COS 102-3 - Predicting population level effects of microplastics ingestion on the behaviour of stream-dwelling rainbow trout (Oncorhynchus mykiss) using inSTREAM 7

Background/Question/Methods

Monitoring behavioural changes in animals can tell us how pollutants, like microplastics, are likely to affect populations. High numbers of microplastics are currently present in freshwater habitats, and these habitats are becoming more polluted over time. Freshwater fishes, including salmonids, are known to consume microplastic particles, while laboratory studies show that behavioural changes often result from microplastics ingestion, including altered swimming and foraging behaviour. To determine how behavioural changes resulting from microplastics consumption scale up to affect populations, we modified an existing Agent-Based Model (ABM), ‘inSTREAM 7.3’, an individual-based model of a stream-dwelling rainbow trout (Oncorhynchus mykiss) population. Firstly, inSTREAM 7.3 was modified to assign personality traits (boldness/shyness, dominance) to the trout. Three scenarios of different potential effects of microplastics consumption were then explored: 1) reduced consumption of real food, 2) reduced swimming speed after a threshold of microplastics is consumed, and 3) reduced foraging ability in high water velocity once a threshold of microplastics is consumed. Each scenario was evaluated with microplastics concentrations of 0%, 0.5%, 1%, and 3% of available drift food.

Results/Conclusions

In all three scenarios, dominant age-0 trout were more abundant, relative to subordinate and intermediate trout, while dominant age-2 trout consumed disproportionally more microplastics, especially with higher microplastic concentrations. Dominant trout were consistent in body length, while length of subordinate trout was negatively affected by microplastics consumption. The length of shy and subordinate trout was affected with reduced food consumption, while length of bold and subordinate trout was affected with reduced swimming speed. Overall, microplastics consumption did not exert a strong impact on trout populations. Less competitive trout were the most susceptible to the effects of increased competition resulting from microplastics ingestion, while dominant trout were more likely to experience direct, negative costs of ingestion as they consume substantially more microplastics.