Comparison of the Fish-Faunas of the Northern and the Southern Faces of the Great Himalayan Range

SUMMARY

Attention is directed to the conclusions reached by Day and Stewart as a result of the comparison of the fauna on the northern and southern faces of the Hilamayan range. From a critical examination of the fish of Central Asia and of India evidence is adduced in support of the earlier conclusions that the two fish faunas are very distinct from each other. The physical factors governing fish life in Central Asia and on the southern face of the Himalayas are discussed and it is shown that the fish of the two regions are adapted to suit the nature of their respective streams. The characteristic features of the two fish faunas are examined and their close correlation to environmental factors is indicated. The probable origin of the two faunas is described and it is shown that though the Central Asiatic and the Indian faunas are derived from the same source in south-eastern Asia, especially Yunnan, the former probably became differentiated at an earlier age when the parental stock was of a generalised nature, whereas the fauna of the southern face of the Himalayas was derived from a younger and more vigorous stock which had already become specialised in southeastern Asia for life in torrential streams.