Earth Today: Fish could be best indicators of global climatic trends

The best indicator of what's happening to global climate could turn out to be fish, scientists said Thursday. According to biological oceanographer Francisco Chavez, a small change, perhaps less than two degrees Fahrenheit, determines whether huge schools of sardines, or anchovies, occupy fishing grounds off California, Japan and Peru.

When the Pacific is warm, sardines abound. When it's cool, anchovies thrive. These periods in which one or the other dominate appear to run in 25-year cycles. Perhaps we are about five years into a cooling trend.

"What surprised me most was that people in different parts of the world were seeing this, but without realising they were all the same thing," said Chavez, at the Monterey Bay Aquarium Research Institute, in California. "It's seen all around the Pacific."

He added, however, that "I wasn't the first one to notice these cycles. The Japanese first published on it in 1983. They saw the sardine population changes, and they were first to plot the sardines off Japan, California and Peru."

Now Chavez and three colleagues – whose work was published in Friday's issue of Science - suggest that fish populations and where the fish are can offer clues to changes in global climate. "Because … (the changes in fish) are fairly long-term and significant, they can play into the global warming interpretations," he said.

Oceanographer Frank Schwing, at the National Oceanic and Atmospheric Administration laboratory in Pacific Grove, California, said Chavez's report "is a nice summary of things we've been looking at for some time. A lot of scientists have speculated there is a relationship between these climate cycles and fish population cycles."

While more study is needed, what seems clear is that a 25-year cycle does exist, and it resembles the known, but more frequent, climate changes called El Niqo and La Niqa.

These occur alternately in roughly four-year cycles, with impact on winter weather, the number of hurricanes that form, plus droughts and floods at various places around the world.

Even though the temperature changes involved in "swapping" the domination of fish species are subtle and don't come often, the economic impact is indeed large. When California's sardines suddenly disappeared about 1950, for example, Cannery Row in Monterey, California, soon died.

"I think what happened to the sardine fishery in the 1940s was that the population was vulnerable to changing climate," Schwing said, "and that, combined with continued heavy fishing pressure, led to the drop in numbers of fish available," and the demise of Cannery Row.

The huge anchovy fishery off coastal Peru is still very lucrative, however, although it goes through distinct cycles of boom and bust.

These small, silvery fish are caught in the thousands of tons, and are processed into fertiliser and chicken feed. Right now, Chavez said, the ocean is cool and the anchovies are there. The Peruvians are benefiting from "the largest single-species fishery in the world."

As a result of recent research, Chavez added, "a lot of people have started to realise there are these 25-year periods, when certain species tend to dominate.

So these organisms may be better indicators of climate change than some of our sophisticated measuring devices."

There is also evidence that these longer climate cycles are involved in the abundance of salmon and other fish in the waters off Alaska, Washington, Oregon and Northern California, the researchers said.

© Los Angeles Times-Washington Post News Service