Chiang Mai Journal of Science

Phytoplankton in the freshwater fishing area of Pak Phanang River Basin (PPRB), Nakhon Si Thammarat Province in southern Thailand was monitored at three different habitat sites over three different seasons in 2006, in order to assess water quality condition and suggest any fishery management measures. The water quality parameters still remained suitability for inland fisheries. A total of 62 genera and an average density of 10,020 units L -1 of phytoplankton belonging to six divisions were identified. The third-most abundant genera were Peridinium sp, Protoperidinium sp which most related to velocity and Trachelomonas sp. which most related to ammonia nitrogen. Shannon-Wiener diversity index showing that phytoplankton diversity was generally in medium level and implied that water quality condition was moderately-polluted. Also, the AARL-PP score assessed that the water quality condition in the area was considered meso-eutrophic and moderately-polluted, but it was still suitable for aquatic animal growth and survival. Furthermore, fishery management through water monitoring should be regularly conducted. Restocking aquatic animals/fishes should be implemented at sites and times with the best condition for survival.