Scientists Try to Count Fish in Sea
Monday, April 10, 2006
Braced against a stiff wind, Paul Piavis, Butch Webb and Keith Whiteford hauled a net heavy with fish from the Choptank River into their motorboat and spilled them into a tub. Flapping among dull-colored catfish, yellow perch gleamed like tarnished gold.
The biologists, in camouflage gear and heavy boots, looked like any other anglers, but they were fishing for science. Back in their barracks-style office at the Maryland Department of Natural Resources, they would plug statistics about the fish they caught into mathematical models, taking a measure of the yellow perch population.
With nets and divers, sonar and surveys, scientists around the world grapple with one of Earth's great unknowables: how many fish in the sea.
Fish counts are the science behind regulations from Virginia's Northern Neck to the South Pacific, dictating a charter boat's take and an island nation's diet. But this is a science so inexact that some call it an art. And when the counting ends, the fighting often has just begun.
That's what happened this winter when Maryland tried to open the Choptank River to commercial yellow perch netters for the first time in nearly two decades. Counts had documented a 530 percent increase in the Eastern Shore river since 1988, Piavis said.
But sport anglers disputed those findings in raucous public hearings, questioning how the fish could be so plentiful when they have trouble catching their limit of five. The department withdrew the proposal.
"Science is only one part of the equation," Piavis said. "Who gets the fish . . . is a whole other equation."
What is clear is that over the past century, the world's fish stocks have shrunk. The U.N. Food and Agriculture Organization says that one-quarter of the world's marine stocks are overfished, or harvested faster than the fish can reproduce to replace them, and another half are approaching that point.
Nearly half of the two dozen fisheries managed by the Atlantic States Marine Fisheries Commission are listed as depleted or unknown, including the American lobster, red drum and river herring.
The loss of a stock even temporarily, scientists say, can cost the industry hundreds of millions of dollars and echo throughout the ecosystem, affecting humans, too.
But measuring nature's bounty remains a challenge. Where science leaves a gap, politics rushes in.
In 1992, the collapse of the North Atlantic cod fishery, which devastated Canadian and American fishermen and uprooted entire towns, came about partly because politicians ignored dismal harvest figures in favor of more optimistic forecasts, scientists say.