Although few doubt the importance of highly protected marine reserves for coral reefs and reef-dwelling species, the idea that MPAs such as the Chagos Protected Area could also hep conserve migratory fish species such as tuna has sometimes been contested. New research, recently published in the journal Naturewissenschaften, provides some of the first direct evidence that such large scale no-take reserves can boost populations of migratory fish species.

In 1939, the North Sea became almost entirely closed to fishing fleets due to the outbreak of World War II. This created an unintended no-take zone, which remained in place until hostilities ended in 1945. But cod, haddock and whiting – all migratory species – were not protected throughout their range, as British fishermen were still catching them between in UK and Iceland. However, this paper by Beare et al shows that populations of these species nevertheless increased dramatically, although with some interesting age-related patterns.