Causes of the decline in fish stocks

The main cause of overfishing is market demand. Over 80 million tonnes (approximately 75%) of the world marine catch is sold on the international markets each year. The most important worldwide catches include herring, smelt, cod, haddock, perch, tuna, mackerel, salmon, trout, shrimp, smelt and flounder. The collective value of the global fish catch is worth US$70 billion.

Fisheries are the most globalised food industry and the world’s marine catch has increased significantly in the past forty years; almost four times from 19 million tonnes in 1950 to 90 million tonnes in 1997 to meet market demands. This demand has placed huge pressure on fish stocks. The FAO indicated that almost three-quarters of marine fish stocks and 11 of the 15 major fishing grounds are fully exploited, overfished or depleted.

China is the world’s leading fishing country averaging about 25% of the world catch, while the United States has averaged about 5%. The bulk of the fishing crisis stems from some twenty fishing countries whose ships land 80% of the total marine catch world wide:

1. China

6. Russia

11. India

16. Spain

2. Peru

7. Thailand

12. Iceland

17. Taiwan

3. Japan

8. Indonesia

13. Phillippines

18. Canada

4. Chile

9. South Korea

14. North Korea

19. Mexico

5. USA

10. Norway

15. Denmark

20. Vietnam

The three main sources of global fish production are the marine catches (e.g. coastal waters and high seas), inland catches (e.g. lakes and rivers) and aquaculture. The global fish production exceeds that of cattle, sheep, and poultry. The Southern Hemisphere currently has the largest numbers of fish because the waters have not been so severely exploited by man.

Open access to fish stocks to anyone with a boat or gear leads to overfishing. It is not feasible to have private ownership of either stock or habitat so this is open to exploitation. Individual vessels have no incentive to conserve the resources since any fish they leave can be taken by the next vessel. This results in more intensive fishing, more stock depletion, higher harvest costs and elimination of both current and future industry profits.

Fishing/industrial fleets are increasing twice as fast as the rise in catches. FAO estimates the world’s fishing fleets have at least 30% more capacity than they need. Between 1970 and 1990 global fishing fleets increased from 0.56 million to 1.2 million fishing vessels. Poor management and control mechanisms also have an effect as do new and improved technologies such as faster vessels and fish finding electronics.

Many governments heavily subsidise their industrial fishing sector because it is such an important source of employment, food and export earnings. Little consideration is given to the long-term damage of fish stocks and relating eco-systems. The fishing industry receives up to US$50 billion in subsidies each year.

Growth in overfishing occurs when too many small fish are being harvested and not given time to reach their maximum growth potential. This reduces the potential yield from future fish stocks.

As well as overfishing, stocks are reduced by factors such as:

  • By-catch which is the indiscriminate catching of fish other than those targeted by a fishing vessel. These fish are the wrong species, sex, size or quality. They have no market value (but are ecologically important). By-catch can destroy an additional 30 million tons of fish.
  • Destructive fishing techniques due to interaction with the fishing gear.
  • Poor control of size limits of fishing catches.
  • Natural processes for example ocean climate, number of predators.
  • Limited knowledge of management techniques to ensure a sustainable fish population.

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