Collapse of a Food Chain

Fifty years ago, the waters off southern California teemed with life. In addition to the large marine mammals--whales, dolphins, and seals- -the ocean was filled with the microscopic animals called zooplankton and with the fish that eat them, such as anchovies, mackerel, and sardines. Seabirds, feeding on both the zooplankton and the small fish, flew above the ocean waters by the hundreds of thousands.