Mass mortality of the black sea hare Aplysia gigantea (Gastropoda: Aplysiidae) at Augusta, Western Australia in the austral summer of 2021

A mass mortality of the sea hare Aplysia gigantea at Augusta, Western Australia was first reported to local authorities on 10 February 2021. The number of dead sea hares on the beach increased rapidly, until thousands were to be seen on a 4 km stretch; the maximum density of dead individuals was estimated at 20-30/m(2). We suggest the mortality was caused by weather conditions that washed the animals ashore, where they died. Weather conditions changed on 17 March and the dead sea hares were washed back out to sea.