Researchers have been adding to the database for the previous ten years, and with today's publication, they update the worldwide condition of fish populations. They discovered that fish populations are, on average, above goal levels. Not every stock is performing well, but things are significantly better than they were two decades ago.
The study was led by Carl Walters at the University of British Columbia and will be published in the journal Science. He and his team used data from 90 percent of the world's fisheries to estimate how many fish there are currently left in the stocks. They then calculated how much fishing would need to be stopped to ensure that fish populations remain at or below this estimated "optimum" level.
They found that nearly all stocks are overfished, with some severely so. The majority of these overfished stocks can still produce large catches if they were just given a chance. For example, the total global catch was about 70 million tons in 1996, but it could have been as high as 110 million if certain depleted stocks had not been completely removed from the fishery.
Some depleted stocks cannot recover even with current fishing practices stopped immediately. For example, the largest known marine predator, the great white shark, has fewer than 5000 individuals left in the wild. There are also several major tuna species that are overfished. This means that they could only sustain further fishing efforts for a few more years at most.
According to the United Nations Food and Agriculture Organization, one-third of commercial fish stocks are fished at biologically unsustainable levels, and 90 percent are fully utilized. This means that only 10 percent of known fish populations are being exploited. A further 30 percent are being exploited beyond what is considered sustainable by most scientists.
Fish are also dying from a variety of causes not related to human activity. The world's oceans contain more than 500 million tons of dead fish. Most of them come from overfishing. When there aren't enough fish to catch, fishermen turn to other sources of income, like crabbing or fishing for shark fins. Both practices are becoming less profitable as well.
In conclusion, one-third of all fish are being fished at unsustainable levels.
Overfishing and other unsustainable fishing methods have reduced almost all commercial fish populations and harmed the ecosystems that sustain them. Despite huge gains in fishing effort and technological advancements, worldwide fish catches have actually decreased since the late 1980s. Fish stocks are now generally estimated to be stable or even increasing in some cases.
The world's largest fishery is likely the global seafood industry, which produces about $70 billion worth of food each year. Fish play an important role in many people's diets, but they are also valuable for their flesh which can be used for cooking or as a source of protein. Some species are also used for oil or leather like products.
Fish are harvested from the wild for both consumption and commerce. In the case of commerce, fish are captured for sale or trade. For example, fishermen may sell their catch directly to consumers or to fish markets where it is sold over the counter. Alternatively, they may sell their catch to middlemen who then take it to market.
Commercial fishing was once the main cause of extinction for marine animals, but today's fleets capture only a small fraction of the total number of fish. The remaining population consists of individuals protected from capture by being left alone or in small groups, so-called "wild" fish. Harvesting too many of these "unsafe" fish could have disastrous effects for fisheries down the road.
Many stocks have been overfished for decades and continue to provide viable fishing opportunities; yet, they are overfished because it is assessed that they might have provided greater yield. Overfishing is defined by FAO as a fish population that is less than 80% of its target biomass. Stocks can be overfished through both intentional and unintentional means. Intentional overfishing occurs when fishermen remove too many fish from a stock for their own benefit or the benefit of others. This can be done to ensure a supply of fish for sale at market or because fish are used as bait or fuel.
Stocks can also be overfished unintentionally. This usually happens when fishing pressure is high and there are few, if any, restrictions on catch limits. When this happens, the only way to reduce the risk of overexploiting a stock is to stop taking fish. Overexploitation can also occur when fishers take more fish than there are available to maintain their annual catch limit, which is required by law in many countries but not all. This can have serious consequences for the future survival of the stock because insufficient offspring will be produced to replace those lost to mortality.
Overfishing has negative effects for both humans and animals who rely on healthy fisheries for their livelihood. It increases the risk of extinction for species whose populations depend on stable numbers of mature adults. It can also cause significant economic losses due to increased costs of recovery efforts.