Marine protected areas (MPAs) are an essential tool for marine biodiversity conservation. Yet, their effectiveness in protecting marine ecosystems from global stressors is debated. Biological invasions area major driver of global change, causing biodiversity loss and altering ecosystem functioning.

This study explored the relationships between MPAs and alien/native range-expanding fishes in the Mediterranean Sea, the world’s most invaded area. To do so, fish and benthic communities were surveyed in nine MPAs and adjacent unprotected areas across six countries.

The results show that in the South and Eastern Mediterranean MPAs, the biomass of alien and native range-expanding fishes often exceeded 50% of the total fish biomass. Conversely, in the North and Western Mediterranean, alien fishes were absent.

The authors found a negative relationship between native and alien species richness, and sea surface temperature (SST) over six consecutive years was positively correlated with the total biomass of alien species. A negative relationship between alien fishes’ biomass and the distance from the Suez Canal was also found.

It was found that the biomass of alien and native range-expanding fishes was found to be higher in the South and Eastern Mediterranean MPAs than in adjacent unprotected areas. The authors highlight that, currently, the level of fishing pressure exerted on alien and native range-expanding fishes seems to be the most influential factor determining the lower biomass of invasive fishes at unprotected sites compared to MPAs.

Following these findings, the authors suggest that complementary management actions, such as species-targeted removals, should be taken in MPAs to effectively control invasive fish populations.

https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/eap.1809

Giakoumi et al. (2018) Exploring the relationships between marine protected areas and invasive fish in the world’s most invaded area. Ecological Applications 0:1-12.