Fishing mortality can exert strong, directional selection on wild fish populations, driving evolutionary change in growth, maturation, behaviour, and physiology. In aquatic systems where harvest rates often exceed natural mortality, such selective pressures may alter trait distributions over relatively short timescales. In lutruwita (Tasmania), southern sand flathead (Platycephalus bassensis) represents a valuable case study for examining physiological responses to exploitation. This ambush predator dominates recreational flathead catches in the state, with southern populations exposed to intense fishing pressure and northern populations experiencing comparatively less exploitation. These regions show pronounced differences in life history traits such as size at age and size at maturation, but the underlying mechanisms, whether environmental, genetic or anthropogenic, remain unresolved. This study investigates regional differences in digestive performance, energy allocation, and growth under controlled laboratory conditions. Size-matched sand flathead were collected from a heavily exploited southern population (North-West Bay, D'Entrecasteaux Channel, n = 44) and lightly fished northern populations (Flinders Island, Musselroe Bay, Eddystone Point, n = 44). Fish were assessed for specific growth rate (SGR), feed conversion ratio (FCR), and postprandial metabolic oxygen consumption (SDA) using intermittent flow respirometry. In vitro gut sac experiments quantified nutrient and ion fluxes across the intestinal epithelium in fed and fasted states. Fish from the high-fishing-pressure region exhibited reduced growth rates, lower feed efficiency, and shorter SDA duration. These findings suggest altered digestive efficiency and energy allocation consistent with directional selection under size-selective harvest, with implications for population productivity and recovery potential.