Marine fisheries – the state of affairs
Exploitation on a massive scale
Total global production of fish and fishery products from capture fisheries and aquaculture currently stands at around 140 million tonnes per annum. Until the early 1990s, the harvest from marine fishing followed an almost constant upward trajectory, with landings worldwide increasing fourfold from an annual figure below 20 million tonnes in 1950 to around 80 million tonnes in 1990. Since the 1990s, the total amount of fish, shellfish and crab caught in the sea has remained more or less constant.
Due to the great demand for fishery products, fish farming is also steadily expanding, especially in Asian countries. With an annual growth of around 7 per cent, aquaculture is one of the most rapidly expanding food industry sectors. Aquaculture already provides more than 40 per cent of the global consumption of fish and shellfish. However, many fish species raised in the aquaculture sector are predatory fish, which rely on a supply of other fish for food. Wild-caught fish are therefore used as feed. Although the amounts vary considerably according to species, it takes an average of around 5 kilograms of fish meal and fish oil to produce 1 kilogram of farmed fish.
Wild-caught fish are also used as breeding stock. Switching to consumption of farmed fish alone, therefore, does not necessarily protect wild fish stocks.
The expansion of marine fishing has contributed significantly to the decline and in some cases the depletion of global fish stocks. Overexploitation particularly affects long-lived fish species such as redfish (Sebastes marinus) which take several years to reach maturity and begin spawning. In extreme cases, it may even lead to the depletion of the stock. For example, stocks of cod in the Northwest Atlantic off the United States coast have
collapsed after years of overfishing.
- 6.1 > The example of North Sea cod shows how a fish stock collapses (i.e. becomes depleted) if there are no longer enough mature fish (spawning stock, green) available to produce offspring.
- 6.2 > Aquaculture is a booming industry today and fish are being farmed on a large scale, as seen here on the Chinese island of Hainan. However, fish farms do not necessarily help to conserve wild fish stocks as they require large quantities of fish meal or wild-caught forage fish for feed.
Decline of spawning stock
North Sea cod stocks, too, have been greatly reduced by intensive fishing. This species is a particularly good example of the effects of the exploitation of the seas. Experts define a stock as a self-sustaining population of a fishspecies within a geographically defined area. The spawning stock – i.e. the mature individuals that are capable of reproduction – are particularly important in scientific terms. The Food and Agriculture Organization of the
United Nations (FAO) does not provide any precise definitions of the various status categories of stocks. For example, the boundary between “fully exploited” and “overexploited” status is somewhat fuzzy. According to the FAO, the term “fully exploited” means that a fishery is operating at or close to an optimal yield level, with no expected room for further expansion. A stock is termed “overexploited” if it is being exploited above a level that is believed to be sustainable in the long term, evident from the steady decline of the stock. A stock is said to be depleted if catches are well below historical levels, irrespective of the amount of fishing effort exerted. A stock is said to be recovering if catches are again increasing after having been depleted.
According to FAO estimates, there has been a steady increase in the proportion of overexploited and depleted stocks since the 1970s. By contrast, there has been a decrease of around 50 per cent in the proportion of underexploited stocks, which stood at an estimated 20 per cent in 2006. This trend may be due to the development of increasingly efficient fishing technology, including technically improved means to locate shoals of fish and ever more powerful fishing vessels. The construction of enormous factory ships means that large catches can be frozen while the vessel is still at sea, enabling ships to exploit fishing grounds at great distances from the port of landing. Continuing advances in fishing technology also allow fish to be caught at ever greater depths. Furthermore, due to a lack of alternatives, commercial fishing is increasingly turning to species that were previously regarded as unprofitable, of poor quality, or unfit for consumption. >