This app was mentioned in 3 comments, with an average of 7.67 upvotes
Try this app. It guides you to eating only sustainable fish using sustainable practices. Its a bit confusing at first, but essentially, eat only fish that aren't highlighted red or even yellow.
Seafoodwatch.org (WEBSITE) https://play.google.com/store/apps/details?id=org.montereybayaquarium.seafoodwatch
Good on you for cutting out beef/chicken/pork! If sustainability is a priority, the Monterey Bay Aquarium has an app called Seafood Watch that lists sustainable fish based on region. I haven't used it in a while but I used it when I was pescatarian before transitioning to veganism. One of the problems is that a lot of times, the same fish will be on the sustainable and unsustainable lists, with the only difference being how they are farmed or caught. Many restaurants are unable to provide this information so it can be kind of a crap shoot, but it did come in a handy quite a few times. Maybe it will help!
Seafood Watch is a great resource for learning about sustainable seafood. They even have an app!