Íslenskar landbúnaðarrannsóknir - 01.09.1978, Side 77

AN EVALUATION OF TWO TAGGING METHODS 75
Fig. 1. Micro-tagging machine and control unit.
■Photo Jón Kristjánsson.
THE TAGGING TECHNIQUES
Carlin tags.
Carlin tags have been used extensively in
Atlantic salmon research in Europe.
These tags have high information
capacity since each fish has a number
which can be seen easily on the outside.
They have given considerable information
about the migration of saimon in the high
seas; a number of Icelandic tags have been
recovered in West Greenland, Norway,
and the Faroe Islands. It is assumed that
these tags cause a considerable mortality
(especially in small smolts) and a consid-
erable fraction may be lost. No quantita-
tive information on these parameters has
been available.
The tagging operation with the Carlin
tag is fairly tedious. The tag is attached by
a double-steel wire through the dorsal
musculature of the smolts. Icelandic ex-
perience indicates that it takes two per-
sons to tag 1 000 smolts with Carlin tags,
or 2 man-days per 1 000 smolts.
Microtags.
The microtagging technique was de-
veloped in recent years for marking Pacific
salmon. Methods of application and re-
covery are described by Bergmann et al.
(1968). These tiny encoded tags are in-
jected into the snout of smolts and must be
excised upon return to be decoded. Gon-
sequently, their use with Atlantic salmon
is restficted to applications where the tag
can be conveniently retrieved. Since the
tag allows many different identifications
and has been shown with Pacific salmon
to have relatively low tag loss or tag-in-
duced mortality, it was felt that the
technique could provide considerable new
information about Atlantic salmon smolt
survival and would be an excellent tool to
calibrate the dangler tags. In contrast to
the Carlin tag, the microtags are labels for
groups of fish and do not allow individual
identification. Also, the tag does not lend
itself to recoveries without considerable
efl’ort by fishermen on the high seas or in
rivers.
It has been presumed that very small
smolts could not survive the effects of the