The Department of Aquatic Biology and Fisheries (University of Kerala) and Agency for Development of Aqua Culture, Kerala, have identified the use of small mesh encircling nets as one of the biggest threats to the biodiversity of Vellayani lake, the second largest fresh water body in the State.
A participatory fish census conducted by the institutions has found that many perennial streams, which supplied water to the lake, have dried up. Paddy fields and wetlands have been land filled. The research team also noticed an alarming depletion of frogs in the lake. Pesticide contamination of the lake and shrinking of its area were other major issues affecting the water body’s survival.
The fishes that recorded sharp decline in availability are ‘Mushi’ ( Clarias dussumieri ), ‘Aattu vaala’ ( Wallago attu ) and ‘Zig-zag eel’ ( Mastacembelus armatus), which were economically very important species in the lake. One recent threat detected during the census was the dominance of the exotic African cichlid Tilapia , which may affect the populations of indigenous fish.
The census team forward the idea of regulating the mesh size of gill nets operated in the lake so that only larger fishes will be retained in the gill net. Fishing should be operated only through the fishermen’s cooperatives and the total number of fishing gears used each day should be regulated in order to ensure sustainability in production and secure the livelihood of local fishermen.
Considering the fact that carps are supporting local fishery, the recommendation says the periodic stocking of fish fry should be maintained by the fisheries department through ranching. The seeds of locally preferred fish such as Karimeen and Varal should also be facilitated.
In order to ensure sustainability of fisheries of the lake, the government should develop an integrated lake conservation plan which includes prevention of encroachment, ecosystem protection and adoption of co-management of lake’s resources with the involvement of local fishermen. The involvement of local fishermen in conservation activities would help, as they currently keep a vigil against sand mining. They also say reinstalling the connectivity of the lake with Karamana River would help the movement of migratory fish such as eels.