Individual differences in horizontal movements of yellowfin tuna (Thunnus albacares) in nearshore areas in French Polynesia, determined using ultrasonic telemetry

This article describes tracking experiments conducted on eleven yellowfin t una using ultrasonic transmitters in French Polynesia between 1985 and 1997 . Nine fish were caught near Fish Aggregating Devices (FADs) while the othe r two were tracked in coastal areas without FADs. The fish showed different patterns of horizontal movements: tight associations with FADs lasting sev eral days, foraging movements confirmed by simultaneous acoustic observatio ns of prey-sized fauna, movements parallel to the shore, and traveling betw een FADs. This intra- and inter-individual variety of behaviour might depen d on the local environment (prey), and on individual biological differences . The influence of FADs, coastlines, and prey on tuna movements is discusse d. The lack of information about the surrounding environment, the internal state of the fish and the recent history of the fish usually prevent scient ists from adequately interpreting the observed movements. Ideas for future research to studying tuna behaviour near FADs are discussed. (C) 2000 Ifrem er/CNRS/INRA/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS.