Salmon farmer explains why gill health funding is so crucial

Scottish Sea Farms is to lead a second applied research project focused on increasing understanding of gill health in farmed salmon, part of its "prevention over cure" approach to fish welfare.

Scottish Sea Farms is investing heavily in projects to improve gill health in a bid to improve fish welfare on its farms. Photo © SSF

The £601,000 project – of which Scottish Sea Farms will fund 62 percent – will be the salmon farmer’s second such collaboration with academics at the University of Aberdeen, feed specialists BioMar and the Scottish Aquaculture Innovation Centre (SAIC).

Combined, the two projects bring the company’s investment in applied research into gill health to almost £750,000 since 2018.

A fish farmer checks the health of a salmon's gills

Scottish Sea Farms’ head of fish health, Dr Ralph Bickerdike, said: “The gills are hugely important to the overall health and wellbeing of Atlantic salmon, yet the factors affecting these vital organs are as highly complex as they are little understood. This second gill health project seeks to explore further the early insights gleaned in our initial collaboration, helping increase knowledge of the key risks and how to pre-empt and avoid them.”

The project team will focus efforts on two key outcomes:

• Exploring the effect of geography and seasonal influences on gill health, in order that additional preventative and continuous measures can be identified and deployed

• Testing the accuracy of a range of new biomarkers; a suite of veterinary tests which help indicate the health status of fish and will enable more informed decisions.

The insights gleaned won’t just benefit farmed fish in the care of Scottish Sea Farms. SAIC aquaculture innovation manager for the gill health project, Caroline Griffin, explained: “Gill health has become one of the biggest challenges facing salmon production – not only in Scotland, but in Norway and internationally. SAIC is supporting a range of projects across Scotland, drawing on the expertise in our academic institutions and industry to understand the issue and develop innovative solutions. The new knowledge gained will be shared across the sector, helping salmon farmers to maintain healthy populations of farmed fish.”

Testament to just how devastating gill-related challenges can be to fish health, Scottish Sea Farms’ Lismore North farm in Loch Linnhe experienced unusually high mortalities of 22 percent during the last crop as a direct result of complex gill health disorder.

“When seawater temperature rises, even by something as seemingly slight as 0.5 degrees, more marine organisms grow. In the summer of 2018 – the joint hottest summer on record for the UK – we experienced a phytoplankton bloom in the Loch Linnhe area which resulted in a challenge to gill health. Increasing our understanding of what more we can do to pre-empt and prevent these kinds of challenges is a priority," explains Bickerdike.

Across our farming estate, average end of crop survival is now 87.2 percent; a strong survival rate that has been aided by Scottish Sea Farms investing over £10 million in applied research into fish health in the last five years alone

Further fuelling the drive to increase knowledge in fish health, the Lismore North farm witnessed 15 percent mortalities earlier in the same crop due to Saprolegnia – a health challenge which arises at freshwater stage and another area currently being researched by Scottish Sea Farms, SAIC and partners – contributing to an overall survival rate of just 59 percent for the total crop. This compares with survival rates in excess of 90 percent for the previous three crops.

As Bickerdike explains: “Across our farming estate, average end of crop survival is now 87.2 percent; a strong survival rate that has been aided by Scottish Sea Farms investing over £10 million in applied research into fish health in the last five years alone. The challenges experienced at Lismore North, whilst isolated, are precisely the reason why we continue to invest and build our knowledge in order to fully deliver our ‘prevention over cure’ approach to fish welfare and boost survival rates even further.”