On the Integrated Study of Tuna Behaviour and Spatial Dynamics: Tagging and Modelling as Complementary Tools

Abstract

In this paper, modelling efforts that seek to describe, explain and predict the behaviour and spatial dynamics of tunas are reviewed and discussed in relation to tagging studies with the same goals. Tagging and tracking of fish with electronic devices can provide valuable observations of free-living animals, which may be used to help derive models and also to test their predictions. But we simply will not be able to derive and validate models for the fine-scale behaviour of tunas unless measurements are made of physiological and environmental variables, representing factors motivating behaviour, at the same time as position and activity are recorded. On longer time and space scales we must assess reproductive motivation, by identifying spawning grounds and times and measuring gonad state for individuals as they migrate throughout their range. Thermodynamics (through bioenergetics), fitness maximisation and adaptive behaviour with evolutionary motivation are appropriate paradigms for the derivation of models. But modelling will remain merely a technical exercise unless it is carried out as an integrated part of research programs pursuing the understanding of tuna behaviour and spatial dynamics as the ultimate goal. An observational framework that simultaneously measures environmental and physiological variables, with a complementary suite of statistical and theoretical models, will truly advance knowledge and enable us to understand these fish. This synthesis will only be achieved through collaboration between scientists with individual skills in field, laboratory and computational ecology and with innovative technical support. Some case studies are presented here to support this thesis, and it is hoped that this paper will stimulate discussion, collaboration and the development of new observational and computational methodologies.