Dr. Pauly: Global fish populations declining

by Sam Wilson
Wednesday, November 13, 2013

In the North Atlantic and North Pacific oceans, humans have removed about 80 percent by weight of the top predator fish, such as tuna and mackerel, Dr. Daniel Pauly said during a presentation on Monday, Nov. 11 at the University of North Carolina Wilmington. And unless the world drastically changes the way it manages fisheries and the natural systems they impact, he said the number will only continue to plummet.

Hundreds of students gathered in the Burney Center’s ballroom for Pauly’s presentation, Impacts of Fisheries and Global Warming on Marine Ecosystems, during which he spoke about changes in the world’s fish supply throughout the past century, and what the future may hold.

Through decades of fisheries scientists’ warnings, Pauly said critics have repeatedly attacked evidence that shows fisheries’ productivity plummeting.

“No evidence whatsoever of fishing down,” he joked repeatedly, while rattling off evidence to the contrary, including one graph that focused on the Gulf of Maine, where depletion of species higher in the food chain had forced fishermen to begin harvesting sea urchins in the late 80s, sea cucumbers beginning in the 90s and finally seaweed in the 2000s.

The world’s supply of commercial fish, usually those at the top of the food chain, is steadily dropping, but meanwhile Pauly said fishing capacity is on the rise. A graph showed Asia’s fishing capacity, mainly in Japan and China, as having increased about tenfold since the early 1970s, while the rest of the world remained relatively stagnant.

“We are essentially modifying these habitats so the big fish aren’t there any more,” he said, calling the result a mess in which plankton and algae populations continue to grow in the absence of predators, ultimately pulling the oxygen from the water and creating vast dead zones where fish can no longer live.

Pauly said the effects of global warming are also working against global fish populations. He showed the audience numerous maps which tracked the migration of different species during the past decades, including one for small yellow croaker that followed a migratory path predicted years earlier based on projected temperature changes and the croaker’s preferred temperature range.

“The English fish a lot of species that were previously confined to Spanish waters,” he noted, adding that on average, fish species are migrating away from the equator at a rate of about one degree latitude per decade.” 

To further illustrate the relatively short attention spans of humans, he showed a progression of top catches at a popular Florida fishing pier where the leviathan fish hooked in the 1950s diminished through the decades to modern catches a fraction of the size.

Formerly a five-year director of the University of British Columbia’s Fisheries Centre, Pauly currently works as the principal investigator for the Sea Around Us Project, which studies, documents and promotes policies to mitigate the impact of fisheries on the world’s marine ecosystems. His online encyclopedia of more than 30,000 fish species, FishBase, and an ecosystems modeling program, Ecopath, are used around the world by biologists and other research scientists.

email sam@luminanews.com

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