An integrated model for growth incorporating tag–recapture, length–frequency, and direct aging data

Abstract

A maximum likelihood method for modelling fish growth is presented that integrates data from three key sources of growth information: tag–recapture studies, length–frequency samples from commercial catches, and direct aging data from hard-parts analyses. Previous studies have almost exclusively modelled growth using only one of these sources of information. Different data sources are often most informative about different portions of the life cycle. The development of an integrated approach allows for the different data sources to complement each other and provide more comprehensive and robust estimates of growth parameters. The integrated method is applied to data sets from southern bluefin tuna (Thunnus maccoyii) using the von Bertalanffy growth curve as well as a more sophisticated growth curve that makes a smooth transition between two von Bertalanffy curves with different growth rate parameters. The latter is found to provide a significantly better fit and supports previous findings that southern bluefin tuna experience a transition in growth during the juvenile stage of life. Many species exhibit a seasonal growth pattern, including southern bluefin tuna for which growth is fastest during the austral summer. A method for incorporating an annual seasonal component into the analysis is described and applied.