Science: “The last century has not been good for large, tasty fish like tuna and cod. Numbers of these and other top predators have plummeted because of overfishing. At the same time, populations of smaller fish, such as sardines and anchovies, have boomed by 130%, according to a new study of marine ecosystems around the world. This shift in the balance of the food web isn’t healthy or sustainable, the researchers argue. And one way to help, they say, would be to shift from eating predators to species lower on the food chain. The researchers, led by Villy Christensen of the University of British Columbia in Canada, analyzed models of about 200 food webs around the world. These models depict marine ecosystems at various time periods from 1880 to 2007. Christensen’s team then estimated the distribution of biomass in ecosystems—how many tons of tuna or shrimp, for example—and extrapolated to cover all of the oceans.”