Deeper than we thought: New depth records for northern Red Sea and eastern Mediterranean Sea fishes

The depth distribution of marine species is essential ecological information, especially within hotspots of biological invasions and given the increasing evidence of climate-driven depth shifts. Due to the scarcity of systematic surveys across depths, most studies rely on coarse-scale compilations of opportunistic data. High-quality depth estimates are particularly lacking in the eastern Mediterranean, a global hotspot of climate change and biological invasions, and the adjacent Red Sea, which serves as the source for most species introductions. Using baited remote underwater stereo-video systems to depths of 150 m, we report new depth records for fish species in the northern Red Sea and eastern Mediterranean Sea, and model their abundance patterns across depths. We found that 96 of the 230 studied species (42%) were found at novel depths compared to their previously known records, with 84 species showing deeper distributions. The mean deep border extension across these species was 22.4 m. Our results highlight the importance of in-situ observations across depths. We offer a comprehensive dataset including species’ depth ranges, modeled central depth niches, abundance, body size, and associated habitat types. This dataset is useful for understanding the role of depth shifts in response to climate change and species introductions into the Mediterranean Sea.