Irrawaddy Dolphin Population at Chilika Lake increases

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The population of the rare Irrawaddy dolphins (Orcaella brevirostris) at the Chilika Lake, Bhubaneswar in the Indian state of Orissa has increased, shows the figures released by Chilika Development Authority (CDA) after a recently concluded census of the dolphin population in the lake. According to CDA, the dolphin population in the lake has increased by 4.6 percent when compared to last year’s census figures.

Irrawaddy dolphin (Orcaella brevirostris)

Image Courtesy: Wikimedia Commons

     Irrawaddy dolphin (Orcaella brevirostris)

During the survey which has taken place from January 18 to 19 this year, teams were able to spot a total of 152 dolphins among which 118 were adults while 16 were sub-adults and 18 were calves and newly born dolphins.

Moreover, the survey teams have also sighted at least eight dolphins in the northern sector of the lagoon. According to experts, this sighting is an indication that the dolphin population in the lake is expanding the habitat.

The rate of presence of calves and neonates has also increased compared to last year’s figures. According to Ajit Patnaik, chief executive of CDA, there has been a 38.9 percent increase in the presence of calves and neonates in the lake.

Line transect method used for sampling

The survey has used the line transect methodology to assess the population of dolphins in the lake. According to sources at CDA, the survey used a total of 18 transects and the sampling in each transect were taken by teams of 7 to 8 members which had at least 3 experienced persons. 10 teams were deployed at the main lagoon while 8 teams at the outer channel and northern sector of the lagoon.

A view of Chilika Lake, Bhubaneswar, Orissa
Image Courtesy: Wikimedia Commons

A total of 130 persons from different organizations and institutions participated in the survey.  To facilitate smooth survey process with accurate sampling, the usual tourist boat services in the lake started operating only after the completion of the census process during the census days.

Geographic distribution of Irrawaddy dolphins

The survey results are a green signal as the population trend of these rare aquatic organisms, according to IUCN, is declining worldwide. At present, it is present only in Asian countries like Bangladesh, Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Viet Nam in addition to India. Chilika Lake is a brackish water lake which retains the only sizable population of this rare dolphin in India, which is categorized as Vulnerable by IUCN. According to IUCN, direct mortality from fishing, habitat fragmentation and habitat destruction due to human intervention are some of the major threats faced by Irrawaddy dolphins.

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.

Subterranean Eco System of Western Ghats – a Mysterious World Still Unexplored

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 If you think the wonder world of unknown fishes exists only in the dark trenches of the deep sea, you may be wrong. There are umpteen fishes and other aquatic creatures which live below the surface of the earth in groundwater tables often moving through the small cervices of the stones under earth’s surface.

Like their counter parts in the deep sea, these shy fishes rarely come out to light, so our knowledge is very much restricted about this hidden aquatic biodiversity. A recent study sheds some light into these lesser known subterranean fishes in India.

Horaglanis and Kryptoglanis - the Enigmatic fish genus of Western Ghats

Horaglanis Krishnai, The Indian blind catfish 

The members of the Horaglanis genus appear to have a prominent mouth at the anterior terminus of the head and transparent skins which reveals the blood vessels. One of the most noticeable feature is the pectoral fin changing into a vestigial bud and the terminal positioning of the anterior nostrils.

Interestingly, the fishes which were observed in laboratory conditions were found to be able to raise their heads up and down with the help of hinges at the Pharyngeal region( photo (a)). This is no mean feat since such an ability is absent in known fish species.

Two species of Horaglanis have been reported from India- H. Krishnai and H alikunhi, both from Kerala. H. Krishnai is distinct with its 23 fin-rays in the dorsal fin and the 16 fin-rays in the anal fin. Another species which is considered as H. inquirenda or species which is yet to identified, is also known and was reported from Kerala recently. This organism has the 20 fin-rays on its dorsal fin and the 15 fin-rays in the anal fin as their distinguishing marks visibly. 

 Kryptoglanis – a new genus to the world of subsurface fishes

 A new study has added Kryptoglanis, an unreported genus among catfishes to the acquatic fauna of India recently. Known as Middu in regional Malayalam, the first identified member of the genus is K. Shajii, spotted in Kerala.

Kryptoglanis Shajii

Members of Kryptoglanis genus can be identified with the absence of dorsal fin and the presence of barbels including the barbell pair on their nose. They have smaller subcutaneous eyes. Other facial features include superior mouth and a projecting lower jaw. They are reported to have fan like pectoral fins and a long based anal fin which is confluent with caudal fin. The caudal fin of the fishes in these species has less than eight fin-rays.

The second species identified from this genus is yet to be christened officially. 

 

Common features of aquatic creatures in subsurface ecosystems

All of these fishes have certain common characters including the absence of eyes and body pigmentation and can be found only in wells that are connected with underground water channels.

They lack of hard structures like spines or fin is a unique characteristic of these fishes that helps their movements through narrow rock cuts. Moreover, they show photophobia or fear for light - and like to stay in darker places. Since their skin is transparent, cat fishes of Horaglanis and Kryptoglanis genus have red colour. However the former changes their colour within hours of continuous exposure to bright sunlight.

Monopterus digressus

An earthworm like fish found from the similar ecosystem which belongs to Monopterus digressus is a typical example for the adapted physical characteristics for living inside congested stone cracks. No eyes, no fin elements, but just a membranous caudal fin tip. Body of Monopterus digressus is sub-cylindrical with no scales.

Experts suggest that such catfishes occur more in springs along the segmented valleys and wetlands in laterite foot hills distributed along the western periphery of Western Ghats. Based on their field experience, experts point out that artificial wells located on laterite hill slopes close to a wetland are places where there is a high chance of finding these enigmatic creatures. The lateritic geography under the earth surface here helps these creatures to move through narrow cavities in laterite stones.

Possible sub-surface ecosystem in Western Ghats?

New reports have spotted Horaglanis species even from 90 km away from the place where it was first spotted, indicating the presence of the fish along a larger area. Similarly, the new study also brings in the second report of M digressus, this time 115 km away from the first locality.

Though it is high time to jump into conclusions, the indications are enough reasons to believe that a sub surface ecosystem exist in the Western Ghats which spreads through a larger area and is almost impossible to explore due to its subterranean nature. 

Now watch a pair of Monopterus digressus in action after the break.

 

What Makes  Kryptoglanis different from other similar fishes?

(Photo Courtesy: Current Science Journal, Video Courtesy: Zoological Survey of India)

A new barb to Puntius sp. identified from Southern Western Ghats Rivers in TN and Kerala

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The endemic aquatic fauna of southern Western Ghats has got one more member recently, when researchers have identified a new barb belonging to the Puntius family of fishes from the streams in Kerala and Tamil Nadu. Christened as Puntius nigripinnis Sp., this new fish was identified from the streams of TamilNadu and Kerala.

Adult male Puntius nigripinnis sp.
collected from Kalindi river in Wayanad in Kerala, India
(collected by Rahul G. Kumar)

P. nigripinnis now adds to the more than a dozen variants of the widely distributed barb Puntius ticto. The major morphological difference P. nigripinnis has with other members of the P. ticto complex is the absence of barbels along with the presence of the last unbranched dorsal ray serrated.

This dark brown fish has a black band which forms a ring around the caudal fins. Being identified for the first time, it is now known to exist only from Moyar River range in Nilgiris and Kalaindi stream in Wayanad district of Kerala, both streams originating from the southern Western Ghats.

Location of the body spots are one major feature which makes the newly identified fish different from the similar looking close relatives. The humeral spot on this fish is on the 3^rd and 4^th scale of the lateral line while it is on the 4^th and 5^th scale below the lateral line for its close relatives like P. punctatus and P. muvattupuzhaensis.

Puntius nigripinnis sp.

Again the black ring is a distinguisher for P. nigripinnis. The large spot which is located on the 18^th and 19^th scales on the caudal peduncle which forms a band is not prominent in other members of the P. ticto complex. They exist as different spots in P. ticto, P. stoliczkanus, P. manipurensis, and P. pookodensis, making them visually different from P. nigripinnins.

According to a research paper published in the Journal OF Threatened Taxa, researchers and naturalists from Zoological Survey of India and Manonmaniam Sundaranar University has named the fish based on these properties, by coupling the Latin words ‘niger’ which means black and ‘pina’ which means fin. J D Marcus Knight, K Rema Devi, T J Indra and M Arunachalam conducted the study.

Currently known distribution of Puntius nigripinnis sp. nov. A - Kalindi stream in Wyanad (~ 11047’N & 7604’E); B - Kakkan Halla, Moyar River (~11034’N & 76049’E).

The new finding also indicates the richness of unexplored flora of Western Ghats and the importance to conserve it. Though conservation of terrestrial fauna has got popular acceptance, aquatic fauna is still under threat from indiscriminate fishing. Use of pesticides and agro chemicals in the upper stream fields of the Western Ghats Rivers also threaten endemic species like P. nigripinnis. 

Other members of the Puntius ticto complex.

P. punctatus

Puntius ticto

P. muvattupuzhaensis

P. phutunio

P. pookodensis

P. setnai