Íslenskar landbúnaðarrannsóknir - 01.09.1976, Side 6

4 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
Table 1
Groups Tagged in 1971 and Recaptures by Electric Fishíng
Group number Age of smolt in years Number of weeks in oufdoor ponds Number of smolts released Number of smolts caught by electric fishing Percent caught by electric fishing
1 1 8 2261 (C) 299 13.2
2 1 10 6086 (F) 943 15.3
3 í 12 2989 (C) 440 14.7
4 2 0 448 (F) 55 12.3
5 2 10 583 (C) 58 9.9
6 2 35 2481 (C) 2 0.08
7 2 35 1294 (C) 2 0.15
C * Carlin tag
F ■= Finclipped
1969 have been presented by GuðjónsSON
(1970 and 1972). The Carlin tag with a
conventional steel wire has been almost ex-
clusively used in these experiments. All the
smolts tagged in any one year are tagged by
the same tagging-crew. This paper is a re-
vised version of ICES report M:2ó 1973-
The 1970 Tagging Experiment.
In 1970 the total number of smolts released
with the Carlin tag was 9219. These were
one-year-smolts reared indoors until their re-
lease. The average fork length of these fish
was 13—14 cm. The total returns to date
have been 1 fish or 0,01%. These results
were disappointingly low but not quite un-
expected after the clear cut results of the
1969 tagging experiment presented by Guð-
jónsson (1970). But the results proved
once more that the rearing of one-year-smolts
under the present circumstances was not
practical at all.
The 1971 Tagging Experiment.
l.The Groups Tagged.
One of the primary purposes of this experi-
ment was to try to improve the returns of
one-year-smolts to the Fish Farm. It was
theorized that by putting the one-year-smolts
in outdoor ponds in February or March one
could improve their returns. It was assumed
that the spring photoperiod would have some
beneficial effects. A two-year-old control
group subjected to the same treatment
was tagged. Some two-year-fish were
compared with respect to tagging time. One
group was tagged before the end of March
(group 6). The other was tagged after the
25th of April (group 7). In addition to
tagging with Carlin tags some groups were
fin-clipped. The groups tagged and fin-clip-
ped are shown in Table 1.
The ocean-going instinct of the various
groups was examined in the outlet from the
release ponds by electric fishing which com-