Jökull - 01.12.1969, Blaðsíða 145

20” 10” 0” 10” 20"
Fig. 3. Herring distribution and temperature at 20 m in May, June and July 1968. Double
hatched squares: very dense concentrations. Single hatched square (4—6/6): dense concentrations.
Single hatched square (15—25/5): scattered concentrations. (Redrawn fronr report of the Joint
Icelandic, Norwegian and Soviet herring-environmental surveys).
was due to this mixing or not the entire herr-
ing concentrations in this region migrated
southwestwards in September and October
1966 and reached the overwintering grounds
east off Iceland during the first few days in
November or approx. 6 weeks later than the
herring coming from the Jan Mayen area.
Thus these two units of the Norwegian herr-
ing mixed in the autumn of 1966 and have
behaved as a single “stock unit” since. Thus
already in 1967 there was only one spawning
centre, i.e. off western Norway (off Möre), and
in the summer the whole stock migrated to
the feeding area previously only occupied by
the “eastern” Bear Islancl-Spitsbergen compon-
ent.
1968
Generally, one can state that the new migra-
tion pattern of the Norwegian herring which
was formed in 1966 and especially in 1967
continued in 1968. The eastern boundaries of
JÖKULL 19. ÁR 1 41