Ancient remains consisting of bones of the now endangered Hawaiian petrels help scientists analyze the impact of human activities on open-ocean food chains.

The once abundant Hawaiian petrels is now listed among the endangered species and according to researchers who analyzed the ancient remains of this species, human activities could be the major cause of  the petrel facing extinction.

While the bird is known to spend a major portion of its life in the open waters of the Pacific, feeding on crustaceans, fish and squid, sometime between March and October, it migrates to the Hawaiian Islands of Maui, Lana'i and Kaua'i to breed.

The bones that researchers from Michigan State University and Smithsonian Institution studied, revealed a lot about the petrel's diet and it was discovered that there was a drastic change in their foraging activities in the open seas, possibly due to industrialized fishing. This has caused researchers to raise serious concerns about the fate of these species and they wonder how many other species have been affected by human activities.

"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, co-author and MSU zoologist. "Our study is among the first to address one of the great mysteries of biological oceanography - whether fishing has gone beyond an influence on targeted species to affect nontarget species and potentially, entire food webs in the open ocean."

The chemistry of a petrel's bones say a lot about its diet and researchers studied the bones' ratio of nitrogen-15 and nitrogen-14 isotopes. The larger the isotopes, the bigger the fish they feast on. Between 4000 and 100 years ago, petrels had very high isotopes, suggesting that they ate bigger fish. However, with the onset of industrialized fishing, their isotopes began declining, which means the species had moved to feeding on smaller fish.