The timing of emergence of Atlantic salmon and rainbow trout, incubated on different substrates
Working paper
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http://hdl.handle.net/11250/104163Utgivelsesdato
1986Metadata
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This report is not to be cited without prior reference to the authorSammendrag
Atlantic salmon (Salmo salar) and rainbow trout (S. gairdneri)
eggs were incubated in plexi-glass aquariums. After hatching,
alevins were kept in darkness, two groups of each species without
substrate, two groups in gravel and two groups in Astroturf
artificial substrate.
Every sixth day after hatching, individual swimming height
above the bottom were monitored with a video recording system.
The use of infrared light made it possible to observe the
positions in the water column in darkness.
Mean swimming height in a coordinate system and percentage
occurrence in specific heights above the bottom were used as
measures on emergence from the bottom.
Emergence was more conspicuous among the rainbow trout
alevins (196 - 226 day degrees) than Atlantic salmon alevins
(335 - 400 day degrees). After emergence, the rainbow trout
alevins swam close to the water surface, and 50 % of them became
photopositive on day 39 (269 day degrees). The Atlantic salmon
stayed closer to the bottom after emergence, and they became
heedless to light at this stage. This reflect different
evolutionary strategies. Neither substrates nor feeding made
influence on overall timing of emergence.