Quality parameters of wild white trevally (Pseudocaranx dentex) natural spawn kept in captivity

The white trevally (Pseudocaranx dentex Bloch & Schneider, 1801) is a widely distributed carangid, commercially exploited in both the Pacific and eastern Atlantic. Most published works refer to the use of hormonal induction with gonadotropin-releasing hormone for egg supply with generally low fecundities and of poor quality. This study aimed to contribute for a better knowledge on the husbandry conditions that allow for natural spawning of white trevally in captivity. Wild white trevallies were kept in captivity for four years until natural spawning occurred. Nine breeders were kept in a 10m3 concrete tank at a density of 5 Kg/m3 , under natural photoperiod and natural water temperature fluctuations. Spawning started when water temperature reached 19 °C and lasted for two months. Viability rates varied between 35 and 79% and the average number of spawned eggs per female was of 280 × 103 . Egg total lipids (16%DW) and fatty acid profile (expressed as a % total detected) remained constant throughout the spawning season and were not correlated with any egg viability parameters. Neutral lipids, a major energy source in marine fish eggs and larvae, accounted for 50% of lipid classes, followed by glycolipids and phospholipids. Within lipid fractions, the neutral lipids presented high amounts of mono unsaturated fatty acids followed by equally high contents of polyunsaturated fatty acids. Docohexaenoic acid (DHA) was mainly found in the phospholipids fraction, though it was present in high amounts in all lipid classes. However, no significant correlations were observed between the DHA content and the egg viability parameters. The percentage of arachidonic acid (Ara) (< 0.1%) was low, possibly due to a deficiency of this fatty acid in the broodstock diet. Polyunsaturated fatty acids content, mostly represented by DHA and eicosapentaenoic acid (EPA), was positively correlated with hatching rate. Correlations observed between chemical composition of the eggs and viability parameters highlight the fact that egg quality is deeply influenced not only by environmental factors but also by broodstock management techniques