Kumarakom Vembanad Lake

This is the largest backwater in Kerala. It is part of Vembanad-Kol wet land system, which extends from Alappuzha in the south and Azheekkode in the north and measures 96.5 km south to north. Each portion of the Kayal (lake) has its own local name like Kochikayal, Vaikom kayal etc. This wetland system (Vembanad – kol wet land system) was declared as a new Ramsar site of international importance in Kerala along with Ashtamudi wetland and Sasthamkotta Lake during the 8th meeting of Conference of the Contracting Parties (COP8) held at Valencia of Spain from 18th to 26th November 2002.
Vembanad wet lands _ A new Ramsar site

Wetlands are among the most productive life-support systems on earth and their conservation is important for biological, hydrological and economic reasons. They provide essential habitats for hundreds of species of waterfowls, fishes, amphibians, reptiles, mammals and plants. They act as natural sponges that control floods and droughts.

In spite of their valuable functions, wetlands in many parts of the world have been destroyed at an alarming rate in recent decades by drainage, land reclamation and pollution. To stem this tide of destruction, a series of international conferences and technical meetings were held in 1960s, mainly under the auspices of the International Waterfowl Research Bureau (IWRB). As a result of these discussions, the Convention on Wetlands of International Importance Especially as Waterfowl Habitat was drawn up and was eventually signed on 2 February 1971 in the Iranian town of Ramsar (hence the name “Ramsar” by which the convention is commonly known and hereinafter referred to). Ramsar came in to force on 21 December 1975.

Initially there were 36 parties to the Convention and 294 wetland sites covering almost 20 million hectares are in Ramsar’s “List of wetlands of International Importance”. Later new parties and new sites were added.
The preamble to Ramsar states that the objective of the convention is “to stem the progressive encroachment on and loss of wetlands now and in the future”. Article 2(1) defines wetlands as `areas of marsh, fen, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salty, including areas of marine water the depth of which at low tide does not exceed six meters”, which may also include adjacent riparian and coastal zones. This is a very broad definition, and Ramsar therefore aims to stem encroachment on habitats as diverse as mangrove swamps, peat bogs, water meadows, coastal beaches, coastal waters, tidal flats, mountain lakes and tropical river systems. To achieve its objective, Ramsar seeks to promote the wise use of all wetlands and special protection for wetlands in the “List”. It also encourages research into wetlands and their fauna and flora, seeks to promote the training of personal competence in the fields of wetland research and management, and requires Parties to cooperate in implementing their obligations under the Convention.

The Vembanad -Kol wetland system is a continuous chain of lagoons or backwaters 96 km long, is one of the largest estuarine systems in Kerala. Ten rivers feed the Vembanad-Kol wetland system. All these rivers originate from the Western Ghats, flow westwards through the wetland system and join the Arabian Sea. The wetland is typically divided into two distinct segments, the fresh water dominant southern zone and salt-water dominant northern zone. The estuarine zone and organically rich sedimentary substratum of the inshore region makes it a highly preferred and desirable habitat for breeding of shrimps. Vembanad is renowned for its live clam resources and sub-fossil deposits. Now the name Vembanad Lake applies to the stretch of 60 kms from Thanneermukkom bund to Alappuzha.
Four rivers namely Meenachil (basin area 1250 km2 length 78 km.), Manimala (850 km2, 90 km.), Pampa (2250 km2, 176 km.) and Achankoil (1500 km2, 128 km.) directly drain in to this lake. The lake has a maximum width of about 8 km and is about 3 to 8 metres deep.

About 23,105 ha. land has been reclaimed from the lake during 1834 _ 1984 amounting to 63% of the lake area. The reclaimed area was converted in to paddy fields and garden lands. The original area of the Vembanad lake was 36,329 ha and due to the reclamation the lake has shrunk to 13,224 ha, 37% of its original area. After the Second World War there was acute shortage of rice in the state. This paved the way for renewed reclamation programmes encouraged by the State Government.

The depth of the lake is reduced by 40-50% in all zones of the estuary except between Aroor and Wellington Island and Kochi port zone. The water carrying capacity of the system has been reduced to an abysmal 0.6km3 from 2.4 km3 with a decline of 78%.
Amongst the wetlands in Kerala, the Vembanad estuarine system, the largest of its kind on the west coast of India, is uniquely endowed with mangroves, waterfowl habitats, agriculture and fisheries. Being in confluence with rivers from Western Ghats and the coastal seas, this vast estuarine expanse has also been the favored nursery area for the rich coastal fisheries and fishing has been an important occupation of the people in these places. In effect, agriculture and fisheries have been the two most important attributes of these wetlands. Just as Kuttanad is described as the `rice bowl’ of Kerala, Vembanad wetlands have been acclaimed as the `Inland fish basket’ of the state.

Fish diversity in Vembanad

The Vembanad backwaters support some of the largest fishery population in the world. Fish fauna includes fresh water species and euryhaline species, capable of withstanding salinity variations. A total of 150 species of fishes belonging to 100 genera under 56 families including marine entrants were reported from this estuarine system in one study . However, on the southern sector, in later studies, only 38-40 commercially important fish species were encountered. The commercially important estuarine fish fauna in the backwater system is constituted by coastal species, freshwater species and truly estuarine species. Mullets (Thirutha/ Kanampu), Mugil sp, (Kalanchi)(Lates calcarifer), Milkfish (Poomeen), (Chanos chanos), Catfishes, (Tachysurus maculatus), Half beaks, (Hyporhamphus sp.), Kanni, (Megalops sp) and pearl spots, (Etroplus suratensis) have been the commercially important estuarine finfish species in the lake. Amongst these, mullets (Thirutha/ Kanampu) are planktonivorous and detritivorous, represented by Mugil cephalus and Liza parsia, the latter species being more tolerant to low salinity. Croakers, Daysciaena albida is Carnivorous, and has been found to penetrate in to upstream reaches. The pearl spot (Karimeen), the commercially most important omnivorous species is extremely tolerant to lower salinities, and this species now constitute over 27 percent of the total catches in the upstream portions of the lake. The breeding habitat of this species is unique, as this species utilize submerged substratum for egg attachment. Megalops cyprinoids (Kanni) and Lates calcarifer (Kalanchi) are almost saline water species while halfbeaks; Hyporhamphus xanthopterus and H. limbatus are truly brackish water forms occurring even in upstream zones south of the barrage during seasons when there is mixing of saline and freshwaters.
The dominant fish species in the freshwater zones are Amblypharyngodon mola (vayambu), Puntius filamentosus (Paral), Puntius sarana, and the catfish, Wallago attu (Attuvaala), Mystus malabaricus, Mystus oculatus, Horabagrus brachysoma, (Manjakkoori), Anguilla bicollar (Manangil), Labeo dussumierii (tooli/Pullan), Ompok bimaculatus, Heteropneusteus fossilis (Kaari), Clarias dussumeiri (Mushi), Mastacembalus armatus (Aarakan), Mastacembelus guentheri, Macrognathus guinteri, Xenetodion cancilla (Morasu), Ambassis dayi, Ambassis thomassi (nandan), Nandus marmoratus, Stenogobius malabaricus, Channa striatus (Varal), C.marulius (Cherumeen), and Anabas
testudineus (Kallada) and Tetraodon leopardus and Dayella malabarica. Catla catla (Catla) and Labeo rohita (Rohu) are late entries mostly got introduced from aquaculture systems.

Truly estuarine species, such as Tachysurus maculatus, Ambassis gymnocephalus, Gerres setifer, Gerres filamentosus, Scatophagus arrgus, Liza parsis, Glossogobius giuris, Daysciaena albida, and Brachiurus orientalis etc that were encountered in all zones of the lake have become extremely rare on the freshwater zones south of the barrage, consequent to the operation of the barrage. Etroplus suratensis is the only true resident estuarine species that thrives well even in the fresh water situation immediately south of the barrage, though reduced in incidence in the riverine areas up streams.

Fish varieties such as Strongylura strongylura, Platcephalus crocodilus, Therapon jarbua, Sllago sihama, Lutianus argentimaculatus, Mugil cephalus, Liza macrolepis, Cynoglossus punticeps, Leiognathus brevirostris, Leioggnathus equlus etc have been restricted to high saline zones in the lake and are extreme rarities even in locations immediately downstream the barrage. Euryhaline species that occur in the mixing zones in the lake are Megalops cyprinoids, Mystus gulio, Tachysurus subrostratus, Hyporhamphus xanthopterus, Hyporhamphus limbatus, Etroplus maculates, Glossogobbius biocellatus and Ehirva fluviatilis. Euryhline marine species that used to penetrate in to the whole lake areas, viz., Dasyatis sephen, Elopes machnata, Nematulosa nasus, Stolephorus commersonii, Thryssa mystax, Thryssa purava, Chanos chanos, Platycephalus indicus, Lates calcarifer, Ambassis commersonii, Epinephalus tauvina, Lutianus johni, Drepana punctata, Eleutheronema tetyradactylum, Leiognathus splendens, Pseudorhombus arssius do not occur in the vast lake zones south of the barrage

Shrimps belonging to the family Penaeidae are represented by the most dominant, `Thelly’ Metapenaeus dobsoni followed by `Naaran’, Penaeus indicus, `Choodan’, Metapenaeus monoceros and rarely `Kara’, Penaeus monodon. Freshwater prawns of the family Palaemonidae in the wetlands are the `Kuttanadan Konchu’, Macrobrachium rosenbergii and M. idella, which thrive well in both brackish and freshwater zones. The other species of fresh water prawns reported from the lake are M idella and M. equidens. The edible crab, Scylla serrata is another commercially important crustacean species in the saline stretches, in northern zones but this species has almost totally disappeared from regions south of the barrage.
Similarly, the black clam, Villorita cyprinoides that support a lucrative lime shell and clam fishery is fast diminishing in the lake consequent to salinity exclusion and over exploitation. This species is of great economic importance as it contributes to over 90 percent of the natural lime shell production in the country and forms the resource base of several industries. The lime shell fishery in the Vembanad lake that ranks first in natural lime shell production is sustained mainly by the clam V. cyprinoides and to a smaller extent by Meretrix meritix and M.casta. The latter two species, restricted to the saline reaches of the estuary is also facing serious threats of depletion. The stock replenishment of the clam species is profoundly influenced by the salinity regime as lime shell clam, Villorita cyprinoides requires a salinity around 17-18 ppt for successful spawning.
The decline in biodiversity of inland fishes in this wetland is also attributed inter alia to unsustainable and unethical fishing practices such as poisoning, dynamiting etc in the river areas. Operation of madavala on the petti and para pumping system in polders of Kuttanad, prior to the annual punja rice season is yet another destructive fishing practice that brings about indiscriminate destruction of all sorts of fish species. The massive trapping and netting of spawner stocks with the onset of monsoons, clandestine introduction of exotics such as African catfish, Clarias garipineus, red pirhana etc are other threats to fish biodiversity in these wetlands.

Endangered endemics

The endemic carp of Central Travancore, Labeo dussumieri (Tooli/Pullan), the esteemed golden catfish of Kuttanad, Horobagrus brachysoma (Manjakoori), the riverine coldwater fish, Gonoproktopterus curmuca (Kooral), Wallago attu (Attuvaala), the glass perch, Parambassis dayi (Nandan), Macropodus cupanus, and Nandus nandus (Andikalli) are some of the endangered endemic varieties of these wetlands. The highly threatened endemic species in the fresh water reaches include Channa micropeltes (Manal waaha), C. leucopunctatus (Piliwaaha), Pristolepis malabaricus (Pannakarimeen), Ompok bimaculatus and Clarias dussumie (Mushi)

Conservation approaches

The State of the art of fish and fisheries in the Vembanad calls for concerted efforts for conservation of the endangered species by habitat protection and recruitment promotion and conservation. There is an urgent need to inventories biodiversity of the wetland covering the riverine zones so as to form a database on endemic species and to delineate biodiversity rich- regions. Precise information on breeding habitats, spawning and migratory behavior etc will go a long way in formulating action plans for protection of fragile habitats and species. Restoration of natural habitats or engineering of simulated spawning grounds is one of the suggested approaches for conservation. Development of hatchery and captive breeding techniques for extremely endangered and commercially important fish species is also essential for launching massive ranching and rehabilitation programs.
Habitat protection

A recent study conducted by the Regional Agricultural Research Station(RARS), Kumarakom indicates that indiscriminate destruction of submerged aquatic weeds in the open lake also pose threats to some of the endemic species in the lake. Shallow lake locations colonized by submerged floral elements such as Aponogeton appendiculatus (Kayippoo), are favored hideouts and habitat areas of giant fresh water prawns. Indiscriminate destruction of such shelter areas by operation of encircling nets, and peruvalai is detrimental to fishery resources.

Open lake fish sanctuary

In the context that the endemic fishery resources are stretched to its upper limits of tolerance, by man made interferences, over-exploitation, poor natural recruitment and habitat alteration, one of the suggested strategies to conserve the endemics is to protect biodiversity rich regions as `protected waters’ or develop `protected sanctuaries’ by engineering stimulated breeding habitats for promotion of natural recruitment. This will also aid to rejuvenate the declining fisheries. Under this approach, a protected `fish sanctuary’ for pearl spot (Karimeen), the first of its kind in the country was established in open Vembanad lake at Kumarakom on an experimental basis. A variety of `nest’ and `reef’ substrates were deposited on the floor of lake to provide artificial nesting surfaces for Karimeen. Half split coconut shells, large boulders of laterite blocks, specially designed cement concrete tetra pods and coconut piles were used as paaru and reefs simulating breeding habitats for fish, in this open lake sanctuary. The increased fishery recruitment and yield of fish, almost six fold, in the sanctuary zone during the succeeding seasons indicates that such attempts are viable strategies for conservation of endemic lake fish. With the increased availability of fish, the fish sanctuary zone in Kumarakom has also become favoured resting places for water birds.
Imposition of ban on undesirable exotics, observing of closed fishing seasons and forbidden zones, mesh regulation with active involvement of fishers, establishment of protected habitats and fish sanctuaries, and promotion of recruitment of endangered species through scientific ranching and release programs are some of the suggested strategies for conservation and management fishery resources in this wetland. Since environment restoration is the keystone for biological conservation, there is a dire need to establish the biological continuity of the wetland with adjacent coastal waters. The Vembanad wetlands can thus be restored again to its original status of Kerala’s `Inland fish basket’. (Padmakumar KG – 2003, Conservation of Fish Diversity in Vembanad Wetland, Kerala, RARS, Kumarakom).

Table – 4 Fishes from Vembanad lake

Compiled by Dr K.G. Padmakumar, Associate Professor, RARS Kumarakom

Fish Species

Sl. No. Scientific Name, Local Name

1. Etroplus suratensis, Pearl spot/karimeen
2. Etroplus maculatus, Pallathi
3. Scatophagus argus, Nachu karimeen
4. Presteolepis marginata, Panna karimeen
5. Labeo dussumieri, Tooli/Pullan
6. Horabagrus brachysoma, Yellow catfish/Manjakoori
7. Arius arius, Koori
8. Wallago attu, Aattuwaala
9. Hyporamphus xanthopterus, Kolan/Morasu
10. Xenentodon cancilla
11. Anabas testudineus, Kallada
12. Channa striatus, Varaal
13. Channa punctatus ,,
14. Channa marulius, Cherumeen
15. Channa micropeltus, Manal waaha
16. Channa leucopunctatus, Puliwaaha
17. Heteropneustis fossilis, Kaari
18. Anguilla bicolor, Manangil
19. Mastacembalus armatus, Aarakan
20. Lates calcarifer, Kalanchi
21. Lutjanus johni, Chempalli
22. Mugil cephalus, Tgirutha/Kanampu
23. Clarias dussumieri, Mushi
24. Chanos chanos, Poomeen / Milk fish
25. Caranx affinis, Vatta
26. Gerres setifer, Prachil
27. Megalops cundinga, Kanni
28. Synaptura orientalis, Nanku
29. Gonoproktopterus curmuca, Kooral
30. Catla catla, Catla
31. Labeo rohita, Rohu
32. Ctenopharyngodon idella, Grass carp
33. Cyprinus carpio, Common carp
34. Amblypharingodon melettinus, Vayambu
35. Puntius ticto, Paral / Kuruva
36. Puntius sarana
37. Puntius filamentosus
38. Puntius dennisoni
39. Puntius bimaculatus
40. Puntius fasciatus
41. Puntius vittatus
42. Aplocheilus lineatus, Poonjan / Manathukanni
43. Aplocheilus blockii ,,
44. Aplocheilus rubrostigma ,,
45. Osteobrama bakeri
46. Nandus armoratus, Antikalli
47. Nandus nandus ,,
48. Ambassis commersoni, Nandan / Glass perch
49. Ambassis dussumieri ,,
50. Parambassis thomassi ,,
51. Parambassis dayii ,,
52. Tetrodon travancoricus, Pufferfish
53. Macropodus cupanus
54. Barilius gutensis
55. Chanda nama
56. Danio malabaricus
57. Macrognathus guentheri
58. Glossogobius giuris Poolaan

Shell fishes
1. Macrobrachium rosenbergii, Aattu Konchu / Giant fresh water prawn
2. Macrobrachium idella, Koonan Chemmeen
3. Metapenaeus dobsoni, Thelli / Poovalan chemmeen

Molluses
1. Lamellidens sp. Freshwater mussel
2. Villorita cyprinoides Black clam
3. Meretrix meretrix Clam
4. Meretrix casta Clam