'Old Woman' of sea ended California's great sardine rush

The collapse of California's sardine fishing industry in the 1950s was due to a cyclical change in ocean temperature, scientists say.

The commonly held view is that overfishing was responsible, but evidence published today suggests the disappearance of the fish, a phenomenon which formed the dramatic backdrop to Cannery Row, John Steinbeck's post-depression novella, was part of a natural, 50-year cycle affecting the entire Pacific region.

A team of biologists and oceanographers investigated records collected over the past 100 years and found that the fall in sardine stocks, which began in the 1940s, was part of a much bigger fluctuation that has gone unrecognised because it occurs over such a long time-frame.

They found that the collapse in sardine stocks can be linked with a change from warm to cold waters off the Californian coast, which in turn were linked to a dramatic rise in the numbers of anchovy, a colder-water fish.

Francisco Chavez, a scientist at the Monterey Bay Aquarium Research Institute in Moss Landing and the leader of the team, said the new cycle was similar to the phenomenon known as El Niño – Spanish for "boy child" – in the southern Pacific which results in a disturbance of the ocean currents once every five to seven years.

Dr Chavez and his colleagues suggest that the new phenomenon in the northern Pacific should be named El Viejo, or "Old Man", because like El Niño it results in warm currents off the western coasts of the Americas. El Viejo's warm waters favour the sardine but when colder waters come to the west coast, the temperature change favours the anchovy. Dr Chavez suggests this part of the cycle should be called La Vieja, or "Old Woman", just like the cold-water counterpart of El Niño is known as La Niña, or "Little Girl". During the 1930s, when the "sardine regime" of El Viejo was at its height, the species supported the biggest fishery and canning industry in the western hemisphere, with more than half a million tons of fish landed each year. By the 1950s, the sardines had virtually disappeared.

The study, published in the journal Science, looked at historical records on fish catches, seabird numbers, sea temperatures, ocean currents, rainfall and several other factors affecting the entire Pacific region.

Dr Chavez found that sardine catches as far apart as California, Peru and Japan followed parallel courses, and when they collapsed, anchovies boomed in a regular cycle that could not simply be explained by overfishing.

"Fish in many parts of the Pacific are marching to the same drummer. This same drummer is causing changes in ocean circulation and in the global carbon cycle," Dr Chavez said.

Sardines and anchovies alternate with each other every 25 years and the last discernible transition took place in the 1970s. "What we've been trying to find out is: what is the drummer and is the beat going to change?" he said.

Dr Chavez said that understanding long-term cycles of the oceans would be essential if scientists are to assess the impact of human activities on the marine environment instead of leaving it to their imagination.

* A Democrat senator for California has called for an investigation into the Bush administration's policy on tuna fishing, after the US Commerce Department's recent decree that it saw "no significant adverse impact" in the way fishermen chased and netted Pacific dolphins swimming above tuna schools. The ruling opened the way for Mexican exporters to sell tuna and stamp the tins with the "dolphin-safe" label required by US law.

Barbara Boxer said she was introducing a bill to overturn the ruling and called for committee hearings to investigate whether the government had ignored work by two of its former scientists, who found evidence of significant harm to dolphins chased by fishing fleets.