An analysis of the bones of ancient and modern Hawaiian petrels has revealed that modern petrels, which forage in the open ocean, are eating prey lower on the food chain than in centuries past, a dramatic shift
that coincides with the rise of industrial fishing. In tests conducted on petrel bones collected over three decades in the Hawaiian islands, a team of scientists found that the bones from 4,000 to 100 years ago contained higher ratios of nitrogen-15 and nitrogen-14 isotopes than the more recent bones, suggesting that the earlier birds ate bigger prey before changes in the food web composition of the Northeast Pacific. According to the scientists, the nitrogen ratio started to decline in the decades after the early 1950s, when industrial fishing started to extend beyond the continental shelves. “Our bone record is alarming because it suggests that open-ocean food webs are changing on a large scale due to human influence,” said Peggy Ostrom, a zoologist at Michigan State University and co-author of the study, published in the Proceedings of the National Academy of Sciences.