A proposal mooted by the Fisheries Department to release Indian Major Carps in reservoirs in Kerala has met with strong opposition from conservationists and environmental activists who fear it may lead to the eventual extermination of indigenous species and whittle down the aquatic biodiversity in the Western Ghats.
The proposal, to be funded by the Central government under a project to promote inland fisheries, seeks to stock 16 reservoirs including Kallada, Kakki, Pampa, Anayirangal, Neriyamangalam, Ponmudi, Kandala, Shenkulam, Mattupetti, Bhootathankettu, Peringalkuthu, Sholayar, Parambikkulam, Karapuzha, Banasurasagar and Pazhassi with carp.
Conservationists feel that the proposed introduction of the carps, which are highly competitive and voracious feeders, would wipe out highly-threatened indigenous fish fauna as well as other aquatic organisms. They point out that the carps, known to be aggressive, prolific breeders, would move out of the reservoirs and expand their range along the river courses, both upstream as well as downstream. They also fear the species would prey upon the local varieties of fishes, their fingerlings or spawn.
According to ecologist Sathish Chandran, the introduction of exotic species into reservoirs is a violation of the Wildlife Protection Act.
?Most of our reservoirs are in the Western Ghats and the catchment areas upstream are reserve forests. At least 20 large reservoirs in the State are within national parks and sanctuaries. Another seven reservoirs are inside wet evergreen forests with very high biodiversity potential where the species richness remains inadequately documented,? Dr. Sathish Chandran points out.
A recent study conducted by Robin Kurian Abraham in the southern Western Ghats shows that the protected areas act as a refuge for highly endemic fish fauna and one of the greatest threats is the presence of exotic species. For example, in the Kulathupuzha river the Common carp introduced for aquaculture has escaped downstream and is in the process of replacing the threatened mahseer fish. This is an indication of possible replacement of indigenous fish by the larger and highly competitive carps.
A study by Dr. Bijukumar of the Department of Aquatic Biology and Fisheries, University of Kerala, observes that exotic fishes such as tilapia (Oreochromis mossambicus), Common carp (Cyprinus carpio), African catfish (Clarias gariepienus),and IMCs have gained entry into the reservoir ecosystems of India through accidental or deliberate introduction. Among them tilapia has already entered into all the upstream rivers of Kerala, including forest streams, and established viable populations, the report notes.
The recent recording of Piranha from Chalakkudy river, African catfishes from many water bodies including Periyar lake and Nile tilapia from Bhrathapuzha river is a matter of concern to the freshwater aquatic diversity, Dr. Bijukumar says.
However, Director of Fisheries, Sheikh Pareed told The Hindu that no adverse impact on aquatic biodiversity had been reported in Kerala since the project to stock reservoirs with fish seeds began 10 years back. He said the project was launched with the objective of generating income and providing a livelihood for local communities.
Mr. Pareed said the government had subsequently decided to exclude four reservoirs located in wildlife sanctuaries from the project, taking into account the views expressed by the Forest Department.
The carps are represented by three species: Catla (Catla catla), Rohu (Labeo rohita) and the Mrigal (Cirrhinus cirrhosus; earlier Cirrhinus mrigala). They grow to a length ranging from 100 cm to 200 cm and weigh from 13 kg to 45 kg.
There are at least 61 species of threatened fishes (listed as either critically endangered or endangered) that occur in the rivers of Kerala. Although explicit information regarding the factors that drive native fish species towards endangerment is still unclear, there is a general consensus that habitat loss and exotic species could be the possible reasons.