Technology has enabled us to fish too wellthere is no place that is too deep, remote or dangerous that is beyond our reach, said Roberts.
Pauly and his colleagues wanted to determine the impact of this fishing on the worlds marine ecosystem over the last century and paint a global picture of fish populations. The first phase of their study, funded by the Pew Charitable Trusts, focused on the North Atlantic.
The researchers painstakingly collected thousands of reports on landings, or fish catches, from ports around the world for the last century. But the landings dont tell you where these fish come from, or where the fishing fleets have been, said Paulys colleague Reg Watson of UBC.
Watson and Pauly backtracked and used the composition of the catch to determine where the fishermen had been fishing. The researchers then divided the North Atlantic into a grid made up of 22,000 squares and superimposed the catch data.
The researchers found that quantity of fish hauled from the North Atlantic has doubled since the 1950s and increased eight-fold from levels harvested at the turn of the last century.
The result has been the collapse of fisheries in the North Atlantic and around the worldfish stocks in the Northern Atlantic are only one third of what they were in 1950 and one sixth what they were in 1900.
And this decline is accelerating, said Daniel Pauly, who led the study.
Fishes depleted one by one
Once a particular fish stock is depleted the fishermen simply move onto another species. They gradually work their way down the food web, catching smaller and smaller fish. This changes the entire structure of the ecosystem. Creatures that were previously prey become the predators, and thrive.
In the last decade there have been huge increases in the populations of non-fish, such as shrimp, scallops and crabs, because the fishermen have removed the large fish. These non-fish are at the bottom of the food web. Once they are gone there is almost nothing left, said Pauly.
Because the ecosystem has been changed so dramatically a fishing moratorium is not sufficient to allow fish populations to recover.
A study of more than 90 marine fish populationsincluding cod, tuna, haddock, herring, mackeral, etcrevealed that many species that suffered more than a decade of more than 60 percent declines did not rebound, even after 15 years, said Jeffrey Hutchings, of Dalhousie University in Halifax, Nova Scotia.
There is a widespread misconception that fish are less prone to extinction, than birds or mammals for example, because they produce millions of eggs and thus low populations can quickly recover, said Hutchings. But this is not true. These fish stocks have been so depleted that there are few young. Fewer still escape predators and fishing nets and survive long enough to reach sexual maturity and reproduce, he added.
Protected marine reserves
What is needed to slowand eventually reversedeclining fish populations is the creation of more marine reserves. In these reserves fish are as safe as bears in Yellowstone National Park and their habitat is also protected.
Fishermen, both commercial and recreational, are happy to have marine reserves in areas where they do not fish, said Andrew Rosenberg, of the University of New Hampshire in Durham, and former deputy director of the National Marine Fisheries Servicewhich creates US marine reserves. The North Atlantic basin is massively overfished and the fisheries are in dire troublebut no one is taking this lesson to heart, said Rosenberg. If the public wanted to protect the oceans they could exert political pressure to oppose the fishing industry, he added. But right now elected officials tend to respond to the fishermans needs, said Rosenberg, because the general public are not interested or engaged in the debate.
Some marine reserves exist along the Northwest Atlanticthree in Georges Bank and one in the Gulf of Maine and a few small reserves have also been established off the coast of Florida.
The reserves in Georges Bank have had a major impactthe scallop populations have grown considerably and the seriously depleted cod fishery, has shown some faint glimmers of recovery. It shows the power of these reserves, said Rosenberg.
Reduce fishing and fleet size
Rosenberg emphasizes that all is not lost. We do know how to make some things better because the science has really improved, said Rosenberg.
We need to reduce fishing pressure and fleet sizes and have broader protections for habitats and ecosystems. No-take zones are the best, but the hardest to achieve politically, he said.
Certain fishing areas in the North Atlantic should be tightly restricted, and catch quotas should all be implemented, added Rosenberg.
We need to close at least 30 percent of the North Atlantic Ocean to fishing, said Pauly. Without such measures we will lose all our fisheries.
The irony, explains Pauly, is that reducing fishing wont decrease the fish catch because small fish will have the opportunity to grow old and produce many offspring. The idea is that the marine reserves be considered money in the bankleaving fishermen to skim the bountiful interest.
National Geographic Today, 7 p.m. ET/PT in the United States, is a daily news magazine available only on the National Geographic Channel. Click here to request it.
SOURCES AND RELATED WEB SITES