The Inter Caledonia, pictured when it was contracted to Mowi (formerly Marine Harvest). The vessel has a reverse osmosis system that can produce 200m³ of fresh water per hour, which will enable Scottish Sea Farms to treat more fish.

Scottish Sea Farms hires second wellboat to tackle gill disease

Salmon producer is also trialling on-site nanofiltration to ensure freshwater availability


Salmon producer Scottish Sea Farms has added a wellboat to its fleet as part of a multifaceted approach to tackling gill health issues by increasing freshwater treatments.

The Inter Caledonia has a well volume of 2,200 cubic metres and a reverse osmosis (RO) system that can produce 200m³ of fresh water per hour.

RO systems mean wellboat crews can spend more time treating fish instead of having to replenish fresh water from land sources.

“Following our successful trials over the last year, we decided to go ahead with increasing our freshwater treatment capacity," Scottish Sea Farms’ head of fish health Ralph Bickerdike told the company's newsletter, The Source.

“The Inter Caledonia will be deployed where and when needed and, with the reverse osmosis technology and state-of-the-art life support system, will help improve health and welfare when treating gills or for sea lice.

“Having increased flexibility gives us the ability to use the right treatment for the right fish at the right time.”

Nanofiltration on site

Among other freshwater options being trialled by the company is a nanofiltration unit, to be piloted at its Lismore North site, Loch Linnhe. This will produce freshwater from seawater and store it in impermeable bags in pens for wellboat collection ahead of future treatments. As well as the Inter Caledonia, SSF has use of the 1,000m³-capacity AquaShip wellboat Aqua Viking, which doesn’t have an RO unit, so must pump its fresh water aboard.

Anne Anderson, SSF’s head of sustainability and development, said: “The idea of having freshwater storage pens is not new but producing your own fresh water for the purposes of wellboat use in Scotland is novel.

“We’re doing a combination approach to sourcing freshwater. As well as the Lismore trial, we’re hoping to capture and store freshwater run-off in Shetland, planning permission pending.

“We’ll be collecting it at the point it arrives in the marine environment, so it’s water nobody else is using.

“The intention is to identify locations where, post the success of the trials, we can roll out freshwater production and storage across the estate.”

First with RO

The seven-year-old Inter Caledonia, owned by Intership, has been contracted to SSF since January. It was previously in service for Mowi Scotland and was the first RO-equipped wellboat in the Scottish sector.

Mowi is now using the new Intership vessel Inter Atlantic, a 72-metre wellboat with an RO system capable of producing 5,000m³ of fresh water per day.

A 76.6-metre wellboat, the Inter Scotia, will follow in July or August. It will also have a high-capacity RO system, and a large battery pack for operations when the engines aren’t running.

These vessels are adding to the capacity already provided by the Sølvtrans-owned Aqua Skye, an 84-metre vessel that generates 4,500m³ of fresh water in a 24-hour period.

Ronja Star

The Sølvtrans wellboat Ronja Star, on a long-term contract with Bakkafrost Scotland, arrived in Stornoway last September. With a well volume of 4,000m³ and high-volume RO, it is currently the biggest wellboat in Scotland and has more than doubled the freshwater treatment capacity the company has with its existing wellboat, the 2,500m³-volume Ronjafisk. It has already made a difference to fish health, the company has said.

Orkney and Shetland salmon farmer Cooke Aquaculture Scotland uses the Marsali, a 63-metre RO-equipped wellboat owned by Scottish company Migdale Transport and delivered from Norwegian shipbuilder Aas Mek in 2020.

Read more about the Scottish sector's efforts to tackle gill disease in the next edition of Fish Farming Expert magazine, which is published later this month and will be available online.