Invasive scalloped jellyfish depletes local fish populations
Istanbul University (IU) Dean of the Faculty of Aquatic Sciences Prof. Dr. Melek Işibilir Okyar stated that one of the invasive species, the scalloped meduz, was transported to the Marmara Sea through the Bosphorus, saying: “The Marmara Sea it is the second most important fishing area in Turkey after the Black Sea. Sea. Here it has caused a very serious decline in fish populations such as sardines and sprats, especially anchovies”. saying.
teacher. Dr. Okyar said that the physicochemical and trophic structure of the Sea of Marmara allows for the settlement of alien and opportunistic species and population surges.
Stating that environmental problems such as eutrophication, overhunting and habitat destruction increase the abundance of invasive species and the number of species, Okyar said: “The scalloped jellyfish is one of these invasive species. Although it resembles jellyfish due to its transparent appearance, it is a scalloped, carnivorous marine animal called ‘mnemiopsis leidyi’, which is included in a different group. he said.
teacher. Dr. Okyar stated that the scalloped jellyfish feeds on zooplankton, fish eggs and larvae, and can eat 10 times its own body weight in one day.
ANCHOR WAS THE FIRST AFFECTED
Pointing out that the ships moved from the Atlantic Ocean, which is the natural habitat of these creatures, to the Black Sea with ballast waters in the late 1980s, Okyar explained that from there they reached the Sea of Marmara and the Mediterranean Sea. through the upper current of the Bosphorus.
teacher. Dr. Okyar stated that the combed jellyfish continued to develop very rapidly in the years when it first arrived in the Black Sea, since no animals fed on it. In other words, it means a living being that has both male and female characteristics in a single individual at the same time. Naturally, a single individual can form quite a large colony on its own.” he used his statements.
Emphasizing that the scalloped jellyfish has a regenerative feature, Okyar said that in this way it can complete the damaged parts of the body, in individuals divided into two or more parts, each part completes itself, and each part survives as an individual.
teacher. Dr. Explaining that the anchovy is an extremely important fish stock in the Black Sea and the Sea of Marmara, Okyar continued as follows:
“The first species of fish to affect the scalloped meduz in the Black Sea was the anchovy. In the 1990s, very serious declines in fish populations occurred. This situation created a very serious economic problem in fish stocks. The scalloped meduz was transported to the Sea of Marmara via the Bosphorus. The Sea of Marmara is the second most important fishing area in Turkey after the Black Sea. Here, it has caused a severe decline in stocks of fish such as sardines and sprats, especially anchovies. We have been following this genre for many years. In the mid-1990s, another species of jellyfish that preyed on this species reached the Black Sea and the Sea of Marmara with ballast water and began to suppress this species somewhat. Compared to the past, the fishing industry has relaxed a bit in this regard. This species, which is relatively less common than in previous years, still shows periodic increases, and other fish stocks, especially anchovy, are experiencing serious problems when this increase is observed.
Emphasizing that there is an increase in the reproduction of the combed jellyfish, especially with increasing water temperatures, Okyar stated that climate change and temperature increases provide an advantageous environment for similar and these exotic species.
teacher. Dr. Okyar added that efforts to improve the ecosystem must be increased in order to restore marine biodiversity. (AA)