Atlantic bluefin tuna (Thunnus thynnus): a state-dependent energy allocation model for growth, maturation, and reproductive investment

The relationship between Atlantic bluefin tuna (ABFT, Thunnus thynnus) life history patterns and environmental conditions was investigated by developing a state-dependent model that optimizes energy allocation between growth and energy stores and the decision to spawn. The model successfully recreates growth, age-at-maturity, and seasonal variability in condition for western ABFT that spawn primarily in the Gulf of Mexico. Eastern ABFT spawning in the Mediterranean Sea display a life history trajectory shifted toward earlier maturation and, perhaps, reduced growth - a pattern predicted by the model when mortality was higher, migration distance shorter, and food intake during migration and spawning higher. Simulations highlight the sensitivity of the optimal ABFT life history strategy to variability in net energy intake, particularly during migration and spawning, a poorly understood component of their life cycle. Results also emphasize the importance for optimal life history patterns of the timing of spawning migrations in relation to the phenology and amplitude of seasonal prey availability. This study provides insight into potential mechanisms that underlie observations that are at the heart of current discussions regarding ABFT subpopulation structure and variable life history patterns.