The physico-chemical and biological parameters, species composition and population dynamic of dominant fish species were conducted in Pedu Reservoir in Kedah. The reservoir is considered safe from human activities, although the level of ammonia concentration (3.84 ± 2.65 mg/L) was exceeded the class recommended in Malaysia. 82.94% of fish families were contributed by Cyprinidae, 11.04% of Notopteridae, 3.01% of Bagridae and 2.51% for others. Twenty-four fish species were recorded in the reservoir and were dominated by Barbonymus schwanenfeldii (38.9%), followed by Oxygaster anomalura (12.4%) and Notopterus notopterus (11.0%). The length-weight relationships of B. schwanenfeldii was an isometric (b = 2.992) form with Kn ranging between 0.75 and 1.01. This fish could attain L? = 30.95 cm at growth rate of K = 0.66 yr-1, given the growth performance index (Ø’) of 2.801 that was represented from two cohorts occurred in August and February, respectively. The cohorts were strongly correlated to rainfall distribution in the area. The total mortality coefficient (Z) was 2.01 and natural mortality coefficient (M) was 1.37 yr-1 given the fishing mortality coefficient (F) and exploitation rate (E) was at 0.64 and 0.32 yr-1, respectively. The exploitation rate of 0.32 yr-1 was lower than the 75% of B’/R (E 0.1 = 0.41) or optimum Y’/R (Emax = 0.53) indicating the yield per recruit of B. schwanenfeldii could be increased slightly by increasing the E. Keywords: Barbonymus schwanenfeldii, length frequency, population parameters, management, Pedu Reservoir; Keda
