Further studies of plankton ecosystems in the eastern Indian Ocean. VI. Ecology of the Euphausiacea

Abstract

Examination of 26 427 euphausiids from 175 samples taken by vertical hauls in the upper 200-m stratum along the 110°E. meridian during 1962-63 indicated that day samples contained mainly larvae and juveniles whereas night samples contained more adults.

The following six species of small euphausiids were the most abundant and ubiquitous: Euphausia mutica, E. tenera, E. brevis, Stylocheiron carinatum, S. suhmii, and S. Affine. Their distribution overlapped according to the distribution, in the upper 150 m, of the tropical and subtropical water masses and their mixtures. These species were commonly observed in breeding condition. Their larval distribution was related to the distribution of the breeding adults.

The rarer and less ubiquitous species, which were mainly younger stages and deeper living species, showed more pronounced relationships with seasonal water movements.

Food resources appeared more important than temperature and salinity in influencing distribution, abundance, and association of species.