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Annual Public Lectures Series > Ellen K. Pikitch
Scientists and Journalists:
Getting the Point Across
June 13-17, 2005
People and Fish: The Environmental Cost of Consumption
Ellen K. Pikitch, Executive Director, Pew Institute of Ocean Science, and Professor, University of Miami Rosensteil School of Marine and Atmospheric Science
Summary of comments from June 17
People around the world have been fishing for thousands of years. Yet as Ellen Pikitch, executive director and founder of the Pew Institute of Ocean Science, pointed out in her lecture, a lot has changed in the world's fisheries, and most of it has occurred in the last 100 years.
Pikitch began by showing the audience a graphic depicting locale and density of fish catch in the world as it was in 1900. Colors representing fish populations sprawled across a map of the globe. Some of the highest densities appeared in red along the Atlantic coast of the U.S. The next image was greeted with gasps as the audience realized that the image before them was the state of the fisheries in 2000, and that the large quantities of fish along the Atlantic Coast had disappeared.
According to Pikitch, the industrial fishing age began in the 1950s. It was then that new technologies were developed to obtain a larger catch with less effort. Better technologies led to a higher yield, and over time depleted many fish populations.
For example, Pikitch said, the Atlantic cod fishery was fished at a sustainable rate for 400 years. With the advent of industrial fishing fleets, the yearly catch reached nearly 800,000 tons, four times the sustainable rate of the previous four centuries, she said. Pikitch explained that the cod populations could not be sustained at such a level and as a result, their stocks collapsed in the 1990s. According to Pikitch, in 1992 a moratorium on the fishing of Atlantic cod was imposed. More than ten years later, there has been little recovery in those stocks.
Overfishing is not only detrimental to the fish being taken, but also to those species taken accidentally along with them, said Pikitch. For instance, Pikitch talked about the North Atlantic White Marlin, which is commonly caught as bycatch with cod and swordfish. It is estimated that there had been a 94 percent decrease in biomass by 2000 due to this incidental catch, she said, eight times the mortality rate at which fish stocks could be sustainably caught.
Industrial fishing has caused a number of adverse effects on fish stocks. According to Pikitch, there has been a 90 percent decline in the number and type of wild fish. Not only that, fish are now half the size they once were. Much of the reason that the fishing industry has been able to maintain such high yields in recent years, despite dwindling stocks, is due to the fact that they change locale and species at a rapid rate, Pikitch said. Accordingly, as the larger fish are depleted, smaller fish began to be pursued, a process she called fishing down the food web.
Pikitch says that in 2003 alone there were 113 documented marine extinctions, although this may be an underestimate due to a lag time in documentation. This comes at a time, when, according to Pikitch, 29 percent of the world, and 37 percent of the U.S. fish populations are being overfished.
Climate change was also on Pikitch's agenda as she touched upon the possible effects overfishing may have on greenhouse gases. According to Pikitch, they have found that in Namibia, where there have recently been toxic gas eruptions in the seas, sardines may play a key role in preventing the release of gases into the atmosphere. She noted that sardines consume phytoplankton, which without a predator to consume it, would eventually die and fall to the sea floor. Forming a decomposing mat on the ocean floor, the phytoplankton release gases that are brought to the ocean's surface by upwelling.
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December 4, 2007