​How Fast Can an Alien Species Establish in the Mediterranean Through the Suez Canal?
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The Suez Canal is much more than a shipping route. Since opening in 1869, it has also connected two previously separated marine ecosystems: the Red Sea and the Mediterranean.

This has allowed hundreds of non-native organisms, often called alien species or Lessepsian migrants, to enter Mediterranean waters. But how quickly can one of these species establish and spread?

The short answer is: sometimes within a decade, although spreading across much of the Mediterranean usually takes several decades.

Arrival is not the same as establishment

A species must pass through several stages before it becomes established:

1. Arrival: individuals, eggs or larvae enter through the canal.
2. Survival: They tolerate Mediterranean temperatures, salinity, food availability, and predators.
3. Reproduction: A sufficiently large population begins reproducing successfully.
4. Establishment: The population becomes self-sustaining.
5. Expansion: It spreads to new coastlines and islands.

Many species arrive but disappear without forming permanent populations. An alien species is only considered established when it can maintain a population without repeated arrivals from its native range.

Also, not every alien species becomes invasive. That term is generally reserved for established species that spread and cause ecological, economic, or human-health impacts.

What does the research show?

A 2024 study examined 772 historical records involving 130 non-indigenous fish species that entered the Mediterranean through the Suez Canal.

The researchers found that:

- More than half of the introduced fish became established in less than 10 years.
- The first major movement beyond the initial detection region took approximately four years.
- Subsequent geographical expansion occurred in steps averaging about 2.5 years.
- Reaching the central Mediterranean from Suez took approximately 21.5–22 years.
- The dominant direction of expansion was northward and then westward, passing through the Levant, southern Turkey, Cyprus, Greece, and eventually the central Mediterranean.

These figures describe broad historical patterns rather than a timetable that applies to every species.

Read the Scientific Reports study: https://www.nature.com/articles/s41598-024-57109-8.

How quickly can a species reach Greece?

Southern Greece, especially Rhodes, Crete, and the southeastern Aegean, is one of the first European regions encountered by species expanding northwest from the Levant.

For a relatively mobile fish, reaching southern Greek waters can take roughly 10–15 years after the beginning of a successful, detectable expansion. Slower species may require several decades.

Lionfish provide a striking example. Genetic and observational evidence indicates that Mediterranean lionfish spread from the Red Sea through the Suez Canal, established in the Levant, and then expanded through Cyprus, Turkey, and Rhodes using a stepping-stone pattern. Their appearance across these locations over relatively short intervals demonstrates how quickly a suitable, mobile species can expand.

Read the lionfish study: https://www.nature.com/articles/s41598-017-07326-1.

Other organisms move much more slowly. The tropical seagrass Halophila stipulacea, for example, was first reported in Rhodes approximately 25 years after the Suez Canal opened.

Review its Mediterranean invasion history: https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2020.00300/full.

Why are some species much faster?

Several factors determine the speed of establishment and expansion.

Mobility and reproduction

Fast-swimming fish and species with widely dispersed larvae can cover large distances. Species that reproduce early, produce many offspring, or spawn several times per year can establish more rapidly.

Sea temperature

Many Suez migrants originate in warm tropical or subtropical waters. The eastern Mediterranean is warmer than the western and northern parts of the basin, making it easier for heat-loving species to establish there.

Continued warming can make areas farther north and west more suitable, although temperature is not the only controlling factor.

Currents and connected habitats

Ocean currents can transport eggs, larvae, and drifting organisms. Continuous rocky coastlines, seagrass beds, or other suitable habitats act as stepping stones between populations.

Unsuitable habitat can slow or stop expansion even when two locations are geographically close.

Shipping

Ships can transport organisms in ballast water or on their hulls. This can produce long-distance jumps between ports, allowing a species to bypass the slower process of natural coastal expansion.

Detection delays

The first scientific record is rarely the exact moment a species arrived. Small populations can remain unnoticed for years, particularly in poorly monitored areas. Reported expansion times therefore combine biological spread with differences in monitoring and detection.

A realistic Mediterranean timeline

A simplified scenario might look like this:

- 0–4 years: Passage through Suez and initial establishment in the southeastern Mediterranean.
- 5–10 years: Expansion along the Levant, Egypt, Cyprus or southern Turkey.
- 10–15 years: Arrival in parts of southern Greece for faster-moving species.
- Approximately 20–25 years: Expansion into the central Mediterranean around Sicily, Malta, Tunisia or southern Italy.
- 30 years or more: Wider expansion toward the western Mediterranean.

Ship-assisted transport could shorten these times dramatically, while unsuitable habitat or reproductive failure could prevent establishment altogether.

 Why early monitoring matters

By the time an alien species is abundant and widely recognized, eradication may already be impossible. Monitoring near the Suez Canal, the Levant, Cyprus, southern Turkey, and southeastern Greece can provide an early warning before a species expands across the basin.

Fisher observations, citizen-science reports, environmental DNA sampling, and coordinated regional databases can all help detect new arrivals sooner.

The central lesson is that the process is not always slow. A successful alien fish may establish itself in less than a decade and reach Greece within roughly 10–15 years. Expansion into the central and western Mediterranean usually takes longer, but shipping, warming seas, and highly mobile life stages can accelerate the journey.

Use the interactive simulation below to compare slow, moderate, and fast-spreading species and explore how habitat suitability and ship-assisted movement change the timeline.

Introducing 'Exotic Encounters: Mapping Alien Species'

We’re excited to announce the launch of our new project aimed at tracking and mapping non-native species, primarily in Greece and the UK, but extending across Europe as well. Exotic Encounters: Mapping Alien Species is all about protecting local biodiversity by raising awareness about the spread of invasive species and understanding their impact on ecosystems.

More on the page: https://www.mermanconservation.co.uk/exotic-encounters-mapping-alien-species.html
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Yesterday, Chris Taklis had the pleasure of being invited by KOUDRASIS FISHING to talk about the pufferfish species Lagocephalus sceleratus in Greece.

This invasive species, commonly known as the silver-cheeked toadfish, has made its way into the Mediterranean waters, posing significant challenges to local ecosystems and fisheries. In this talk, conducted in Greek, we delved into its impact, the reasons behind its rapid spread, and what measures can be taken to manage this marine intruder. If you're interested in the intriguing world of Lagocephalus sceleratus and its implications for the Greek fishing community, make sure to watch the video!