Funafuti is the largest atoll, and comprises numerous islets around a central lagoon that is approximately  (N–S) by  (W-E), centred on 179°7'E and 8°30'S. On the atolls, an annular reef rim surrounds the lagoon with seven natural reef channels. Surveys were carried out in May 2010 of the reef habitats of Nanumea, Nukulaelae and Funafuti; a total of 317 fish species were recorded during this ''Tuvalu Marine Life'' study. The surveys identified 66 species that had not previously been recorded in Tuvalu, which brings the total number of identified species to 607. Tuvalu's exclusive economic zone (EEZ) covers an oceanic area of approximately 900,000 km2.