Diet shift and allometric growth in the early development Odontobutis potamophila

Abstract

The viability of fish during their early developmental stages is pivotal for population recruitment, a period during which individuals are frequently confronted with significant risks of starvation. There is limited knowledge regarding Odontobutis potamophila food selectivity before its transition to feeding on fish. Thus, this study aimed to elucidate its prey composition and diet shift from 0 to 22 days after hatching. We also examined early allometric growth patterns to confirm whether there was a correlation between the rapid onset of exogenous feeding in juvenile carnivorous fish and the earlier appearance of inflection points in various morphological traits. Cluster analysis showed a gradual shift in prey composition from nauplii to predominantly cladocerans and copepods as individuals grew. This adaptive shift in diet revealed a mechanism whereby the larger the individual, the larger the size of the bait ingested, and the faster the growth rate. The results of the allometric growth study demonstrated that O. potamophila emerged from the membrane with a total length of 6.53 ± 0.51 mm and a body weight of 1.93 ± 0.56 mg. The positive allometric growth of body weight relative to total length provides the required energy for organ development and onset of the juvenile stage. Feeding commences at one day post-hatching, with the yolk sac fully depleted by day 6, thereby facilitating the transition into the exogenous nutritional phase as early as possible. The initial manifestation of certain morphological growth inflection points occurred predominantly around 10 days of age, concomitant with the advent of a shift in feeding habits. The prey composition, diet shifts, and growth patterns of early individuals with equilibrium strategy, represented by O. potamophila, have important implications for improving the survival of early life stages, thereby providing new strategies for population replenishment.