Beware the lowly anchovy. A recent Pacific population explosion of the little food fish might be a harbinger of decades-long drought in the Southwest.

Pacific anchovy and sardine populations are like canaries in the climate coal mine, tipoffs that major changes are afoot, according to a paper published today in the journal Science.

Sardines have meant wet spells in the Southwest, while anchovy population explosions in the past have coincided with long-term drought.

Francisco Chavez, a biologist at the Monterey Bay Aquarium, and his Science co-authors tracked the ebbs and flows of sardine and anchovy populations through the 20th century, linking the fish to large-scale climate swings.

They say a new "anchovy regime," as they call it, is here.

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