Nearshore environments are physically dynamic and critical habitats for marine megafauna, yet they face intense anthropogenic pressures. We used drones to assess seasonal abundances of marine megafauna within Cabuyal Bay in northwest Costa Rica. Between September and March of 2017–2018 and 2018–2019, we flew sawtooth-pattern transects at distances of (1) 0–100 m (n = 20) and (2) 100–200 m (n = 16) from the shore. Across 36 surveys, we observed 1891 individual marine megafauna from at least 15 taxa, including 11 that are listed as threatened by the IUCN. Grouped into broader categories (rays, bony fishes, reptiles), rays were the most diverse (≥8 taxa) while bony fishes were the most abundant (76% of individuals). Megafauna abundance and species richness, for all taxa except mobulid rays and sea turtles, were significantly higher in the dry season (December–February) than in the wet season (September–November) and positively correlated with wind-driven upwelling and local productivity. Sixty-five percent of all observations occurred within the 0–100 m transects, a pattern mirrored for bony fish (72%) and marine reptiles (66%), though not for rays (38%) which were more commonly observed in the 100–200 m transects. Our results indicate that Cabuyal Bay supports high biodiversity and abundance of marine megafauna, particularly rays, and thus we recommend it be considered for local protective measures.
Yaney-Keller et al. (Thu,) studied this question.
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