From this story in the Los Angeles Times
_A day after waking up to find a silvery carpet of dead fish on the surface of King Harbor, Redondo Beach set about the enormous task of ridding the marina of an estimated 1 million sardine carcasses before they started to decay. City officials said Wednesday that it would take days and cost at least $100,000 to clean up King Harbor after the sudden fish die-off that began Monday evening. The city declared a local emergency in an effort to obtain state and county aid for the cleanup. A crew of 200 workers has already removed more than 35 tons of fish, mostly by skimming the water's surface. But an additional 30 tons ˜ and perhaps more ˜ are believed to have collected in a 2-foot-thick layer on the bottom of the harbor, about 20 feet below.
_"...The prevailing theory among scientists and wildlife officials is that something ˜ windy conditions, predators or perhaps a column of oxygen-poor water in the ocean ˜ forced masses of sardines into the harbor as a storm blew in Monday evening. Their huge numbers in such a confined area caused oxygen levels to suddenly plummet below life-sustaining levels.