A two-stage growth model for gilthead sea bream (Sparus aurata) based on the thermal growth coefficient

Abstract Several authors have proposed models to describe fish growth taking the influence of temperature into account, and one of the most interesting is the “thermal unit growth coefficient” ( TGC ). Recent research has demonstrated that TGC varies throughout the growth cycle of fish, making it necessary to establish different stanzas. In this work, the original TGC model using 1/3 as an exponent was compared with a new model considering 2/3. Likewise, two stages for the growth of gilthead sea bream under commercial conditions in marine farms were detected by means of TGC seasonal models using the continuous temperature curve. A critical value for weight around 117 g was obtained, which could mark the transition between two growth dynamics. To describe the weight evolution during a complete production cycle, the two growth stages were described by two separate seasonal TGC models (1/3- TGC model and 2/3- TGC model), and with an integrated model named the Mixed- TGC model, which presents interesting properties of continuity and differentiability and could be an important tool for fish farm management.