Water quality of fish cage culture area in Nan River, Phitsanulok Province

Abstract

Water quality in the area of fish cage culture in running water was examined in order to assess the significant factors influencing quality of water at the site and also downstream. Water samples were collected from both large and small fish cage farms on Nan River. For both farm scales, sampling stations were determined at the farm site (cage), upstream, and 20 and 50 m downstream from the cage. The samples were taken in different seasons (dry and wet seasons) and different times of day. In 2012, the samples were collected from January to March and July to September for dry and wet seasons, respectively. Water velocity, DO, EC, pH, salinity, TDS and temperature were determined in the field. Meanwhile, the other water quality indicators: BOD5, TSS, TKN, NO3N, TP and TCB were analyzed in the laboratory. The results showed that most water qualities at the study sites were within the criteria of water quality that was suitable for aquatic animals, and within the range of class 3 of water quality standard for surface water.