Studies on herring larvae off western Norway in 1987 [HELP 22]

Abstract

This report gives some preliminary results from a study on the spawning grounds of the Norwegian spring-spawning herring in April 1987. It deals with the horizontal and vertical distribution of herring larvae in relation to the physical environment as well as growth and diet. The investigation in 1987 seem to confirm the tentative pattern of drift routes and retention areas put up for similar studies in 1986. Herring larvae 12-32 days old were mainly found in the upper 60 m and they seemed to concentrate in the upper 20 m by night. Larvae 3-7 days old were found tbroughout the investigated water column though mainly below 40 m. There seemed to be no clear changes in vertical distribution during a 24 hrs. period of larvae during this stage. These observations do not deviate from observations made during similar studies in i985 and 1986. A mean growth rate of O,36 mm/day in the period 2-26 days post hatching were found. In the yolksac-period the growth was slower, 0.28 mm/day, but in the post-larval period 0.41 mm/day. The specific growth rate can be calculated to be 6.8%. Both the growth rate in length and the specific growth rate are almost identical to the rates found in 1985 and 1986.