Indo-Pacific bottlenose dolphins inhabit waters near Mikurajima on Aug. 2024. (Yumi Nakayama)

Photo/Illutration Indo-Pacific bottlenose dolphins off Mikurajima show an interest in humans on Aug. 10. (Yumi Nakayama)

Residents of an island 200 kilometers south of central Tokyo have developed sightseeing rules to promote a peaceful coexistence with dolphins, the star attractions of the area.

An estimated 130 dolphins inhabit waters around Mikurajima, an island with 300 residents. The marine mammals have long attracted hordes of visitors.

Islanders started a survey to distinguish the dolphins three decades ago. The findings have been reflected in countermeasures to better control tourists at Mikurajima island.

A large passenger ferry departs from Takeshiba Pier in Tokyo’s Minato Ward late at night. By early morning, tiny Mikurajima comes into sight in the dark blue ocean, its contour characterized by precipices formed through wave erosion.

This offers a good habitat for Indo-Pacific bottlenose dolphins.

In mid-August, a tour boat along the coast stopped when a gray dorsal fin was spotted between waves.

The guide signaled it was time to put on fins and a snorkel, saying, “You can go in from the left.”

A pod of dolphins, some looking very young, silently approached and watched a diver entering the sea.

The diver swam with the dolphins for some time, following the rules of neither touching them nor using a camera flash.

Dolphins in the area started drawing considerable attention during the latter half of the 1980s, when divers from nearby Miyakejima island traveled to Mikurajima to view the aquatic mammals.

In the 1990s, the “dolphin swim” trend, in which divers spent time with dolphins under the surface, took off.

The number of visitors, including those using ferries from the Izu Peninsula in Shizuoka Prefecture, surged.

Alarmed by the influx, volunteer islanders founded the Mikurajima dolphin association in November 1993, and started the dolphin identification study the following year.

“The visionary tactics were aimed at working out rules after evaluating possible effects on dolphins via scientific approaches,” said Kazunobu Kogi, 51, one of the members who later established the Mikurajima tourism association.

The volcanic eruption on Miyakejima in 2000 forced all residents to flee and temporarily ended the sightseeing boom. Ferry operations connecting Mikurajima island with central Tokyo were suspended.

During this period, Mikurajima village adopted a nature conservation ordinance and other restrictions to protect dolphins.

Working with the Tokyo metropolitan government, which has jurisdiction over the village, the islanders began an “eco-tourism” project in April 2004. The project came under the responsibility of the newly created tourism association.

Between March and November, up to 45 sightseeing boats can conduct daily dolphin observation tours from Mikurajima and Miyakejima.

The number of passengers and departure times must be reported to the association in advance.

Regulations, such as keeping a safe distance between boats and not chasing dolphins, were introduced.

To prevent violations, a surveillance boat is deployed on the hottest days in summer.

Researchers film dolphins from late June through late October to determine the composition of each pod and the mammals’ relationships with one another.

Dolphins can be distinguished based on damaged fins, cookie-cutter shark bites and other features.

A total of 313 dolphins have been discovered since the survey’s start in 1994. And as many as 131 were distinguished last year.

Over the past 30 years, behavioral patterns and ecological characteristics of the species have been elucidated. Small dolphins cling to their mothers until they turn around 3 years old, while females “babysit” their fellow dolphins’ offspring.

These findings have been released via academic publications.

“We will be preserving the living environment friendly to dolphins by surveying them,” said Itsuki Ogasawara, 32, secretary-general of the tourism association. “One of our objectives is making it possible for us to continue the sightseeing business for long.”

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