Invasive species are changing the nature of the Mediterranean Sea

The Mediterranean Sea is being invaded by hundreds of fish, jellyfish, prawns and other marine species from outside the region.

More than 1 000 non-indigenous species have been identified in the Mediterranean and the Black Sea. Over half have established permanent populations and are spreading, causing concern about the threat they pose to marine ecosystems and local fishing communities.

“Climate change and human activities have had a profound impact on the Mediterranean and the Black Sea,” says Stefano Lelli, a fishery expert for the eastern Mediterranean working for the General Fisheries Commission for the Mediterranean (GFCM).

This regional fisheries management body, established by FAO, is leading efforts to promote sustainable fisheries and aquaculture in the Mediterranean and the Black Sea. It works with fishers, conservationists, scientists and government authorities to better understand the rise in non-indigenous species and help countries improve their mitigation and management measures.

“We have witnessed a swift and significant alteration of marine ecosystems, and this has led to several impacts on local communities' livelihoods. In the coming years, we expect the number of non-indigenous species to continue rising,” adds Lelli.

The Mediterranean Sea is undergoing a “tropicalization” process as water temperatures rise, largely due to climate change. In addition, many species have migrated via well-travelled shipping routes such as the Strait of Gibraltar or the Suez Canal, often attached to the hull of ships or inside them in the ballast waters. Other species, such as the Pacific cupped oyster and the Japanese carpet shell, were introduced for aquaculture during the 1960s and 1970s and have since escaped and colonized Mediterranean ecosystems.

Once established, non-indigenous species can outcompete native ones and alter their surrounding ecosystems, with potential economic implications for fisheries and tourism or even human health. For example, six poisonous and venomous non-indigenous fish species, such as pufferfish, lionfish and several jellyfish species, are now present in the eastern Mediterranean and can be toxic to humans if touched or ingested.

FAO’s GFCM is supporting Cyprus, Egypt, Greece, Lebanon, Israel, Syria and Türkiye in the complex task of mapping, monitoring and managing these invasive species. This Commission also serves as a forum for the affected countries to share information and strategies.

“The results and lessons learnt from this process should build knowledge on non-indigenous species so they can be managed effectively,” says Elisabetta Morello, GFCM Fishery Officer.

Turning a threat into an opportunity

Fishers all over the region have been affected by this trend. However, with the support of the GFCM, they are finding new ways to turn these invasions into opportunities.

In southwest Türkiye, where invasive species can account for 80 percent of the catch in some areas, fishers are gradually creating new consumer and export markets for species like lionfish, urchins and Randall’s seabream.

Lebanon is also training fishers to capture non-indigenous species, encouraging consumers to try them. “Rabbitfish, Red Sea goatfish and lionfish are some examples of non-indigenous species becoming a source of income in Lebanon,” says Manal Nader, Associate Professor and Director of the Institute of Environment at the University of Balamand in Lebanon.

In Tunisia, two non-indigenous species of blue crabs, which were threatening traditional fishing, were turned into a lucrative business when FAO and the Tunisian Government helped connect fishers to new markets. The same is happening in Spain and other parts of the Mediterranean, triggering a dedicated GFCM research programme to manage these species.

“Monitoring and mitigating the impacts of non-indigenous species on marine ecosytems is expensive, and eradication in the majority of cases is impossible,” says Miguel Bernal, GFCM Senior Fisheries Officer.

“When commercialization and utilization are possible, either as a source of food, pharmaceutical products or others, commercial fishing has proven to be the most effective tool for addressing this problem.” 

Protecting native species

To safeguard native species the GFCM supports the creation of fisheries restricted areas. Well conserved areas have proven to be more resilient to the impact of non-indigenous species.

“International and regional cooperation as well as concerted action are needed to tackle non-indigenous species in the Mediterranean and Black Sea,” says Bayram Öztürk, author of the GFCM's study on non-indigenous species in the Mediterranean.

“Needless to say, the impacts of non-indigenous species need to be monitored by all countries in the region. Once a species is introduced, it may be too late to eradicate.”

With the GFCM’s study, Non-indigenous species in the Mediterranean and the Black Sea, as the first step, the Commission is now working with countries of the region to adapt fishing techniques, connect to new markets and help fishers make new livelihoods out of these catches, while also maintaining its crucial work of preserving marine ecosystems through protected areas.

Learn more

• Website: FAO & General Fisheries Commission for the Mediterranean
• Publication: Non-indigenous species in the Mediterranean and the Black Sea
• Website: FAO & Fisheries and Aquaculture
• Story: From invasive species to prized export