Investigating the impacts of biofouled marine plastic debris on the olfactory behaviour of juvenile yellowtail kingfish (Seriola lalandi)

Marine microplastics are rapidly colonised by a microbial community which form a biofilm unique from the surrounding seawater that often contains infochemical-producing species associated with food sources. Here, we investigated whether juvenile kingfish (Seriola lalandi) were more attracted to biofouled plastics compared to clean plastics. Plastics were exposed to unfiltered seawater for one month to cultivate a microbial community. An olfactory behavioural experiment showed little difference in their response to the biofilm compared to clean plastic and control treatment. Further, ingestion experiments demonstrated that S. lalandi ingested fewer biofouled microplastics compared to clean microplastics. However, this was likely due to the bioavailability of the biofouled microplastics. This study highlights that while juvenile kingfish will ingest microplastics, they are not more attracted to those with a naturally acquired biofilm. •Juvenile yellowtail kingfish (Seriola lalandi) did not appear to be more attracted to biofouled compared with clean microplastic odour.•Juvenile yellowtail kingfish consumed both clean and biofouled microplastics - more clean plastics on average, but not statistically different.•The biofilm on microplastics made them negatively buoyant and may have contributed to juvenile kingfish consuming fewer biofouled particles.