VERTICAL MIGRATIONS OF MYSIDS IN THE GULF OF RIGA

Abstract

Vertical migrations of Mysis mixta, M. relicta, and Neomysis integer were studied in the north-eastern part of the Gulf of Riga during May-September 1999. All three mysid species performed diel vertical migrations. These migrations were more intense in late summer and autumn than in spring and early summer. The proportion of juveniles and small-sized adults (< 11 mm) in the vertical migrations was higher than that of adults. Usually N. integer appeared in the water column first in the evening, followed later by Mysis spp. Both Mysis spp., often referred to as cold stenotherms, were found in high abundance in the surf ace waters in spite of very strong temperature gradients.