The promise and perils of Antarctic fishes. The remarkable life forms of the Southern Ocean have much to teach science about survival, but human activity is threatening their existence.

Beneath the surface of the Southern Ocean, in the deep waters of the continental shelf and continental slope of Antarctica, a magnificent fauna consisting of over 320 known species of fish thrives in the cold and dark. These fish are uniquely adapted to the extreme environment in which they live. Over the course of millennia, they have evolved a remarkable range of physiological and biochemical features, the most visually stunning of which is that some lack haemoglobin (Fig 1). Yet, these species are under threat from global climate change and fishing, and the secrets they might unlock for science could be lost in the next decades if action is not taken.