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The eastern area of the Mediterranean Sea is brimming with non-indigenous species – i.e. species that have travelled, often over large distances, and taken root in new waters. These species include fish, jellyfish, snails, prawns, urchins and more.

We know this because a 2021 report by the General Fisheries Commission for the Mediterranean (GFCM) of the Food and Agriculture Organization of the United Nations (FAO) pointed out that of over 900 non-indigenous species spotted in the Mediterranean and Black Sea, about 700 were in the eastern Mediterranean – making the subregion a hotspot for non-indigenous species.

At a market in Lebanon. © GFCM/Claudia Amico 

More than half of the over 900 species are now permanently established and spreading, warns the report. 

“Climate change and human activities have had a profound impact on the Mediterranean and the Black Sea. We have witnessed, specifically in the eastern part of the Mediterranean, a swift and extreme alteration of the marine ecosystems, and this has led to significant impacts on local communities' livelihoods. In the coming years, we expect the number of non-indigenous species to rise. But scientists and those working in fisheries are gaining a better understanding of this phenomenon, helping countries to speed up mitigation and management measures,” said Stefano Lelli, GFCM Fishery Expert for the eastern Mediterranean.

Redcoat, just one of the about 700 non-indigenous species in the eastern Mediterranean. ©GFCM/Stefano Lelli 

How have these species arrived in the eastern Mediterranean? Several ways. Through shipping, through open boundaries like the Strait of Gibraltar or the ever wider and deeper Suez Canal, through which many species from the Red Sea have entered. Sometimes, commercial species like the Pacific cupped oyster have also been introduced on purpose. At other times, by accident.

Once settled, these species can reshape their new homes. They can pose a threat to native species and ecosystems; to fisheries and tourism; and to people’s health. However, they can also provide an opportunity. More on this later.

The invasion of non-indigenous species in the eastern Mediterranean and the whole region for that matter is not new; first records date back to the end of the nineteenth century, and by the early 1960s some Lessepsian species (species that migrate from the Red Sea to the eastern Mediterranean through the Suez Canal) became common in the Levantine waters.

What is new is that this process has sped up in recent years due to climate change and other human-induced drivers, which are rendering the eastern Mediterranean a more favourable environment to non-indigenous species, at the expenses of the native species.

As a result, countries in the eastern Mediterranean – Cyprus, Egypt, Greece, Lebanon, Israel, Syria and Turkey – have been facing the complex task of mapping, monitoring and managing these all these species. 

Providing forums for all concerned to come together and discuss this matter, carrying out a research programme on blue crab – a non-indigenous species on the rise – and publishing the Non-indigenous species in the Mediterranean and the Black Sea study have been some of the ways in which the GFCM has been helping countries with this task. 

Bluespotted cornetfish. ©GFCM/Stefano Lelli

The study offers comprehensive data sets on non-indigenous species in the Mediterranean and Black Sea.

So how are non-indigenous species affecting people’s lives and the environment in the eastern Mediterranean?

A long-spined sea urchin. ©IUCN ROWA/Ziad Samaha 

From foe to friend 

Fishers in southwest Turkey, for example, have been particularly affected by the rising number of invasive species. In certain areas, these species now make up 80 percent of their catch.

In response, hundreds of fishers along 600 km of coastline from Gökova Bay to Kaş have been working to turn this threat into a commercial opportunity, creating new consumer markets for key non-indigenous species. It is a win-win situation for fishers – as this provides them with a livelihood – and the environment – as non-indigenous species are removed from precious ecosystems.

Non-indigenous species such as lionfish, rabbitfish, urchins, Randall’s seabream and soldierfish all have potential markets and can be caught in large numbers in Turkey. 

A lionfish. ©IUCN ROWA/Ziad Samaha

The blue crab has also become common in the waters of the eastern Mediterranean, and boasts a significant market value in Turkey.

Across the eastern Mediterranean, several non-indigenous species have gained economic value. These include: lizardfish, goatfish, mackerels, round herrings, kuruma and green tiger prawns, mantis shrimps, swimming crab and the Japanese carpet shell.

Blue crab. ©GFCM/Claudia Amico

“Lebanon’s coast has been suffering from extreme anthropological pressure like pollution and climate change – to name a few – and this has led to depleted native marine resources. Depleted native resources also facilitate non-native species to settle,” said Manal Nader, Associate Professor and Director of the Institute of Environment, University of Balamand in Lebanon, and author of an FAO report on pufferfish.

“Non-indigenous species can be a curse and a blessing. We just need to make sure that the “blessing” part outshines the “curse” part. The “blessing” part is best achieved by training our fishers to capture non-indigenous species, and convincing our consumers to accept these new species and our culinary industry to promote them. This will go a long way towards better managing non-indigenous species – reducing their number and impact whilst making the blue economy more resilient. The rabbitfish, the Red Sea goatfish and the lionfish are only some examples of how invasive, non-indigenous species can become a source of income in Lebanon,” added Nader.

The poisonous or venomous kind

While fishers target many non-indigenous species, many other species are discarded due to a lack of value, or in some cases, such as with pufferfishes, lionfish, striped catfish and several jellyfish species, because they are poisonous or venomous, and thus, dangerous for people.

In addition to an increase of blooms of indigenous jellyfish, due to a combination of factors related to global warming and ecosystem degradation, new species of Indo-Pacific origin, like nomad and upside-down jellyfish, have established themselves in the eastern Mediterranean, further affecting local economies as they get entangled in fishing nets or stranded on beaches, frightening visitors.

Silver-cheeked toadfish – a highly toxic species. ©IUCN ROWA/Ziad Samaha   

Six poisonous and venomous non-indigenous fish species are now present in the majority of eastern Mediterranean countries and predicted to expand across the region in the near future.

Several countries, such as Cyprus, Greece, Israel and Turkey, have been rolling out public awareness campaigns to educate about and warn against the threats of poisonous species.

Toxic or not, non-indigenous species also affect fishers as they can damage fishing gear and catches.

Impact on local species

Reports relate the appearance of some new non-indigenous species with the decline of abundance of some local species. In some areas of the Turkish coast, for example, grazing by the non-indigenous herbivorous rabbitfishes has resulted in a shift from well-developed native algae areas to “barrens” with a concurrent dramatic decline in biodiversity and alteration of habitat.

Overall, non-indigenous species compete with indigenous species for space, food and other resources and can lead to a decline or replacement of populations of several local species. For example, an increase in the Lessepsian goldband goatfish is linked to a decline of the indigenous red mullet in shallower waters, while the native barrel jellyfish has been replaced by the non-indigenous nomad jellyfish in the eastern Mediterranean Sea.

Way forward

Apart from fishing and creating new markets for non-indigenous species, what can be done to mitigate the negative impacts of these species?

Rabbitfishes (or spinefoots), another non-indigenous species, spotted in Lebanon. ©GFCM/Stefano Lelli. 

The GFCM report and ongoing GFCM-led discussions with countries in the eastern Mediterranean point to several measures, including: creating marine protected areas to keep native species safe; raising awareness on harmful species; reinforcing regional cooperation and legal measures to monitor and protect marine biodiversity; improving assessments on the risks of non-indigenous species; creating monitoring programmes for commercialised non-indigenous species; and boosting the participation of stakeholders.

“The GFCM is working closely with countries and partners to deepen understanding of non-indigenous species in the eastern Mediterranean. The results and lessons learnt from this process could then be used to build knowledge on non-indigenous species across the Mediterranean and Black Sea so they can be managed effectively,” said Elisabetta Morello, GFCM Fishery Officer.

A reticulated leatherjacket. ©IUCN ROWA/Ziad Samaha

“International and regional cooperation as well as concerted action are needed to tackle non-indigenous species in the Mediterranean and Black Sea. Needless to say, the impacts of non-indigenous species need to be monitored by all countries in the region,” said Bayram Öztürk, author of the GFCM's non-indigenous species in the Mediterranean and the Black Sea study, a professor at the Istanbul University, Faculty of Fisheries and Head of the Turkish Marine Research Foundation.

Ahead of #WorldEnvironmentDay: Focus on eastern #Mediterranean - a hotspot for non-indigenous species

Of over 900 non-indigenous species in the Med & Black Sea, about 700 are in eastern Med

How has it happened? What are the impacts? How is it addressed? https://t.co/hF83Il9c5c pic.twitter.com/0poeWNk4HZ

— General Fisheries Commission for the Mediterranean (@UN_FAO_GFCM) June 2, 2022