Aliens; a catastrophe for native fresh water fish diversity in Pakistan.

Abstract

Pakistan has introduced several alien exotic fish species e.g. grass carp ( Ctenopharyngodon idella ), bighead carp, (Hypophthalmichthys nobilis ), silver carp, ( Hypophthalmichthys molitrix ), common carp ( Cyprinus carpio), gold fish (Carassius auratus),and three species of tilapia ( Oreochromis aureus, Oreochromis mossam bicus, Oreochromis niloticus)in warm watersalongwithtwo trout species: the rainbow trout ( Onchorynchus mykiss) and the brown trout (Salmo trutta fario ) in colder regions for specificpurposes like sport fishing, yield enhancement and biological control of aquatic weeds andmosquitoes. The exotic species arebecoming invasive in the freshwater biomes of the Punjab and other provinces of Pakistanby reason oftheirpotent reproductive po tential and feeding competitions with the native freshwater fish fauna. Resultantly the native fish species viz; Channa marulius, Wallago attu, Rita rita, Sperata sarwari, Gibelion catla, Cirrhinus mrigala andLabeo rohita,which are of economic value areunder threat.