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Invasion in our Rivers Text: Unmesh Katwate, Deepak Apte, and Rupesh Raut W trade and bio-control of mosquitoes are major ‘vectors’ of non-native exotic fish species. Cumulative impacts of exotic fish species are resource competition and predation and niche overlap that results in an ecological havoc, like species extinction. West flowing rivers of the northern Western Ghats are its least studied biomes. While exploring rivers of northern Western Ghats in December 2011 at Gadhi river in Panvel, Maharashtra, we angled a huge pomfret-like silvery fish, later identified as Red-belly Pacu Piaractus brachypomus. Subsequently, we collected eight full grown Piaractus brachypomus in the main river channel. Pacus are commonly found in aquarium shops and have a high demand in the international aquarium trade. Detailed investigation revealed that in Panvel area Red-belly Pacu were commonly preferred for aquaculture. It is likely that the presence of Pacu in the wild is from an accidental release of aquaculture stock. Interaction with local fishermen revealed that sighting of Pacus increased from 2010. Incidentally, locally known as Riverine Pomfret, Pacu are now commonly sold for food. UNMESH KATWATE estern Ghats, a biodiversity hotspot harbours a rich freshwater fish diversity, which currently totals 290 species. With around 189 species, the endemic freshwater fish fauna of this region is remarkable. The IUCN Red List assessment of freshwater fishes of the Western Ghats indicates that the native and endemic fish fauna are far more threatened than the non-endemics. Around 97 freshwater fish species of the Western Ghats were found to be Critically Endangered, Endangered or Vulnerable. Deforestation, drainage alteration, pollution, increased urbanisation and industrialisation, damming, fishing and overharvesting, the major threats, ensure that this list continues to grow. Besides these, invasive alien fish species are one of the emerging potential threats to the natives of the Western Ghats. Invasives are found to be the second major cause of extinction of endemic and native species around the world. Catastrophic impacts of invasive fish species in the Western Ghats are well documented, but their ecology is poorly studied. Increasing trade of aquaculture, international ornamental aquarium fish Diverse tributary of Arjuna river at Ratnagiri northern Western Ghats 42 H O R N B I L L April-June, 2012 April-June, 2012 Red-bellied Piranha Pygocentrus nattereri is popular in the aquarium trade UNMESHA KATWATE Another predatory alien species – Red-bellied Piranha Pygocentrus nattereri – was recorded by our co-researchers later from the same area. Aquarium trade is possibly an important vector for its release in rivers and associated streams of Panvel area. Piaractus brachypomus and Pygocentrus nattereri are Amazonian natives found in Colombia, Venezuela, Peru, Bolivia and Brazil. Introduced populations are thriving in various parts of the world, mainly in Far Eastern countries, such as China and Taiwan wherethey are farmed for food. Pacu and piranhas are shoaling fishes and always occur in big shoals in the wild in the Amazon. Based on gut content analysis, some researchers report that pacus and piranhas are herbivores, but it is well-known that at least piranhas are voracious predators. Nibbling fins and scales, biting and giving strong competition for food resources is common behaviour of pacus and piranhas. The Red-bellied Piranha was first introduced in Kerala for aquarium trade in 1999. Recently, in 2011, a scientist recorded it in Periyar river of Kerala, and in Dimbhe reser voir near Pune, Maharashtra, far north in the Western Ghats. Multiple cases of bio-invasions have been recorded in this hotspot, and pacus and piranhas are the new competitors in the race for survival of the Western Ghats fish. A classical and well-known example is that of the African Catfish Clarias gariepinus. An escapee from aquaculture practices, it now dominates most of the river systems of the Western Ghats. The exotic C. gariepinus is a regular in the fish catch of Periyar lake, Kerala. The introduced population of Amazonian Pacu in the tropical waters of Chalakkudy river is also established and reproducing well. Recent studies on the endangered Glyptothorax poonaensis, in Indrayani river, indicates that the African Catfish may pose a serious threat to its AJINKYA SAWANT CONSERVATION NOTES The sharp-toothed predatory, Amazonian Pacu creates resource compeition for the native species HORNBILL 43 UNMESHA KATWATE CONSERVATION NOTES An invasive, the African Catfish Clarias gariepinus is spread all over Western Ghats and competes strongly with the native species Poecilia reticulata are known to threaten the native Aplocheilus lineatus population because they share the same niche. Oreochromis mossambicus – listed in the ‘100 of the World’s Worst Invasive Alien Species’ – has already spread in most rivers of the Western Ghats; several cases of its invasion have been recorded from different parts of this area. At times, fish like Catla catla, Cirrhinus mrigala and Labeo rohita, native to the Ganges river system, are introduced in greater numbers for mass aquaculture practices. It is assumed that these species will not breed in the ecological conditions of rivers in the Western Ghats. However, our recent collection of juveniles of C. catla and breeding males and females from Kundalika river, Maharashtra, indicates that they are breeding easily in our rivers. Our recent studies in the river systems of Raigad district, northern Western UNMESHA KATWATE existing population. Alien aquarium fish species introduced purposely or accidentally into natural waterbodies may adversely affect native fish species by way of genetic impacts, disease introduction, and catastrophic ecological impacts, such as predation, competition and environmental modification. Aquarium fishes like Sword-tail Xiphophorus helleri, Platy Xiphophorus maculatus and Guppy Gambusia affinis, Sun Catfish Horabagrus brachysoma, an endemic of the Western Ghats is threatened by the increasing load of invasives and exploitation of wild stock for international trade 44 H O R N B I L L April-June, 2012 UNMESH KATWATE CONSERVATION NOTES Ghats, suggest that exotics are one of the major threats for the endemic fish fauna of this region. We have recorded nine exotic ‘pest’ fish, i.e. c. 13% of the total fish fauna. In more than 20 provinces of United States countries pacu and piranha are legally banned for aquarium trade and aquaculture because of their deleterious impact on native fish fauna and ecosystems. Nationwide invasive fish species eradication programmes are needed in India to sustain our precious freshwater ecosystems. Education, awareness, and spread of scientific knowledge among locals, aquaculturists and aquarium traders will hopefully control exotic species dispersion in the wild. Strong rules and regulations should be set for selection of fish species for aquaculture practice. Use of endemic species should be promoted for aquaculture instead of exotic varieties, reducing the ecological loss of natural ecosystems. Awareness about catastrophic ecological impacts of exotic fishes among aquarium stakeholders, shopkeepers and buyers will prevent Unmesh Katwate is Scientist – A at the Bombay Natural History Society. April-June, 2012 UNMESH KATWATE (L): Melon Barb Dravida fasciata is a beautiful native barb of the west and east flowing rivers of southern India (R): Filament Barb Dawkinsia filamentosa is an endemic barb of peninsular India The vulnerable Ratnagiri Minnow Parapsilorhychus discophorous is endemic to the northern Western Ghats further loss. Captive breeding programmes of native aquarium fish species may reduce exploitation of the wild stock and minimize use of exotic varieties. Scientific monitoring of spread of invasive alien fish species to implement and achieve conservation goals is the need of the hour. Effectively implemented Deepak Apte is Deputy Director, Conservation, at the Bombay Natural History Society. policies are needed to control spread of exotic alien species in global biodiversity hotspots. Recent records of predatory pacus and piranhas have set the alarm bells ringing for ecological havoc in the Western Ghats biodiversity hotspot. Should we ignore them for now or act before it is too late? Rupesh Raut is Head of the Zoology Department, Elphinstone College, Mumbai. HORNBILL 45