IDENTIFICATION OF NORWEGIAN SPRING SPAWNING HERRING (CLUPEA-HARENGUS L) LARVAE FROM SPAWNING GROUNDS OFF WESTERN NORWAY APPLYING OTOLITH MICROSTRUCTURE ANALYSIS

After the stock collapse in the 1960s the main spawning grounds of Nor wegian spring spawning herring have been located off the More coast (n orthern grounds) and after 1989 spawning has also occurred at previous important grounds off the south-western coast of Norway (southern gro unds). An overall objective of this study is to identify offspring fro m the different main spawning grounds in their nursery areas several m onths later. This requires criteria for identification of larval compo nents from the main hatching areas. Peak hatching time at the two main spawning areas differ by approximately one month, being earlier at th e northern spawning grounds. Passive drift from the southernmost areas adds another 2-3 months to this time difference until the larvae from the southern spawning grounds reach the spawning grounds off More. Ot olith microstructure analysis of larvae collected along the drift path of the separate larval populations are used to trace past growth patt erns. The results show a significant difference in back calculated inc rement width at age and in back calculated hatching distribution, and indicate that otolith microstructure can be used to separate component s of offspring from the two spawning grounds.