Jökull - 01.12.1969, Síða 142

low salinity covered most of the fishing
grounds off the western part of the north
coast. This cold surface water was actually
deserted of herring food and to all appear-
ances acted as a barrier for the north ancl
eastward invasion of the Icelandic herring
in 1963. The westward migration of the Nor-
wegian herring to the north coast was also
much delayed as compared with 1962. It was
not until about the middle of June that the
westernmost shoals had reached the fishing
grounds off Northeast-Iceland and they had
not reached the area off the central north
coast until the 12th of July or almost 4—5
weeks later 'than in 1962. This invasion of
Norwegian herring did, however, not remain
for long off tlie north coast but soon retreat-
ed eastwards probably due to very low con-
centrations of foocl that were available in the
north coast areas after the middle of July.
In the annual report from the joint Ice-
landic, Norwegian and Soviet herring surveys
(Anoti. 1965) it is especially pointed out that
tlie temperature in the cold East Icelandic
current during the . first weeks of June was
consiclerably lower in 1963 tlian in 1962, the
difference being up to 1.3° C. In addition
the 3° C isotherm was about 130 n.m. furtlier
east than in 1962. Thus there appears a close
correlation between changes in the hydro-
graphic conditions both NW and NE off Ice-
land on one hand and the timing of the herr-
ing invasions to tlie Icelandic areas because
not only was the arrival of the herring to-
wards the north coast delayed or even barred
as already discussed but also was the herring
invasion on the east coast fishing grounds de-
layed almóst a month as compared wútli tliat
in 1962.
The proportion of Icelandic herring in the
landings decreased from 54% in 1962 to 29%
in 1963. This drastical clrange makes 1963 a
turning point as regards the migrations of the
Icelandic herring to the north coast fishing
grounds.
1964
Herring migrations towards the Icelandic
herring fishing areas in the spring of 1964
were characterized by the early arrival of the
herring to the east coast fishing grounds dur-
138 JÖKULL 19. ÁR
ing the first days of June or some 4 weeks
earlier than in the previous year. As regards
herring migrations towards the north coast
proper it should be notecl that the westward
migration of the Norwegian herring only
reachecl as far west as the areas off the eastern
part of the N-coast (Melrakkaslétta) in early
June. This herring invasion then turned north-
eastwards and disappeared from the Icelandic
areas. In the annual report of the joint herr-
ing surveys it is stated tliat by that time (about
June lOth) the concentrations of C. finmarch-
icus, i.e. the most important food species of the
herring, had been very low on the northeast
coast fishing grounds whereas in the oceanic
areas northeast of Iceland and in the areas
south and southwest of Jan Mayen the feeding
conditions for tlie lierring were very favour-
able. It should also be noted that the sea
temperature was generally higher than in 1963
and the influence of the warm Atlantic waters
was traced further north and east than usual
(Anori. 1966). Once again it is quite clear that
the migration of the Norwegian herring was
dependant on the position of boundary areas
of Atlantic and Arctic waters: The further
these areas are off the north coast the further
are the lierring. As already stated the opposite
situation occurred during July 1962 (Fig. 2).
Tlie early arrival of the herring on the east
coast fishing grounds is probably correlated
with the early arrival of spring due to the
relatively high temperatures in that area in
1964.
The eastward migration of the Icelandic
herring failed in 1964 as in 1963 probably due
to drastic reduction of the Icelandic herring
stocks during 1963—1964 (Jakobsson 1959).
Tlie main lierring fishery during the tradi-
tional summer fishing period mainly took
place off the east coast and in the oceanic
areas between Iceland and Jan Mayen. In addi-
tion herring purse seining was conductecl for
the first time on the over wintering grounds
off the east coast cluring the periocl October—
December. Thus tlie duration of the season
was doubled. The Icelandic north and east
coast herring landings of 425,000 tons were al-
most twice that of the previous year. This in-
crease in catch was entirely due to the exten-
sion of the season throughout the autumn.