Seamounts are topographic rises of the seabed with a limited extent across the summit. There is evidence that seamounts form hotspots of biological activity in the oceans. Why seamounts host abundant populations of fish and other pelagic and aquatic predators is still uncertain. This publication examines seamounts in general and specifically those in the Southern Indian Ocean, focusing on the biodiversity of these ecosystems and management of deep-sea fisheries on seamounts and surrounding high seas.