In various areas, the population of large fish has dwindled to extinction
Zafarir Rinat
A shark caught in Rio de Janeiro, April. The authors of the study warn that fishing endangers half of the shark species
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Japanese fishing vessels off the coast of Brazil are currently having difficulty catching bluefin tuna. Until 15 years ago, there were about 200 fish of this species in the area, but since the arrival of the Japanese ships, they probably managed to bring about the extinction of almost the entire population in the area.
This is not a problem unique to the coasts of Brazil: two Canadian scientists claim that extensive industrial fishing resulted in a rapid process in which the oceans were emptied of the large fish species that lived in them. According to them, today only about 10% of the populations of large fish species - such as tuna, swordfish, cod and halibut - remain in the oceans compared to a few decades ago. This is a serious damage to the ecosystem of the oceans, which is an important source of food mainly in developing countries - where most of the world's population lives. Following the study, experts recommend setting fishing quotas around the world.
The findings of Dr. Ransom Myers and Dr. Boris Worm from Dalhousie University, which were published yesterday in the journal "Nature" are based on research that lasted about ten years. During this period, the two gathered information about the spoils of fishing vessels in different parts of the world, and compiled data from the last 50 years. They focused on four areas close to the coasts and nine large areas in the oceans, and examined species of predatory fish, which are an essential part of the marine food chain.
In view of the findings, the researchers concluded that the commercial fishing fleets greatly harm the regeneration capacity of fish populations, to the point of extinction of about 90% of the individuals in a certain area within a few years.
In interviews following the publication of the study, Myers Worm told about the severe damage to the bluefin tuna population near Brazil in the last 15 years. In other areas, they said, the disappearance of fish is even faster. In the Gulf of Thailand, commercial fishing began in the 60s and the big fish disappeared within a few years. Along the continental shelf (the continuation of the continental cliff into the sea) on the coast of Georgia Island, in the South Atlantic Ocean, it took only two years, in the 70s. Today there is a rapid decline in the shark population: according to Myers, if fishing is not significantly reduced, More than half of the large shark species will no longer exist.
"You think the ocean is so big and the fish will always have a place to hide," Myers said, "but no matter what area you check, you find a sharp decline. We are simply good at eliminating these creatures." The deadly efficiency is achieved by pulling fishing lines up to 100 km long and more, to which hooks are attached, or by pulling huge nets that catch large quantities of fish.
The damage to the fish is not only expressed in their number, but also in their size and weight. According to the Canadian scientists, the fish caught today are small in length and weight, because the constant fishing does not allow many individuals to develop at the proper rate and reach maturity. Thus, for example, Myers estimated that the size of a fish of the "marlin" species today is about a fifth of the size of the fish of this species in the past.
Another consequence of the extensive fishing is a reduction in food from the sea eaten by humans. According to Myers, if fishing continues at the current level, there will be a severe shortage of such food. According to data from the Food and Agriculture Organization of the United Nations (FAO), there is still an increase in the total amount of fish in the world (which, besides wild fish, also includes fish in ponds and cages in the sea) - however, it does not catch up with the growth rate of the human population. The increase in population also explains how at the same time as the largest fish production in history (94.8 million tons in 2000) there was a decrease in fish consumption per capita (13.1 kg in 2000 compared to 14.6 in 1987).
Myers Worm's research provoked reactions from experts around the world. Many defined it as an important step in assessing the true state of wild fish. However, there are also those who want to qualify the findings. Prof. Lev Fishelzon, a marine biologist from Tel Aviv University, claims that the conclusion that 90% of the large fish have disappeared is excessive. "There are areas where overfishing did cause the disappearance of fish of certain species, but it is not possible to conclude from this what the state of the global population of that species is," he explained. "Even in areas where there was overfishing, the population can be restored, if severe fishing quotas are imposed. 30 years ago, experts thought that the herring fish had disappeared from the north of the planet, but after restrictions were imposed on their capture, they returned in large quantities."
And it is true that severe restrictions on the scope of fishing are the main recommendation of the study authors and other experts. According to Prof. Callum Roberts from the University of York in England, clear fishing quotas must be created, and in some areas fishing must even be completely prohibited for some species, so that they can recover and not become extinct.
The UN also claims: in half of the areas, fishing endangers the regeneration of the population
The Food and Agriculture Organization of the United Nations also monitors the state of fishing - including wild fish - in the world. According to the organization's data, about 47% of the areas where wild fish live are fully exploited, and have reached a situation where the expansion of fishing will harm the ability of the fish populations to regenerate. About 18% of the fishing areas are overexploited: a continuous and long-term decrease in the number of fish caught is expected, unless fishing is limited to allow the restoration of the populations. The main areas where there is still a trend of growth in the scope of fishing are the eastern Indian Ocean and the western Pacific Ocean, in its central part. However, in these areas there is not enough information about the state of fishing, and it may turn out that there is overexploitation in them as well.
The big fish following the dinosaurs - on the BBC website
They know endangered animals
Zoology B - amphibians and reptiles - by Lev Fishelzon - on the Mythos site
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