The Fresh Water Fauna of Gough Island (South Atlantic)

Gough Island (40o 20′S.; 9o 54′ W.) is one of the world'S most isolated islands. It lies almost midway between South Africa and South America, and is of volcanic origin. Tristan da Cunha, 230 miles north-north-west is the nearest other land. Torrential streams are the principal fresh water habitats. Fourteen sample stations examined during the southern summer of 1955–56 yielded only 8 species of aquatic animal. Five are discussed individually. Three have also been recorded from fresh water on Tristan da Cunha: 2 are marine species not previously recorded from fully fresh water. Carnivorous species appear to outnumber the others, and also to range most widely. Various non-aquatic food sources seem to be available for them. The most abundant individual species is however the Ephydrid dipteran Dimecoenia tristanensis, whose larvae feed on diatoms and algal filaments. There is no clear evidence that any aquatic species is especially dependent on any other: distribution appears to be related directly to habitat factors. The aquatic fauna of the island seems to have been recruited from immigrants arriving at very different times. The fauna appears typical of such habitats on remote islands.