Descriptive morphology and allometric growth of the larval development of Sarda chiliensis chiliensis (Cuvier, 1832) in a hatchery in northern Chile

Abstract This research describes for the first time, and necessary for its practical application in aquaculture, the morpho-physiological development, the allometric growth patterns, and behavioral characteristics of the early stages of larval development of the South Pacific bonito (Sarda chiliensis chiliensis). Bouyant eggs, from natural spawning, were collected from the conditioning rearing tank where wild-broodstocks were stocked for over a year in a recirculation system. The viable eggs were distributed among three aquariums to investigate the morphological and morphometric characteristics of the larval development periods that were unknown before this investigation. We described that the larval development periods extended to 519 h for the pre-juvenile stages and from 519 to 591 h for the juvenile stage. The total reabsorption of the oil globule occurred between 81 and 108 h, and this description corresponds to a differentiating characteristic of S. chiliensis chiliensis since it would now be one of the three Sarda species that presents a single oil globule in the larval period. Allometric growth patterns showed that the eyes, mouth, and head developed faster than other bodily characters. Therefore, the larvae are prioritizing for a fully-functional mouth when they enter the exogenous feeding stage. It was also observed that the visual development of the larvae was closely related to the height and length of the head and with the height and length of the eyes. Finally, and in accordance with the morphological and morphometric characteristics of the observed larvae, in this research six post-embryonic stages were described: larval stages 1 to 4, pre-juvenile and juvenile.