Genetics and RAS: does the new frontier in global aquaculture require a fresh approach to selective breeding?

by Operations Director Dr Tom Ashton

One of my first experiences of working in the aquaculture industry was on a tilapia farm in Cambridgeshire, thousands of miles from anywhere a tilapia would normally call home. Those were the early days of recirculating aquaculture systems (RAS) – it was the beginning of a new frontier that was technically and economically risky. Many tried and many failed.

Today RAS operations are succeeding on a global scale. Coldwater fish like Atlantic salmon are being produced in the heat of Miami and China. Yellowtail kingfish are being grown in northern Europe – even vannamei shrimp being farmed in Scotland.

Recirculation technology is inherently complicated. At the heart of the systems are the mechanical, biological and chemical filtration of water. Mechanical systems for aeration, degassing and waste removal are also vital for ensuring a healthy and clean tasting product. There is a lot that can go wrong, but with rapid advances in technology, especially in the informatics and monitoring space, these risks are being overcome and RAS is gaining a strong position in the future of aquaculture. As aquaculture diversifies, species selection is important. A good candidate species for RAS has reliable market demand with a high value, relatively short life cycle and ready acceptance of dry feeds.

RAS brings a host of benefits over open cage aquaculture. Biosecurity is tight – it is much easier to control the entry of pathogens into the system when it is in a building on industrial land. It is almost impossible for fish to escape and cause environmental issues, and the release of parasites into wild populations is not an issue with RAS. Pollution isn’t a problem – it is simply collected and can be converted into valuable nutrient by-products for other industries. RAS facilities bring the product close to market, meaning fresher supply, with lower food miles – a big advance in quality and sustainability for the industry. 

In open systems, Atlantic salmon are bombarded by pathogen challenges of one sort or another on a daily basis, resulting in production losses, animal welfare issues, and significant costs associated with vaccination, medication and the treatment of residues. An important component of the armoury to combat disease is genetic selection for tolerance against specific pathogens, such as sea lice or the infectious agents that cause IPN, ISA and AGD disease. Not surprisingly, disease resistance and growth have had top priority in the long running genetic improvement programmes that have contributed so much to the development of the industry.

Small improvements made in each generation are cumulative, resulting in large gains over time. However, RAS does away with the problem of pathogens and parasites and makes past gains in disease tolerance redundant. As in so many other areas, RAS will prove to be a truly disruptive technology. Thus, whilst growth and feed efficiency will always be important traits for improvement, top priorities for RAS will include tolerance to stress and high CO², fillet yield and flesh quality.

Genetic performance is highly dependent on environment and, for RAS investments to succeed, new genetic lines will need to be developed. These must select animals that perform optimally under the particular conditions of these systems, focussing improvement on the right traits, rather than growing ‘off the shelf’ juveniles from genetic lines developed for cage culture. Fortunately, today, the cost of genotyping is lower than ever before, meaning individual aquaculture companies of almost any scale can afford to run their own genetic breeding programme. 

Similarly, advances in genomic technologies and statistical methods are making genome assisted breeding cost-effective for many species, allowing for faster and more targeted gains. Doing the whole process in house is a tall order, given the highly specialist nature of the science, but Xelect have assembled an expert team that works together with hatcheries to deliver the latest genetic management. By focusing on the selective breeding of highly tailored strains that suit their unique environmental conditions and production requirements, RAS enterprises will be able to advance into a profitable and environmentally sustainable future.