Effect of monsoon on water quality, trophic state and growth parameters of barbonymus schwanenfeldii and barbonymus gonionotus in the Kuantan river

Abstract

Kuantan River is a major river, which is playing a very important and life-sustaining role in providing 350,000m3 daily freshwater for many peoples in Kuantan settlement. Monsoonal rain cause surface runoff that may affect water quality, nutrient concentration and condition of aquatic organisms in Kuantan River. To elucidate temporal changes of water quality (physical and chemical properties), trophic state and growth of fish in the Kuantan River, a twelve-month study was conducted from April 2014 to March 2015. Water quality was estimated from downstream area (5km from Kuantan River mouth) and upstream area (15km from Kuantan River mouth) of the river. Two model fish was used (Barbonymus chwanenfeldii and Barbonymus gonionotus) in this study due to their abundance in the river. Water quality parameter tested in-situ were temperature, dissolved oxygen, pH, salinity and conductivity and in laboratory were total alkalinity, nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), ammoniacal Nitrogen (NH3-N), phosphate-phosphorous (PO4-P), silicate (SiO2), chlorophyll a and total suspended solid (TSS). Results showed that temperature, salinity, dissolve oxygen, conductivity, total alkalinity, nitrate ammonia, chlorophyll a, total suspended solid, and silica concentrations in the water varied spatially (P<0.05). NO3-N, SiO2 and chlorophyll a increased while temperature, alkalinity, conductivity, TSS and inorganic nitrogen decreased during monsoon compared dry season. Overall, mean temperature, pH, salinity, conductivity, total alkalinity and dissolve oxygen (DO) and ammonia were higher in downstream water compared to upstream water. An opposite trend was observed in the case of Chlorophyll a. Water temperature and DO were found to be the highest in surface water, while the opposite was observed for salinity, total alkalinity and ammoniacal nitrogen, whereas no significant difference was observed for other water parameters. Water of upstream and downstream zones were equally productive (P>0.05). Kuantan river water was more productive in during monsoon season (October-February) and rainy season compared to dry season. Overall productivity was the highest in surface water, followed by middle and bottom layers of the water column. Barbonymus schwanenfeldii, showed a negative allometric growth (b<3, P<0.05) in May-Oct while a positively allometric growth (b>3, P<0.05) in Nov-April. This fish showed better growth and condition during the North-East monsoon compared to the dry season. B. gonionotus, showed a negative allometric growth (b<3, P<0.05) for almost all months. The spawning season of B. gonionotus is very long extending from December to August while the B. schwanenfeldii showed a shorter spawning season exhibiting two recruit times (February and July). In addition to use as the baseline information, the results of this study can be used for a proper management particularly imposing rules and regulation regarding fishing for sustainable production of B. schwanenfeldii and B. gonionutus from Kuantan River.