Overfishing leading to jellyfish invasion, threatening Dolphins in Istanbul Strait
With jellyfish numbers rising at alarming rates and dolphins suffering in Turkey’s Bosphorus due to overfishing, experts are warning officials to take measures to check fishermen from exploiting the waters.
Three short-beaked common dolphins were found dead on the Karaköy neighborhood on the European side and Vaniköy neighborhood on the Asian side of Istanbul on the morning of Feb. 23.
“We figured out that they [dolphins] died while entangled in fishing nets. They had scars on their bodies, and it seemed that they suffered from abnormal bleeding,” said Arda Tonay, the head of the Turkish Maritime Research Foundation (TÜDAV).
Stating that fishermen onboard during midnights should be kept an eye on, Tonay said, “Those who are responsible for the death of these dolphins should be punished.”
Speaking to Demirören News Agency, Tonay highlighted that these short-beaked common dolphins are open-sea fish and blamed fishermen who are using the seine-hauling fishing method for the problem of overfishing seen in the strait.
“We should limit industrial fishing in the Istanbul Strait because it is a very narrow migratory path for fish,” Tonay added.
Making a call to those who use the seine-fishing method to catch fish, he said, “When you realize that there is a dolphin in your nets, please take it out and release it back to the sea.”
Meanwhile, on the same morning of Feb. 23, residents in the neighborhoods of Arnavutköy, Ortaköy, and Bebek on the European side of the city witnessed a large number of jellyfish accumulating near the shore.
“Normally, there are jellyfish in the Marmara Sea, but lately, there is a massive increase in its population,” said Melek İşinibilir Okyar, the dean of Aquaculture Faculty of Istanbul University.
According to her, the north-east winds and overfishing are two major reasons to blame.
“Istanbul experienced harsh snowy days at the beginning of February. The winds from the Black Sea affected the current in the sea,” Okyar said.
Highlighting the danger of overfishing in the Istanbul Strait, she said: “Some fish species feed on jellyfish, like mackerel or sprat fish. What happened to both these species? Due to overfishing, these species do not exist in the Marmara Sea anymore.”
According to Okyar, the increase in the jellyfish population is a result of a chain of events.
“When you overhunt, you kill fish species. When you kill fish species, jellyfish feel no threat from other species who feed on them. When there is no threat, the population of jellyfish increases.”