Líffræðifélag Íslands
Líffræðiráðstefnan 2015
Erindi/veggspjald / Talk/poster V50
Nicolas Larranaga (1,2), Frédéric Hadi (1), Stefán Óli Steingrímsson (1)
1. Hólar University College, Department of Aquqculture and Fish Biology, 2. University of Iceland, Institute of Life and Environmental Science
Kynnir / Presenter: Nicolas Larranaga
Tengiliður / Corresponding author: Nicolas Larranaga (nicolas@mail.holar.is)
Theory suggests that foragers should select habitats and feed at times that optimise the ratio of food intake over predation risk, which in turn should shape their fitness via growth and mortality. Young salmonids have flexible diel activity patterns, but cannot always select optimal habitats because of competitive exclusion or homogeneous environments. We studied the diel activity and growth of young Arctic charr in semi-natural enclosures with contrasting water depth (mean = 13 and 24 cm) and current velocity (mean = 5, 15 and 25 cm/s). We predicted that fish should be more active in deep (lower predation risk) and slow (lower energetic cost of swimming and food availability) habitats, and more diurnal in deep (lower predation risk) and fast (better visibility and lower predation risk) habitats. Fish were more active (opposite to prediction) and more diurnal (as predicted) in fast habitats. Water depth affected neither overall activity rates, nor activity patterns (opposite to prediction). Higher activity rates in fast habitats contrast with the previous literature on Arctic charr's habitat use, which suggest they prefer slow-running waters. Fish grew faster in deeper and faster waters. Within each enclosure, more active fish also grew better overall, but this effect was only statistically significant in fast habitats. Overall, these results should help understand how habitat modifications can affect the behaviour and fitness of stream salmonids and foragers in general.