On the hook: Fisheries’ impact on the environment

Valeria Vlasova
12.04.2021
3 min read

Fishes are great. They are a part of a rather sustainable diet, very nutritious and an easy source of omega-3 fatty acids. In 2018, over 156 million tonnes (88%) of total fishery and aquaculture production was used for direct human consumption – global per capita consumption of fish was around 20.5 kg (1), and this number is growing.

People say there are plenty of fish in the sea, but there are many worries from scientists that it could change drastically. In the second half of the 20th century overexploitation or full exploitation of fishing stocks first became an important problem. When poorly controlled, fisheries develop excessive fishing capacity with major ecosystem, social and economic consequences.

Overfishing

Overfishing transforms an originally stable, mature and efficient ecosystem into one that is immature and stressed. The number of overfished stocks globally has tripled in half a century and today fully ⅓ of the world's assessed fisheries are currently pushed beyond their biological limits, according to the Food and Agriculture Organization of the United Nations (1). 

Marine ecosystem is a finely organized system, and by targeting and reducing the abundance of, for example, high-value predators, fisheries deeply modify the trophic chain by reducing food provisioning to non-target species and other elements of the ecosystem (2).

Besides damaging the marine ecosystem, excessive fishing also contributes to global CO2 production and growth of marine litter. Plastics pollution from marine sources refers to the pollution caused by fishing fleets that leave behind fishing nets, lines, ropes, and sometimes abandoned vessels (3).

Bycatch

Bycatch usually refers to the incidental capture of non-target species such as dolphins, marine turtles and seabirds. But it can also change habitats of many other species, most notably by destroying and disturbing bottom topography and the associated habitats (e.g. seagrass and algal beds, coral reefs) and benthic zones (2).

Longlines, trawling and the use of gillnets are the fishing methods that most commonly result in bycatch. It is estimated that over 300,000 small whales, dolphins, and porpoises die from entanglement in fishing nets each year, along with hundreds of thousands of endangered loggerhead turtles incidentally captured on longline sets for tuna, swordfish, and other fish (4). 

Overall impact

In 2020 roughly 39 million people depend on capture fisheries for their livelihood. Healthy seas are also important for food security, with fish providing 20% of animal protein needs on average for 3.3 billion people (5).

Some aspects of fisheries can have significant and long-lasting effects, e.g. destructive fishing techniques (including cruel methods of using dynamite or cyanides); pollution from fish processing plants; marine litter and loss of fishing gear (possibly leading to ghost fishing); lack of selectivity resulting in wasteful discarding practices, etc (2).

Unfortunately, the damage done by poorly-managed fisheries not only leads to overfishing and bycatching, but goes beyond the marine environment. Regulating the overall fishing pressure and moving to cooperative rather than competitive fisheries seem most likely to provide for biological, social, and economic sustainability (3).