Íslenskar landbúnaðarrannsóknir - 01.09.1978, Side 21

THE ATLANTIC SALMON IN ICELAND 19
TABLE 1. Salmon tagged at the Kollafjördur Fish Farm as smolts, and caught abroad.
Number of salmon Tagged Recovered Place of recovery
1 1966 1967 Off West Greenland
1 1969 1970 Norway
2 1971 1972 Off West Greenland
1 1972 1973 Off West Greenland
2 1974 1975 Off West Greenland
1 1974 1975 Off Faroe Islands
1 1974 1975 , In a lake on the Faroe Islands
In spite of the great amount of fishing
taking place in the sea around Iceland,
salmon are very rarely caught in the fish-
ing gear used, i.e., otter trawl, gillnets,
longline and purse seines. Records show
single salmon being caught most often in
the spring and summer in gillnets off the
south and west coasts, and in former years
in purse seines off the north coast during
the herring fishery. Once several salmon,
28-30 cm in length of unknown origin,
were caught in purse seines with herring
north off the Faroe Islands in September
1967. Danish research vessels in recent
years have made several experiments
fishing for salmon in the sea southwest of
Iceland and have caught some salmon
there.
Limitations of salmon distribution in Iceland
Iceland is the northern boundary of the
area occupied by the Atlantic salmon. It is
therefore only to be expected that there
are factors limiting its distribution within
the country. One of these factors is temp-
erature.
Fort and Brayshaw (1961) maintain
that when the temperature is below 7°C
growth of Salmonidae is retarded and that
,,an upper limit to the optimum growth-
temperature range“ is about 16°C. The
temperature of water in the rivers follows
fairly well the air temperature in runoff
rivers when it is above 0°C and the snow
and ice have melted. This is not true, how-
ever, when rivers discharge from lakes,
since the temperature of the river water
under such circumstances starts out the
same as that of the surface water of the
lakes, but warms or cools as it flows along
in accordance with the ambient air temp-
erature. Eythórsson and Sigtryggsson
(1971) plotted the diurnal amplitude,
based on bi-hourly averages, of air temp-
erature at Reykjavík in the southwest and
Akureyri in the north from March to
November for the period 1936-1945. The
daily amplitude is very small in mid-
winter. In May the air temperature ex-
ceeded 7°C during the day at the two
places mentioned, and varied in Reykja-
vík from 10°-13.8°C in July and from 7.8°-
10.9°C in September, with the air temp-
erature at Akureyri being about 1°C below
that of Reykjavík in both instances (Fig.
6).
In small lowland rivers where ice and
snow usually have melted already in May,
the river water warms up comparatively
early and follows the air temperature. In