Eight hatchery-reared Atlantic salmon Salmo salar post-smolts, implanted with acoustic depth sensing transmitters and manually tracked for 5–12 h in the Hardangerfjord (Norway), spent most of their time (49–99%) at 1–3 m depth during the day, whereas four of seven fish tracked were found close (<0·5 m) to the surface at night, with a strong negative cross-correlation between general swimming depth and surface light intensity. Hence, the actual swimming depth of post-smolts during their early marine migration may depend on the light conditions, although the individual variation in vertical movement pattern was large. No cross-correlations were found between light intensity and swimming depth during daytime periods with rapid changes in light intensity, indicating that other factors than light intensity were important in initiating the irregular dives that were recorded down to 6·5 m depth.
No Supplementary Data
Document Type: Research Article
The University of British Columbia, Centre for Aquaculture and Environmental Research, 4160 Marine Drive West Vancouver, BC V7V 1N6, Canada
Norwegian Institute for Nature Research, NO-7485 Trondheim, Norway
Norwegian College of Fishery Science, University of Tromsø, NO-9037 Tromsø, Norway
Publication date: 2008-09-01