A meta-analytical review of turbidity effects on fish mobility

Human activities have resulted in higher levels of turbidity in aquatic systems due to increased sediment runoff from agriculture, urbanization, and mining activities into nearby water bodies. Previous research has suggested that as turbidity increases, fish may increase their mobility to counteract the reduction in low visual acuity and maintain prey consumption similar to those in clear water. However, other studies have reported negative and non-significant relationships between turbidity and fish mobility. Here, we conducted a systematic review and meta-analysis to investigate the effect of turbidity on fish mobility. We analysed potential sources of variation in the turbidity–fish mobility relationships (moderators), such as body size, eye size and the trophic position of fish, as well as turbidity type, range and ecosystem types, while also accounting for phylogenetic relationships among fish species. Our results revealed that the overall effect size of turbidity on fish mobility was not significantly different from zero, indicating that turbidity does not consistently affect fish mobility. Instead, some fish species may increase their mobility, while others decrease or remain unchanged. Furthermore, the effects of turbidity on fish mobility varied greatly among studies. However, none of the moderators tested explained such variability in the turbidity–fish mobility relationships. These findings demonstrate that the effects of turbidity on fish movements are complex and that some fish species and populations may be particularly vulnerable to increasing turbidity levels in water bodies worldwide caused by human activities.