CoCoNet Press Release 32

CoCoNet Press Release NOVEMBER 2014



Biota of the Black and Mediterranean Seas have started to change with the introduction of alien species in the last few decades due to lessepsian migration (through the Suez Canal), Atlantic influx, intentionally or unintentionally introduction and climate change. The dispersion of alien species is a dynamic process that shows an increasing trend and is likely to continue in the future. This phenomenon causes severe ecological, socio-economical and human health problems in the entire basin.

A comb jelly, Mnemiopsis leidyi, which was transported to the Black Sea with ship ballast water from the North Atlantic coast, caused enormous ecological impacts and economical damages to the riparian countries' fisheries due to feeding of mostly the larvae and eggs of small pelagic fishes, mainly anchovy, horse mackerel and spratt. A gastropod, Rapana venosa, originally from the Sea of Japan, is the first alien commercial species in the Black Sea and after 1980s it became an export product for all the Black Sea countries. Meanwhile, its impact on the native fauna, especially on mussel and oyster beds, was detrimental.



Rapana venosa preying on mussel beds in the Black Sea coast

As for the Mediterranean Sea, alien species enter from the Atlantic Ocean through the Gibraltar Strait, the Red Sea through the Suez Canal, from the Black Sea through the Canakkale Strait (Dardanelles) and by intentional or unintentional introduction. Some lessepsian sprinter fish species pass the Sicily Strait which is known as a biogeographical boundary between the eastern and western Mediterranean Sea. On the other hand, some species of Atlantic-origin penetrated into the Mediterranean Sea farther east reaching the coast of Sicily from the originally established areas near the Gibraltar Strait. Overall, the main vectors of the Mediterranean alien species are the Suez Canal, shipping and aquaculture.

Alien species have had several consequences on fisheries, biodiversity, human health and economy. Some of the alien fish species have become economically important after the establishment of sustainable populations, such as lizard fish, goatfishes, Spanish mackerel and round herring mostly in the eastern Mediterranean Sea. Similarly some of the crustacean species have become also commercially important, such as kuruma prawn, green tiger prawn, mantis shrimp, swimming crabs, and blue crabs. Some introduced mollusc species, such as the Japanese oyster and Pacific carpet clam, already have a market value.

There are some species which have negative impacts on human health, mostly puffer fishes, Legocephalus spp., an alien jellyfish, Rhopilema nomadica, and a hydroid, white stinger, Macrorhynchia philippina, in the eastern Mediterranean coasts. The eradication of Caulerpa taxifolia and Caulerpa racemosa negatively impact the fisheries and ecosystem in the Mediterranean Sea.

Some species badly affect fishing gears by causing mesh clogging, fouling and damaging. Some alien species impacted also on marine biodiversity, mainly by habitat competition and species displacement.

In Marine Protected Areas (MPAs), as elsewhere, impacts from invasive alien species are seen on ecosystem function, ecosystem structure, and at the level of species communities or habitats as well as at the level of species. What do we have to do ? Key species and key habitats, for example Posidonia meadows, should be protected to combat their invasion. We also have to assess the risk of invasive alien species, prevention, early detection and rapid response as well as eradication and control. Foster development of consolidated information sources at national, international and global levels, on invasive alien species impacts, threats and management in MPAs are also requested in both basins. Through the network of MPAs, these can be done more efficiently.

The CoCoNet Project aims to extract all information related to alien species and MPAs in both the Mediterranean and Black Sea basins to serve all stakeholders, such as managers of MPAs, fishermen, divers and sailors.

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