai Univ. 20: 113-125
In: Bulletin of Institute of Oceanic Research and Development. Tokai University. Tokai University. Institute of Oceanic Research and Development: Shimizu. ISSN 0289-680X, more
Peer reviewed article  

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  • Itoh, H.
  • Mizushima, T.

Abstract
    Seasonal occurrence of pelagic copepods of the order Poecilostomatoida was investigated on 48 samples taken at a station off Miho Key in Suruga Bay., central Honshu, Japan from April 1979 to June 1980.On the samples 41 poecilostomatoid species belonging to 3 families, 6 genera and 5 subgenera were identified. Among them, 13 species were sampled and were grouped into 5 types on seasonal occurrence.(1) Summer-autumn type (7 species): The highest population density occurred from September to December, being characterized by their occurrence at relatively high temperature and low salinity. The species of this type seem to occur in surface or subsurface layer and to be strongly influenced by surface water temperature.Corycaeus (Corycaeus) crassiusculus, C. (C.) speciosus, C. (Ditrichocorycaeus) andrewsi, C. (Onychocorycaeus) pacificus, C. (O.) catus, Farranula gibbula and Oncaea venusta.(2) All season type (2 species): These copepods had wide range of optimum temperature, and did not decrease in winter. Oncaea conifera and O. mediterranea.(3) Spring/autumn type (2 species): More abundant in spring and autumn, being characterized by occurrence at relatively low temperature and high salinity. These species seem to inhabit the layer below thermocline in summer. Corycaeus (Agetus) flaccus and C. (A.) limbatus.(4) Autumn-winter type (1 species): Corycaeus (Urocorycaeus) furcifer, occurred at relatively low temperature and high salinity during autumn to winter.(5) Spring type (1 species): Corycaeus (Ditrichocorycaeus) affinis increased from Match to April and maintained high population-density from May to June. This species had a wide optimum range of salinity.All the species classified into summer-autumn type, all-season type, spring and autumn type, and autumn-winter type are warm oceanic. The difference of their seasonal occurrence might relate with the difference of optimum ranges of temperature and salinity, as well as range of vertical distributions. On the other hand, C. (D.) affinis, the sole spring type, is only neritic species of which high abundance in spring seems to be related to high abundance of potential prey.

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