SCIENCE

But Mumby and his colleagues discovered that while the grouper did prey more aggressively on the parrotfish, the ones that survived were those large enough to escape from the grouper. It turned out that the bigger fish were better grazers, which improved the health of the reef overall, the researchers found.

"Our results indicate that the long-term impact of Caribbean no-take marine reserves is enhanced grazing, a process that is key to the ecosystem functioning of coral reefs," the researchers wrote in Friday's issue of Science.

In an accompanying editorial, Ove Hoegh-Guldberg of the University of Queensland in Australia wrote that "the complexity they have uncovered . . . just scratches the surface of what is required to understand the functioning of protected regions."

-- Rob Stein

DNA Test Tracks Shark Catch

With genetic tests similar to those used by criminal investigators, federal law enforcement agents are identifying fins taken from imperiled great white sharks by illegal traffickers.

In late 2003, agents from the National Oceanic and Atmospheric Administration confiscated about one ton of dried shark fins that a New York City seafood dealer was planning to ship to Asian markets. The operation was outlined in an article in the January edition of the journal Conservation Genetics.

Scientists from the Guy Harvey Research Institute at Nova Southeastern University in Florida, working with federal agents, took tiny samples from 21 sets of fins using a novel and quick identification method that uses both nuclear and mitochondrial DNA markers. They ran the test after noticing that one of the confiscated sacks of fins was labeled "porbeagle," a close cousin of the great white shark that cannot be killed in U.S. waters under federal law, and another label hidden inside read "blanco," white in Spanish.

"The discovery of so many smaller shark fins from a highly protected species in the possession of a single trader indicates that there may be a specialized market for white shark fins not only as trophies but also food, putting additional pressure on the species," said principal author Mahmood S. Shivji, director of the Guy Harvey Research Institute. "By applying DNA techniques to track the species or origin of shark fins on the market, we can put 'teeth' into the enforcement of fishing regulations."

The case has not gone to trial; possessing or selling prohibited sharks species carries maximum fines of $100,000.

-- Juliet Eilperin