This is a U.S. aquarium and they're pretty well known around the world. One of their main tasks over the last few years was to establish this seafood watch rating. They use a very simple approach: it's red, yellow or green. If you're on the green side, it means, obviously, without any doubt the product you're putting on the market is sustainable. If you're in the red, the advice they provide to the ENGO committee and the consumer as a whole is that you need to avoid those products because they are not fish that are produced in a sustainable manner based on their criteria.
In the middle, there's the yellow one where you can see improvement. It's not a bad choice, but it could be better.