Íslenskar landbúnaðarrannsóknir - 01.09.1978, Blaðsíða 76

ÍSL. LANDBÚN.
J. AGR. RES. ICEL. 1978 10,2: 74-99
An evaluation of two tagging methods and survival rates
of diíferent age and treatment groups of hatchery-reared
Atlantic salmon smolts
ÁRNI ÍSAKSSON
Inslilule of Freshwaler Fisheries, Reykjavík.
and
PETER K. Bergman
I Vashiuglon Deparlmenl of Fisheries,
Olympia, Washington.
ABSTRACT
'i'hc cxpcrimcnis wcrc conductcd during thc 1974 and 1975 tagging scasons. Returns from smolts of the
Atlantic salmon, wltich had bccn microtaggcd, wcrc contparcd to thc rcturns of smolts tagged with Carlin
tags. Microtaggcd sntolls ltad considcrahh highcr survival ratc and onh a fractional tag loss compared
wilh thc Carlin-taggcd smolts. Carlin lags impaircd occanic growth. There is an indication thal thc
incrcasc in survival ratc witli sizc ofsmolts, oftcn found willt Carlin tags, is an artifact of the tag.
Diffcrcnt rclcasc linics wcrccomparcd and rclcascs in latcjunc appcarcd tobemorc favorablc-a statement
wich cannot bc gencralizcd for othcr ycars. Sonic dilfcrcnccs wcrc notcd in lavourablc relcase timc between
diflcrcnt smolt groups, dcpcnding on thc cxposurc to hcatcd watcr iu thc spring.
INl RODUCTION
Extensive experimentation involving
smolt tagging has been conducted at the
Kollafjördur Experimental Fish Farnt in
Iceland. A review of the facilities and
tagging experiments is presented by Guð-
jónsson (1972) and Ísaksson (1976). Most
of the tagging experiments have been car-
ried out, using Carlin or Plastic tags.
These are external dangler-type tags
which have been shown to have consid-
erable negative effect on survival
(Ísaksson, 1976). It is therefore of great
importance to ftnd a salmon tag which
does not affect the survival of the ftsh and
can be economically applied to great
number of smolts. The purpose of the pre-
sent experiment is to determine whether
the microtag of Jefferts et al. (1963),
which has been used extensively for simi-
lar purposes with Pacific salmon (On-
corhynchus sp.). is better than the conven-
tional tags used for Atlantic salmon, with
respect to survival, tag retention, and gen-
eral applicability.