With cascading waterfalls and as many as 103 rivers, all major groups of vertebrates can be found in Sri Lanka. Of these, the highest endemic species are found in the amphibian and reptile group. Most of the 107 species of fish are found in marsh and river dwelling. The 39 endemic species – the Carplet group – being restricted to the perennial streams of the wet zone. The British introduced trout into the clear, cold streams of Horton Plains. Of the 54 species of amphibians, 33 are endemic to the island. According to ongoing research, the largest number of endemic amphibian fauna in the world may soon be found in Sri Lanka. One endemic genus, the Nannophyrus, with three species, is common in the wet zone living on rock ledges, covered by a continuous trickle of water, and sharing the same habitat with tadpoles.