When habitat complexity increases predation risk: experiments with invasive and neotropical native fishes

Abstract

We tested the predator–prey relationships between a native piscivore (Salminus brasiliensis) and introduced and native fish species of the Paraná River, Brazil. We hypothesised that S. brasiliensis can exert biotic resistance against invasive fishes but not at the same degree for all species. Three invasive (Cichla piquiti, Oreochromis niloticus and Ictalurus punctatus) and two native (Astyanax altiparanae and Prochilodus lineatus) species were offered as prey to S. brasiliensis in 300 L aquaria trials at three levels of cover (0%, 50% and 100% of artificial macrophytes). S. brasiliensis had a greater ability to capture prey in complex habitats, so predation success did not decrease with habitat complexity and even increased on I. punctatus. Prey survival was variable through time and among species, being high for I. punctatus. The three most consumed species (P. lineatus, C. piquiti, and O. niloticus) were less active and occupied the aquaria surfaces, changing strongly their behaviour with habitat complexity. Except for P. lineatus and C. piquiti, S. brasiliensis preferably preyed on smaller individuals of the other species. Our experiments support that S. brasiliensis is an interesting candidate to resist the invasion by C. piquiti and O. niloticus but not to control the abundance of I. punctatus.