A full lifecycle dynamic energy budget model for albacore tuna

Biological parameters or data about the growth, reproduction, and natural mortality are important factors that affect the results of the stock assessment of albacore tuna (Thunnus alalunga); however, these parameters or data are often derived from different data sources and lack of internal consistency and uniformity, and even can’t cover the full lifecycle of T. alalunga which will make the stock assessment results uncertain. Therefore, in this paper, we tried to construct a full lifecycle dynamic energy budget (DEB) model for T. alalunga. Based on the DEB theory and the growth and reproduction data of T. alalunga, the full lifecycle dynamic energy budget model for T. alalunga was developed and the model parameters was estimated. The results show: ① the DEB model can correctly fit the growth process of T. alalunga throughout its life history, estimate the potential annual fecundity of T. alalunga, and make the processes of growth, maturity, spawning, and mortality of T. alalunga interrelated and intrinsically unified; especially, the growth equation for T. alalunga larvae can be got even without the age and length data of the larvae which VBGF (Von Bertalanffy Growth Function) can’t provide correctly; ② according to the DEB theory, there exists two different stages in the growth of T. alalunga before or after its sexual maturity, i.e., before the sexual maturity, the energy which is used to enhance the maturity is dissipated and not used to raise the body weight; however, after sexual maturity, the energy is stored for reproduction and also raise the body weight; thus, its length-weight relationship will be affected by the samples which have different ratios of the mature and immature individual; as a consequence, our results show that it is not appropriate to use a single power function to fit the length- weight relationship for the two stages; ③ the natural mortality coefficient is always assumed as constant (for example, 0.3/a) in the T. alalunga stock assessment, but according to our results, the aging mortality varies greatly with age or length; because the assumption of natural mortality coefficient have greatly influence on the results of the T. alalunga stock assessment and the management, we suggest the assumption of natural mortality coefficient of T. alalunga should consider the effect of variation with age or length. Although the parameter estimation of the dynamic energy budget model has great uncertainty due to the lack of observation data, the dynamic energy budget model can effectively and correctly fit the growth, reproduction, aging mortality processes of T. alalunga and make them interconnected and internally unified, which embody the highly valuable application of the dynamic energy budget model in those studies. The results of this paper will be able to provide scientific support for the growth study and the reasonable stock assessment of T. alalunga.