Aquaculture industry considers innovative solutions to rising cases of salmon deaths

The scale of mass mortality events impacting the aquaculture sector not only threatens global food security but is concerning from an economic and animal welfare perspective.

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Since 2012, mass mortality events (MMEs) affecting farmed salmon have become more frequent and severe, leading to the deaths of millions of fish in certain aquafarms, as detailed by a study published in Scientific Reports.

These incidents highlight the critical need for enhanced welfare practices and monitoring in open-sea salmon farming. An examination of mortality data from six leading salmon-producing nations – Norway, Canada, the UK, Chile, Australia, and New Zealand – indicates an alarming increase in such events, which could cause the annual deaths of millions of salmon in the future. (New Scientist)

Why does this matter? Fish are a vital source of nutrition for billions of people. Aquaculture is critical to supplying this nutrition and is now the leading source of fish production globally.

The scale of MMEs impacting the aquaculture sector not only threatens global food security but is concerning from an economic and animal welfare perspective. Although the study’s findings are concerning, innovative technology firms have presented solutions to help the aquaculture sector combat the rise of MMEs.

For example, WellFish, an aquaculture diagnostics start-up, provides rapid fish health assessment using blood-based clinical chemistry analysis. Its technology utilises blood biomarkers and artificial intelligence to evaluate fish health, enabling aquaculture operators to enhance the well-being of their stocks and optimise production.

The solution potentially allows salmon aquafarms to reduce the frequency and scale of MMEs through improved monitoring standards. Solutions such as WellFish are crucial aids to the fastest-growing food production system in the world, with salmon consumption increasing three-fold since 1980.

However, mass production fosters an increased risk of mortality – between 2012 and 2022, an estimated 865 million salmon perished in the six major salmon-producing markets. In Scotland, 17 million salmon died last year, the most ever recorded, while 17% of Norwegian-farmed salmon died suddenly in 2023.

The rising number and severity of MMEs in salmon populations are linked to various catalysts. For example, environmental influences, including higher ocean temperatures, compound problems like disease, sea lice, and harmful algae blooms that afflict the industry.

Environmental factors are often not the only drivers – combinations of natural events, human oversight, and unsafe practices create conditions for significant MMEs. For instance, the overuse of antibiotics can lead to bacterial resistance, while thermal delousing may compromise fish health.

If not managed correctly, salmon aquaculture can also affect the surrounding marine ecosystem. Nets that define the pen perimeters may be coated with copper oxide, which can pollute the water. Furthermore, salmon escaping from captivity can interbreed with and weaken the gene pool of the wild population, including endangered species like the wild Atlantic salmon.

Despite the ecological and welfare issues associated with certain forms of salmon aquaculture, simple operational adjustments can mitigate the worst effects. Measures such as reducing the density of salmon in pens can improve fish welfare and reduce the spread of disease and lice – RSPCA standards recommend a target ratio of 15kg of fish per m3.

Other welfare practices include regular cleaning and general maintenance of nets, sea lice shields, and environmental monitoring equipment able to monitor shifts in water temperature or oxygen levels.

The salmon industry could also take pointers from the practices pursued by other aquaculture sectors. Tilabras produce thousands of tonnes of fresh tilapia annually and manage the stock through their entire lifecycle from egg to harvest. Here, the tilapia are fed on locally-produced plant-based feed rather than fishmeal and the stock has ample room to swim in.

The technological and operational solutions now available to the salmon aquaculture industry can improve fish health monitoring, welfare conditions, and disease prevention, working towards a reduction in the frequency and scale of MMEs even as ocean temperatures rise.