Word: oceanic
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Sharks play a crucial role in keeping aquatic wildlife in balance. Scientists now understand that the ocean ecosystem has been evolving over hundreds of millions of years as an integrated whole--a biological machine in which each component has a vital function. For most sharks, that function is to serve as what biologists call an apex predator, the ocean equivalent of a lion or tiger or bear. Not only do they keep prey populations in check, but they also tend to eat the slowest, weakest and least wily individuals. In so doing, they improve the target species' gene pool, leaving...
...counting its tail beats, how much energy it has used. "We still have a lot of data to gather," he says, "but once we really understand what role the hammerhead pups play here, we can use that to begin understanding how adults fit into the ecosystem of the open ocean...
Sharks that are at least 10 ft. long get a 6-in.-long cylindrical beeper deposited inside an incision in the belly. Every time the shark nears an acoustic receiver anchored on the ocean floor, it leaves a record of its visit. Based both on these records and on open-ocean shark chases, Holland has come to several conclusions. "First," he says, "we've established that tiger sharks do have home ranges." Those ranges, however, are huge: Holland's crew has tracked sharks all the way to Molokai, 25 miles away...
...observing sharks repeatedly over the years, Klimley was able to solve the long-standing mystery of why hammerheads gather in schools. It's clearly not for protection, since nothing preys on what Klimley calls "the big tough guys of the ocean." It turns out that they gather, at least in part, for an elaborate mating ritual, in which large, dominant females fight their way to the center of the school. The males know which females are most desirable by their position in the pack...
...implemented any sort of shark-management plan, and only a handful have enacted laws protecting especially vulnerable species. Probably the most comprehensive undertaking is the U.S. National Marine Fisheries Service's Atlantic shark-fishery management plan, which since 1993 has limited the catch of 39 species in the Atlantic Ocean, Caribbean Sea and Gulf of Mexico. The plan sets annual quotas, bans finning and mandates species-specific tracking programs to help scientists. "It's having an impact," says NMFS's Rebecca Lent. "The 1996 assessments show that the large coastal sharks are still being overfished, but the rate has slowed...