Farmed salmon and trout are the main species in farmed fish production.
Farmed salmon is by far the largest, accounting for around 40% by value of Scottish food exports and contributing £2bn annually to the UK economy.
The main challenge in farmed salmon has been Furunculosis, a bacterial fish disease that is also found in wild salmon. From fairly widescale use of antibiotics in the 80s to control the inevitable bacterial infection the fish would develop, the development of an effective vaccine has virtually eliminated the use of antibiotics to treat the disease. Controlling it in the farmed fish has also helped reduce the disease reservoir in wild fish.
Sales of antibiotics into the fish sector have been low in recent years albeit with annual fluctuations depending on sales patterns and seasonal differences. In 2014, sales of products licensed only for fish totalled 2.4 tonnes of active ingredient; 2015 saw 0.7 tonnes sold, and 2016 was 1.6 tonnes.
The targets for the fish sector range from maintaining current usage levels at 5mg/kg and achieving an average usage of 20mg/kg for trout, to further increasing vaccination rates including use of autogenous vaccines where no other effective vaccines are available.For more detail on the fish sector targets, please refer to the Targets Task Force Report.
The latest data on vaccination of salmon smolts provided by the Annual Marine Scotland Science Scottish Fish Farm Production Survey shows:
Most, if not all, salmon smolts are currently vaccinated prior to transfer to sea
All will be vaccinated against Furunculosis, with a range of other vaccines against bacterial and viral pathogens also available and in use
Vaccines may be monovalent or multivalent
It is not possible to protect against all pathogens
Where the number of fish vaccinated exceeds the number of smolts produced, the difference is explained by the fact that some will have been vaccinated than once
The graph implies that not all fish were vaccinated in 2104. However, a proportion of the smolts placed at sea that year were imported from Norway. These will have been vaccinated in Norway, so this is not recorded in the Scottish production survey.