Da macro para a microescala: uma abordagem integrada para desvendar os determinantes ambientais da distribuição do tubarão-lixa do Atlântico

Abstract

Habitat loss constitutes one of the principal threats to biodiversity, particularly for marine species inhabiting shallow habitats due to their vulnerability to fishing and sensitivity to pollution and climate change. The Atlantic nurse shark (Ginglymostoma cirratum), classified as 'Vulnerable' by the IUCN Red List, faces threats from fishing, habitat loss, pollution, and climate-related habitat degradation. This study aimed to provide an updated distribution of the species across the entire Atlantic Ocean and identify its ecological determinants at various scales, estimating potentially suitable habitats. The study emphasizes the significance of marine protected areas (MPAs) as a conservation strategy through diverse approaches and analyzed variables. Gaps in the literature regarding ecological factors associated with this species' habitat were addressed. Occurrence data for the species, coupled with environmental data, were employed to construct a macro-scale distribution model encompassing its entire range. Additionally, at the micro-scale, juvenile and adult nurse shark densities were compared across different environments within the Rocas Atoll Biological Reserve, considering abiotic and biotic variables. The results underscore the importance of marine protected areas (MPAs) in safeguarding critical habitats and stress the necessity for further investigations in large, underrepresented regions, such as the Eastern Atlantic. Remarkably, a minor proportion of suitable habitat was situated within MPAs. Despite the Southwestern Atlantic exhibiting the lowest habitat suitability, it displays a higher proportion of habitat within MPAs. The findings reveal preferences for specific habitats, particularly coastal areas, and islands. In the South Atlantic, sharks are more associated with sandy areas rather than reefs, contrary to literature indicating a stronger reef correspondence, especially in the Northwest Atlantic. At the Rocas Atoll, juveniles favor reefs, sandy, and rocky areas. The modeled sea temperature (27-28°C) corresponds with the temperature sampled at Rocas Atoll (23 to 33°C), aligning with existing literature (25°C to 34°C). On the micro-scale, significant correlations were found between shark abundance and pool area. Juvenile sharks were more abundant than adults, suggesting that the Rocas Atoll serves as a critical nursery and breeding ground for this species. While adults exhibited a preference for open pools, there were no significant differences among pool types for juveniles. Benthic cover variables such as "Bare Substrate" and "Cnidaria" played a role in predicting juvenile density. To ensure the long-term survival of the species in the face of environmental challenges and human pressures, it is imperative to adopt an adaptive and holistic approach to conservation. This approach should encompass the active protection of critical habitats, the promotion of sustainable fishing practices, and the continuation of studies on habitat usage in both pristine and degraded environments. The acquisition and application of these data are critical for guiding marine spatial planning and predicting habitat availability, contributing to the effective conservation of the Atlantic nurse shark.