New Model Charts Swings in Crab Populations

摘要

It's not easy being a crab. Hatched in the dead of winter, crab larvae mature at sea for 3 months before swimming to shore to settle. And once there, they not only have to compete for food, they run the risk of becoming food for other creatures--fellow crabs included. But if you think living a crab's life sounds hard, ecologists joke, try modeling it. Crab populations are notoriously erratic, skyrocketing one year and tumbling the next. Catch figures in Eureka and Crescent City, California, for the Dungeness crab, for instance, have been known to plunge from 7 million to 130,000 kilograms in just 4 years. For decades, ecologists have wondered what forces drive these swings: Is it biology--behaviors such as competition and cannibalism, which depend on the density of crabs in a given locale? Or is it environment--random changes in water temperature, ocean currents, and other aspects of the crabs' habitat?