Impact of wet and dry seasons on water quality and Asian seabass Lates calcarifer mortality at Sri Tujuh Lagoon, Kelantan

This study is to monitor water quality in Sri Tujuh Lagoon during wet and dry seasons as well as the impact of two seasons on the production of Asian seabass. The water quality parameters such as temperature, pH, dissolved oxygen, salinity, conductivity, turbidity, total dissolved solids and fish mortality of Sri Tujoh lagoon were assessed using water samples collected from 13 sampling points (S1 – S13) at 0.3 m, 1.2 m and 2.1 m water depth during dry season (April – August 2014) and wet (September – October, 2014). Water quality data during the dry season and wet were compared using T-Test and data from 3 different depths were analysed by using One Way Anova followed by Tukey test at p < 0.05. The water parameters of dry season, wet season, and a combination of the dry and wet season were subjected to Pearson correlation analysis separately and a matrix was tabulated. Water parameters were also subjected to cluster analysis by using Ward’s method with squared Euclidean distances as a measure of similarity. In the present study, Ward’s method used ANOVA followed by Tukey post hoc to minimize the sum of squares. The result was represented by a dendrogram. The findings show water parameters such as dissolved oxygen (DO), salinity and turbidity were significantly different between the dry and wet seasons. However, no significant difference was found in term of fish mortality. The water parameters of Sri Tujuh lagoon during the study were as follow: temperature 29.4 - 33.3 oC; pH 7.0 – 9.3; DO 0.8 – 6.8 mg/L; salinity 10.7 to 31.3 ppt; conductivity 17.5 to 50.5 μs/cm; turbidity 5.4 to 59.8 NTU; TDS 23.3 to 32 ppt. The fish mortality was recorded ranging from 9.3 to 15.5 % from March to November 2014 through interviews with farmers. The positive and significance (p < 0.01) correlation was recorded between temperature and pH (0.434), temperature and DO (0.472), DO and pH (0.315), salinity and pH (0.615), conductivity and pH (0.595), conductivity and salinity (0.992), TDS and pH (0.340), TDS and salinity (0.322) and TDS and conductivity (0.322). Fish mortality showed no correlation with all water parameters’ change in the whole study at Sri Tujuh lagoon. Based on the water parameter records from 13 sampling stations, the sampling stations can be divided into 5 clusters. Cluster 1 possesses the huge number of stations namely S3, S4, S6, S7, S8, S9, S11, and S12 whereas Cluster 2 has S1, S10, and S13. Only one station was found in Cluster 3 (S5), Cluster 4 (S2), and Cluster 5 (S9). Based on the findings of the present study, it indicates that Sri Tujuh Lagoon is one of the best places to conduct aquaculture activities in Kelantan.