Inland Fisheries

3.1.2.1 Adaptations of fishes of rhithron zones

The resident fish species in rhithron zones are entirely rheophilic and fall into two main groups.

· Those species which live on or among the rocks and vegetation of the bottom and are distributed mainly in the riffles. These are of small size and are adapted to grip or cling to the substrate. Such adaptations include mouth suckers, for instance Chiloglanis, ventral friction pads as in Astroblephus or pectoral fin spines adapted as hooks as in Glyptothorax. Other species such as Mastacembelus have long sinuous shapes that enable them to twine among the holes in the rocky bottom.

· Those species such as Barbus or Salmo which are adapted to swim sufficiently fast as to resist the current and even move against it. This they cannot do on a sustained basis, however, and frequently take advantage of cover provided by the slack water of the pools and by snags, overhangs and other features which disrupt the current. Because of the severity of the habitat diversity of resident species tends to be low.