Researchers backed by funding from the European Maritime and Fisheries Fund (EMFF) are exploring novel production techniques centred around seaweed worms. Traditional fish fry production relies heavily on rotifers and Artemia, which necessitate enrichment with fish oils or algae, leading to costly and time-consuming processes with suboptimal nutritional quality.
Enter Aarhus University, where researchers have unlocked the potential of decomposing seaweed to mass-produce marine enchytraeids, small worms naturally occurring in decaying seaweed. Their findings reveal that live enchytraeids as feed can boost growth rates of juvenile fish—such as turbot, European flounder, and common whitefish—by up to 200%, while also reducing overall mortality rates.
Key benefits of enchytraeid worms include their ideal nutrient composition—high protein and lipid content with abundant long-chain omega-3 fatty acids—and their ability to sustainably grow in terrestrial environments, thus reducing pressure on marine food sources. By postponing weaning onto dry feed until fish reach optimal size, fish farmers can potentially improve feed utilization efficiency. The research team meticulously explored optimal production conditions, efficient extraction procedures, and the utility of enchytraeids as juvenile fish feed for six cultured species.
Optimal production conditions were identified as temperatures between 15-22°C and substrate salinity between 8 and 15 parts per trillion. Laboratory trials using potting soil mixed with dried and re-wetted seaweed yielded approximately 90g of fresh biomass per litre of substrate every three months. Scaling up to a semi-industrial level, around 200g of fresh biomass per 6 liters of substrate every two months was achieved with minimal manpower and low running costs.
The extraction process, based on heat extraction, exhibited over 90% efficiency. Enchytraeids were found to synthesize essential omega-3 fatty acids independently, making them a valuable protein source for fish feed, containing about 50% protein on a dry weight basis. Tests with six cultured fish species demonstrated significant growth improvement with live enchytraeids compared to standard dry feed, offering promising prospects for the industry.
While further investments and awareness are needed for widespread adoption, the support from EMFF has been instrumental in driving innovative and sustainable changes in aquaculture practices.
