Ontogenetic development of the digestive system in golden pompano (Trachinotus ovatus, Linnaeus 1758) larvae was histologically and enzymatically studied from hatch to 32 day post-hatch (DPH). The development of digestive system in golden pompano can be divided into three phases: phase I starting from hatching and ending at the onset of exogenous feeding; phase II starting from first feeding (3 DPH) and finishing at the formation of gastric glands; and phase III starting from the appearance of gastric glands on 15 DPH and continuing onward. The specific activities of trypsin, amylase, and lipase increased sharply from the onset of first feeding to 5-7 DPH, followed by irregular fluctuations. Toward the end of this study, the specific activities of trypsin and amylase showed a declining trend, while the lipase activity remained at similar levels as it was at 5 DPH. The specific activity of pepsin was first detected on 15 DPH and increased with fish age. The dynamics of digestive enzymes corresponded to the structural development of the digestive system. The enzyme activities tend to be stable after the formation of the gastric glands in fish stomach on 15 DPH. The composition of digestive enzymes in larval pompano indicates that fish are able to digest protein, lipid and carbohydrate at early developmental stages. Weaning of larval pompano is recommended from 15 DPH onward. Results of the present study lead to a better understanding of the ontogeny of golden pompano during the larval stage and provide a guide to feeding and weaning of this economically important fish in hatcheries.

Jaw malformations of hatchery reared golden pompano Trachinotus ovatus larvae were studied from 1 day post hatch (DPH) to 31 DPH. The severity of jaw deformities was classified into three levels where '0' represents normal jaw; '1' is intermediate jaw malformation; and '2' is severe jaw malformation. The severe jaw malformations of golden pompano larvae were clearly observed on 3 DPH. Starting from 3 DPH, both intermediate and severe jaw malformations were observed and the total incidence of jaw malformations ranged from 9.6% to 46.6%. The highest severe jaw malformation occurred on 5 DPH, and 25% larvae exhibited serve jaw malformation. On 11 DPH, jaw malformations reached the peak with 46.6% fish exhibiting jaw malformations of either category 1 or 2. On 26 DPH, the percentage of intermediate jaw malformation reached the peak value (36.4%). This was the first study reporting jaw malformation of golden pompano larvae, and the result can be used as a reference point for future research on the control of jaw malformation in golden pompano.

The osteological ontogeny and the incidence of deformities occurred in vertebral column and caudal complex were studied from 1 day post hatch (DPH) to 31 DPH in Trachinotus ovatus. Results indicate that the development of both caudal complex and vertebral column initiated between 7 DPH and 9 DPH along with the calcification of haemal arches and neural arches, and occurrence of caudal elements. The last element of caudal complex, uroneural, appeared on 18 DPH. A high number of malformations in the vertebral column and caudal complex were detected in this study. More than 33% experimental fish exhibited at least one type of malformation. Results from this study provide the first reference on the osteological ontogeny and malformation of golden pompano. Such information can be applied to the quality control for fingerling production in golden pompano.