Tamable using fish baskets from aberration. They seem to flee from the baskets once placed. It is a good strategy to pen then in with fence foundations and walls, or kite them to a pen. Place your basket on the other side of the wall and catch.
You don't need to build a pen to tame, I just tamed my first thanks to the tips on here. Just wait and check the traps that have salmon near and when the basket says pick with salmon (words to that effect) pick it up and you've tamed a salmon! Thank you 😘