A model ranks Red Sea fish by their potential to enter the Mediterranean, highlighting three species for closer monitoring.Underwater surveys linked invasion potential most strongly to independence from coral habitats, with habitat flexibility also playing a role.Established migrants overlapped with native fish in habitat use, suggesting possible competition without demonstrating specific population losses.<\/p>\n
More than 120 fish species have already passed from the Red Sea into the Mediterranean.<\/p>\n
The route opened with the Suez Canal more than 150 years ago. Since then, tropical fish have steadily entered a sea that once blocked their northward movement.<\/p>\n
The next arrivals may no longer be complete surprises.<\/p>\n
A model developed by Tel Aviv University<\/a> researchers ranks Red Sea fish by their chances of invading the Mediterranean. Three species stand out: the stellate pufferfish, cinnabar goatfish, and yellowspotted trevally.<\/p>\n Their scientific names are Arothron stellatus, Parupeneus heptacantha, and Turrum fulvoguttatum.<\/p>\n Conceptual framework of the multi-comparison approach used to characterize Lessepsian invasion. (CREDIT: Journal of Animal Ecology) <\/p>\n The forecast rests on an unexpected trait. Successful migrants are not simply fish that tolerate many habitats. They are fish that do not depend heavily on coral reefs.<\/p>\n That difference may help authorities watch for new arrivals before they become established. It also points to greater competition between newcomers and native Mediterranean fish.<\/p>\n A Journey with a Difficult First Stage<\/p>\n The study was led by Dr. Shahar Chaikin during his doctoral research at Tel Aviv University.<\/p>\n Dr. Tal Gavriel, doctoral student Avery Deveto, and Shahar Malamud also contributed. <\/p>\n Researchers examined the invasion route from both sides of the canal. That choice mattered.<\/p>\n Earlier studies often concentrated on species that had already entered the Mediterranean. Such an approach can blur two separate questions.<\/p>\n One concerns the traits that allow a fish to invade. The other concerns changes that happen after it arrives. Chaikin and his colleagues studied both the source populations and the established migrants. Their analysis covered 179 fish populations across the Red Sea and Mediterranean.<\/p>\n Study regions and the stereo-BRUVs design. (CREDIT: Journal of Animal Ecology) <\/p>\n They used stereoscopic baited remote underwater video systems. The equipment recorded fish at depths between 5 and 150 meters.<\/p>\n Hundreds of hours of footage allowed the team to compare species that had migrated with those still confined to the Red Sea.<\/p>\n Coral Dependence Becomes a Barrier<\/p>\n A fish living comfortably in many settings might seem like the obvious invader.<\/p>\n The results did not support that simple idea. The strongest predictor was whether a species relied on coral reefs.<\/p>\n \u201cThe Suez Canal and the Mediterranean contain very few coral reefs like those found in the Red Sea,\u201d Chaikin said.<\/p>\n \u201cSpecies that depend on coral reefs are therefore unlikely to complete the journey.\u201d<\/p>\n The fish that succeed already know how to live without those reef systems.<\/p>\n That gives them an advantage before they enter the canal. They do not need to find the same coral habitat<\/a> at each stage.<\/p>\n The model also suggested that shallower-living species had greater invasion potential. However, coral independence carried far more weight. This finding reframes the first stage of migration.<\/p>\n The three fish species ranked by the new model as having the highest invasion potential (left to right): the cinnabar goatfish, the stellate pufferfish, and the yellowspotted trevally. (CREDIT: Tel Aviv University Trust) <\/p>\n The challenge is not merely crossing a long waterway. A species must pass through environments that may lack the structures it normally uses.<\/p>\n A coral specialist can swim into the canal and still fail to establish a path onward. A fish accustomed to sand, open bottom, or other non-coral settings faces fewer habitat breaks.<\/p>\n Three Fish Move onto the Watchlist<\/p>\n After identifying the most useful traits, the team built a forecasting system.<\/p>\n The model ranked Red Sea species by their similarity to fish that had already invaded. Three high-potential candidates emerged near the top.<\/p>\n The stellate pufferfish can grow into a large, strongly marked fish. The cinnabar goatfish and yellowspotted trevally also matched the ecological profile linked with successful migration.<\/p>\n The full list appears in the published paper.<\/p>\n The researchers do not claim that each species will certainly invade. A statistical ranking identifies potential, not a timetable. Still, such predictions can focus monitoring.<\/p>\n Marine scientists cannot watch every Red Sea species with equal intensity. A shorter list gives them a practical place to begin. The Mediterranean\u2019s<\/a> warming waters add urgency.<\/p>\n Species that depend on coral reefs are less likely to migrate from the Red Sea to the Mediterranean, resulting in a lower invasion potential. (CREDIT: Tel Aviv University Trust) <\/p>\n As temperatures rise, tropical fish may find it easier to survive farther north. Species that once encountered unsuitable conditions may gain new opportunities to establish populations.<\/p>\n The watchlist therefore combines current habitat traits with a changing environmental background.<\/p>\n Arrival Does Not Preserve Old Habits<\/p>\n The research did not stop when a fish crossed into the Mediterranean. Once established, migrant species changed how they used habitat.<\/p>\n The team had expected some newcomers to retain the preferences seen in the Red Sea<\/a>. Instead, the fish shifted toward what the Mediterranean offered.<\/p>\n They did not all move in one consistent direction. Some used rocky areas. Others expanded into silt, macroalgae, or broader habitat ranges.<\/p>\n The important pattern was flexibility after arrival. A species could enter because it lacked coral dependence, then reorganize its habitat use in the new sea.<\/p>\n That two-step process helps explain why predictions based only on native behavior can fail.<\/p>\n A fish may appear tied to one set of conditions in the Red Sea. After migration, it may occupy something quite different.<\/p>\n This adaptability makes established invaders harder to contain within expected boundaries.<\/p>\n No Empty Niche Waiting for Them<\/p>\n Another finding challenged a common idea about biological invasions. Introduced fish did not mainly settle into unused habitat.<\/p>\n They occupied the same types of places as native Mediterranean species.<\/p>\n That overlap suggests newcomers may compete for food, shelter, and space. The study found that established migrants became difficult to distinguish from native fish by habitat<\/a> use alone.<\/p>\n In ecological terms, they blended into the existing community.<\/p>\n Yet visual similarity in habitat does not mean the arrival has no effect. If two species rely on the same rocky bottom, depth range, or feeding area, their needs can collide.<\/p>\n Competition may become stronger than earlier assumptions suggested.<\/p>\n The researchers did not directly measure every competitive interaction. Their habitat findings identify the conditions where such pressure may occur.<\/p>\n That distinction matters. The work predicts where overlap exists, not which native species will decline.<\/p>\n A Model Built for Early Warning<\/p>\n \u201cUntil now, researchers have tried to understand biological invasions primarily by examining species that had already reached the Mediterranean,\u201d Belmaker said.<\/p>\n \u201cWe took a step back and asked what characterizes these species before they begin their journey.\u201d<\/p>\n That shift turns a historical question into a forecasting tool.<\/p>\n Instead of asking only why yesterday\u2019s invaders succeeded, the model asks which fish deserve attention now. Early detection could give environmental<\/a> agencies more options.<\/p>\n A newly arrived species may remain limited to a small area. Once it spreads widely, monitoring and management become more difficult.<\/p>\n The researchers believe watchlists could guide surveys, environmental planning, and decisions about marine protection. The model may also improve as scientists collect more observations.<\/p>\n Field data from both seas remain essential because invasion involves more than climate. Habitat, depth, abundance, and post-arrival flexibility all shape the outcome.<\/p>\n Practical Implications of the Research<\/p>\n Marine monitoring programs could use the rankings to decide where to place cameras, surveys, and identification efforts.<\/p>\n Species near the top of the list may deserve closer attention around the Suez Canal and Israel\u2019s Mediterranean coast. Authorities could also train observers to recognize likely newcomers before their populations expand.<\/p>\n The study suggests that coral dependence should become part of future risk assessments.<\/p>\n