Fish in danger
Enemy no. 1: the human being
Despite what the film ‘Jaws’ may let you believe, only thirty people are killed by sharks every year. Although those are still thirty lives, one should pay attention to the number of sharks killed every year - approximately 700,000 tonnes worth. Many different types of sharks, including the large white shark, are greatly overfished. Sharks are particularly vulnerable to overfishing, because it takes them many years before they are able to propagate. As a result, there is a great chance that they are caught before propagating. This is not only bad for the present number of sharks, but also for the sharks in the future.
Different types of wild fish are also fished too heavily. Every species of fish needs a minimum number to be able to maintain the population. When too many fish are caught, the population decreases, and in the long term, fishery will decrease as well. Also, if fishermen do not pay close enough attention to the reproductive capacity of the fish, they cause themselves problems in the long term. The question was raised whether human beings are capable of handling the natural marine sources. Decades will pass before fish populations will be back to their original levels. Primarily fish that cross national borders, such as some types of tuna, are hard to control, because they are under authority of more than one country. Even the Pacific sardine and the Peruvian anchovies, which were once in large numbers and thought to be immune to overfishing, have decreased drastically. Fishers can take the negative consequences of overfishing into account, by planning the open season accurately. Fishing before or during the mating season is not a good idea. It may also be helpful to temporarily not fish the most vulnerable types of fish.
The most threatened types of fish are freshwater fish. They live in rivers and lakes in areas with large environmental problems, caused by the presence of heavy industry for instance. Many special freshwater fish are found in waters with small areas, because their natural boundaries do not allow them to swim away. For example, after the closure of the Haringvliet, many salt-water fish could not go anywhere. It is easier for salt-water fish which live in seas or oceans to find another living area. Because certain types of freshwater fish often live at one place and are unable to leave, water pollution usually has an enormous impact on the fish stock. If no preventive measures are taken now, pollution will continue to rise because of the increasing world population.