LAUSR

Reef fish assemblages are exposed to a wide range of anthropogenic threats as well as chronic natural disturbances. In upwelling regions, for example, there is a seasonal influx of cool nutrient-rich waters that may shape the structure and composition of reef fish assemblages. Given that climate change may disrupt natural oceanographic processes by altering the frequency and strength of natural disturbances, understanding how fish assemblages respond to upwelling events is essential to effectively manage reef ecosystems under changing ocean conditions. In this study, we used baited remote underwater video stations (BRUVS) and traditional underwater visual census (UVC) to investigate spatiotemporal patterns of reef fish assemblages in an upwelling region in the North Pacific of Costa Rica. We recorded a total of 183 reef fish species from 60 families, of which 166 species were detected by BRUVS and 122 by UVC. Only 66% of all species were detected by both methods. Our study showed that the upwelling had an important role in shaping reef fish assemblages in this region, but there was also a significant interaction between upwelling and location. In addition, other drivers such as habitat complexity and habitat composition also had an effect on reef fish abundances and species. To our knowledge, this is the first study in the Eastern Tropical Pacific that combines BRUVS and UVC to monitor reef fish assemblages in an upwelling region, which provides more detailed information to assess the state of reef ecosystems in response to multiple threats and changing ocean conditions. This article is protected by copyright. All rights reserved.