Jökull - 01.12.1969, Blaðsíða 143

1965
As in two previous years the Icelandic herr-
ing dicl not migrate to any extent to the north
coast in this much discussed “ice year’’ o£ 1965.
Tliis spring the westward migration o£ the
Norwegian herring was first located in the far
off shore waters east of Iceland about the
middle of May. Contrary to previous years it
was the southerly part of this first herring in-
vasion which penetrated farthest westwards or
some 40 n.m. off the east coast of Iceland. The
northern part of the invasion tliat normally
invaded the north coast herring grounds re-
mained some 100—200 n.m. off NE Iceland
where <0° C or even <—1° C sea tempera-
ture prevented any further westward penetra-
tion of the herring. As could be expected con-
sidering the abnormal hydrographic conditions
(Anon. 1967) the herring soon turnecl away
from these polar waters and migrated at a
high speed north and northeast along the easi-
ern borders of the polar front. About the 20th
of June this herring migration had reached
the more temperate waters S and SE of Jan
Mayen.
In the spring of 1965 a new chapter in the
migration history of the Norwegian herring
towards the Icelandic areas is started. Tlie
herring concentrations had during several pre-
vious years been observed migrating slowly
westwards as the conditions in the sea changed
from winter to spring and from spring to sum-
mer conditions. The speed of such westward
movement was then observed in the range of
40—50 n.m. per week or usually less than 10
n.m. per day. The speed of the northeast ancl
north migration in 1965 was on the other hand
in the range of about 30 n.m. per day ancl
had in this repect very different behaviour
pattern as compared with usual feeding migra-
tions in spring and early summer. It is prob-
able that the high migrational speed encount-
ered in June 1965 was caused by a kind of
escape reaction — the herring trying to get
away from almost unviable or at least very un-
favourable conditions prevailing at or witliin
the regions of the polar water, i.e. tempera-
tures about or less than — 1° C. It should also
be noted that in the years prior to 1965 we
have described the westward migration of the
Norwegian lierring towards the fishing grounds
off the North coast. Since these migrations
were observed on their way coming through
the cold current or along its southern boundary
areas the lierring must inevitably have been
migrating against the main direction of the
current which in this area has an easterly or
southeasterly flow (Stefánsson 1962, p. 57). In
1965 on the other hancl the herring obviously
travels with the current, i.e. northwards along
the eastern border of the cold East Icelandic
current (Stefánsson 1962). At the same time as
these revolutionary changes in the migrational
pattern took place it is o£ interest to note
that a new generation became predominant in
the Norwegian herring. During the periocl
1961—1964 the herring which dominated in the
west and northwest feeding migration towards
the Icelandic herring fishing grounds were 11 —
14 year old herring, i.e. belonging to the very
strong 1950 yearclass.
As from 1965 it is on the other hand the
1959 yearclass which predominates in all areas
visited by the Norwegian herring.
The herring concentrations (i.e. the more
westerly proportion, see later) remained at the
eastern border of the cold current in the area
S and SE of Jan Mayen throughout the sum-
mer but assembled in the conventional over-
wintering area off east Iceland in September.
The Icelandic catclr during the summer and
autumn season amounted to 570,000 tons of
which 94% were Norwegian herring according
to our scale analyses.
1966
The westward migrations of the Norwegian
herring in 1966 were in many respects similar
to those in 1965 with a few exceptions. In
1966 the migrations did not go as far west as
in the preceeding year and turned north along
the eastern border of tlie East Icelandic cur-
rent without forcing their way into the reallv
cold water as in 1965. The first portion of
the migration turned north between 6° and
10° w.l. where the sea temperature at a depth
of 20 m was about 3° C. A seconcl and smaller
proportion of the migration arrived in Julv
and spent the summer off the east coast. In the
annual joint Icelandic-Norwegian-Soviet report
from the herring surveys in 1966 it is, however,
especially mentionecl that the westernmost herr-
JÖKULL 19. ÁR 139