Ecological studies on the deep-water community of Korsfjorden, western Norway

Abstract

Absstract Five species of chaetognaths were found in Korsfjorden: Eukrohnia hamata (84 %), Sagitta elegans (11 %), E. bathypelagica (4 %),S. setosa (1 %), and S. maxima (1 % by numbers), Only E. hamata completes its life cycle within the sampled area. In Korsfjorden it appears to have a life span of two years. Breeding reaches maxima in spring and fall but is continuous at a low level throughout the summer. Growth during spring and summer is about 4 mm per month. During the winter no discernible growth takes place. Most increase in length occurs during the first year of life while sexually immature. Maturation occurs during the second year S. elegans breeds in the area in late spring but not in great numbers. A sizable immigration of 15-21 mm individuals in the fall suggests a more successful breeding ground further away, E, bathypelagica is represented by a transient population that enters the sampling area after having attained full size (>15 mm), S.setosa and S. maxima are indicator species in Korsfjorden. S, setosa, a neritic species, enters the area in Summer in the low salinity, warm surface waters from the inner fjord systems. S. maxima, an oceanic species, appears in late winter when high salinity water from the open ocean enters the area over the Outer sill. Surface currents and flushing of basin water appear to play a major role in abundance and distribution of all five species in Korsfjorden