Overfishing – Causes and Impacts

Overfishing is a serious threat for the oceans, and it is caused by a variety of factors and results in a variety of impacts.

One of the causes of overfishing is a lack of protected areas, as only 1.6% of the world’s oceans have been declared as Marine Protected Areas (Discover more about MPAs here), and of these MPAs 90% are open for fishing. Having MPAs is important because they help protect habitats such as coral reefs from destructive fish practices.


http://www.protectplanetocean.org/official_mpa_map [Accessed 14th Feb 2017]”

The above image shows the Marine Protected Areas worldwide, and it shows just how sparsely distributed they are. They are mainly situated around the Oceania area due to the Great Barrier Reef off the North coast of Australia.

Open access fisheries are a severe problem of overfishing because of the “open access” nature of fisheries. Because there are no or very few property rights, there is a lack of incentive for fishermen to leave the fish in the oceans. Open access fisheries are

Overfishing causes continue further to the management of these fisheries being poor. The lack of management oversight, the regulations of governments and the ability to trace fishing activities have been problems in the fishing industry for a long time. There are current rules and regulations, such as quotas, but they aren’t strong enough to limit the fishing capacity to a sustainable level. This is particularly the case for the high seas, where there are very few international fishing regulations, and those that do exist are not always implemented and enforced. Many of the management bodies for these fisheries are not able to regulate fish quotas, and they cannot always ensure that the fish entering their country was caught legally and in a sustainable way.


https://www.igfa.org/Conserve/RFBs.aspx [Accessed 14th Feb 2017]”

The above image shows the regional fisheries management organisations and the advisory bodies (scientific and/or management)(Learn more about them here)

Another cause, and one that is a serious problem worldwide, is illegal fishing. This fishing is illegal, unregulated and unreported. It occurs across all types of fisheries, within national and international waters, and also with small scale to large scale industrialised operations. It is estimated that illegal fishing accounts for 205 of the worlds current catch and can result in fisheries having 50% of their catch being illegally fished. The cost of this illegal fishing is vast, with the value of the fish being estimated between 10-23.5 billion USD$ annually.


Economic Loss is an impact of overfishing. Because fishing is integral to economies all across the globe, overfishing threatens coastal nations down to local levels. These local level communities, who rely on fishing as not only a source of food, but also a source of labour, whose revenues hinge on the fish they catch. Overfishing not only affects fish but also affects humans, by destroying their income. Also these coastal communities depend on fish as a source of food, normally their primary source of protein. Overfishing therefore threatens their long-term food security, especially in developing countries, such as Angola and Mauritania of the Western coasts of Africa.

Marine Life Imbalance is another impact. Because as targeted fishing of top predators such as sharks, tuna and billfish, disrupts marine communities, causing an increased abundance of smaller marine animals at the bottom of the food chain. Which as a result has impacts on the marine ecosystem, such as increased growth of algae and the threats to coral reef health. Also, overfishing is linked to bycatch, which is the unwanted fish and other creatures caught in commercial fishing nets during fishing for a different species. This causes the needless loss of billions of fish along with Marine turtles and cetaceans (Whales, Dolphins and porpoises).

There is a whole host of impacted species such as:

  • Albacore Tuna
  • Bigeye Tuna
  • Bluefin Tuna
  • Skipjack Tuna
  • Yellowfin Tuna

But it isn’t only species that are affected, places are affected by overfishing  as well, such as:

  • The Arctic
  • Coastal East Africa
  • The Coral Triangle (triangle of tropical marine waters), situated in waters of Indonesia, Malaysia, Papua New Guinea, Philippines, Solomon Islands and Timor-Leste. The Coral Triangle is recognised as the global centre for marine biodiversity.
  • Gulf of California
  • Mesoamerican Reef (Also known as Great Mayan Reef, stretches 620 miles from the Yucatán Peninsula to Belize, Guatemala and Honduras)
  • Southern Chile
  • The Galapagos (Volcanic archipelago in the Pacific Ocean)

A term called “ghost fishing” is an impact of overfishing.  This is where large fisheries stay for weeks and months in the deep sea and sometimes they lose their nets. However, these nets continue to trap and catch fish under the water and end up killing them. They stay underwater for decades and cause significant damage to the ecosystem.

Then there is the obvious impact, pollution. Oil and liquid spills, and other methods are discharged into the water by the fishing boats, and trawlers etc which hurt marine life. It is very easy to think that due to the scale of the oceans that pollutions isn’t a big threat, but put it into context, thousands of boats and trawlers everyday all polluting. They all have a contribution to something very large and rather scary. Water pollution has devastating consequences. (read more here)




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