56 SEPTEMBER 2019 • WORLD AQUACULTURE • WWW.WAS.ORG The lake provides essential spawning and breeding habitat for a variety of biologically and economically important resident and migratory aquatic and avian fauna. Nearly 117 aquatic species have been recorded from Vembanad Lake. Fish biodiversity includes two introduced native fishes (catla Catla catla and rohu Labeo rohita) and two exotic fishes (sutchi catfish Pangasianodon hypophthalmus and tilapia Oreochromis mossambicus). Major fishery resources of the wetland include the black clam Villorita cyprinoides and the green chromide Etroplus suratensis. The area has a tropical humid climate with an average annual rainfall of about 3,300 mm. In Kerala, the mean rainfall has decreased by nearly 6 mm from 1981 to 2016. During 1901-2017, the annual mean temperature has increased by 0.66 C/century with a significant increasing trend of maximum temperature (1.06 C/century) and a relatively lower increasing trend (0.26 C/century) of minimum temperature. A water regulator at Thanneermukkom of nearly 1.25 km was constructed across the lake to control saltwater intrusion to safeguard agriculture around the lake. The regulator has greatly affected the opportunity for anadromous migration of fish and shellfish, caused rampant proliferation of water hyacinth and restricted natural flushing of pollutants. Uncontrolled mining of shells from the lakebed, sewage effluents and a heavy load of organic material have seriously damaged the ecosystem. Fishers have started to rely on alternative livelihood options such as agriculture, fishing, tourism, inland navigation and coir retting due to reduced income from the disrupted ecosystem. The Black Clam Project at Thycattussery During 1988-1989, the Thycattussery area had a clam bed of 28 ha with an estimated production of 297 kg/ha but production has now declined to 17 kg/ha (Kurup 1990). The trophic status index of Thycattussery indicated an oligo-mesotrophic condition, suggesting that conditions were suitable for pen culture of black clams. Salinity, dissolved oxygen and sandy loam soil substratum are Current development efforts aimed at fishers and fish farmers in the developing world focus on building their resilience capacity to adapt to climate change (IPCC 2007, Prowse et al. 2009). Climate change has been identified as one of the greatest threats to environment conservation and livelihood security. Many fishing communities in tropical countries are dependent on stocks that fluctuate regularly and hence many have already developed considerable coping capacity (Easterling et al. 2007). The black clam Villorita cyprinoides in Vembanad Lake is one such species with stock fluctuations. The average annual clam harvest from the lake has decreased from 334 kg/ ha in 1988-1989 to 133 kg/ha in 2016, impacting nearly 5,000 clam fishers. The Central Inland Fisheries Research Institute (CIFRI) estimated that clam fishers have incurred occupational losses of US$292 and livelihood losses of nearly US$145 relating to various climate change scenarios. The study indicated a need for adaptation strategies to cope with climate change by devising various income enhancement programs for clam fishers. The adaptation strategy recommended by CIFRI relative to climate change is diversification of livelihood systems, where farmers alternate between farming in Climate-Resilient Pen Structures (CRPS) and fishing in response to seasonal and interannual variation in shellfish availability (Allison and Ellis 2001). Ecological Significance and Current Status of Vembanad Lake Vembanad Lake, the longest lake in India, is spread across an area of more than 2000 km². It is the second-largest (151,250 ha) brackishwater lake in Kerala, located between 9.512o N and 10.186o N latitude and 76.163o E to 76.429o E longitude. It was designated a Wetland of International Importance under the Ramsar Convention in 2002 and is also classified as a “Critically Vulnerable Coastal Area” as per CRZ Notification, 2011 by the Ministry of Environment, Forest and Climate Change. Demonstration of a Climate-Resilient Multitrophic Pen System in Vembanad Lake, Kerala, India Thankam Theresa Paul, G. Kuberan, Preetha Panikker, Deepa Sudheesan, U.K. Sarkar and B.K. Das Study area of Vembanad Lake, Alappuzha. The adaptation strategy recommended by CIFRI relative to climate change is diversification of livelihood systems, where farmers alternate between farming in Climate-Resilient Pen Structures and fishing in response to seasonal and interannual variation in shellfish availability.
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