Why is this fish biting swimmers at Mediterranean beaches?
The white seabream is no newcomer, but it seems to be becoming more aggressive. One Israeli expert blames climate change, and cites changes in behavior of insects and germs, too
Rachel Ashur had been swimming for 20 minutes in the Mediterranean waters off the coast of Tel Aviv earlier this summer when she felt something bite her leg — “not like a jellyfish, but a sharp, piercing sting.” The laceration drew blood, leaving a small wound, said Ashur, 30, who recently moved to the city.
Tzvi Bar-David, a New Yorker, was on a summer vacation to Israel when he got bit. He was about 30 feet (9 meters) out into the water at waist level when, “all of a sudden, there was a little school of fish that came and bit me.”
Up and down the Israeli coast and even in the Sea of Galilee, swimmers are reporting being nibbled on, often painfully.
The main culprits in the Mediterranean, the experts say, are Diplodus sargus fish, also known as sargo or white seabream, usually about 10 to 15 centimeters (four to six inches) long, which are native to the Sea. (The species can reach up to 40 centimeters long, but the larger fish tend to stay in deeper waters and avoid humans.) The fish biting in the Sea of Galilee, meanwhile, are cichlids, also called St. Peter’s fish, and other tilapias.
Although the sargo is not new to the waters off Israel’s shore, the incidence of biting seems to be escalating, with news reports and social media posts on the rise in the past year. TripAdvisor has had posts documenting tourists being bitten in 2015 and 2016.
What’s going on? Some experts cite climate change as a major factor, and say the biting fish are only one, minor manifestation of the impact of warming temperatures. Certain insect behaviors are changing too, they note.
Elad Goren, a medic on Gordon Beach in Tel Aviv, said he started noticing the biting fish about three years ago.
The fish bite in both shallow and deep water, and are attracted to old cuts, dead skin and varicose veins, he said.
“They smell blood; if you have small cuts they open them,” said Goren, who has patrolled Tel Aviv’s beaches as a medic for the past 16 years, treating small beach emergencies.
Goren estimated that in August, the height of the beach season, he was treating about 20 people a day for the bites.
They smell blood; if you have small cuts they open them
In one extreme case in 2015, a bacterial infection from untreated wounds landed two people in the hospital. But most bites are small and require nothing more than initial cleansing, if that. Rachel Ashur’s bite didn’t require any care, she said, and healed quickly on its own.
What’s going on?
“This is not a new story,” said Dr. Menachem Goren (no relation to the beach medic), a professor and principal research associate in the Department of Zoology at Tel Aviv University, who noted that the sargo fish are ancient inhabitants of the Mediterranean. “[The fish] are seeking food. When they see our feet, they bite. They consider it plankton,” said Goren. “People shouldn’t take it too seriously.”
Dr. Goren said sargo fish like shallow water and that the young ones in particular try to bite the little bubbles that humans make while swimming. “Other fish are frightened [of humans] and they don’t go into shallow water,” he said.
Prof. Yoav Yair, dean of the School of Sustainability at the Interdisciplinary Center (IDC) Herzliya, confirmed that the fish are veterans, but said the sargo fish are “notoriously curious and territorial,” and that he had noticed an increase in reports of them biting in recent years.
Stressing that no thorough research has been carried out to check if there is an actual rise, Yair said any verifiable increase in biting could be tied to several factors, including but not limited to climate change.
After he and his daughter were bitten on separate Tel Aviv beaches, Yair met with several marine biologists to try to pin down the cause. “It was really surprising, since I’ve been swimming [here] since childhood,” said Yair.
He posited that increases in average temperature and the warming of the sea may be to blame, as well as changes in the habitats of the fish, which disturb them and possibly make them more aggressive.
The Eastern Mediterranean has warmed by 3 degrees Celsius (5.4 degrees Fahrenheit) over the past 30 years, according to research by the Israel Oceanographic and Limnological Institute.
Meanwhile, over-fishing, commercial shipping, leisure sailing from tourism, and offshore drilling for oil and gas have significantly impacted the fish populations near the Israeli coastline, said Yair. Pollution runoff also threatens the fish’s natural habitats, he added. These factors combine together to produce a more stress-inducing environment that could make the fish more aggressive.
Not just fish
Yair pointed to other unusual patterns of behavior, by insects, due to increasing temperatures.
During this summer’s heatwaves, anecdotal reports of cockroaches flying to the tops of apartments in Tel Aviv were widespread. Cockroaches usually walk on the ground unless temperatures reach a threshold too unbearable for them, which is about 35 to 36 degrees Celsius (95-97 degrees Fahrenheit). This past July was one of the hottest Julys ever recorded in Israel, with an average temperature nearly 3 degrees Celsius higher than normal.
Climate change is spelling other troubles, too, he warned.
“Trees are dying because of the invasion of the palm beetle, which is also an intruder of tropical origin,” said Yair.
Palm beetles are native to South Asia and feed off of coconut, oil and date palm trees. Previously, Israel was too cold for the small red insect to thrive in; now, it’s one of 60 countries where they are to be found. Eradicating them is difficult, but possible, with pesticides and traps.
Yair added that there is even evidence that malaria, usually found in warm, humid areas where the mosquitos that carry it thrive, is migrating north — though not as far as Israel, yet. (Malaria is typically found in sub-Saharan Africa and parts of Latin America. But researchers predict it will move into the Eastern Mediterranean basin by 2050, including Turkey and parts of Egypt. The same is true of other mosquito-borne diseases like dengue fever, where climatic pattern change could lead to incidences in new places.)
Maintaining a tolerable environment
So how should people avoid getting bitten?
Beach medic Elad Goren suggested swimmers avoid standing too close to other people or standing too long in one spot.
But TAU’s Menachem Goren said the only way to be certain not to be bitten was to stay out of the water altogether. “There’s no [other] way to prevent it,” he said.
Still, Dr. Goren sounded somewhat amused by the biting fish fascination. “It’s amazing that people are complaining about this,” he said, but “then go to a spa to get this treatment.”
Goren was referring to the fact that in some spas worldwide, including in Israel, people pay for a different species of fish to nibble off dead skin, leaving the soles of their feet smooth and soft. At Doctor Dag in Eilat, and at spas on Tel Aviv’s Allenby Street just a few hundred meters from the beach, for instance customers pay 50 shekels (about $15) for about 400 fish to bite for 20 minutes.
Not entirely joking, Yair said cockroaches, fishes, beetles, and even germs are seeking “revenge” on humans for wreaking havoc on the environment.
“But seriously,” he warned, “if we want to maintain tolerable environmental conditions, we need to stop altering the planet.”
