Focus on gills at Oban workshop

THE Scottish salmon farming industry came together yesterday to discuss gill health at a workshop in Oban, organised by the Scottish Aquaculture Innovation Centre (SAIC).
About 65 representatives from farming companies, academic institutions, government bodies, feed and pharmaceutical firms met at the Scottish Association for Marine Science (SAMS) to hear from experts about one of the biggest challenges to production in most salmon farming nations.
Hamish Rodger, of the Fish Vet Group, said gill disease was ‘something we need to address urgently’ as it had a global impact even greater than sea lice.
Spelling out the seriousness of the issue, he said:  ‘We can’t manage sea lice because of gill problems.’
He provided an update on the different types of gill disease, from AGD, which most companies know how to control, to Complex Gill Disease (CGD), the term the industry now uses when more than one gill disease is detected.
Gill disease is ‘dynamic’, he said, changing all the time, and there are many knowledge gaps. Scientists have ‘good tools’ at their disposal, but don’t necessarily know how to use them to effectively control disease outbreaks.
Karin Pittman, from the University of Bergen, described one of these sophisticated tools – ‘mucosal mapping’, based on an understanding of the slime layer of fish.
Farmers know that some feeds make skin more slimy and better able to deal with parasites, but Pittman said mucosal mapping can measure and document slime production for the first time.
‘Despite our knowledge of the mucous layer of fish as a key indicator for stress and fish health, a comparative method for the quantification and use of such data was lacking.’
Now samples from skin, gills and guts can be measured to determine the status of the mucous cells and thus the responsiveness of treatments and vulnerability to disease.
The workshop also heard from Iain Berrill of the Scottish Salmon Producers’ Organisation, who gave a summary of an SSPO gill health workshop in the spring, and from Sandra Adams of Stirling’s Institute of Aquaculture, who discussed a summer meeting at the university on the same subject.
Ongoing research into finding autogenous vaccines to control AGD was presented by Sophie Fridman from Stirling, while Callum Whyte of SAMS talked about harmful algal blooms.
There was an update on selective breeding from Diego Robledo of the Roslin Institute, and an explanation, by Ross Davidson of Scotland’s Rural College, of how models can be used to inform disease management.
In the afternoon, delegates were put into groups to decide collectively what the research priorities should be in tackling gill disease, ahead of funding proposals being submitted to SAIC in the New Year.
There was general agreement that the industry needs to ‘know the enemy’ better and understand what exactly is killing the fish.
There was consensus, too, that relatively recent changes in farming protocols should be examined, especially in relation to biofouling, and also freshwater practice.
Hamish Rodger said: ‘We’ve changed the way we clean nets in the last few years and it may be that these methods are contributing to the problem.’
SAIC has asked for expressions of interest in its gill health funding call to be submitted by December 20, and for full proposals to be in by January 31, 2017. A decision will be made on which projects to support by February 22 and, said SAIC’s Jason Cleaversmith, vital research could be underway by Easter.
A full report on the SAIC workshop will appear in the January issue of Fish Farmer, out early in the New Year.
Picture: Heather Jones, SAIC CEO