Íslenskar landbúnaðarrannsóknir - 01.09.1978, Page 127

ÍSL. LANDBÚN.
j. agr. res. icel. 1978 10,2: 125-134
Growth rates of brown trout and Arctic char
in Iceland
JÓN Kristjánsson
Institute of Freshwater Fisheries,
Reykjavík
ABSTRACT
Several limnological studies have been made of freshwater lakes and rivers in Iceland, but only a few
investigations of the resident fish fauna. The increasing interest in and use offreshwater fish creates a need
for estimates of vital parameters. Foremost among these are age and growth and abundance which are
discussed for three lake/river types.
INTRODUCTION
In Iceland there are 15 lakes with a sur-
face area exceeding 10 km2. The largest
one, Thingvallavatn, covers 83 km2. Six-
tyeight other lakes have a surface area
ranging from 1.0 to 10.0 km.2. Finally ab-
out 1200 lakes have a linear extent of 300
m or more.
Five species offish are endemic: salmon
(iSalmo salar), brown trout (Salmo trutta),
Arctic char (Salmo alpinus), the European
eel (Anguilla anguilla), and three-spined
stickleback (Gasterosteus aculeatus).
Brown trout appear in two forms; a true
freshwater form and sea-run variety. The
latter type is found especially in rivers
along the southern and southeastern parts
of Iceland, less frequently in the north-
eastern part, and is almost absent in the
eastern part of the countrý. The resident
form of brown trout is found in every lake
which provides adequate spawning
grounds.
Char occupy all trout lakes except in
one group of lakes, Veidivötn, in south-
central Iceland. Pelagic char are found in
the larger lakes. Char are encountered in
rivers and lakes in every part of Iceland;
but are far less abundant in the south-
western and southern parts than
elsewhere. As an Arctic fish it is often the
only salmonoid species inhabiting the col-
dest rivers, and it is most abundant in the
northern and eastern part of Iceland.
Commercial fishing for trout and char is
still of minor importance and only occurs
in three lakes. Lake Thingvallavatn yields
3-5 tons of benthic, and up to 70 tons of
pelagic char annually. In Apavatn the