Infection protection with new fish farm design

Before ending up in your chopsticks or sushi roll, few people are aware that farmed salmon are commonly plagued by parasitic lice on their skin and amoebae on their gills. Fish farmers continuously struggle to control them, and the control methods themselves are often rough on the fish. An innovative new fish farm design has taken a different approach to prevent lice from infecting salmon in the first place.

Lice use light cues to aggregate in the surface layer – this behaviour is their Achilles heel which can be used against them. The new farm design has a deep net roof and a lice-proof ‘snorkel’ tube up to the surface. This surface access tube is needed as salmon use the snorkel to swallop air to re-inflate their buoyancy-controlling swim bladder. If they can’t get to the surface to do this, they are too heavy and keep sinking.

In a new paper published in Preventative Veterinary Medicine, Melbourne University PhD student Daniel Wright and colleagues document how these new snorkel farms are working at industry scale. They clearly reduce lice, but gill amoebae infections were elevated from holding fish in less space. To solve this problem, snorkels were filled with freshwater to remove the freshwater-sensitive amoebae. Danny’s work shows that farmed salmon of the future could be less burdened by these two important parasites using this new method.

Danny finished his PhD in late 2016 and moved to Norway to do a post-doc to further this exciting work. We wish him well.