Showtime for shellfish

Farming sea squirts

In the processing hall, I came across Smart Farm, whose specialist farming and harvesting system is used in more than 20 countries around the world, primarily for growing mussels. The Smart Farm system comprises nets suspended up to 30 metres deep from long black pipes floating on the water surface, and a bespoke harvesting machine, which enables husbandry and harvesting to be done entirely in the water. This set-up also makes it easier to reduce the impact of fouling and predators. 

Prominent on the Smart Farm stand this year was a film featuring their SmartUnits being used for tunicate (sea squirt) farming in Norway.  

Tunicate farming is an emerging aquaculture sector in the West, although it is well established in Japan and South Korea. Tunicates, which are marine invertebrates, are a highly sustainable animal, with a minimal environmental footprint and high protein content that can be incorporated into animal feed and human food. They also have applications in the biomedical, electronics and food packaging industries. There are more than 3,000 species of tunicate in the world, some of which are eaten as raw delicacies. 

Species grown in Japan and South Korea include Halocynthia roretzi, known as the sea pineapple, which typically take 2–3 years to reach harvestable size, and Styela clava, the clubbed tunicate, which is often found as a nuisance biofouling species on aquaculture farms.

Pronofa ASA, which is based in both Norway and Sweden, has worked with Smart Farm to help perfect a system for growing and harvesting Ciona intestinalis, the vase tunicate. This species grows naturally along the coasts of Norway and Sweden and easily colonises the growing nets, producing up to 82kg of biomass per square metre. It is also fast growing, with a one-year harvest cycle. 

Pronofa processes the tunicates into a product similar to traditional minced meat, under their food brand Purply. This mimics the taste, nutritional value and uses of minced meat, so can be incorporated in dishes such as lasagne as an alternative to meat, or turned into products like burgers, tacos and meatballs. The company claims a climate footprint for Purply of just 0.2 kg CO2 eq/kg of protein, which is less than 1% of that of red meat, making it one of the world’s most sustainable animal proteins. 

REMA 1000 stores in Norway sell and heavily advertise Purply lasagne, including the fact that it is made from tunicates. Purply is also a popular ingredient used by food service companies across hospitals, schools etc. 

According to Smart Farm co-founder Björn Aspøy, partnerships such as the one his company has with Pronofa show what’s possible when innovation aligns. 

“Pronofa brings the vision for low-carbon protein and we bring the infrastructure.

“Our SmartUnits make underwater cultivation and harvesting possible at an industrial scale and we are delighted to see Pronofa steadily expanding their production capability. Together we are proving that sustainable ocean farming doesn’t need to compromise on efficiency or profitability,” he said. 

“We are proud to be part of this journey with Pronofa. When innovation meets execution, the future of food becomes today’s reality.”

The Smart tunicate farm system is fully automated, which helps to improve efficiency and further reduce environmental impact. The underwater growth structures can stay submerged throughout their 25-plus year lifespan, are visually discreet, and resilient to waves up to 7m high. 

The remote-control SmartCat harvesting catamaran, which brushes along the nets, is capable of harvesting up to 30 tonnes of biomass per hour. Björn explained that by setting the brushes to dislodge the largest tunicates from the nets, smaller ones are left attached to continue growing.

Biomedical uses too!

Interestingly, tunicates are the only animals known to synthesise cellulose, which Norwegian company Ocean TuniCell extracts and refines for use in 3D tissue models and organ regenerative medicine. According to the company, the cellulose from 

C. intestinalis resembles our body’s own collagen in structure, has a high mechanical strength and is an ultrapure polymer consisting of over 99% glucose. This cellulose has been found to be of superior quality and purity when compared to cellulose isolated from plant-based sources, making it very well suited for biomedical purposes.  We are likely to hear a lot more about this type of application in the future, as scientists continue to explore the properties of marine organisms and seek out sustainable species. 

As far as human food goes, perhaps tunicates could be the food of the future, but getting people to accept them as an ingredient may take quite some time!