Lacustrine sockeye salmon return straight to their natal area from open water using both visual and olfactory cues |
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Authors: | Ueda H; Kaeriyama M; Mukasa K; Urano A; Kudo H; Shoji T; Tokumitsu Y; Yamauchi K; Kurihara K |
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Institution: | Toya Lake Station for Environmental Biology, Faculty of Fisheries, Hokkaido University, Abuta, Japan. hueda@ccms1.hucc.hokudai.ac.jp |
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Abstract: | Mechanisms of the amazing ability of salmon to migrate a long distance from
open water to natal streams for spawning are still unknown. Lacustrine
sockeye salmon (Oncorhynchus nerka) in Lake Toya offers an excellent model
system for studying the orientation mechanism in open water, because mature
fish return to the natal area with a high degree of accuracy. First we
examined the percentage of fish returning to the natal area after they were
released 7 km south of the natal area. Forty percent of control male mature
fish and 25% of the fish blinded by injection of a mixture of carbon toner
and corn oil into the eyeball were captured in the natal area within 5
days. Forty-four percent of fish with brass rings (control) and 31% of fish
with NdFe magnetic rings which interfere with the magnetic cue were
captured in the natal area within 3 days. These experiments suggested that,
although the number of blinded fish captured in the natal area was less
than that of the controls, the difference was not statistically
significant. In the fish captured in the natal area within 3 or 5 days,
fish which found the natal area using their olfactory cue after random
swimming for a long time and returned to that area may be included. Hence
we tracked fish telemetrically using an ultrasonic tracking system, and
found that mature males released at a long distance (3.6 or 6.8 km) from
the natal area swam straight to the vicinity of the natal area.
Interference of the magnetic cue by the attachment of a magnetic ring did
not affect their direct return. Blockage of the visual cue caused them to
move randomly. These data suggest that lacustrine sockeye salmon return
straight to the vicinity of the natal area using their visual cue and
finally reach the exact homing point using their olfactory cue.
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