A pod of 15 dolphins was spotted off the coast of Tel Aviv and Herzliya on Saturday - a now not-uncommon sight that has led experts to conclude that the sea mammals have taken up permanent residence near Israel's shores.

The annual report released last week by the Israel Marine Mammal Research and Assistance Center says it has identified 181 bottlenose dolphins by the distinctive markings on their dorsal fins. The most frequently sighted dolphin this year is Ziggi and her calf, Zigmund, and another female that recently gave birth. Among the 15 sighted yesterday are some that are known from previous sightings as well as a few new calves.

"We believe there are between 300 and 400 Mediterranean bottlenose dolphins near Israel's shoreline," Dr. Aviad Scheinin chairman of the research center, which is a non-profit group, said yesterday. "The data of the past year strengthens research I did at the University of Haifa showing that the bottlenose dolphin has a permanent population near Israel's shores and is an inseparable part of Israel's flora and fauna."

Bottlenose dolphins, which feed mainly on fish from the sea bed, can usually be found at depths of between 40 to 80 meters and about 6 kilometers offshore. But according to Scheinin, the dolphins sometimes venture much closer and can sometimes be seen in ports.

Scheinin, who also coordinates the surveys for the research center, says the dolphins are threatened mainly by marine pollution and by fishing nets, in which they become trapped. In all cases when sick dolphins reached the shore, he said, it was too late to save them, and not always was it clear what had harmed these dolphins.

About two weeks ago, two striped dolphins were found dead on the shore, apparently after they drowned in fishing nets.

Sea turtles are another marine animal at risk of being caught in fishing nets. According to the Israel Nature and Parks Authority, hundreds of sea turtles die this way every year.

The Israel Marine Mammal Research and Assistance Center, which is headquartered at the Mevo'ot Yam Naval School at Michmoret, halfway between Tel Aviv and Haifa, conducted 52 surveys last year covering some 1,500 kilometers, assisted by yachting clubs, private yachts, Israel Nature and Parks Authority boats and the research ship Mediterranean Explorer. One of these surveys made an extremely rare sighting of a gray whale close to Israel's shoreline.