FISH HEALTH AND WELFARE

Maintaining fish health remains one of the most significant challenges faced by industry professionals. The threats are many and constantly evolving. 

Viral infections can spread rapidly in aquaculture environments, often with devastating effects. Notable examples include infectious salmon anaemia (ISA) and salmonid alphavirus, a variant of which causes pancreas disease (PD). These diseases can lead to high mortality rates and substantial economic losses. 

Bacterial diseases such as vibrio, aeromonas, and Edwardsiella are common in aquaculture. These pathogens can cause severe health issues, including ulcers, haemorrhages, and septicaemia. In the past, the overuse of antibiotics to combat bacterial infections has led to antibiotic resistance, making treatment increasingly difficult. Sustainable alternatives, such as probiotics and improved husbandry, are being explored to mitigate this challenge. 

Parasites, including sea lice and various protozoans, pose a significant threat to fish health. Sea lice, for example, can cause extensive skin damage and secondary infections, while so-called “micro-jellyfish” can damage gills and open the fish up to bacterial infections. 

Water quality is also an issue. Dissolved oxygen levels are crucial to fish health, whether in cages at sea or in recirculating aquaculture systems (RAS).  RAS facilities also need to ensure there is no build-up of harmful substances like ammonia and nitrite, and that the biome in the system consists of benign rather than harmful microorganisms. 

The level of knowledge around fish health and welfare increases every year, and developing new solutions for diagnosis, cure and prevention is now a major industry.