Question: how do you manage pathogen transmission between farmed and native populations? is there a risk of introducing a pathogen that might endanger native sea-life?

Clemence Fraslin answered on 27 Nov 2023:

That is a good question and many labs are trying to answer it in the world. There are different level of answer.
At a farm level: there are protocols to try avoid spreading diseases. For example if the fish are in tank/raceways/recirculating systems the water is treated before it goes back to the environment so it’s clean and there are no more pathogens in it.
If the fish are in a cage in the sea it’s more complicated as it’s not possible to isolate the water that goes in and out the cage and could spread disease. That is why we work on disease resistance and vaccines.
If the farmed fish are resistant to a disease the pathogen can not reproduce and then you limit the spread (could be natural resistance, could be resistance using a vaccine, as with the covid pandemic). In research we try to understand resistance to pathogens, but also how pathogens spread between fish (with mathematical models) to try to prevent it.
We also have to treat the fish that are sick to kill the pathogen (for fish welfare, you can’t let them suffer), that limits the spread of the disease.
There is always a risk of spreading a disease between farmed and wild populations but farmers (and scientist) are working on the best way to avoid it through increasing natural resistance and also best farming practices (as treating the fish early and reducing the number of fish per cages because if you have less fish there is less opportunity for the pathogen to spread).