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Geology LibreTexts

13.4: Overfishing

[edited 3/12/15]

Overfishing: A Non-Sustainable Use of the Oceans



Simplest way to define: "to catch too many fish so that there are not enough remaining"1Overfishing occurs when we take too much fish resources with a rate faster than they can reproduce or recover. And as a result, fish populations are getting depleted and some commercial species (e.g Southern Bluefin Tuna Thunnus maccoyii) are even at the edge of extinction2,3 . The end result of overfishing is a permanent collapse in fish supplies10. Even when these events are isolated to specific regions, they affects the ocean food web globally12.



Until 2012, about 85% of global fish stocks have been "over-exploited, depleted, fully exploited or in recovery from exploitation"4. Large areas of sea bed in North Sea and Mediterranean, as well as the East China Sea of Asia, have become "desert[s] in the sea", where over fishing has wiped out almost all the fish stocks 4,5 . Fisheries in other parts of the world are also declining,  West Africa, for example, has lost 50% of its coastal fisheries in the past 30 years6

Another example of overfishing is with Atlantic Cod between the 1970s and the 1990s. As technology increased in these years, cod stocks became more accessible to fishermen. Although cod stocks were once believed to be unlimited, this was proven wrong as fish stocks diminished. The issue is partially political because TACs (Total Allowable Catches) must be set to allow for recovery of fish stocks in order to prevent a situation of overfishing.



Each country has control over their exclusive economic zone (EEZ), which is an area of no more than 200 nautical miles off the coast of their continental territory in which they have complete control over fish stocks and regulations7. Areas outside of this zone, known as the high seas7 are not regulated by any clear authority and suffer from a lack of effective fishery management8. Therefore, "Tragedy of the Commons" arises, which was first introduced by Hardin as the idea that individuals work in their own self-interest. As each individual does this, the outcome is that the resource is depleted and no one benefits.








In order to prevent overfishing, fishermen need to be incentivized to stop catching specific amounts of fish at certain locations. It is all dependent on Maximum Sustainable Yield and the ability of the fish stocks to recover.11 By limiting, banning, or regulating the use of bottom trawling nets, juveniles can be protected, allowing them to reach sexual maturity and reproduce before they are caught. Setting an Individual Fishing Quota would incentivize fishermen to catch the largest and most mature fish and avoid bycatch or juveniles.11 This would be beneficial to both the fish and the fishermen because it prevents exploitation of specific stocks.