The rainbow parrotfish (Scarus guacamaia) does not depend on mangroves as nursery habitats in the Parque Nacional Arrecife Alacranes, Southern Gulf of Mexico
The rainbow parrotfish (Scarus guacamaia) the largest herbivorous reef fish in the Atlantic Ocean, is considered a mangrove dependent species since its juvenile stages use the mangrove prop roots as nursery habitats (Mumby et al. 2004; Dorenbosch et al. 2006; Machemer et al. 2012) Such mangrove dependency has been endorsed by Serafy et al. (2015) a Caribbean wide study revealing that mangrove forest size increases the densities on neighboring reefs of fishes that use mangroves as nurseries. Mumby et al. (2004) found high densities of S. guacamaia on reefs near mangroves in Glovers Reef, Belize, a condition they referred to as a functional dependency on mangroves (Rhizophora mangle) This functional dependency implies vulnerability to local extirpation from habitat loss, so if mangrove habitats are cleared, adult S. guacamaia should not to be present on the nearby reefs. Mumby et al. (2004) emphasized that populations of S. guacamaia have undergone local extirpation in the last 30 years in Glovers Reef through a combination of mangrove clearing and parrotfish overharvesting. Here, we report the presence of S. guacamaia on Alacranes Reef (22deg21'44, 22deg35'12 N; 89deg36' 30, 89deg48'00 W) the largest reef complex in the Southern Gulf of Mexico. Alacranes Reef is located approximately 130 km off the northern coast of the Yucatan Peninsula, Mexico, and is considered an important fishing ground f o r l o b s t e r (Panu l i r u s a rgu s a n d g r o u p e r s (Epinephelidae) In 1994, it was declared a protected area known as the Parque Nacional Arrecife Alacranes (PNAA) covering a total area of 333,778 ha comprised by coral reefs and five small keys <1 km each) The presence of mangroves in the PNAA is almost negligible, with only a couple of trees on one key (Isla Perez) without proximity to water and thus preventing any function of nursery habitat. Between 2010 and 2015, we detected several schools of up to 50 individuals of S. guacamaia with a size range between 30 and 80 cm in total length (TL) (Fig. 1) on the southeastern zone of the PNAA at depths between 5 and 20 m. We also found juveniles (10 to 20 cm TL) in areas of coral rubble and octocorals of the same zone. The presence of adult S. guacamaia, in such a high abundance and large body size, and its juvenile stages in the PNAA is remarkable because of the absence of mangroves to function as nursery habitats. The mangrove dependency of S. guacamaia populations reported in Belize (Mumby et al. 2004) Aruba (Dorenbosch et al. 2006) and Florida (Machemer et al. 2012) is not evident in the PNAA where S. guacamaia cannot depend on mangroves as nurseries and thus is forced to use alternative habitats (e.g. coral rubble, seagrass, octocorals) The nearest areas containing coral reefs and mangroves in the Mexican Caribbean Sea are Communicated by R. Thiel
Marine Biodiversity