Variability and relationships between flow preference, aggregation size and forage frequency, duration and trajectories of juvenileHaliotis discus hannaiIno

The behaviour of individual abalone in a population is known to vary, and higher levels of activity are linked to better survival rate and faster growth. Considering that continuous illumination at night may cause stress to the abalone which would affect their behaviour over time, in this study observations were made under brief and minimal illumination. The observation lasted for 30 days. The relationships between activity traits were analysed in juvenileHaliotis discus hannaiIno, such as forage frequency, duration and trajectories; flow preference; and aggregation size. The aim was to identify an indicator of the abalone activity status, with the ultimate objective being to provide activity-related data that might be useful in farm rearing. Ten traits related to locomotion behaviour of 47 juvenile abalone were recorded under laboratory conditions. The results showed that the exploratory level varied between individuals. More exploratory individuals foraged more frequently, spent more time outside hides, started foraging earlier and preferred higher water flow rate than less exploratory individuals. More exploratory and less exploratory individuals also differed in their extensive movements, hide-shift frequency and aggregation size.