Bathing our fish

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Relatively high water temperatures in Tasmania promote the settlement on the salmon’s gills of Amoeba (a single celled microscopic animal). ‘Bathing’ is the term we use to describe how we treat the Amoeba by immersing the salmon in freshwater.

We perform gill checks on our fish every seven days to monitor the amount of Amoeba and ensure that it is treated before it can impact on the welfare of our fish.  Treatment for Amoeba is simple and chemical free by bathing the fish in fresh water. Bathing salmon in fresh water bursts the Amoeba like a balloon and cleans the excess mucus off their gills. At peak farming times in the summer, fish are bathed every 30 to 40 days to keep them happy and healthy.When Amoeba lands on their gills, the salmon develops an autoimmune response that thickens the gill surface and increases the production of mucus. This reduces the salmon’s ability to breathe, increases stress and will cause death if not treated properly.

To transfer the fish from their normal pens to the fresh water bath pen we use a fish race, special airlift or impeller pumps. The fish race is unique to Huon and was developed by its Co-founder and Managing Directer Peter Bender. The fish race uses the salmon’s natural behaviour of swimming against the current to move the fish between their normal pen and the bath pen. The race allows us to transfer approximately one tonne of fish per minute. Airlift pumps are like a big syphon tube. They have no moving parts and are gentle on the fish. Our largest pump, Optimus, can transfer two tonnes of fish per minute.

As the farm becomes larger and we move off-shore, we will be more exposed to weather. This means that we will need to transfer fish more quickly, but just as gently.

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To do this we are building the world’s biggest fish pump with a specialist company, Environmental Technologies, in the United States. It will be able to gently transfer over 3 tonnes of fish per minute between our normal pen and bath liners.