Feeding behavior responses of a juvenile hybrid grouper, Epinephelus fuscoguttatus♀ × E. lanceolatus♂, to microplastics

In recent decades, microplastic (MP) pollution has become a severe problem in aquatic environments. Yet the behavioral and selective responses of fish toward different types of MPs remain unclear. We therefore conducted laboratory-based video observations to investigate the behavioral responses of hybrid grouper juveniles (tiger grouper Epinephelus fuscoguttatus♀ × giant grouper E. lanceolatus♂) to eight different types of MPs. We observed four distinct feeding behaviors: (i) normal ingestion of MPs, which rarely occurred (0%-6%); (ii) pursuit, capture, and tasting of MPs, after which MPs were quickly spat out; (iii) detection and rejection of MPs without attack; and (iv) no significant response to MPs. Our results indicate that juveniles can distinguish MPs as inedible particle and behave differently between MPs with different sizes, colors, and materials, primarily using visual and gustatory senses. Notably, 50%-90% of MP rejection events occurred before capture. Juveniles spent double the time evaluating large nylon particles than they did evaluating large polyvinyl chloride particles before capture, but half the time tasting after capture. Although we observed no sub-lethal or lethal effects of MPs, we conclude that the presence of MPs can still have an impact on groupers in aquaculture. For instance, in the densely stocked conditions of an aquaculture unit, the fish could lose visibility and can inadvertently ingest MPs, thus suffering from their toxic impacts.