Well, it's not a yes or no answer.
Trawlers tear up the ground. Yes, they do. Bottom trawlers tear the ground to pieces. Whatever is in their trawl is caught, and basically the market dictates what you take out. What you throw away or discard is what the market says too.
With a trawler, you take everything. You can say that there's some technology that yields.... For shrimp, there's a thing. With some technology, you can get away with some things. But for most stuff, what's in there you take or you discard.