at a length of more than 100 kilometres, abrolhos is south america's largest coral reef complex. on this trip, two reefs are being compared. on one, fishing has been allowed. on the other, it's not. ronaldo francini has been monitoring them since then: keeping track of fish species, coral stocks and the concentration of algae. he sees immediately that there's been extensive fishing here recently. there are just a few small parrotfish. ten years ago it was full of large blue fish. it's clear the reef has been overfished. to explain how special this species is, he's taken a baby parrotfish on board, a year-old specimen. it will reach a length of a metre and live to be thirty, if it's allowed to. >> in comparison to other species, this species grows very slow, and it's a late maturation, so it's characteristic that this species is more vulnerable to fishing. >> parrotfish have brought fishermen like za comparative prosperity. and they don't want to lose it. they can buy engines for their boats, and they can now travel fast on land as well. this bare chunk of coral is a silent witnes