Assessment of Physicochemical Characteristics and Fish Diversity in the Vamsadhara Estuary, Andhra Pradesh, India

Abstract: Estuaries are facing a wide range of human-induced impacts due to uncontrolled developmental activities, both direct and indirect. Social anthropogenic activities play a major role in influencing water quality in estuarine ecosystems. Physico-chemical changes tend to accumulate in various organs of estuarine organisms, especially ichthyofauna, which may enter the human metabolic system through the food chain, causing serious health hazards. Ichthyofaunas in estuaries are influenced by various physico-chemical parameters such as temperature, pH, salinity, dissolved oxygen (DO), and others. The present study was carried out to analyze various physico-chemical parameters along with ichthyofaunal samples collected from eight sites (S1 S8) over a period of one year, from August 2024 to July 2025, in the Vasadhara estuary on the east coast of India. Environmental parameters such as temperature, salinity, pH, dissolved oxygen, nitrates, and silicates were measured. In the study area, atmospheric temperature varied from 26.8 °C to 34.3 °C, while surface water temperature ranged from 24.2 °C to 32.5 °C. The monthly mean values of hydrogen ion concentration (pH) varied from 7.2 to 8.3. Other parameters showed the following ranges: salinity 5.8 to 34.5 ppm, dissolved oxygen 4.2 to 6.9 mg/L, phosphorus 0.41 to 2.26 mg/L, nitrate 0.65 to 3.89 mg/L, silicate 32 to 98 mg/L, and total alkalinity 152 to 217 mg/L in the estuary. A total of 892 fish specimens were collected from the various sites, belonging to six orders and five families. In the study area, Mugilcephalus was the dominant species, accounting for 24.32% of the total ichthyofaunal composition.