title: Foraging behaviour of larval cod (Gadus morhua) at low light intensities.
abstract: The ability to forage at low light intensities can be of great importance for the survival of fish larvae in a pelagic environment. Three-dimensional silhouette imaging was used to observe larval cod foraging and swimming behaviour at three light intensities (dusk~1.36 × 10-3W/m2,night~1.38 × 10-4W/m2anddarkness~3.67 × 10-6W/m2) at 4 different ages from 6 to 53 days post-hatch (dph). At 6 dph, active pursuit of prey was only observed underduskconditions. Attacks, and frequent orientations, were observed from 26 dph undernightconditions. This was consistent with swimming behaviour which suggested that turn angles were the same underduskandnightconditions, but lower indarkness. Cod at 53 dph attacked prey indarknessand turn angles were not different from those under other light conditions. This suggests that larvae are still able to feed at light intensities of 3.67 × 10-6W/m2. We conclude that larval cod can maintain foraging behaviour under light intensities that correspond to night-time at depths at which they are observed in the field, at least if they encounter high-density patches of prey such as those that they would encounter at thin layers or fronts.
authors.affiliation: Uni Miljø, LFI, PB 7810, 5020 Bergen, Norway.
authors.forename: K W
authors.initials: KW
authors.lastname: Vollset
authors.affiliation: Department of Biology, University of Bergen, 5020 Bergen, Norway.
authors.forename: A
authors.initials: A
authors.lastname: Folkvord
authors.affiliation: Institute of Marine Research, Austevoll Research Station, 5392 Storebø, Norway.
authors.forename: H I
authors.initials: HI
authors.lastname: Browman