Ecosystems deprived of high-level predators due to overexploitation may be more vulnerable to invasive alien species as the latter are subject to reduced predation control. Marine protected areas (MPAs), and particularly no-take reserves were fishing is banned, can be effective tools for the restoration of predatory relationships within their boundaries.

This study explored whether the restoration of high-level predatory fish populations within Mediterranean MPAs can exert top-down control on alien fish. Fish tethering experiments, including native (Sardina pilchardus, Boops boops) and alien (Siganus rivulatus) dead specimens, were conducted to quantify predation rates and prey type preferences. A subsample of experimental units was filmed to document predation events and related fish behaviour.

The obtained results showed that more high-level predators interacted with the tethered fish inside the MPAs than in unprotected areas. The authors state that native S. pilchardus was consumed more in comparison to the other tethered fishes, regardless of protection status and location, and highlight that the alien S. rivulatus was consumed by native predators in the western Mediterranean locations where this alien fish is not established.

It is concluded that this study provides evidence on the ability of some native predators to feed on and potentially control certain alien species without requiring “adaptive” time-lag periods.

https://www.sciencedirect.com/science/article/abs/pii/S0141113619303708

Giakoumi et al. (2019) Patterns of predation on native and invasive alien fish in Mediterranean protected and unprotected areas. Marine Environmental Research 150:104792