Budiões brasileiros: de assembleias a populações

Abstract

Parrotfishes (Labridae: Scarinae) are known for affecting the structure and functioning of reef ecosystems through bioerosion and grazing of macroalgae. Despite being extensively studied worldwide, parrotfishes in Southwestern Atlantic are relatively understudied and critical information about their patterns of distribution, habitat preference and demographic attributes are still scarce, often hampering our ability to propose effective management strategies. Ten species within four genera of scarinae labrids occur in Brazil, six of which are endemic. Most of the endemic Brazilian parrotfish are now threated at some level because of overfishing, especially the largest one, Scarus trispinosus, which is now considered an endangered species under the International Union for Conservation of Nature (IUCN) criteria. This thesis approaches different topics related to patterns of distribution and habitat preferences of parrotfish assemblages, demographic information and habitat use of Sc. trispinosus, along three chapters: (1) “Drivers of abundance and biomass of Brazilian parrotfishes” which assess the abundance, biomass and size class distribution of six parrotfishes (Sc. trispinosus, Sc. zelindae, Sp. amplum, Sp. axillare, Sp. frondosum and Sp. radians) and relates habitat preferences and reef attributes; (2) “Demography of the largest endemic and endangered Brazilian parrotfish, Scarus trispinosus, reveals overfishing” which provides information on age, growth and reproduction of Sc. trispinosus, discussing differences between inshore and offshore populations and applications for fisheries management; and (3) “Protection of nursery areas is not enough to conserve endangered species without enforcement and fisheries management” which maps the main nursery areas of Sc. trispinosus and assess abundance trends of juveniles in the Abrolhos Bank, discussing the roles of Marine Protected Areas (MPAs) and fisheries management in the conservation of this endangered species. The main outcomes are: (1) the attributes of the studied reefs affected the composition of parrotfish assemblages but had different effects on each species. Offshore reefs sustained larger-sized individuals and higher biomasses for most species, while inshore reefs concentrated higher abundances of small-sized individuals (juveniles); (2) Demographic attributes of Sc. trispinosus indicated that the species is being overfished in the inshore reefs of Rio Grande do Norte state, despite having a late maturation with an estimated median age and size at maturity of 4.2 years and 39.2 cm of fork length, respectively. Additionally, there were marked differences in size class distributions, reproductive stages and ages between inshore and offshore reefs, which have important implications for fisheries management; and (3) nurseries habitats of Sc. trispinosus in the Abrolhos Bank are within no-take MPAs, but the abundance trend of juveniles is declining, indicating that MPAs alone are not enough, if there is not enough enforcement and proper fisheries management in the adjacent areas. These results indicate that the conservation of Brazilian parrotfishes requires the protection of reefs’ heterogeneity and sensitive habitats, but mostly, proper fishing management and enforcement.