Morphometric Indices of Nutritional Condition and Sensitivity to Starvation of Spot Larvae

When spot Leiostomus xanthurus larvae began to feed (age 3 d at 24°C, 4 d at 22°C, 5 d at 20°C, 5–6 d at 18°C), little endogenous energy was available to them. If food was withheld 3 d or more, most larvae died even if food then became available. Larvae were equally vulnerable to starvation throughout the preflexion stage (≤3.8 mm standard length, the stage occurring before the upward flexion of the notochord tip). Later-stage larvae (flexion and postflexion, during and after notochord flexion, respectively) survived food deprivation significantly longer than preflexion-stage larvae. Discriminant analysis of six body measurements (standard length, head length, eye diameter, body depth at anus, body depth at cleithral symphysis, body depth at pectoral fin base) identified significant changes in larva body shape during starvation and successfully classified larvae according to nutritional condition. Moderately starved and starved (food withheld for 1–2 and 3–4 days, respectively) preflexion larvae were morphologically similar, indicating that the effects of starvation proceeded rapidly. Fed and moderately starved (food withheld for 1–4 days) flexion-postflexion larvae were morphologically similar, indicating that starvation of older larvae proceeded more slowly. The proportion of preflexion larvae correctly classified improved when starved and moderately starved fish were combined into a single category (83% correctly classified); classification of flexion-postflexion larvae improved when fed and moderately starved fish were combined (87% correct).