Fish fauna in Bharathapuzha under severe threats, warn scientists

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A view of Bharathapuzha (Image Credit: Wiki Media Commons/ Jjvellara)

Implement urgent conservation efforts or the rich and endemic fish wealth in the largest river in the Western Ghats of Kerala will remain only on papers, warns a new assessment on the threats to the fish diversity in the Bharathapuzha River, locally known as River Nila.

Through a survey on all the four major tributaries of the Bharathapuzha River system - Gayathripuzha, Chitturpuzha, Kalpathipuzha and Thoothapuzha – the study recorded 117 species of fishes in Nila with the highest species richness from the stretch between Parali to Purathur estuary. Among this, 33 are found only in Western Ghats and three are found only in Bharathapuzha River system. 

A group of researchers including A Bijukumar, Department of Aquatic Biology and Fisheries, University of Kerala, Siby Philip from Department of Zoology, Nirmalagiri College, Koothuparamba, Anvar Ali and Rajeev Raghavan from Conservation Research Group, St Albert’s College, Kochi and S Sushama from Department of Zoology, NSS College Ottapalam carried out the study which is published in the Journal of Threatened Taxa.

Top Ten Threats to River Nila

Despite the richness, the river system of River Nila is under threat from human interference, says the study which is published in the Journal of Threatened Taxa. “Several anthropogenic stressors including deforestation and loss of riparian cover, dams and other impoundments, pollution, sand mining, non-native species, climate change and destructive fishing practices are threatening the fish diversity of Bharathapuzha River system”, it says.

Threat #1: Sand mining

Most notorious, most widely known but most rampant, despite being regulated (encouraged ?) by the il-legal machinery. If we number the threat based on the calamity it brings, this one goes to top. The study marks the region between Pattambi and Thiunavaya as the superhot stretch of legal and illegal sand mining. Studies conducted by CESS in 1997 itself has shown that the rate of sand mining is way too above the rate of sand generation in Nila. For many fishes in Nila, Sand is the breeding substrate, and is the single crucial link that supports the aquatic food web. With the indiscriminate sand mining, it is just a matter of time for fishes like Glossogobius giuris and Sicyopterus griseus to vanish from Nila forever, warns the study.

Threat #2: Dams and impoundments

Known fact: Big dams are a major threat to the rich and endemic fish diversity of Nila, since they change the turbulence of the river causing high sedimentation and other problems. Lesser Known fact: Dozens of smaller check damk dams across Nila are also doing the same. Bigger dams are fixed in number so far – Nila has 11 irrigation dams. Impoundments are still proliferating, turning out to be a lesser noticed diversity killer in Nila. It has severely affected the movement of certain fish species and is believed to be a reason for the near absence of eels in the river system.

Threat #3: Pesticide pollution

When it comes to a River system like Nila, don’t think it is just the factories that are pushing chemicals to the water. River basin dependent extensive agriculture and plantations are also contributing their fair share to polluting this blood line of middle Kerala. Chemical fertilizers, pesticides, chemical nutrients, weedicides, you name it. The resulting eutrophication- the facilitation of aquatic plant growth which in turn decreases the available oxygen in the water, killing the aquatic fauna- is a major issue, especially from Chamravattom to Purakkad, says the study.

Threat #4: Urban sewage

Read Pattambi. According to the study, the town of Pattambi which falls under the Palakkad District of the state of Kerala is a major source of urban sewage which pollutes the river extensively, taking over the pollutant cocktail made by the agro-pollutants. “The urban sewage canals directly open into the river, through which the municipal waste is dumped. Such large scale pollution not only degrades the habitat but also causes endocrine disruptions and several other physiological imbalances in fish including breeding failure which could ultimately lead to their extirpation”, says the study.

Threat #5: Deforestation

According to the study, deforestation in its catchment areas like Mangalam, Nelliyampathy, Walayar, Malampuzha, Nellipuzha, Dhoni and Kalladikode is a major threat. The loss of natural native vegetation has triggered the invasion by exotic plants. Not only that the fishes loose a food resource, the high sedimentation rate due to deforestation is changing the natural composition of the river bed. It makes survival difficult for many endemic loaches in the river since they use the pebbles in the river bed for breeding.

Threat #6: Lime stone mining

Lime stone mining is rampant in certain areas of the catchment of the river, says the study. This is especially prominent in Malampuzha, part of the Kalpathipuzha tributary. The study claims that the lime stone mining in the catchment areas is leading to pollution and siltation in the stream. Apart from triggering an unnatural rise in the silicate content in the water, the dumping of mining debris also damages smaller streams in the system like Seemanthinipuzha.

Threat #7: Alien species

The study has spotted at least six non-native fish species in Nila. While three of them were non-native to Indian rivers, three were from the Gangetic plains. Though the Indian major carps were introduced as part of aquaculture, considered as a success, the study was able to spot them from lower reaches of the river, revealing that they have proliferated though the river beyond their actual reservoirs. Such proliferation of non-native species often wipes out native species in the fight for resources. Species foreign to India like the Nile Tilapia and Mozambique Tilapia were also spotted from Nila, showing that the alien invasion is possibly stifling the endemic fish fauna of the river. However, the surprise factor was that the study reportedly failed to fetch another notorious alien species – African catfish- which is a known diversity killer in Western Ghats Rivers.

Threat #8: Climate change

Studies conducted in 2010 and 2011 discovered that the temperature in the Bharathapuzha basin has been on the rise for a 36 year period from 1969 to 2005. Moreover, rainfall data shows that the Nila watershed gets less rainfall than the state average. Though the temperature rise is often cited as an impact of climate change phenomenon and the increasing anthropogenic pressure in the river banks of the Nila, its effect on the biodiversity of the river system is scarcely studied.

Threat #9: Aquarium fish trade

 Comes in many colours –state supported as well as clandestine. This greed trade is especially wiping away endemic and beautiful fishes like Miss Kerala (Sahyadri denisoni) and Mesonoemacheilus remadevii, the latter being found only in river system in Silent Valley which is part of the Bharathapuzha River System. As per a recent study, Miss Kerala has been found to be collected in massive amounts from Thoothappuzha tributary for pet trade.

Threat #10: Destructive fishing practices

Last, but not the least, as always. Poisoning, use of mesh nets and dynamiting – small effort, good catch. Though traditional fishermen abstain from practices like dynamiting, it is raising a major threat to the fish diversity in the tributaries where the traditional fishermen are lesser in number, warns the study.

Action Time: Conservation Points to save Nila

• Prioritizing integrated watershed programmes.
• No more new medium or big dams, cautious about new check dam proposals.
• Channelize district River Management Fund to Eco restoration of stretches of Nila.
• Regulation of sand mining has been proved to be futile. So finding an eco-friendly alternative to sand is the only option left. But that will be like legalizing marijuana- you have to first convince the cartels before you convince the government. (They will have to take it, since the sand is running out and the weed is on the rise).
• Beg people not to use pesticides or agro-chemicals near the river bed cultivations (otherwise also).
• Regulate large scale riverbed cultivation.
• Establishing Aquatic Biodiversity Management Zones (ABMZ) to conserve river stretches known to shelter endemic and rare fishes.
• Regulate the greed pet trade and destructive fishing practices, not to say dynamiting.
• Above all, let people know – ask them, request them, beg them, threaten them – You may go the extreme since water is the life blood of the green earth, as River Nila is for Kerala.

Fighting the aliens at Periyar Tiger Reserve

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Periyar Tiger Reserve (PTR) is not just a safe haven for the tigers, but for some aliens too, in the ecological sense. African cat fish (Clarias gariepinus), one of the most dangerous invasive alien species, is lurking in the Periyar Lake, raising serious threat to the rare fishes found only in Periyar, say researchers. To bring a twist to the story, PTR is going to have the first of its kind action against exotic fish species in Western Ghats as a group of researchers and activists are aiming to manually remove African cat fish from Periyar with public participation.

African Cat Fish (Clarias gariepinus)
Image Credit : W.A. Djatmiko (Wikimedia Commons)

According to Conservation Research Group- a research and activist platform based in St Albert’s College in Cochin- which organises the exotic fish removal campaign at Periyar Tiger Reserve, the endemic fishes found in the Periyar Lake are severely threatened by the biological invaders like African Cat fish, which inspired them to organise such a crusade against the alien fish species of PTR.  “Eight endemic fishes in Periyar Lake are fighting for survival as their only remaining habitats are threatened by several stressors of which biological invasion is the most significant one.”, says an official statement from the group.

Importance of Fish fauna in Periyar Lake

An on-going Rufford Foundation supported project to study the impact of alien species in Periyar Lake points out that the fish fauna in the Lake are very unique and valuable. “It (The Lake) holds the only remaining population of six globally threatened endemic fish species viz. Crossocheilus periyarensis, Garra periyarensis, Hypselobarbus periyarensis, Lepido pygopsistypus, Nemacheilus menoni and N. Periyarensis”, it says. According to an IUCN report on the Status and distribution of freshwater biodiversity in the western Ghats, Lepido pygopsistypus  is the only member of its subfamily of snow trout fishes to be reported from south of Himalayas.

According to the researchers, there are four exotic fish species found in Periyar Lake which comes under the reserve among which African Cat fish is the most dangerous one when it comes to threat to native species. Cyprinus carpio, Oreochromis mossambicus and Poecilia reticulate are the other exotic fish species found in the Periyar Lake Stream System (PLSS). Recent studies have indicated that the population of these exotic fish species are showing an increase which means that the threat to native species is growing. “C. carpio and O. mossambicus now dominate the fishery of Periyar Lake and are known to compete with endangered species such as L. typus and Crossocheilusperiyarensis”, says a recent study report issued by IUCN.

The invasive species have swept away many native fish species found in the lake earlier. During the last 50 years, at least 16 fish species earlier found in the lake has disappeared, say researchers.

Fighting the Aliens

African Cat fish in Periyar Lake and other freshwater ecosystem in Western Ghats is the usual story of an introduced species turning viral threat to native species. African Cat Fish was once widely used as a farm fish in Kerala and elsewhere for its rapid growth. It soon became very popular with its ability to survive in a range of water qualities and to devour anything from slaughter house waste to standard fish foods. However, the alarm started ringing when some of them have escaped through the natural water channels from fish farms during monsoon and reached the fresh water systems in Western Ghats. 

Exotic Fish removal campign at Periyar Tiger Reserve

The IUCN report has suggested that “the biggest future challenge to fish conservation in PLSS will be the management and control of C. gariepinus, whose opportunistic strategy and ability to establish large and persistent populations makes it an imminent threat.”

To fight the alien menace, a workshop conducted by researchers and forest officials at PTR in December 2012 has decided to take pro-active action against the invasive species. Field work has revealed high population of African cat fish in the canal draining into the Lake. The authorities and researchers are planning to net out the exotic fishes from the canal and manually remove the exotic fishes from the Lake. The organisers of the event were not available for immediate comment. However, according to an official invitation, the programme is scheduled on April 29^th and 30^th of this month. 

African catfish, Clarias gariepinus – a major threat to native fish species in Western Ghats Rivers

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African Mushi, that is what the farmers in Kerala called that beefy fish, which guaranteed profit for meager investment and care. It ate anything from wastes from slaughter houses and was able to live in any type of water qualities. Moreover, the fish grew faster and bulkier. Within months, a harvest will fetch you kilograms of fish meat from an average fish pond.

Clarias gariepinus

But the after effects were horrid. Recent research reports indicate that the fish has started appearing in fish catches from rivers and lakes in Kerala. Multiple reports suggest that this fish is now commonly caught by fishermen in the lower reaches of Periyar River in Kerala, which is known to house fresh water fresh species only found in Western Ghats Rivers.  Similar reports also indicate that the fish is present in the commercial catches from the Periyar Lake also.  

The writing on the wall is clear. The fish has escaped from fish farms which were connected to natural water bodies and have proliferated in the Western Ghats Rivers and other water bodies in the area. The species is known to devour and sweep away native fish species and other aquatic organisms locally.

The issue is not restricted to rivers in Kerala. It is reported that this invasive fish has also reached the Indrayani River in the southern Deccan Plateau eco-region. It presently raises serious threat to the only existing population of rare Sisorid catfish Glyptothorax poonaensis found in India. Sisorid catfish is listed as endangered by IUCN.

According to IUCN, the southernmost region of the Western Ghats Rivers house more endemic and lesser known fishes in the region. Unfortunately, the devouring African Cat fish has infected the same parts.

Abundance of Globally Threatened fish species 

in Western Ghats Rivers. It can be seen that they are 

more found in the Southern region.

Experts have also expressed concern over the impact of the presence of this African catfishes on lesser known subterranean fishes in Western Ghats. Ichthyologists were able to record just six to seven species from these enigmatic fishes which live in a subsurface ecosystem found under the laterite foot hills of Western Ghats. The chances of the African Cat fish eliminating many of these enigmatic creatures even before the researchers are able to spot and record them are not rare.

There is an urgent need to restrict the aquarium trade and unregulated fish farming. Educating buyers and farmers as well as formulating a proper policy for the management of invasive species are exigencies in this regard. 

Presence of Invasive Species in Western Ghats Rivers: A Major threat

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Western Ghats is the catchment area of 3 large rivers, 13 medium and 17 minor rivers which play a crucial role in the rich biodiversity of the region and the prosperity of some 105 million people living in the area. However, these blood lines of the region are under threat mainly from the burgeoning anthropogenic factors in the name of development and flawed policies.

Abundance of Globally Threatened fish species in the Western Ghats Rivers

According to an in-depth study report submitted to the Western Ghats Ecology Expert Panel about major threats to the riverine ecosystem in the region, dams, mining, tourism, pollution, flawed agriculture practices and deforestation of the riparian cover (forest patches along the river banks) are causing visible degradation to the riverine ecosystems in this World Heritage site. However, K. A. Subramanian who made the study also includes the presence of alien species in the riverine ecosystems in the region as another threat.

Alien species, despite their name, do not come from another planet, but are introduced from non-native ecosystems often for agricultural purposes, as ornamental organisms or even as biological controllers. IUCN has identified introduction of invasive as one of the possible reason for the population decline of native organisms.

Invasive Plant Species in Western Ghats Rivers

Many of the aquatic invasive species in streams and water bodies in the Western Ghats like Salvinia molesta, Pistia stratiotes, Eichhornia crassipes, Hydrilla and Ipomea fistulosa were first introduced as ornamental plants in aquariums. They later found their ways to the water bodies, now spreading to almost all rivers in the Western Ghats.

The changes in the flow pattern and excessive pollution have also helped in the spread of these weeds, especially in catchments which are reeling under the pressure of populated areas. By spreading over the water, they clog the flow of the stream and increase the rate of sedimentation. They cover the water surface, often without allowing the sunlight to pass through, eventually wiping away the submerged species of plants by blocking their chances of photosynthesis.

Mikania macarantha – a Green Threat to the Riparian Biodiversity

Mikania macarantha, is a similar weed which raises serious threat to other plant species in the streams and riparian ecosystem of the rivers in the Western Ghats. This plant forms a thick layer over the stream and the associated riparian forest blocking the sunlight. 

Mikania macarantha, an invasive plant in WG rivers

It is often observed that the invasion of the Mikania macarantha is closely connected to the presence of degraded riparian forest patches in the course of the stream. For instance, in many places like Agasthyarmalai and Anamali region, the weed has been observed as first colonizing streams using degraded shores in estates and forestry plantations, gradually invading into the healthy riparian cover in the adjacent forest areas in the upstream gradually degrading them over a period f time.

Exotic fishes: friend- turned foes?

Exotic fishes are another destructive species which is raising serious threat to native organisms in the Western Ghats Rivers. Introduced for aquarium trade, fish farming and as biological controllers, they have invaded the rivers spreading all over the river network in the area.

Gambusia affinis was widely used as a biological agent to check the growth of mosquitos. However, their introduction to water bodies in the region paved their way to reaching Western Ghats wide river ecosystems. The species have now reportedly colonized many hill streams, especially in parts of Maharashtra. Though they don’t eat up each and every native species like some other invasive species do, they raise fierce competition for resources with native species, often wiping them away locally.

Clarias gariepinus

Clarias gariepinus, the notorious African catfish pet named African Mushi among fish farmers in Kerala and neighboring states, has made a bad example of bringing in foreign species for increased production.

According to an IUCN report on threats on fish diversity in Western Ghats Rivers, Cyprinus carpio, Oncorhyncus mykiss, Pangasianodon hypophthalmus, Oreochromis niloticus, O. mossambicus, Osphronemus goramy, Pterygoplichthys multiradiatus, Piaractus brachypomus, Trichopodus trichopterus, Xiphophorus maculatus, Poecilia reticulata and Gambusia affinis are listed as major invasive threats.

Among these, C. carpio, O. mykiss, G. affinis and O. mossambicus are listed among the top hundred worst invasice alien species database. According to IUCN, these dangerous species are more present in the Southernregion of the Western Ghats where the endemism is highest compared to other areas.

Absence of a national policy for managing invasive species

According to the report submitted to the Convention on Protection of Wetlands, Government of India admits that presence of invasive species has been raising serious threat to the conserved areas in the country. The document also admits that there is no management policy or guidelines issued in this direction. But the government should take immediate actions to make a management policy to check more invasive species reaching to the pristine ecosystems and degrading them gradually.