Íslenskar landbúnaðarrannsóknir - 01.09.1978, Side 14

12 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
The size of salmon at smoltification in known cases ranges from 11 to 13,3 cm on the average for individual
years, and the age from 1-5 years. In most cases examined, they have spent 3 years in fresh water, although
in the colder rivers a numeber of them may be 1 year older than the scale readings seem to indicate. The
mature salmon spend from 1 to 2 years in the sea, occasionally 3 years. Among 1,799 salmon analyzed,
52.9% had spent 1 year in the sea and 46.6% 2 years, and only 0.5% 3 years. The ration of 1- and 2-year
ocean age fish varies from one river to another. The percentage of repeat spawners varied from 0-18.4%,
determined from spawning marks on thescales. Weight ofsalmon after 1 year in thesea is usually 1.5-3.5 kg
and after 2 years 4—6 kg; and the larger ones have normally stayed 3 years in the sea.
Salmon culture in Iceland is a rather recent undertaking. It started with the ardficial hatching ofsalmon
ova and liberation of unfed fry decades ago. In the early fifties feeding of fry was started and the fry were
liberated in late summer. In the sixties feeding offry and parr up to the smolt size was inidated. Today there
are 8 rearing stations in Iceland, and mainly 1-summer-old fry and salmon smolts are liberated in the rivers.
Such stocking is carried out on a large scale, but little direct evidence is available of its beneficial effect.
Improved stocking methods may change this in the future.
INTRODUCTION
Geography
Iceland is an island in the North Atlantic,
situated between 63.5° and 66.5° N latit-
udes and 13.5° and 24.5° W longitudes. It
covers an area ofl 03,000 km2. The central
part of the country is a plateau from 500-
700 m high, with many snowcapped mo-
untains, the highest ones being about
2,000 m high. Several large glaciers are
located mainly in the south and south-
eastern part of the country and in the cen-
tral highlands. Iceland is a mountainous
country with lowland areas inhabited
either along the coasts or at the bottom of
Qords.
Climate
The climate of Iceland is cool, temperate,
and oceanic, with rapid changes. The
summers are cool and the winters are re-
latively warm. The average temperature
in the capital city of Reykjavík, in the
southwestern part of the country, is
11.2°C in July and — 0.4°C in January.
The average air temperature is highest in
southern and southwestern Iceland. It de-
creases north- and northeastward in lower
areas decreasing still further on the cen-
tral plateau, being at its lowest over the
glaciers.
The mean precipitation recorded at
several weather stations, 1931-1960,
varied from 353 mm in northern Iceland
to 2,256 mm in the southernmost part
(Eythórsson and Sigtryggsson 1971).
The Rivers of Iceland
In Iceland there are about 250 large and
small rivers. They have been classified
into three main groups according to their
origin (Rist 1956). These groups are gla-
cial rivers, direct runoffrivers, and spring-
fed rivers. The discharge from the silty
glacial rivers is small in the winter. It
increases in June and reaches its peak in
July or August with a daily variation
during the warmest part of the year. The
temperature of the glacial rivers is close to
freezing level at source, but the rivers