Ægir - 15.06.1972, Blaðsíða 14

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ÆGIR
south and west coast. After spawning the
cod migrate mainly along the west coast
to the feeding grounds. Cod grown up in
the warm water area rather stationary
through their life.
The tagging experiments at Greenland
show that the cod from S- and E-Green-
land immigrate to the Icelandic spaAvning
grounds, sometimes on a large scale, and
these immigration can be of very great
importance to the Icelandic spawning
fishery.
Systematic investigations on the Icelan-
dic stock of cod during the last 40 years
have demonstrated great fluctuations in
the strength of various yearclasses. These
fluctuations greatly influence the annual
catches. At the age of 8—13 years the
1922 yearclass yielded 705 thousand tons,
but the same agegroups of the 1927 year-
class yielded only 19 thousand tons.
Another very strong yearclass, which
yielded nearly 700 thousand tons was the
1945 yearclass. These two strong year-
classes were mainly of Greenlandic origin.
Since dr. Sæmundsson started his in-
vestigations on cod there have been great
changes in the catch, fishing effort and
the state of the stock. At the beginning of
this century the total annual catch from
Icelandic waters was less than 100.000
tons a year. During the last decade the
average annual catch was about 400.000
tons.
But the increase in catch does not tell
everything. Changes in effort and fishing
mortality demonstrate much better the
changes in the state of the stock. During
the years between the World Wars, the
annual average total mortality in the
spawning part of the Icelandic stock of
cod was about 45%, and fell during the
World War II, and the first years there-
after to the average of 37%. Since then
the total annual mortality has been in-
creasing steadily due to increasing fishing
effort and during the period of 1966—
1969 it was nearly 70%.
The spawning potential of the stock
has also been steadily decreasing. During
the period of 1945—1949 the cod had on
the average the possibility to spawn 2.5
times in its life — but during the period
of 1965—1969 only 1.2 times.
Investigations on stock size and year-
class strength have shown that the 1964
yearclass is the best one recruited during
the last two decades. From the same period
we know other two relatively good year-
classes, i. e. the 1956 and the 1961 year-
classes. When these three yearclasses had
reach the age of 4 years, their stock size
was about the same, i. e. about 230 million
fish each yearclass (assuming M = 0.2),
asaresult of higher fishingmortality in the
1964 yearclass. At the age of 4 and 5 years
these yearclasses were exploited heavely,
especially the 1964 yearclass. According
to our calculations about 40 million cod
of the 1956 yearclass, 50 million of the
1961 yeai’class and about 80 million of
1964 yearclass were caught from these two
agegroups. Therefore it is evident that the
yield of the 1964 yearclass will not be as
rich as might have been expected.
Scientists agree that the Icelandic stock
of cod is now fully exploited and further
increase in fishing effort will not increase
the average total yield. On the contrary by
increasing fishing effort the catch per
unit effort will decrease leading to less
profitable fishing so it is in interest of all
concerned to prevent further increase in
fishing effort on cod.
It has been mentioned here earlier that
the immigration of cod from Greenlandic
waters is of great importance to the Ice-
landic spawning fishery. Since 1963 the
yearclasses at East-Greenland are all poor
so we cannot in near future expect any
big migrations from there. At Iceland the
1964 yearclass is the last good yearclass.
The other yearclasses which will enter the
Icelandic spawning fishery in the near
future are all average or under average
size. The total catch of cod from Icelandic