Fine-scale variation in the proximity of baited remote underwater video stations (BRUVS) to rocky reefs reveals changes in the structure of temperate fish assemblages

We investigated changes in the structure of coastal fish assemblages in Northern Patagonia, Southwestern Atlantic, by using baited remote underwater video stations (BRUVS) deployed at increasing distances from rocky reefs: 0-5 m, 15-20 m and 50-60 m. We estimated species richness and abundance (total and by preferred habitat type) and searched for diagnostic species in each distance range. We recorded 14 taxa across 11 families in 19 areas surveyed. Species richness and abundance were higher on reef ledges and decreased with distance from them, at a finer spatial scale than previously reported. Acanthistius patachonicus and Sebastes oculatus were indicative of reef ledges; they were less abundant at 15-20 m and disappeared at 50-60 m. Callorinchus callor-ynchus and Odontesthes spp. occurred only at distances >15-20 m from the reefs, while Galeorhinus galeus was distributed homogeneously throughout the surveyed area. Our findings have practical implications for moni-toring ecotone demersal habitats with BRUVS.

Automated summary

We used BRUVS to investigate the changes in fish assemblages along the Northern Patagonian coast. Our results showed that species richness and abundance decreased with increasing distance from rocky reefs. Some species, such as Acanthistius patachonicus and Sebastes oculatus, were indicative of reef ledges and were less abundant or disappeared at greater distances. Callorinchus callorynchus and Odontesthes spp. were found only at distances >15-20 m from reefs, while Galeorhinus galeus was distributed evenly throughout the surveyed area. These findings have practical implications for monitoring demersal habitats with BRUVS.