Adaptation of an assessment system for establishing a River Physical Quality Index and testing its effectiveness with fish‐based metrics in Malaysia

This study shows how the Stream Visual Assessment Protocol Version 2 that originated from United States was readapted to formulate the River Physical Quality Index (RPQI) for Malaysia. The approach emphasizes that it is not necessary to “reinvent the wheel” as globally, there are already a range of established best practices in developed countries to emulate. The proposed RPQI protocol was tested on four eco‐hydrological zones in Kampar River for 18 months to measure and detect temporal and spatial physical impairment induced by natural and anthropogenic factors. To be relevant to the Malaysian context, local fish community structure metrics were deployed to test and validate RPQI sensitivity and effectiveness. The results showed that RPQI values were able to reflect river physical degradation and correlated strongly with most fish‐based metrics. However, the RPQI values were weakly linked to fish population abundance and evenness metrics. The results implied that species niche responses need to be considered when applied for testing river assessment system, particularly when introduced species are present. The novel insights provided herein are constructive to inform similar endeavours in other Southeast Asia tropical countries for testing river physical assessment systems with biological metrics.