As the footage shows, the problem with bottom trawling is not only that it trashes habitat on the sea bed but that it indiscriminately catches any fish in its path. Yet trawler crews are usually focused on catching just one species, so the rest is discarded.
(£) https://www.thetimes.com/uk/environment/article/david-attenborough-ocean-exposed-bottom-trawlers-gg2p6nc20