DO WE NEED SPECIFIC WEANING DIETS FOR LARVAE OF FAST GROWING MARINE FISH SPECIES?

Fast growing species such as groupers (Epinephelus sp.) amberjacks/yellowtails (Seriola sp.), and bluefin tuna (Thunnus thynnus) may play a key role in aquaculture diversification worldwide. These are species that qualify as premium products with a high market value and an increased demand for their global supply is currently observed). Yet, industrial farming of most of these fast growing species his hindered by difficulties in controlling reproduction and because larval weaning from live-feeds to inert microdiets constitutes a major bottleneck for mass production of high quality juveniles.

Although several commercial weaning diets exist with relatively high success for larvae of other marine fish species, additional challenges are faced when considering fast-growing species. Namely, tremendous growth rates during the larval stage indicate these species may have particularly high requirements in protein and other nutrients. Therefore, special diets may be required, both in terms of nutrition and feed production technologies. Most available commercial microdiets were developed in Europe and Japan targeting slower growing marine species.

We evaluated a novel microdiet (FAST) developed after a thorough evaluation of revision of the inclusion of optimal levels of all essential nutrients for fast growing larvae, and a careful selection and testing of premium ingredients. This microdiet was compared with a current premium microdiet (COMM) for marine fish larvae, in a growth performance trial with greater amberjack (Seriola dumerili) post-larvae.

Greater amberjack fed on the novel microdiet developed for FAST growing larvae showed a 68%  higher growth in wet weight compared to the control commercial microdiet (see Fig 1). Size dispersion and cannibalism were also lower with the FAST microdiet. These results will be discussed in function of mass budgets for protein and energy in microdiets, and compared to a mass budget for Gilthead seabream (Sparus aurata), a marine species slower growing larvae.

These results suggest that larvae of fast growing marine fish species have higher nutritional requirements, and that use of microdiets developed for slower growing marine species may lead to sub-optimal performances.