UTTAR PRADESH JOURNAL OF ZOOLOGY

Retteri Lake is an urban freshwater ecosystem in Chennai, Tamil Nadu, India, that supports aquatic biodiversity while being subjected to anthropogenic pressure. This study assessed selected physicochemical characteristics of lake water and ichthyofaunal diversity during the post-monsoon period from January to March. Water samples were collected monthly in triplicate from three sampling locations and analysed for 15 physicochemical parameters using standard procedures. The parameters included electrical conductivity, pH, major ions, nitrate, fluoride, total dissolved solids, total hardness, and total alkalinity. Fish specimens were collected using cast nets and drag nets, identified with standard taxonomic keys, and evaluated using diversity indices. The results showed moderate monthly variation in water quality. Total dissolved solids ranged from 521 to 631 mg/L, and total hardness ranged from 249 to 281 mg/L, indicating elevated ionic content. Magnesium slightly exceeded the desirable limit of 30 mg/L during all months, while nitrate increased from 26 mg/L in January to 38 mg/L in March, suggesting nutrient enrichment during the study period. A total of 481 fish specimens representing eight species, five orders, and five families were recorded. Cypriniformes was the dominant order, and Carassius carassius was the most abundant species, with 116 individuals. Shannon-Wiener diversity values ranged from 1.926 to 2.029, while Simpson’s index ranged from 0.837 to 0.867, indicating moderate diversity and low species dominance. The findings indicate that Retteri Lake supports a moderately diverse fish assemblage under measurable urban environmental pressure.