This study aimed to evaluate benthic macroinvertebrates assemblages using the application of ecological indices in the Rawang sub-basin of the Selangor River with reference to determining the impacts of aquaculture practices on benthic macroinvertebrates. In total, seven sampling sites were selected, namely Guntong (SR1), Guntong’s tributaries (SR2, control site), Kuang (SR3 and SR7), Gong (SR4), Buaya (SR5) and Serendah (SR6) Rivers. Sites were selected using a random sampling technique and the accessibility and proximity to aquaculture farms. Macroinvertebrates were sampled from April 2019 to March 2020 using an aquatic kick net, a hand spade, and a D-frame dip net. Water samples were also taken. Twenty-seven families belonging to the Annelida, Mollusca and Athropoda phyla were identified using taxonomic keys. Tubificidae was found to be the most dominant family (36.79%) followed by Chironomidae (28.84%). The highest number of individuals from family Tubificidae was recorded in Gong River, where effluent was discharged from an aquaculture farm. The total abundance of benthic macroinvertebrates increased with increased proximity to the aquaculture farm. Based on Biological Monitoring Working Party score value, the water quality of sampling sites in close proximity to the aquaculture farm was polluted as compared to the control location. Family Biotic Index score showed that all sites were substantially polluted with organic pollution, with the control site being much less polluted. In conclusion, benthic macroinvertebrates assemblage was affected by effluent originating from aquaculture farm outlets. It is therefore necessary to conduct aquaculture farming using methods that are deemed to be environmentally friendly.

The main goal of this study was to develop a model for organic pollution assessment. Seven sampling sites in six rivers in the Rawang sub-basin, Selangor River, Malaysia, were selected with one reference site. The sampling sites near the fish farm were used to develop the model. SR2 was used for the validation of the developed model. Benthic macroinvertebrates and water sampling were conducted from April 2019 to March 2020. The Principal Components Analysis (PCA) and regression were conducted to select the most representing benthic macroinvertebrates family. Based on the score value (variance coefficient) of each benthic macroinvertebrates family, the cumulative score value of each sampling site was calculated (i.e., 18=6 sampling sites x 3 replicates). The nine benthic macroinvertebrate families (Baetidae, Libellulidae, Protoneuridae Chironomidae, Curbicullidae Hydropchysidae, Tubificidae, Lumbriculiade, and Naididae) were identified using PCA and regression. The cluster analysis and mean confidence intervals were used to classify water quality classes precisely. Finally, three different value scales were produced to represent the level of contamination (i.e., <0.69 as organically polluted, 0.69-0.87 as slightly organic polluted, and >0.87 as clean status). The newly developed model was validated. The results produced after validation were better than the water quality status from other studies based on the BMWP/BMWPThai score. This study concludes that the developed model can evaluate river organic contamination successfully. model can evaluate river organic contamination successfully.

Freshwater aquaculture is a prominent activity in Rawang sub-basin of the Selangor River. Despite the importance good water quality in daily life, there is limited study on the impact of aquaculture activities on water quality. This paper discusses water quality parameter status (pH, dissolved oxygen (DO), ammoniacal nitrogen, turbidity, total suspended solids (TSS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD)) based on Water Quality Index (WQI) in the aquaculture-impacted Rawang sub-basin of Selangor River and develops the Inverse Distance Weighted (IDW) maps showing water quality status by using GIS (ArcGIS 10.2.1 software) in order to identify the potential aquaculture impacted sites. Seven river sampling sites were selected including Guntong (SR1), Guntong’s tributaries (SR2/control), Kuang (SR3 and SR7), Gong (SR4), Buaya (SR5), and Serendah (SR6) using random sampling techniques based on accessibility and proximity to aquaculture farms. Seven water quality parameters were recorded and analysed on a bi-monthly basis. Results revealed that Guntong, Kuang, Buaya and Serendah rivers had moderate water quality, whereas Gong River was significantly polluted. The control river recorded clean water quality status. One-way analysis of variance (ANOVA) showed that there were significant differences in all measured water quality parameters among sampling sites (P<0.05).

This study examined the influence of fish farming activities on water quality and benthic macroinvertebrates at the Rawang sub-basin of Selangor River. Multivariate statistical techniques were used to determine major influencing water quality parameters causing organic contamination and the dominant pollution-tolerant benthic macroinvertebrates. Sampling was conducted at Guntong River (SR1), Guntong River’s tributary (SR2, the control site), Kuang River (SR3 and SR6), Gong River (SR4), and Serendah River (SR5) using random sampling techniques based on accessibility and proximity to fish farms. Benthic macroinvertebrates and water samples were collected from April 2019 to March 2020. Based on the principal components analysis (PCA), electrical conductivity (EC), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal-nitrogen, and total suspended solids (TSS) were major water quality parameters influenced by fish farming activities. The Canonical Correspondence Analysis (CCA) revealed that several taxa of benthic macroinvertebrates (Chironomidae, Naididae, Lumbriculidae, Tubificidae, unidentified Oligochaeta, Leeches (Helobdella sp.), Planorbidae, and some Odonata) were moderately or highly sensitive to TSS, BOD, COD, turbidity, ammoniacal-nitrogen, and EC. These taxa were dominant in the sampling sites, which were close to fish farms. Findings in this study showed that fish farming activities impacted the water quality and benthic macroinvertebrates in this sub-basin.