The waterfalls of Hawaii guard uninhabited pools: perfect fish spawning habitat, free from predators and competition. But reaching them involves an extraordinary climb, says Adam Chapman.
Certain species of goby pit themselves against the waterfalls, some of which exceed 120m in height, in order to reach the pools above.
How do they climb?
Different species of goby use different climbing styles. Lentipes concolor favours an athletic butterfly stroke, whirling away with its pectoral fins to power it up the vertical face. It rests between these bursts of intense activity - clinging on with its fused pelvic fins.
Sicyopterus stimpsoni, on the other hand, favours a steady crawl, using its chin and fins in combination to inch up the cliff face. Many fish fall to their doom, but enough make it to ensure survival of the species.
The gobies are pioneers that epitomise how fish have managed to colonise almost every watery habitat on the planet - no matter how remote.