DR Ambedkar IAS Academy

The Central Marine Fisheries Research Institute’s (CMFRI) effort to rejuvenate the black clam (Villorita cyprinoides) resource in the Vembanad Lake has yielded results with fishermen starting to harvest good catch from the region.

CMFRI’s initiative of relaying baby clams in various sites in the Vembanad facilitated increasing the clam production which in turn helped fishers harvest around 10 tonnes of clamper day from two areas of the Lake.

Aimed at boosting the clam fishery and enhancing livelihood options for the clam fishery in the region, the Molluscan Fisheries Division of CMFRI re-laid (stocked) baby clams after identifying suitable areas on the northern side of the Thanneermukkom Barrage. As part of this initiative, which was under a project on ‘Rejuvenation of Clam’ taken up by the Fisheries Department of Kerala using the District Panchayat Scheme, approximately 200 tonnes of baby black clams were re-laid in Keecheri and Chakkathukadu areas of the Vembanad Lake under the technical guidance of CMFRI.

Vembanad Lake

Vembanad, also known as Punnamada is the longest lake in India, as well as the largest lake in the state of Kerala. With an area of 2033 square kilometres and a maximum length of 96.5 km, it is the second-largest Ramsar site in India only after the Sunderbans in West Bengal. Spanning several districts in the state of Kerala, it is known as Vembanadu. Several groups of small islands including Vypin,  Mulavukad,  Maradu,  Udayamperoor,  Vallarpadam,  Willingdon Island are located in the Kochi Lake portion. Kochi Port is built around Willingdon Island and the Vallarpadam island. Kuttanad, also known as The Rice Bowl of Kerala, has the lowest altitude in India and is also one of the few places in the world where cultivation takes place below sea level. Kuttanad lies on the southern portion of Vembanad.

The Nehru Trophy Boat Race is conducted in a portion of the lake. High levels of pollution have been noticed at certain hotspots of the Vembanad backwaters. The Government of India has identified the Vembanad wetland under the National Wetlands Conservation Programme.

Black clam (Villorita cyprinoides)

Villorita cyprinoides, the black clam, is found in the backwaters of Kerala, mainly in Vembanad backwaters.  It does not show sex reversal or hermaphroditism. It spawns twice a year, from May to August, and from January to late March. A change in salinity is the most important factor that triggers spawning, while the temperature is not a factor. The optimum salinity for spawning is about 10–12 ppt.

The species is harvested extensively from the wild population and this could be a potential threat to this species. Other recorded threats are the closure of the Thaneermukham Barrage near Vembanad Lake, frequent dredging, pollution from effluents from shrimp processing plants/factories, ecotourism and Water Hyacinth weed.