Impact of urbanization on stream fish fauna in tropical catchments of the Malay Peninsula

• Urbanization has caused significant habitat loss, impacting fish fauna in urban watersheds. • Non-native species dominate urbanized waters, with concrete coverage influencing their presence. • Native species, including those on the IUCN Red List, were found in urbanized waters. • Preserving forests and restoring floodplains is critical for native species conservation. • The study suggests strategies combining climate adaptation and biodiversity conservation. Since the 20th century, rapid urbanization has led to various environmental challenges. These include urban flooding due to changes in the water cycle, poor water quality, and the degradation of aquatic ecosystems. Additionally, urbanization has caused a loss of habitats, leading to a decline in species diversity. In particular, aquatic organisms have been significantly affected by habitat loss resulting from river modifications and the introduction of non-native species. However, research on urbanization’s effects on biodiversity in tropical regions is limited, and knowledge about ecosystem conservation and restoration in these areas is scarce. This study aimed to examine the fish fauna in urban and surrounding non-urban areas of the rapidly developing Malay Peninsula. By examining fish populations in urbanized watersheds and comparing them with those in non-urban areas, the study investigated the relationship between environmental factors, including urbanization, and fish fauna. The survey revealed that non-native species like Poecilia sphenops and Mayaheros urophthalmus dominated urbanized watersheds. Habitat modeling showed that factors like concrete coverage on riverbeds, conductivity, and urban land use significantly influenced the presence of these non-native species. These species appear to have adapted to the urban environment. However, native species, including those on the IUCN Red List, were also found in urban watersheds. The results emphasize the need to preserve remaining forests and restore floodplains for native species conservation. This highlights the importance of conservation efforts to protect natural habitats and rehabilitate degraded ecosystems in urban areas.