Broodstock nutrition research on marine finfish in Japan

Broodstock diet formulations are essential for the development of marine fish breeding and propagation. Japanese research has mainly focused on red sea bream (Pagrus major), yellowtail (Seriola quinqueradiata), the Japanese flounder (Paralichthys olivaceus) and striped jack (Pseudocaranx dentex), and indicated that the required quantities of essential dietary components may vary according to species. The more recent work carried out on yellowtail and striped jack consolidated the trends already observed in red sea bream. In yellowtail, soft-dry pellets were used and astaxanthin was found to be the determining factor for good egg quality, when supplemented at around 30 mg/kg. Paprika powder supplementation that provided about 30 mg/kg paprika esters further improved the spawning performance of yellowtail in terms of egg production, egg quality and larval survival whereas squid meal inclusion also showed potential as an effective ingredient. Work on the development of dry pellets for striped jack broodstock revealed that egg production and quality were affected by separate nutrients. Even though striped jack eggs do not contain carotenoids, dietary astaxanthin, added at 10 mg/kg to the diet, increased fecundity whereas egg quality was improved through the replacement of half the fish meal with squid meal. The combination of these two ingredients in dry pellets produced a spawning performance that matched the widely used raw fish mix. Fatty acids, especially n-3 highly unsaturated fatty acid (HUFA) in fertilized eggs, were derived from dietary lipids in all the species studied. From the present information, it is evident that optimal levels of astaxanthin or paprika esters that have high oxygen quenching abilities, squid meal and n-3 HUFA play an important role in gonadal development of different marine fish. These dietary components should be utilised for the development of wholesome dry pellets for marine broodstock.