Balancing the odds: the relationship between growth and energy storage in juvenile snapper (Chrysophrys auratus: Sparidae)

Abstract. Larval and early juvenile fish living in temperate environments with limited resources face conflicting metabolic demands. To optimise their survival probability, fish must balance the need to out-grow predators by maximising their growth, while also accumulating sufficient energy reserves to sustain them through winter. We tested the hypothesis that resource allocation in Chrysophrys auratus changed from maximising growth to maximising energy storage over their first summer–autumn by measuring recent growth rates from otolith increments, and lipid, protein and carbohydrate concentrations in fish. Lipid concentrations showed the greatest change over the growing season, increasing three-fold between summer and mid-autumn. Growth rates showed the opposite trend, being significantly lower in mid-autumn than in summer. The relationships between growth rate and lipid or protein concentrations were consistent with a shift in resource allocation from growth to storage. During summer and early autumn, growth rates were independent of protein or lipid concentrations, but during mid-autumn there were significant positive correlations between the variables. Biochemical concentrations were independent of fish size, indicating that the accumulation of sufficient energy reserves for winter is determined by the timing of settlement and subsequent feeding conditions, which are likely to affect interannual recruitment variability of this important species