They are extraordinarily rich and support great biodiversity. They are critically important for sea-birds, especially boobies and albatross, and for all the marine mammals, as well as numerous other less visible marine species. The bajos are located to the south and east of the archipelago. The majority, but not all, are within the 40-mile limit. Another factor determining optimal size for the Reserve is the requirement to protect far-ranging species.
Some marine organisms stay in one place throughout their lifecycle, but others range extensively.
Prominent amongst the latter are sharks, whales, dolphins, sea turtles, fur seals, sea lions, albatross, red-footed boobies and masked boobies, all of which are vulnerable to industrial fishing. Forty is not a magic number. For example, ideally the Reserve would be bigger to the south and east to include all the bajos. Nevertheless, the 40-mile limit is simple and is sufficient to make the GMR one of the world's most important protected areas. Unavailability of detailed catch data has impeded serious analysis, but rough calculations of costs and trade-offs, based on data from the National Fisheries Institute, show that the potential losses to the industrial fishing sector have been wildly exaggerated.