Íslenskar landbúnaðarrannsóknir - 01.09.1976, Side 7

TAGGING EXPERIMENTS AT KOLLAFJÖRÐUR 5
Table 2
Returns from the 1971 Tagging Experiment
Group number Age of smolt in years Number of weeks in outdoor ponds Number of tagged smolts released Mean length of tagged smolts R e t u r n s
1972 (after one year) 1973 (after two years) Total re- turns Re- turns % Type of tag
K O.P. Total K O.P. Total
1 1 8 2261 14.8 3 1 4 3 0 3 7 0.31 Carlin tag
2 1 10 6086 13.2 13 0 13 Not valid 13 0.21 Adipose clipped
3 1 12 2989 14.5 9 0 9 1 0 1 10 0.33 Carlin tag
4 2 0 448 13.5 0 0 0 0 0 0 0.00 Fin-clipped
5 2 10 583 13.5 2 0 2 1 0 1 3 0.51 Carlin tag
6 2 35 2481 15.0 91 ^xx 98 18 0 18 116 4.7 Carlin tag
7 2 35 1294 15.6 53 2 55 4 1 5 60 4.6 Carlin tag
Total 1+3 K 1 8-12 5250 14.6 12 1 13 4 0 4 17 0.32 Carlin tag
Total 6+7 k 2 35 3775 15.2 144 9 | 153 22 1 23 176 4.6 Carlin tag
»< Garlin tagged only excluding group 5 and fin clipped
kk Two recaptures off West-Greenland
K = KollafjörSur
O.P.* Other places
menced soon after the fish were supposed to
have migrated out to sea.
The total number tagged with Carlin
tags was 9608 whereof only 3775 were
viable two-year-old migrants. The rest of the
fish were experimental groups from the
photoperiod experiment mentioned earlier.
2. The Electric Fishing.
The electric fishing was performed several
times during the summer of 1971 after the
25th of June. Experience in previous years
had shown that if not properly smoltified the
one-year migrants did not want to leave the
outlet creek. Is was assumed that if the photo-
period treatment of the one-year-old smolts
had been successful, they would migrate to
sea to the same extent as the two-year-olds.
The results are shown in Table 1. It is
evident that group 1, 2 and 3, which are
one-year-olds, have remained to a great ex-
tent in the creek, since their remrn in the
electric fishing is 13 — 15%. The two-year-
old control groups 4 and 5 were caught 10
—12% which shows that they also were
reluctant to leave the creek. Groups 6 and 7,
on the other hand, were hardly cought at all
in the electric fishery with means that they
migrated directly to sea soon after release.
3. The Adult Retum.
Since the one-year migrants did not seem to
leave the station very promptly in 1971, it
was not expected that they would remrn in
great numbers in 1972. However they show-
ed a considerable improvement over earlier
releases of one year smolt at the Fish Farm
(see the 1970 experiment in this report).
The adult remrns are shown in Table 2.