Salim Ali School of Ecology and Environmental Sciences, Pondicherry University, Pondicherry 605 014, INDIA.
The ecology of Catfishes was studies in 10 wetlands in Kancheepuram and 15 wetlands in Kanyakumari districts of Tamil Nadu State, Southern India. The study period was from February 2003 to April 2004.
Twelve species of catfish were recorded, 10 in Kanyakumari and 6 in Kancheepuram. Four species are common to both districts. All these species belong to 5 fmilies. Four and roind in Kanyakumari and 3 are found in Kancheepuram. Family Bagridae is species rich than other families. The Silurid species are not seen in Kancheepuram and Schilbeid species is not seen in Kanyakumari.
A few species, (Aorichthys aor, Wallago attu, Clarias dussumieri, Mystus oculatus, Arius dussumieri, Arius sagot, Mystus bleekeri and Clarius batrachus) which were recorded earlier were not recorded in this survey and one species (Airus subrostratus) is a new record.
Mystus vittatus is the most abundant, Mystus keletius, Mystus cavasius and Ompok bimaculatus are the least abundant. Four species are common and 8 are restricted in distribution. Mystus vittatus and Heteropneustes fossilis are the widely distributed species and they can survive in almost all kind of wetlands with diverse environmental conditions. Airus subristratus and Mystus keletius have a narrow distribution, Arius subrostratus is seen only in clean water and large estuaries. Mystus gulio is distributed in wetlands that are located in a certain distance from the sea.
Wetlands such as Puthery and Erachakulam of Kanyakumari and Chembarampakkam wetland of Kancheepuram district have more catfish species. The fresh water wetlands have more species than the brackish water.
Among the environmental factors only the substrate and microhabitat diversity significantly influenced catfish species richness. The fish assemblage in the wetlands clustered with regard to region.
Heteropneustes fossils has a wide range of size distributions and Ompok malabaricus has a narrow range of size distributions. The catfishes are medium in size, compared to species from other tropical sites.
The polulation structure of certain species such as Heteropneustes fossils, Mystus gulio and Mystus vittatus considerably varies in the two regions and also for the two reasons (Heteropneustes fossils and Mystus vittatus in Kanyakumari and Mystus vittatus in Kancheepuram).
Heteropneustes fossilis breeds more than once a year and Ompok species is seasonal breeder. Mystus vittatus breeds in different seasons in two study regions. In Kanyakumari, the breeding season of Heteropneustes fossils, Mystus armatus and Mystus vittatus is before the North East monsoon.
Among the 12 species if catfish studies, 7 species are omnivored (Arius arius, Artus subrostratus, Heteropneustes fossilis, Mystus armatus, Mystus gulio, Mystus montanus and Mystus vittatus) and five are carnivores (Mystus cavastus, Mystus keletius, Ompok bimaculatus, Ompok malabaricus and Pseudeutroptus athertinoides).
Although, different species takes various diet items, the primary fresh water species such as Heteropneustes fossilis, Mystus armatus, Mystus montanus and Mystus vittatus commonly prefer insects. Among the micro diet items detritus is preferred by almost all the species.
The food preferences of these species are more or less similar to the same species from the other regions of India and some other catfish species found in different regions of the world. The feeding habit of catfish species influences their status (commonness and rarity) in wetlands, the carnivorous fishes are rather than the omnivores.
The threats for catfish in the study region are mainly caused by habitat destruction and over exploitation due to anthropogenic and biological factors.
The conservation measured such as conducting surveys, identifying the threats, intervention by the government bodies, educating the fishermen and ex-situ, in-situ conservation methods will help the catfish to retain in the wetlands.