Íslenskar landbúnaðarrannsóknir - 01.09.1976, Page 18

16 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
Table 1
Preliminary Returns of Tagged Salmon from the 1973 Tagging Experiment *
Group number Type of taq Treatment attribute Age at tagging Mean length at tagging cm Number tagged Returns at Kollafj. Returns other places Total returns number Total returns %
i Carlin polyethylene attachment Polyethylene attachment 2-year 16.2 700 81 0 81 11.6
2 Carlin wire attachment Wire attachment 2-year 16.3 1300 118 4 122 9.4
3 Carlin wire attachment Progeny of qrilse 2-year 15.5 1000 103 4 107 10.7
5 Carlin wire attachment Progeny of 2-year-sea salmon 2-year 14.8 1000 89 5 94 9.4
6 Plastic polyethylene attachment Plastic tag 2-year 16.7 1000 91 4 95 9.5
7 Carlin wire attachment Cold- branding 2-year 16.7 1000 92 i 93 9.3
8 Plastic polyethylene attachment Exercise 1-year 14.9 700 56 i 57 8.1
9 Plastic polyethylene attachment No exercise 1-year 14.6 700 62 0 62 8.8
10 Plastic polyethylene attachment Nonfatty feed 1-year 15.2 700 73 1 74 10.6
11 Plastic polyethylene attachment Fatty feed 1-year 15.1 700 46 0 46 6.6
12 Plastic polyethylene attachment Floating pen Mixed ages 18-25.0 430 14 1 15 3.5
13 Adipose clipped Untagged 1-year 15.0 2300 340 0 340 14.8
h Returns after two and three years at sea are not in at the time of this writing.
could be easily seen and 62% were poorly
or not visible. It should be noted that the
double marking and handling of the fish did
not affect their remrn-rate.
2. One-year-smolts.
The returns of one-year-smolts range from
6,6 to 10,6 percent. These fish were fairly
uniform in size at tagging and can be easily
compared. If groups 8 and 9 are compared,
there does not seem to be any beneficial
effect from the exercise that the fish in group
8 were subjected to.
The difference between fish fed a fatty
diet and nonfatty diet does seem to be signi-
ficant. The fish on the fatty diet (group 11)
are not remrning as well as the fish on the
nonfatty diet (group 10). This is not sur-
prising since data from wild steelhead
smolts indicate a lowering of fat content
during smoltification (Fessler and Wag-
ner 1969) and it is not unreasonable to
assume the same for Atlantic salmon.
The adipose clipped smolts had a record
remrn rate of 14,8%. Since adipose clipping
is the least detrimental method of marking,
it is probably a very good indicator of the
return rate of untagged fish to get the ratio
of tagged to untagged. This group should be
compared to group 10 since both were sub-
jected to the same conditions until released.
This comparison indicates that approximately