Assessing the risk of microplastics in feeds to salmon health and quality (FS126)

Project Outcome:

This project achieved several significant outcomes. Initially concerns were raised within the industry about the threat that microplastics presented as a contaminant within fishmeal. Evidence from this project showed that the levels and types of microplastics in fishmeal are consistent with earlier reports, but that significant levels of microplastics exist in virtually all feed ingredients and in some cases, levels are significantly higher than that seen in fishmeals.

We were able to demonstrate that there is some geographic variability in the types and levels of microplastics within fishmeals. For the most part the point of entry of microplastics is with the capture of the fish. This means that there may be limited capacity to control entry of contamination into fishmeals by the industry itself. The main point of control it is suggested is to focus on limiting entry of plastics into the ocean in the first place. Though processing of fish for human consumption does appear to result in a slight increase in the microplastic levels in the fish by-product, this itself is also geographically variable.

We were able to demonstrate that when fishmeals contaminated with any of four different types of microplastics were fed at a standardised inclusion level (based on the typical microplastic abundance level found in fishmeals) that they had no impact on clinical indicators of salmon health, digestion, or the presence of microplastics in the edible parts of the fish. Similarly, varying the levels of microplastics up to three times the typical abundance level had no impacts on the fish. From this project we have been able to prove that microplastics themselves are quite benign within the feed and represent little threat to the animal or human food safety.