It makes sense that industrialized fishing has altered marine food webs, but understanding exactly how it has can be challenging. We don't have that much in the way of background data on what - and how much - was swimming about the oceans before industrial fishing began - let alone a full picture of what is there now. We also lack a full record of who was fishing what, when, where and how much they were taking. For Dr Anne Wiley and colleagues at Michigan State University...challenge accepted!
A little out of the box thinking saw the team delving into the nitrogen-15 and nitrogen-14 isotopes in the bones of the endangered Hawaiian petrels. Using stable isotopes, scientists can figure out exactly where in the food chain these birds have been feeding. And because the isotopes remain in the bones the team were able to compare the diet of modern-day petrels with petrels that were flying around hundreds and even thousands of years ago.
Pretty neat huh.
What they found was that the petrels used to feed on bigger species quite high up in the food chain. So what happened when industrial fishing began? With this new and efficient predator, the petrels switched to catching smaller prey from further down the food chain.
For those with access to the journal PNAS, the original paper can be found here http://dx.doi.org/10.1073/pnas.1300213110