Model predicts which Red Sea fish will invade Mediterranean next

Over a century and a half ago, when the Suez Canal first cut through Egypt, it opened a waterway that would quietly reshape the Mediterranean. More than 120 fish species have since slipped through that passage from the Red Sea, establishing themselves in waters where they had never existed before. Now researchers at Tel Aviv University have built a tool to see what comes next—a statistical model that can identify which Red Sea fish are most likely to make the crossing and thrive on the other side.

The work began with a simple question: what separates the fish that successfully invade from those that don't? Dr. Shahar Chaikin, working under the guidance of Prof. Jonathan Belmaker at the university's School of Zoology, led a team that deployed underwater cameras at depths ranging from 16 to 492 feet, capturing hundreds of hours of footage in both the Gulf of Eilat and along Israel's Mediterranean coast. They analyzed 179 fish populations, comparing species that had already made the journey with their close relatives still confined to the Red Sea. The model identified three leading candidates for future invasion: the stellate pufferfish, the cinnabar goatfish, and the yellowspotted trevally.

What emerged from the data was unexpected. The researchers had assumed that successful invaders would be ecological generalists—fish flexible enough to thrive in many different environments. Instead, they found the opposite. The fish most likely to establish themselves in the Mediterranean were those that depended least on coral reefs. The logic is straightforward: the Suez Canal and the Mediterranean lack the extensive coral reef ecosystems that define the Red Sea. A fish that cannot survive without coral simply cannot complete the journey. Those that succeed are the ones that never needed coral in the first place.

But the story does not end with arrival. The research revealed that invading fish do not simply transplant their old habits to a new home. Once in the Mediterranean, they shift their behavior, occupying different habitats than they used in the Red Sea. They also do not settle into empty ecological niches waiting to be filled. Instead, they move into the same spaces used by native Mediterranean species, suggesting that competition for food, shelter, and space is far more intense than scientists had previously understood. The invaders are not finding refuge in unused corners of the ecosystem—they are pushing into occupied territory.

As Mediterranean waters continue to warm, tropical fish will find the conditions increasingly hospitable. Belmaker notes that previous research focused almost entirely on species that had already arrived, trying to explain invasions after the fact. This study took a different approach: it looked backward to the source populations, asking what characteristics existed before the crossing. That shift in perspective opens a door from explanation to prediction. Environmental authorities and conservation planners could use models like this one to identify new arrivals sooner, to understand what ecological pressures might follow, and to prepare for the changes ahead. The Mediterranean is warming, and the Red Sea is sending its fish. Now science has a way to see them coming.