Seamounts are hotspots of pelagic biodiversity in the open ocean

TLDR

Biodiversity hotspots are hypothesized to aid conservation, yet coarse global datasets obscure small‑scale patterns around coastal habitats or seamounts. The study aimed to investigate how seamounts aggregate large pelagic biodiversity and to identify the pelagic species associated with them. The authors used tuna longline observer data to assess seamounts’ role in pelagic biodiversity. Seamounts are hotspots of pelagic biodiversity, exhibiting higher species richness and diversity within 30–40 km of the summit, greater capture probability and fish numbers for sharks, billfish, tuna, and other by‑catch species, thereby supporting their importance for marine predator management.

Abstract

The identification of biodiversity hotspots and their management for conservation have been hypothesized as effective ways to protect many species. There has been a significant effort to identify and map these areas at a global scale, but the coarse resolution of most datasets masks the small-scale patterns associated with coastal habitats or seamounts. Here we used tuna longline observer data to investigate the role of seamounts in aggregating large pelagic biodiversity and to identify which pelagic species are associated with seamounts. Our analysis indicates that seamounts are hotspots of pelagic biodiversity. Higher species richness was detected in association with seamounts than with coastal or oceanic areas. Seamounts were found to have higher species diversity within 30–40 km of the summit, whereas for sets close to coastal habitat the diversity was lower and fairly constant with distance. Higher probability of capture and higher number of fish caught were detected for some shark, billfish, tuna, and other by-catch species. The study supports hypotheses that seamounts may be areas of special interest for management for marine pelagic predators.