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In the seas off Alaska, modern factory fishing started in the 1960s, when large Japanese and Soviet factory stern-trawlers replaced the smaller, less efficient side-trawlers. Catches of Pacific ocean perch, Pacific herring and yellowfin sole reached record levels by the early 1960s, Followed by collapses as each stock was overfished. As stocks of one species crashed, the fleets shifted their fishing effort to another species.
Overfishing is suspected as the reason for the steep declines in many wildlife populations of the Bering Sea. Nearly forty years of intensive industrial-scale fishing have led to the collapse of fish stocks in the Gulf of Alaska and in the Bering Sea. The continuing decline of many seabird and marine mammal populations indicates an ecosystem in trouble.
Overfishing happens when a fishing effort removes a volume of fish from a fish population in numbers that exceed the stock's ability to replenish itself. Diminishing numbers of fish without a corresponding decrease in the fishing effort eventually leads to a population collapse, rendering the fish stock commercially extinct.
Policy Definition: Overfishing - A rate of fishing mortality that jeopardized the capacity of a fishery to produce the maximum sustainable yield on a continuing basis.2
Legal Definition: Overfishing - A rate or level of fishing mortality that jeopardizes the capacity of a fishery to produce maximum sustainable yield on a continuing basis.
Scientific definition: Overfishing - Occurs when the quantity of fish harvested exceeds the amount that can be re-supplied by growth and reproduction.
Diminishing Fish Stocks
According to the United Nation's Food and Agriculture Organization (FAO), six percent of all major marine fisheries are underexploited, 20 percent are moderately exploited, 50 percent fully exploited, 15 percent overfished, six percent depleted and two percent recovering.3
Overfishing on a Global Scale
The July 27, 2001 edition of Science describes the ecological extinctions of marine megafauna-vast populations of whales, manatees, dugongs, monk seals, sea turtles, swordfish, sharks, giant codfish and rays from overfishing at a global scale never before realized.
Using data from sediments, archaeological sites, historical documents and scientific literature, Jeremy Jackson of the University of California at San Diego, and colleagues wrote that “Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change.” The data revealed a pattern of progressive “fishing down” that began with the removal of the largest food fish, which tend to be top predators of their environments. Once fishermen had depleted those species locally, they moved farther afield, but they also shifted down to the next-largest edible fish.
Eventually, commercial fisheries ended up depleting top predators in even the most distant parts of the globe, and providing what formerly had been regarded as trash fish or bait fish to restaurants for human consumption.4
Most marine scientists believe that overfishing contributes in large part to the worldwide decline of marine fisheries, and many believe it is the primary cause. A growing body of research also indicates the ever-growing fishing effort may now be altering the balance of ancient marine ecosystems that nearly all fisheries and marine life depend on. This could lead to the future collapse of a growing number of fisheries.5
1 B.A. Megrey and V.G. Wespestad, “Alaskan Ground Resources: 10 Years of Management Under the Magnuson Fishery Conservation and Management Act,” North American Journal of Fisheries Management, Vol.10, No.2, Spring 1990: 127.
2 www.oceana.org
3 Press Release 99/11 Governments Support New International Commitments to Reduce Overfishing and Overcapacity
4 Historical Overfishing and the Recent Collapse of Coastal Ecosystems, Jeremy Jackson et al, Science, 27 July, 2001, pp. 629-37.
5 Copyright © 2000 - 2002 Habitat Media Empty Oceans, Empty Nets
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