Social standing may determine which fish bear the brunt of plastic pollution, according to University of Glasgow research on European minnows. Monitoring groups across repeated feeding bouts, the team found that dominant individuals in hierarchical groups were more likely to ingest microplastic particles than their subordinates. Intriguingly, groups with clearer social hierarchies appeared collectively better at telling food from pollution, lowering overall ingestion across the shoal.
The study also examined how water movement changes the picture. Flowing water reduced microplastic ingestion for most fish, but for dominant individuals it increased the proportion of plastic particles in what they consumed. The experiments spanned group sizes from a few individuals to several hundred fish, allowing the researchers to link individual behaviour, social context and environmental conditions to pollution exposure in a way that single-fish laboratory studies cannot.
Led by senior author Professor Shaun Killen and first author Dr Weiwenhui Liang in the School of Biodiversity, One Health and Veterinary Medicine, the work is published in Proceedings of the Royal Society B. It was funded by a China Scholarship Council grant and the UKRI Natural Environment Research Council. The findings suggest that ecological assessments of microplastic risk should account for social behaviour, not just the concentration of particles in the water.