Pazhaverkaadu lake, formally known as Pulicat lake and the India's second largest brackish lagoon after Chilka in Odisha, is facing a serious ecological crisis with its area shrinking and fish dwindling due to silting and indiscriminate fishing.
A recent study found that the continuing dry spell and poor rainfall have also led to low water storage in the Pulicat Lake Bird Sanctuary. As most of the outlying areas remain dry, migratory birds are finding it difficult to find food.
Pulicat Community Based Disaster Preparedness, a survey conducted recently by a team of the Loyola Institute of Frontier Energy, revealed that the lake area, which once extended to 460 sq km, has reduced to 350 sq km in a few decades, leading to a huge reduction in aquatic population. This was due to rapid shrinking of the water spread area mainly due to silting in the lake’s northern part.
Earlier, the lake’s depth used to be four metres, but now it is 1.5 m. This has led to “lower aquatic life”, Project Chief Co-ordinator Dr Selvanayagam said. During summer, sea water inflow decreases and evaporation due to summer heat saturates the salinity of the lake water.
P J Sanjeeva Raj, professor and noted environmentalist who did research on the lake over the last 55 years, said that major ecological crisis facing Pulicat Lake is the rapid rate of siltation. “In some areas of the lake, during the monsoon, even one-foot deep silt gets deposited. Such heavy siltation only impedes navigation for fishing,” he said.
According to him, Pulicat Lake has been shrinking not only in its area of water spread, but also in its depth. Because of this, fish that prefer deeper waters are rapidly dwindling in the lake. “About 12 to 15 species of fish and one or two species of prawns have either vanished from the lake or are fast declining in population, for the past 20 years,” he claimed.
Adding to the already prevailing fishing pressure from the traditional fishermen is use of destructive fishing gear and methods like drag-nets (konda-valai), which destroy both bottom habitats on which they tread and the fishery stocks, by catching even tiny juveniles.
Sanjeeva Raj, former head of the department of Zoology, Madras Christian College, and founder of the college’s Estuarine Laboratory at Pulicat Lake, said that prawn and crab farms set up by private entrepreneurs along the margins of Pulicat Lake, also add to the draining of the lake water, right round the year.
“More than this, these aquafarms, unfortunately discharge untreated effluent water from the culture ponds, back into the lake, degrading the quality of water and substratum, and bringing about changes in the “Benthos” (bottom biodiversity), “Nekton” (swimming organisms), including fish,” he said. Such polluted effluent water may even inject toxic pollutants and pathogenic organisms into the biodiversity, food chains and into locally consumed and exported sea food like prawns, crabs and fish.
Listing out measures to solve the crisis, he said the government should make lake mouth wide and deep. “All the dredged silt can be deployed to construct artificial island on which mangroves and other vegetation can be grown. This will not only enrich the fertility of the lake but also attract more water birds to roost their nests,” he said.
A senior official from the Tamil Nadu Forest Department said that steps are being taken to desilt the lake and impose restriction on fishing. “We have already engaged in widening the lake mouth. Efforts are also being made to raise mangroves and vegetation along the lake bank to maintain the eco system of the lake,” the official said.
Pulicat Fishermen Association member Justin Devasagayam said extensive use of nets with small mesh take away sea plants while fishing. “Earlier, there were some restrictions on night fishing. But today no one is following the rules and regulations,” he said.
He said motor boats are used indiscriminately in the lake where only paddle and row boats were used earlier. The lake traffic continues throughout the day and night and this unsettles both aquatic and bird life thereby affecting the ecology, he said.The study has demanded setting up of an organisation along the lines of the Chilka Lake Development Authority in Odisha for managing Pulicat.
Global Nature, a Germany-based NGO, which deals with protection of environment and nature, has described Pulicat Lake as “threatened lake of the year 2010”. “The once species-rich fishing grounds and the ecologically important mangrove forests in the lagoon north of the city of Chennai have reached an alarming dimension,” it said in a communique.
The organisation also claimed that over-exploitation, mismanagement as well as improperly treated industrial effluents (containing heavy metals) from over 25 industries from neighbouring Chennai deteriorate the water quality.
The organisation said that in Andhra Pradesh around 4,700 hectares have been allotted for a marine chemicals and salt manufacturing industry while on the Tamil Nadu side, a petrochemical complex, power plant and the satellite port on Ennore Creek were major ecological threats.
Local fishermen allege that the North Chennai Thermal Power station (NCTPS), located at Ennore in the south, draws its coolant water indirectly from Pulicat Lake in the south, through Buckingham Canal, which passes through this lake. Thus, the NCTPS adds to the rapid draining of the lake, even from early summer onwards.
Pulicat Lake Bird Lovers Society member K Dhanasekar Rao said as a part of environment conservation and awareness programmes, the organisation regularly conducts seminar on bio-diversity and importance of Pulicat Lake for graduate students.
The lake, which is believed to have formed some 6,650 years ago during the Holocene geological period, is lying along the Tamil Nadu-Andhra Pradesh coast. About 15,000 flamingoes visit the lake and more than 60,000 migrant water birds feed and breed in the northern part of the lake during winter.