2.2. Sampling
Between 2005 and 2012, the fish assemblage and various environmental factors were monitored twice a year (mid-summer and early winter). The fish population was sampled using a dip net (1-mm mesh), cast net (9.5-mm mesh) and minnow trap (60- mm entrance diameter) for 30 min at each monitoring time. After 2008, dissolved oxygen levels of surface water (DO; Lutron DO-5509), maximum depth (cm), vegetation coverage (nearest 5%) and turbidity (cm) were recorded during fish sampling. DO and turbidity of surface water were monitored in an area of open water 10:00 and 14:00 h.