alien and invasive freshwater fish species in iran: diversity, environmental impacts and management

more than 32 alien (exotic) fish species belonging to 10 orders and 12 families (cyprinidae, gobiidae, salmonidae, anguilidae, mugilidae, centrarchidae, heteropneustidae, gasterosteidae, cichlidae, poecilidae, adrianichthyidae and pleuronectidae) were reported from iran of which 25 species are confirmed by specimens. some of the alien fishes (e.g., cyprinus carpio , carassius auratus , pesudorasbora parva , xiphophorus hellerii and gambusia holbrooki ) have already established breeding populations, acting as invasive species. some others are regularly stocked by the iranian fisheries company (e.g., hypophthalmichthys molitrix , hypophthalmichthys nobilis , ctenopharyngodon idella ) and few others are occasionally recorded from natural waters. amatitlania nigrofasciata and tilapia zillii are two alien cichlids recently reported from iran. aquaculture, sport fishing, control of malaria, ornamental purposes, research activities, demonstration in national fairs and accidental introduction are the main reasons for these introductions. pseudarasbora parva was introduced accidentally along with other exotic carps and now is widely distributed in inland waters. the intentional introduction of alien species is an extraordinarily complex issue and requires taking into account a broad number of variables. understanding the risks that alien species, especially aquatic invasive species (ais) pose, comparative studies on the ecology and life history strategies of the introduced and invasive species and closely related indigenous species with similar ecological life traits, monitoring the rate of invasion, and the causal relation between population dynamics and species invasion and public awareness, could be effective management strategies to minimize the bio-invasion impacts.