Effects of intraspecific competition and predation risk in the littoral-benthic community: a case study of juvenile burbot (Lota lota)

The diel activity pattern and substratum preferences of juvenile burbot (Lota lota) were investigated in mesocosm experiments. Single specimens as well as groups of six burbot fed ad libitum, starved and with a predator present, were continuously monitored over 24 hours. The diel pattern of activity did not change among treatments but absolute activity levels were significantly different. High levels of activity were observed in solitary and starved fish, intermediate when conspecifics were present but significantly lower in the presence of a predator. Solitary specimens preferred stones while fish in a group showed a size dependent use of the substratum. The results classify the crepuscular to nocturnal behaviour of burbot as stenotype behaviour with little modulation due to external stimuli. The absolute levels of activity as well as the substratum selection however seem to be dominated by individual decisions based on a specimen's environment and predation risk.