Fish ecology of a wetland in the southern Western Ghats, India

Abstract

Fish assemblages and abiotic environmental conditions in a wetland in the Western Ghats, southern India, were investigated from August 2000 to July 2001. Rainfall showed a seasonal pattern of dry, major wet, and minor wet seasons. The hydrology of the wetland system did not fluctuate seasonally as the water level was maintained fairly stable due to operation of sluice gates by local authorities. Regulated inflow and outflow connection of the Valliar River to the wetland facilitated faunal exchange to some degree. Abiotic environmental parameters (e.g., temperature, turbidity, pH, DO, and rainfall) showed seasonal variation and were significantly associated with fish assemblage structure. Fish assemblages revealed seasonal variation and habitat associations throughout the annual cycle. Fish abundance and biomass was highly correlated with rainfall and turbidity. Maximum juvenile abundance and maximum number of species were observed during the major wet season in all habitats. The littoral region had more species and higher fish abundance than the offshore region, although the offshore region had higher biomass due to the presence of larger fish. Chanda nama was the most abundant species in the fish assemblage, and was found in higher abundance in the littoral region. C. nama is a facultative lepidophagous fish, and exhibited ontogenetic diet shift from feeding on aquatic insects and microcrustacea in the juvenile stage, to scale feeding in adults. It bred throughout the year, with two distinct spawning peaks coinciding with high rainfall during the months of April and August.