Inland Fisheries

7.1.5 Ecological adaptation

The coldwater fishers often endowed with great powers of locomotion.

Such species have streamlined body.

The occurrence and distribution of coldwater fishers in addition to temperature, are also dependent upon the swiftness of current and nature of substation and plant and animal communities present or available in the bottom.

Majority of coldwater fisheries possesses structures especially adapted for clinging borrowing or otherwise to withstand fast water currents.

The variable features of environment have induced remarkable made fixations among coldwater fishes, both externally and internally. Normally there is little food available in hill stream for resident fish species. Coldwater fish species have acquired modifications of mouth suitable for rasping encrusted organisms and boulders. The modification of lips for removing periphytic organism is well seen is snow trout, mahseer and certain minor carps.

Another characteristic feature of coldwater fish is their adaption to living in highly oxygenated water available in torrential streams of mountains. Such oxygen rich environment has induced structural modification in organs of respiration also. Owing to richness of water in its oxygen content, the gill opening have narrowed and gill themselves are greatly reduced so much so that such fishes cannot survive for long in waters poor in oxygen.