24 SEPTEMBER 2013 • WORLD AQUACULTURE • WWW.WAS.ORG breeding can be applied to aquatic animals to accelerate selection. Genomic sequence comparison with model species can help to identify best breeding aims. Sooner rather than later we can think about selecting and even designing new varieties that are better adapted to, for example, the adverse effects of climate change. Priority 5 – Bacteria in Aquaculture. Thanks to the availability of new genomic tools, a lot of research has been initiated in recent years on the role of microorganisms in agriculture, in human health and food quality, inter alia. Because water is an ideal environment for microbial development, the role of bacteria – beneficial and harmful – in aquaculture systems requires much more research attention. Their role in the aquatic environment, especially in water quality control but also how they convert organic waste matter into nutritious biomass. These so-called bioflocs are rich in protein and often also high in specific micronutrients, such as omega-3 fatty acids and vitamins. Controlled biofloc production could greatly contribute to increased sustainability and more biosecure production systems, through reduced needs for water exchange and more efficient feed conversion. Rather than limiting its application to production of tilapia and shrimp, bioflocs can be more effectively used in multi-species farming. For example, intensive fish or shrimp production and the bioflocs these generate can be integrated with the farming of filter-feeding species that could convert bioflocs into mollusk meat or brine shrimp biomass that can easily be harvested for use as food ingredients for other species. As with terrestrial livestock (chicken, pigs and cattle), hostmicrobe interactions can greatly influence production results not only at the start of larval development as discussed earlier but also in juvenile and adult stages. Such interactions can be applied to improve the health status of animals or control the bacterial flora, both in quantity and composition, to impact animal performance. For example, reducing the digestive tract pH of juvenile seabass from 7.7 to 7.3 by delivery and release of a mild organic acid (e.g., butyric acid) results in a significant shift of the microbial composition, as documented by DNA fingerprinting of bacteria, and a larval growth increase of about 20 percent (Figs. 18 and 19). These empirical observations require further nutrition research to reveal the functional role of bacteria in the animal’s digestive physiology and most probably its immunology. Priority 6 – Health Control. Our knowledge of health control in aquatic animals remains very limited, especially in invertebrates, crustaceans and mollusks. Much more basic work using molecular tools should improve knowledge of activation, good functioning and disruption of the animal’s immune systems. Only then we will be able to move from empirical trial and error practice today – with all kinds of putative immunostimulants, prebiotics and probiotics – to knowledge-based strategies and products. With some species (e.g., Atlantic salmon), knowledge is well advanced and different generations of vaccines have proven their efficacy. However, vaccines are not a magical solution and scientific progress should only be part of a more concerted effort in health management. Priority 7 – Ecological Aquaculture. When addressing sustainability issues in future aquaculture developments we must embrace ecological principles and reconsider the monoculture ABOVE, FIGURE 17. Figure 17. Research approach for the development of innovative microbial management systems in fish and shellfish larviculture. TOP, FIGURE 18 AND 19. Dietary effect of polyhydroxybutyrate (PHB) in sea bass nursery rearing (after De Schryver et al. 2010).
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