Íslenskar landbúnaðarrannsóknir - 01.09.1978, Side 156

Fig. 10. A mature male char which converted from plankton feeding to predation on smaller char which
resulted in the tremendous growth of the specimen caught in October of 1977. Photo Rafn Hafnfjörd.
m2 to a high of 136.7 fish/100 m2 of the
lake surface, with the mean being 43.0
fish/100 m2; nearly twice those found in
Thingvallvatn. A population estimate of
5.4 X 106 fish was made by expansion of
this over the lake surface area for depths
greater than 5 m. The echograms pro-
duced during the survey are shown in Fig.
7. The areal and depth distribution of the
fish are given in Figs. 8 and 9, respectively.
CONCLUSION
These two Icelandic lakes support com-
mercially important quantities of Arctic
char, and it is not unreasonable to assume
that similar quantities of fish are present
in some of the other large lakes.
The traditional Icelandic char fishery
has been by gillnets, either on the bottom
or at the surface of a lake, in relatively
shallow water, usually 10 m or less. The
hydroacoustic surveys of Thingvallavatn
and Skorradalsvatn indicated, however,
that most of the fish are pelagic and are
found in deeper water (Figs, 4, 6, 7, and
9). Therefore, because of the difficulty and
expense for individual fishermen to at-
tempt to develop new and efficient gear
and fishing techniques, expert advice
should be made available as part of the
development of the resource. Another
major consideration is a further develop-
ment of a demand for the fish. At the
present time, all of the commercial catch is
taken only form spawning grounds in
shallow water. A small commercial fishery
has existed for many years in Thingval-
lavatn. The major product of the catch is
canned, whole char, which is marketed
mainly outside of Iceland as brook trout.