Íslenskar landbúnaðarrannsóknir - 01.09.1978, Blaðsíða 13

ÍSL. LANDBÚN.
j. agr. res. icel. 1978 10,2: 11-39
The Atlantic salmon in Iceland
Thór Gudjónsson
Institute of Freshwater Fisheries,
Reykjavík.
ABSTRACT
Iceland, is situated in the North Atlantic, has a cool, temperate, oceanic climate, the summers being cool
and short. There are about 250 rivers in the country, large and smail, ofthree main types: glacial, direct run
oíf, and spring-fed rivers. There are only flve species of freshwater fishes native to Iceland, the Atlantic
salmon being the most economically valuable species. It is grouped with freshwater fishes, although it is an
anadromous species, because fishing for salmon in the sea is prohibited by law in Iceland.
Salmon enter about 80 rivers in the country, most of which are found in the western half, yielding about
91% of the total catch during the years 1966-1975. In 16 rivers catches during the mentioned period
exceeded on the average over 1,000 fish each. Fishing methods are mainly rod and line sport fishery, and
gillnets only in a few instances. Salmon catches have increased from about 15,000 salmon annually from
1910-1955 to about an average catch of 64.000 salmon during the years 1966-1975.
Icelandic salmon migrate far and wide in the North Atlantic. Tagged Icelandic salmon have been caught off
western Greenland, the Faroe Islands, and offNorway.
Iceland is on the northern outskirts of the distribution area of the salmon, low temperature of river water
being a limiting factor. During summer the water temperature in the rivers in the south is highest and
decreases toward the north and northeast.
The salmon ascend the rivers from late May to October, with the main run occurring in July. There are
several factors initiating ascent of salmon and orhers delaying it, such as low water temperature.
Salmon spawn from September to December, earlier in the colder rivers in northern and northeastern
Iceland and later in the warmer streams in the southwest and the south, with the effect that hatching time is
synchronized.
The density ofjuvenile salmon in the rivers varies from 677 salmonid fry and parr per 100 m2 of river bottom
in the river Úlfarsá in southwestern Iceland toless than 126 and as low as 0.4 fish per 100 m2. The mainfood
of the 0+ group ofjuvenile salmon in the river Úlfarsá was chironomids, while trichoptera and gastropods
predominated in the food of the 1+ and 2+ groups.
All native freshwater fishes can be present in the nursery areas of salmon. They compete for the samefood in
spite ofvarious habitats. The food supply in the rivers varies since low waters or floods have deleterious
effects on it.