Jökull - 01.12.1969, Blaðsíða 140

This year the distance of the ice border
from NW Iceland was similar to the average
of the preceeding 10 years but off the north
coast and in the area west of Jan Mayen the
research vessels dicl not encounter any ice. The
sea temperature dicl not appear to have any
preventing effect on the westward migration
of the Norwegian herring and in their report
the scientists draw attention to the fact that
the herring shoals mainly kept to the uppermost
50 m where the sea temperature was 3—4° C
in early June and increased considerably in
the surface layers during the following weeks.
It should aiso be noted that the herring did
not invade the warrner Atlantic water but re-
mained in the boundary areas of warm and
cold currents. Although a considerable cjuantity
of herring thus invaded the north coast fishing
grounds in June 1961 the major part of tlie
Norwegian herring dicl not enter the areas off
the north coast of Iceland but stayecl off the
east coast throughout the summer and autumn
where rich concentrations of food, especially
C. finmarchicus had developed. The sea temjr-
erature off the east coast was similar to that
of the north coast herring areas. The total
north and east coast landings amountecl to
about 200,000 tons and were on the same level
as during the rich herring period in the early
forties. According to our scale analyses the Ice-
landic herring stocks contributed 60% to the
catch whereas 40% were of Norwegian origin
in 1961.
1962
According to the ice observations made dur-
ing the annual herring environmental surveys
carried out by Icelandic, Norwegian ancl Soviet
research vessels in the spring of 1962 (Anon.
1964) it appears that the ice border was some-
what nearer the NW coast of Iceland than in
the previous years. West of Jan Mayen the ice
border was on the other hand as far west as
17° W or further west than in previous years.
As far as the migration pattern of the herring
stocks was concerned the spring of 1962 was
characterized by the early timing of the west-
ward migration of the Norwegian herring. By
the first days of June the first shoals had al-
ready reachecl the off shore waters of the
136 JÖKULL 19. ÁR
middle of the north coast (About 18° W) where
the sea temperature at 20 m depth was 2—3° C.
The herring were concentrated in large 40—
50 m thick shoals near the surface. The migra-
tion pattern of the Icelandic herring was on
tlie other hand similar to that of 1961, i.e.
they were found off NW Iceland at the be-
ginning of June. During the seconcl half of
June and the first tliree weeks of July both
herring stocks were scattered in small shoals
in the off shore waters some 60—100 n.m.
off the north coast. As in previous years the
herring were mainly to be found in the mixed
waters of Arctic and Atlantic origin. During
the seconcl half of July tliese current boundar-
ies of colcl and warm water masses meandered
towards certain parts of the coast. Fig. 2 shows
how tlie herring concentrations follow the 5° C
isotherm as the colder water is forced south
towards the coastal banks. As the herring thus
approach the shelf areas the scatterecl shoals
assemble into larger ones (Fig. 2) resulting in
a goocl herring fishing off the western and
middle nortli coast during the last 10 days of
July (Jakobsson 1962).
As in 1961 large concentrations or herring
also invaded the east coast fishing grounds in
July and remained in that area throughout
the summer and autumn wliere the major part
of the fishing took place.
During the thircl week of August very clense
concentrations of herring were located near
the edge of the continental shelf some 80—100
n.m. N off Langanes (NE Iceland). This late
invasion of herring consisted exclusively of 3
year old Norwegian herring i.e. immature fish
belonging to the 1959 year class. Herring con-
centrations in that area so late in the summer
usually have an easterly or southeasterly direc-
tion, but this immature herring migrated in
westerly direction until it had reached the
area off the middle of the north coast. Then
the herring turned east and southeast and over-
wintered in the same area as the older year-
classes i.e. off the east coast of Iceland. Dur-
ing the 1962 season the proportion of the Ice-
landic herring was 54% whereas the Nor-
wegian herring made up 46% of the catch.
The Icelandic herring was predominant in the
catch off the western north coast in June but
otherwise the proportion of Norwegian ancl