According to the FAO's Fisheries and Aquaculture Department some of the major environmental problems are:
- Overfishing, leading to changes in biodiversity and species composition. Often the result is a reduction of large, long-lived, and high value predator species and the increase in small, short-lived, and lower value species – this is known as 'fishing down the food chain'.
- Bycatch of juvenile fish, benthic [deep sea] animals, marine mammals, marine birds and vulnerable or endangered species that are often discarded dead. This occurs through the use of non-selective fishing gear.
- Ghost fishing which occurs when certain gear such as pots or gillnets are lost or abandoned at sea and, although untended, continue to catch and kill fish until the gear falls apart.
- Trawling and dredging which disturbs and can change the bottom habitat and productivity. The effect is particularly obvious when these gears are used in sensitive environments where there are sea grass and algal beds, coral reefs, sponges, and tube worms.
- Fishing entailing the use of dynamite and poisons can have severe and broad-reaching impacts, particularly on coral reefs.
- Direct dumping of debris (gear, twine, plastic etc) and the accidental introduction of pathogens and foreign species.
- Organic pollution from at-sea processing, unregulated wastes and effluents from coastal processing plants.
- Exhaust fumes and refrigerant gases from fishing vessels and processing plants also contribute to global warming.
Reference: FAO, Fisheries and Aquaculture Department, Impacts of Fishery Activities