To promote marine conservation and sustainable resources use it is highly important to understand reef fish population structure and dynamics. The sergeant major, Abudefduf saxatilis, is a common and abundant fish usually found in the Brazilian coasts, being considered a keystone-species for structuring benthic communities on reef habitats in the Atlantic Ocean. This study examined the morphology (shape indices and elliptic Fourier descriptors) and chemistry (Element:Ca) of A. saxatilis sagittal otoliths, collected in seven locations along the coast of South Brazil. Otolith morphology and chemistry were compared at short (range 0.5–2 km) and large (range 70–140 km) spatial scales using univariate and multivariate statistical approaches. Reclassification accuracy rates obtained from linear discrimination function analyses using both morphology and chemistry of otoliths were 61% and 82% for short and large spatial scales, respectively. No clear separation for individuals collected in islands within the Tamboretes Archipelago were observed suggesting that water masses are relatively homogeneous and/or that individuals could be highly mixed over short spatial scales. However, the higher reclassification success of the individuals belonging to Bom Abrigo, Galheta and Paz islands, indicates a limited movement of adults between habitats, a larval retention mechanism or a self-recruitment process occurring at large spatial scales.

Developing survey strategies for threatened species is often limited by access to sufficient individuals to acquire information needed to design appropriate conservation measures. The goliath grouper (Epinephelus itajara) is a large reef fish, globally classified as critically endangered. In Brazil, fishing has been prohibited since 2002. Herein we investigated habitat use and abundance of E. itajara in Brazil drawn from a participative survey, which engaged volunteer divers in data-collection. A total of 188 reports were recorded between 2005 to 2011 throughout 13 Brazilian states. Our results revealed that habitat type influenced the relationship between total length and depth of occurrence of E. itajara. We observed a significant difference between habitats, artificial presented a nonlinear and natural an asymptotic relationship. This study underscores the importance of developing conservation measures addressing specific habitats and locations to enhance population recovery. Artificial structures (shipwrecks and manmade reefs) are critical habitats that must be considered as highly sensitive areas to E. itajara strategic conservation policies. We suggest the creation and implementation of marine protected areas, as key strategies for E. itajara conservation, especially for artificial habitats and aggregation sites.

In the present paper, we document a recent record of the Bannerfish, Heniochus acuminatus, an Indo-Pacific species, in the southwest Atlantic Ocean and comment on biological aspects of the Azores Chromis, Chromis limbata, an invasive reef fish in the western Atlantic Ocean. We suggest that investigations of invasive species along the Brazilian coast can use data provided by citizen science, strengthening the non-native reef fish control strategies.