Overexploitation is the disappearance of so many individuals that the population is cannot maintain itself. Since the 1600s, worldwide overexploitation of animals for food and other products has caused numerous species to become extinct or endangered.
One of the most well known models of commercial exploitation is the whaling hunting industry, in which whales are slaughtered for oil and meat. This custom has led many whale species to the brink of extinction. A century ago, humans could not seriously threaten whales because of their rather primitive technology. A three-year long cruise could kill fewer than a hundred whales. However, by 1967, about 60,000 were killed, yielding roughly 1.5 million barrels of oil. And hunting had expanded to the smaller whales, Sperms and Minkes, because the larger ones had almost disappeared completely. Although preservation groups continually warned whalers to let the whale populations recover, they continued to hunt, using technologically advanced equipment and increasing the slaughter.
The whaling industry, however, thinks strictly in economic terms. To their point of view, the best strategy would be to continue hunting until catches could no longer return a suitable profit. The whaling ships could then be used for other purposes or sold, and the money made used to exploit some other resource. People believe that the future is so distant that it will not affect them. This attitude is known economically as "discounting the 
future," in which the future is ignored and the value of an oil- and meat-producing whale a century from now is zero. Whales are also what is known as a "common property" resource. This just means that no one owns all the whales, so they are "free for the taking." When everyone feels this way, pursuing his or her own self-interest so unthinkingly, the result can be very tragic.
Not only the whaling industry but the fishing industry has developed greatly as well. Larger, faster ships, sonar, better nets, and other similar improvements have increased the ability of commercial fishermen to catch fish. In the 1960s, a single modern Romanian factory ship could catch in a single day as much fish as all 1,500 boats of the New Zealand fishing fleet. These mass increases in consumption have greatly reduced the fish populations. Between 1966 and 1970, herring catches decreased by almost a hundredfold, from 1.7 million tons to 20,000 tons. Indeed, marine fisheries have been wiped out because their catches are no longer profitable. The California Sardine fishery took 750,000 tons in the 1936-1937 season, but twenty one years later, only 17 tons were brought in. The fishery has not, to this day, recovered. In addition, when a specific type of fish becomes more rare, its value and price rises. Consequently, fishermen are given greater incentive to hunt it. It then becomes even more difficult for that species to survive.
Smaller fish populations are obviously more vulnerable to extinction than large schools. In certain instances, the population decline created by overexploitation can affect changes its surrounding ecosystem, which may then cause its eventual extinction. This may be why the California Sardine company never recovered - the decrease in sardine population allowed an increase in its main competitor, the anchovy, which may have changed the sardine's environment.
However great overexploitation is, the greatest damage to marine life is done by general environmental decay. Most ocean life is c concentrated in shallow waters close to land, where most upwelling currents are found. The open sea itself actually resembles a biological desert, producing only a tiny fraction of the world's fish catch. Consequently, marine populations that are already exploited are also most subject to heavy pollution (because most pollutants are dumped into the sea near the shore). Moreover, many organisms live in estuaries, the mouths of rivers and streams where fresh and salt waters mix. These areas are highly threatened because so much pollution, and urban development occur near them. In this way, many marine species are pushed over the edge and into extinction by a combination of factors.
Many other organisms have found a similar fate to that of the whale and the sardine. They have reached economic extinction, when it is no longer profitable to harvest the species. Though the species is not actually extinct, the enormity of economic extinction cannot be ignored. That a species can be reduced by such incredible numbers is a sobering thought. And the effects of such great population declines are so extraordinary and dangerous that we may not realize our own folly until it is too late.
Natural Causes
