More than 120 fish species have already migrated from the Red Sea to the Mediterranean since the opening of the Suez Canal over 150 years ago. Now, researchers at Tel Aviv University have developed a statistical model capable of predicting which species are likely to be next. Based on extensive field observations in both seas, the model has identified three species with particularly high potential to invade the Mediterranean in the future ( the full list is available in the published paper ): the stellate pufferfish ( Arothron stellatus ), the cinnabar goatfish ( Parupeneus heptacantha ), and the yellowspotted trevally ( Turrum fulvoguttatum ).
The study was led by Dr. Shahar Chaikin as part of his doctoral research at Tel Aviv University, under the supervision of Prof. Jonathan Belmaker of the School of Zoology, the Wise Faculty of Life Sciences, and the Steinhardt Museum of Natural History. Additional contributors included Dr. Tal Gavriel, doctoral student Avery Deveto, and Shahar Malamud. The findings were published in the Journal of Animal Ecology .
The new model ranks Red Sea fish species according to their likelihood of becoming future migrants to the Mediterranean. The researchers explain that the model is intended not only to understand how past invasions occurred, but also to enable authorities and marine scientists to prepare in advance for future invasions, particularly in light of the warming of the Mediterranean Sea, which is accelerating the northward spread of tropical species.
According to the researchers, such watchlists could become an important tool for the early detection of invasive species, environmental monitoring, and informed decision-making aimed at protecting the marine ecosystem.
What Makes a Fish a Likely Invader?
To answer this question, the researchers deployed stereoscopic baited remote underwater video systems (stereo-BRUVs) at depths ranging from 5 to 150 meters in the Gulf of Eilat and along Israel's Mediterranean coast. Using hundreds of hours of video footage, they analyzed 179 fish populations and compared species that have already invaded the Mediterranean with those that remain confined to the Red Sea. Unlike previous studies, which focused primarily on species that had already invaded, this study also examined the source populations in the Red Sea, making it possible to distinguish between the traits that enabled the invasion and the changes that occurred afterward.
The central finding was surprising: the strongest predictor of invasion success was not whether a fish species is a "generalist," capable of living in a wide range of habitats, but rather its lack of dependence on coral reefs.
Dr. Shahar Chaikin explains: "The Suez Canal and the Mediterranean contain very few coral reefs like those found in the Red Sea. Species that depend on coral reefs are therefore unlikely to complete the journey. The fish that succeed in invading are those that do not rely on coral reefs for survival in the first place."
Once They Reach the Mediterranean, the Fish Change Their Habits
The study also revealed how fish behave after successfully establishing themselves in the Mediterranean. Contrary to expectations that they would continue using the same habitats they occupied in the Red Sea, the researchers found that they quickly shift their habitat preferences and take advantage of the habitats available in their new environment.
Moreover, contrary to the common assumption that invasive species occupy "empty ecological niches," the study found that the migrating fish use the very same habitats occupied by native species. This suggests that competition for food, shelter, and space between invasive and native fish may be much greater than previously thought.
Prof. Jonathan Belmaker concludes: "Until now, researchers have tried to understand biological invasions primarily by examining species that had already reached the Mediterranean. We took a step back and asked what characterizes these species before they begin their journey. This distinction allows us to move beyond explaining invasions that have already occurred toward predicting the next ones."
The researchers add that as the Mediterranean continues to warm, tropical species are expected to become increasingly capable of establishing themselves there. They believe that incorporating models of this kind into environmental monitoring programs could help detect new species at an early stage and improve preparedness for the ecological changes expected in the Mediterranean ecosystem.
Link to the article:
https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.70293