Riddle of the Shells
An eternal wind rips across San Miguel Island, scouring stretches of open sand and bending the blackened branches of shrubs. The most far-flung of a chain of islands that dot the Santa Barbara Channel off the coast of southern California, San Miguel has drawn fishermen ever since the earliest people settled North America. This stark landscape is surrounded by a thriving submarine jungle of kelp that is prime habitat for an array of fish, shellfish, and marine mammals. For millennia, it was the best place in southern California to collect abalone, the giant mollusk that once carpeted the seafloor of the Channel Islands. Now, after decades of over-harvesting, southern California abalone populations are badly depleted, echoing a global pattern in which the bountiful ocean morphs into a sea of ghosts.
During the past decade, scientists have come to understand the extent to which overfishing has emptied the oceans. In 2003 an influential study in the journal Nature concluded that many populations of large fish had plummeted to 10 percent of their 1950 levels. The research drew on coastal marine surveys and catch data from Japanese long-lining, an intensive industrial fishing method used in all the world's oceans except the circumpolar seas. The study showed that predators such as marlin and tuna are now caught when they are relatively small; many don’t live long enough to reproduce. This grim trend is evident on coral reefs, in the deep waters of the open oceans, and in kelp forests off southern California.
The sluggish abalone may not be as charismatic as a free-roaming ocean giant like the tuna, but its plight encapsulates the human foibles that have led to devastation of marine life around the world. What had been a highly profitable abalone fishery began to crash in the late 1970s and was completely closed in 1997 to protect remnant stocks from obliteration. Now, a dozen years after the emergency closure, a group of former abalone fishermen is lobbying hard for a renewed harvest at San Miguel Island, the last, best place for the great snails in southern California.
The powerful tendency of fishermen and resource managers to take what they've seen in their own time as the natural norm is known as the shifting baseline syndrome. It allowed fishermen in the North Atlantic to over-harvest cod for centuries. Each generation accepted increasingly scattered stocks of smaller and smaller fish as the norm, until the population collapsed in the 1990s. The same syndrome explains why advocates of a renewed abalone fishery insist that the population at San Miguel is strong, while ecologists, conservationists, and now even archaeologists see it as the tattered shreds of a once plentiful stock in desperate need of protection.