Íslenskar landbúnaðarrannsóknir - 01.09.1978, Page 102

ÍSL. LANDBÚN.
j. agr. res. icel. 1978 10,2: 100-113
An evaluation of smolt releases into a salmon-
and a non-salmon producing stream
using two release methods
ÁRNI ÍSAKSSON
Instilute of Freshwater Fisheries, Reykjavík
TONYj. RASCH,
Washington Deþartment of Fisheries,
Olympia, Washington
and
PATRICK H. Poe
College of Fisheris, University of Washington,
Seattle, Washington.
ABSTRACT
Microtagged Atlantic salmon smolts of hatchery origin were released into a salmon stream and into a
stream with no salmon, using two release methods: The smolts were either adapted to the stream water in a
release pond on the river bank for 2-3 weeks, or they were planted directly into the stream after
transportation from the hatchery. Downstream migrants were also fyke-netted and microtagged at the
salmon stream for comparison with the hatchery smolts.
The release pond method doubled to quadrupled the oceanic survival as compared to the direct plant
method. Considerable straying ofhatchery fish from the nonsalmon producing stream to the hatchery took
place which was practically nonexistent in the case of the salmon stream, even though the distance to the
hatchery was similar. Wild smolts experienced very high survival rates (20-25%) relative to their smali size
at tagging. They also went further upstream than their htchery counterparts. A preliminary estimate of
egg-to-smolt survival in the salmon streams was 0.4 %.
INTRODUCTION
In Iceland there are productive salmon
streams where releases of salmon smolts
augment the natural production of smolts
for the purpose of increasing the number
ofadult salmon returning. Another kind of
strearn is the cold and nonproductive
stream which may be fed either by unsta-
ble runoff from the mountains or from a
stable flow of groundwater from springs.
In both cases the temperatures are fairly
cold and neither type of stream can sup-
port a population of salmon.
Salmon smolts return to the place of
release, and there is therefore a potential
fishery in releasing smolts into such a
stream each year and harvesting the re-
turns by trapping or a sports fishery. Since
the salmon will not be able to propagate in