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Battling Bonamia in native oyster aquaculture using eDNA

The Fish Site
by The Fish Site
18 June 2021, at 1:48pm

A new DNA-based method of detecting the pathogen Bonamia in European flat oysters has been developed by two Scottish companies.

Bonamia ostreae is a major problem for many wild native oyster populations and is linked to the major decline in abundance throughout their range. Bonamia testing is widely available but is typically destructive – meaning that the oyster is damaged or killed, limiting the ability of the hatcheries to identify and then utilise disease-free broodstock for larval production.

The new technique, however, is non-destructive. It is the result of a collaboration between Orkney Shellfish Hatchery, which specialises in the provision of disease-free shellfish products for aquaculture and restoration projects, and Xelect – which manages broodstock and genetic improvement programmes for major aquaculture producers around the world.

Bonamia has infected many of the UK's wild native oyster populations
Bonamia has infected many of the UK's wild native oyster populations

© Blue Marine

Xelect previously used a tried and tested method known as a Taqman Assay but adapted it to the specific challenge of testing for the presence of the pathogen from a filtered water sample – a technique called environmental DNA (eDNA) analysis.

Dr Paolo Ruggeri from Xelect oversaw the analysis. “Bivalves like the flat oyster filter large volumes of water every day, and in the process shed tiny amounts of their own DNA, and the DNA of any parasite they are carrying. Using a highly sensitive DNA test we can sample the waters the oysters live in to identify the presence of the pathogen. It’s an extremely cost effective and humane approach, and the oysters don’t even need to leave their hatchery”.

Orkney Shellfish Hatchery can now comprehensively ensure the Bonamia-free status of each individual incoming native oyster broodstock. This guarantees a much higher degree of hatchery biosecurity and wider options for native oyster broodstock sourcing.

Responding to the breakthrough, Nik Sachlikidis from the Cadman Capital Group, owners of Orkney Shellfish Hatchery, commented: “This is another demonstration of our commitment to using science-backed, cutting-edge technology to provide the highest possible standard of product. We know that our oysters are exceptional, and now we can also demonstrate that they’re disease-free too. We’re continually looking at new ways to improve our native oyster spat product, and to set new standards for industry best practice in this area. Xelect have done a great job of working hand-in-hand with our team to solve some key issues facing the native oyster hatcheries and ensuring our broodstock are Bonamia-free.”

Xelect’s operations director, Dr Tom Ashton, added “Our customers are spread all around the globe, so it’s been a great pleasure to work with such an innovative customer based so close to home. Orkney Shellfish Hatchery came to us with a challenge, and the team always love breaking new ground”.