Vertical Migrations of Larvae of the Atlanto-Scandian Herring (Clupea harengus L.)

Abstract

Vertical distribution of herring larvae was studied from data collected at diurnal and standard ichthyoplanktonic stations over a 24 h period. As they passed to external feeding on the second day after hatching, larvae made a characteristic migration to the upper 50m layer. At 6-9 days, larvae started their regular diurnal migrations. The amplitude of diurnal vertical migrations was found to reach 75-100 m. Temperature differences of 1.0-1.5C between top and bottom did not prevent vertical migration. It was concluded that a positive phototaxis at the beginning of feeding which has appeared in the process of evolution provides for migration to the upper layers. (See also W77-05821) (Chilton-ORNL)