Improving our Understanding of Tropical Tuna Movements from Small to Large Scales

One tactical objective of behavioural studies in fisheries sciences is to understand the 3-D movements of fish, with the ambitious strategic objective of being able to explain some large-scale movements and distributions from knowledge of small-scale behaviour. The present paper reviews different possibilities to improve our understanding of tropical tuna movements, from small (days) to large scales (weeks and months). We propose some ideas for better observations of fine-scale movements of fish (sonic tags) and of the surrounding environment of the tagged fish. After determining behaviour rules, appropriate modelling should be developed in order to extrapolate results to larger-scale movements. This process can be achieved only if we can simultaneously observe the relevant factors of the environment at appropriate scales and the large-scale movements of fish (using pop-up archival tags), in order to force the models to reproduce the observed movements. This paper shows the importance of (i) small-scale studies, (ii) appropriate observations of large-scale movements and environment, and (iii) models of behaviour in order to extract relevant processes necessary to predict tuna dynamics.