DNA metabarcoding reveals the diet of the invasive fish Oreochromis mossambicus in mangroves of São Tomé Island (Gulf of Guinea).

Abstract Invasive species can trigger profound effects on recipient ecosystems, namely through the food web. Despite being recognized as one of the worst invasive species, little is known about the feeding ecology of the Mozambique tilapia (Oreochromis mossambicus). To understand how this invasive species might impact food webs, we applied metabarcoding to analyze its diet’s composition in two mangroves, in the Obô Natural Park in the oceanic island of São Tomé. Given the particular importance of mangroves as fish nurseries, we specifically aimed to determine if this invader might predate on other fish species. However, tilapias were mostly phytoplanktivorous, and there were few indications of predation on native fish eggs or larvae. Instead, tilapias may impact low trophic level resources and nutrient availability with the potential to cascade through the food web by means of bottom-up disruption. In addition, we recorded important changes in the taxonomic composition of the diet, linked to locations and life stages, suggesting that its opportunistic feeding associated with its aggressive territorial behavior may result in resource competition with native species with which it has overlapping dietary niches.