V. Johannsson et al., THE STRAYING OF ICELANDIC RANCHED ATLANTIC SALMON, SALMO-SALAR L - RELEASE AND RECAPTURE TECHNIQUES, Aquaculture research, 29(9), 1998, pp. 679-686
The straying rate of ranched Atlantic salmon, Salmo salar L., into riv
ers in Iceland was estimated on the basis of coded wire tag recoveries
. Out of a total of 15 158 recaptured tagged salmon from the releases
between 1987 and 1992, 189 fish (1.3%) strayed into 25 out of the 79 s
almon rivers observed. Most of the strayers were found in neighbouring
rivers to the ranching stations. There were no significant difference
s in straying rate between different age classes of salmon returning f
rom the same smelt year class. Generally, there was a delay of 26-27 d
ays in running time between strayers in rivers and salmon returning to
the ranching station. Higher straying rates were observed for ranchin
g stations using riverine traps than for stations using estuary traps.
By close inspection of seven key rivers in Iceland and assuming a 50%
exploitation rate (fishing effort) in the rivers, on average, 2.1% of
the returning salmon in ranching were estimated to stray to native sa
lmon rivers over the years. A limitation of using these numbers to est
imate geneflow between ranching stocks and wild populations is discuss
ed.