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More fish invade Mediterranean after Suez Canal expansion

Published online 8 September 2020

As a major shipping corridor, the Suez Canal is a hotspot for biological invasions, but the socio-ecological consequences remain poorly understood.

Kira Walker

The recent expansion of the Suez Canal has accelerated the introduction of non-native marine organisms from the Red Sea to the Mediterranean, according to a new study. Since the expansion was completed in 2015, eight new fish species have passed through the canal into the Mediterranean. This represents an eight percent rise in species numbers and double the average annual detection rate compared to the period between 1869 and 2015, explain researchers at the Smithsonian Tropical Research Institute (STRI), Panama, and the Leibnitz Center for Tropical Marine Research (ZMT), Germany, who also looked at invasions following the expansion of the Panama Canal.

Historically, the Bitter Lakes of the Suez Canal acted as a hypersaline barrier that constrained marine species’ movements between the Red and Mediterranean seas. Over time, human activities and the canal’s gradual enlargement diluted the lakes and eroded the natural barrier, facilitating the establishment in the Mediterranean of more than 400 non-native marine species, including more than 100 marine fishes, from the Red Sea.

Climate change is likely to amplify the pace of non-native species introductions through the Suez Canal, as the warming of the Mediterranean is predicted to make conditions more conducive for species from the Red Sea.

The socio-ecological consequences of invasions remain poorly understood because it is unknown how these species will perform in new environments, says study co-author Gustavo Castellanos-Galindo, postdoctoral fellow at STRI and guest scientist at ZMT. “More non-native species in the Mediterranean implies more chances for species to become established, some of which could become invasive and have dramatic impacts on ecosystems and on the societies that depend on them.”

To mitigate further invasions through the Suez Canal, the study authors suggest considering the re-salinization of the Bitter Lakes using brine from desalinisation plants along the Suez Canal, or using sophisticated monitoring tools, including environmental DNA and sonar detection, to detect and catch invaders early.

They also suggest that canals be explicitly included in maritime legal agendas implemented by the International Maritime Organisation, the UN agency responsible for regulating shipping.

Michel Bariche, professor at the American University of Beirut investigating biological marine invasions in the Mediterranean, contends the new wave of invasions through the Suez Canal is not related to its expansion, but to the disappearance of natural barriers to the movement of organisms, and probably also to new factors linked to habitat degradation, overfishing and climate change.

Nonetheless, Bariche says the Egyptian government should put more effort into reducing the arrival of organisms to the Mediterranean, noting the best and most cost-effective way to do so is by building a natural barrier. “A hypersaline region can easily be created within the canal and would not allow the survival of marine organisms because of the high salinity.”

doi:10.1038/nmiddleeast.2020.93

Castellanos-Galindo, G. G. et al. A new wave of marine fish invasions through the Panama and Suez Canals. Nat. Ecol. Evol. https://doi.org/10.1038/s41559-020-01301-2 (2020).