Researchers predict which Red Sea fishes will colonize the Mediterranean, threatening native species

An international study involving the National Museum of Natural Sciences (MNCN-CSIC) has presented a model capable of predicting which Red Sea fish species are most likely to colonize the Mediterranean, along with the risks this poses to native species. The study, published in the Journal of Animal Ecology, presents a predictive model based on underwater video recordings from both seas and identifies the starry pufferfish, Arothron stellatus, the cinnabar mullet, Parupeneus heptacantha, and the yellow-spotted trevally, Turrum fulvoguttatum—which have not yet become established—as some of the species that may pose the greatest risk if they colonize the Mediterranean. Understanding the risk posed by each species is a key tool for the management and conservation of local ecosystems

Species that do not require coral reefs are better able to adapt to the new habitat and pose a greater threat  

The opening of the Suez Canal in 1869 connected the subtropical Red Sea with the temperate Mediterranean, creating a corridor through which more than 120 species of fish have migrated in the Mediterranean, causing a significant ecological impact. Historically, the reverse flow—species migrating south from the Mediterranean to the Red Sea—has been extremely rare. This is probably due to established environmental barriers: northward-flowing currents passively carry larvae toward the Mediterranean, while the Red Sea's hotter, saltier, and hyper-diverse ecosystem acts as a physiological and competitive barrier for temperate Mediterranean fish. “In the context of what is largely a one-way invasion, we set out to identify which species will be the next to colonize the Mediterranean from the Red Sea and to predict which ones are ready to make the journey next,” explains MNCN researcher Shahar Chaikin.

Surviving Outside the Reef

“Contrary to what we thought, the study has shown us that the main factor determining a fish’s ability to invade is not being a generalist, but rather its ability to survive without coral reefs,” explains Chaikin. “The Suez Canal and the Mediterranean Sea lack the complex coral reefs that characterize the Red Sea. Species that depend on them are most likely filtered out and rarely survive the journey,” he continues.

A list to help preserve the Mediterranean ecosystem

To collect the data, the research team deployed remote underwater video systems at depths ranging from 5 to 150 meters. These devices recorded 179 fish populations in the Gulf of Aqaba (Red Sea) and along Israel’s Mediterranean coast.

The list, compiled from the monitoring of 179 populations (representing 170 species), is a key tool for managing local ecosystems

The recordings revealed that, after arriving in the Mediterranean, species that manage to establish themselves exhibit a high degree of plasticity—or adaptability—since they are able to abandon the habits they had in their original ecosystem and quickly adapt to the resources of their new habitat. the study shows that the new species pose a problem for native species. “The two groups overlap entirely in their habitat use, which suggests an elevated potential for direct competition for resources and space between native and migrating species,” notes Chaikin.

Based on the data collected, the statistical model identifies the Red Sea species most likely to migrate to the Mediterranean in the future. In the current context, in which ocean warming is accelerating the spread of tropical marine species towards higher latitudes, the creation of these lists is a key tool for the management and conservation of local ecosystems.