Overfishing hurts ecosystems as it is disrupting food webs. On top of food webs are top predators, like tuna or sharks. Others form the base of food webs, like salmon and herring. Entire ecosystems and fisheries can be affected when the populations of these fish decline or disappear.

Additionally, the methods used in fishing practices themselves are also causing significant harm to marine ecosystems. With industrial fishing in particular, nets the sizes of football fields are dragged along the sea floor (trawling or driftnets), taking everything with them and damaging ecosystems like coral reefs, kelp forests, seagrass meadows and many more.  A lot of fish and other sea life is caught as bycatch, but tossed back overboard dead as they are not commercially valuable or not targeted in the first place.