Schizochytrium algae can be grown heterotrophically on industrial scales at USD $1.50 kg −1, using low-cost food waste and agricultural side-streams as inputs 12, 20, 21, 22. New advances in algal production and microencapsulation technology offer a groundbreaking solution to reduce the environmental footprint of bivalve aquaculture. FAO and EU sustainable aquaculture policies identify urgent and immediate needs to reduce land, energy, and antibiotic use in aquaculture 15, 17, 18, 19. Non-live diets are more sterile, and hence since the 1990s the bivalve aquaculture industry has been seeking non-live alternative feeds to reduce antibiotic needs 6, 7, 11, 16. In Europe twice the number of antimicrobial substances were sold for animal versus human use in 2014 15.

In the world's largest bivalve producers including China no veterinary prescriptions are required for antibiotics with use essentially unregulated 15. Antibiotics cause severe damage to marine ecosystems, 80% of aquaculture antibiotics are not metabolised by stock, persist in the open sea, and drive proliferation of antibiotic resistant bacteria 15, 16. Live algal feeds are the primary vector of bivalve disease, which is controlled with antibiotics 6. Furthermore, algal stocks are difficult to maintain and frequently lost due to contamination and disease, so greater quantities must be produced, to the extent that each unit of viable hatchery-grown algae is 20-fold more expensive than units grown in contamination-free commercial photobioreactor facilities 6, 10, 11, 12, accounting for 50% of bivalve production costs at USD $220 kg −1 algal biomass in 2016 13, 14.Īlgal production presents a major disease control issue.

High-intensity artificial lighting, temperature, and air control systems are needed to support algal growth 9. Typical hatcheries require 400 m 2 of algal tanks to maintain just 400 broodstock, equating to 220 million m 2 worldwide, an area larger than Washington, D.C. At present broodstock must be fed live algae, production of which drives unsustainable land, energy and antibiotic use 6.Īlgal production in hatcheries makes highly inefficient use of land and energy 6, 7, 8. Current estimates suggest 220 million broodstock bivalves are held in hatcheries worldwide 1, 2, 3, 4, 5, 6. The USD $17.2 billion global bivalve shellfish industry relies upon a supply of juvenile bivalves produced by adult broodstock in hatcheries 1. Further research into microencapsulated diets could support bivalve industry expansion, and contribute towards a step-change in sustainable global food production through improved aquaculture practices. Every tonne bivalve protein produced instead of fish spares 9 ha, 67 tonnes CO 2, and 40,000 L freshwater. Physiological, histological, and cutting-edge metabolomic analyses demonstrate that in commercial settings sustainable microencapsulated diets facilitate improved sexual development and 12 × greater omega-3 levels in oysters relative to conventional live algal diets. We developed microencapsulated Schizochytrium algae diets, which can be produced sustainably at < $2 kg −1 from organic side-streams, and are shelf-stable to minimise waste. New advances in algal and microencapsulation technology provide solutions. Today large quantities of live algae are grown to feed broodstock at $220 kg −1, driving highly unsustainable energy and resource use. The global bivalve shellfish industry makes up 25% of aquaculture, is worth USD $17.2 billion year −1, and relies upon a supply of juvenile bivalves produced by adult broodstock in hatcheries.

Oyster spat feed