Microplastics in freshwater habitats are consumed by fish, including stream-dwelling salmonids, which can alter food consumption or negatively affect swimming and foraging behaviour. As population-level effects are largely unknown, a simulated population of stream-dwelling rainbow trout (Oncorhynchus mykiss) was created using the agent-based model ‘inSTREAM 7’ to model population-level effects (biomass) of behavioural changes caused by microplastics consumption. Individual fish were assigned all possible combinations of two personality traits (dominance, boldness/shyness), and consumed microplastics while foraging, while their abundance, body size, and microplastics consumption were tracked for three different life stages (fry, juvenile, adult) for a 10-year simulation period. Three additive scenarios were explored: a low-impact scenario with decreased food consumption, a medium-impact scenario with added lower swimming speed, and a high-impact scenario with added reductions in prey capture efficiency. Each was tested with microplastics concentrations of 0%, 1% (i.e., current levels), and 3% (i.e., future levels) of drift food. Overall, microplastics consumption did not strongly affect trout population abundance. Dominant adult trout consumed disproportionally more microplastics than all other fish, especially with higher microplastics concentrations. Different personality types were affected differently in the three scenarios: dominant and bold adults were smaller when food consumption was reduced, shy and subordinate adults were smaller when swimming speed was lowered, and all dominant adults, regardless of boldness, were smaller when foraging efficiency was impeded, with dominant and bold fry also less abundant in this scenario. However, effects on fish body size were only found with microplastic concentrations of 3%, indicating these outcomes can be prevented, as current levels of microplastics pollution are unlikely to affect salmonid body size. Nevertheless, microplastics ingestion represents an additional stressor that may potentially interact with a myriad of anthropogenic impacts that already affect wild salmonid populations.

This dataset was collected from 10-year model simulations using a modified version of the agent-based model 'inSTREAM'. The data comparing the abundance, body length and microplastics consumption of a simulated population of rainbow trout was collected annually on the census day (i.e., September 23) from years 3-10. The data was analyzed using mixed models, to see how microplastics pollution (concentrations of 0%, 1% and 3% of drift food) affects this fictional population of rainbow trout, specifically the abundance and body length of fish with all different combinations of two personality traits (dominance, boldness/shyness) of three life stages (fry, juvenile, adult).