Photo/Illutration The specimen of a juvenile Japanese spiny lobster found in Hokkaido (Provided by Tokyo University of Marine Science and Technology)

A juvenile Japanese spiny lobster has been captured along the coast of the northern main island of Hokkaido, a discovery that scientists primarily attribute to rising seawater temperatures due to global warming.

The Japanese spiny lobster, a coveted delicacy called “ise-ebi” in Japanese, typically inhabits warmer waters to the south. 

Researchers from organizations including Tokyo University of Marine Science and Technology, the Hokkaido Research Organization and the Japan Fisheries Research and Education Agency studied an approximately 5-centimeter-long specimen caught off Hakodate in November 2023.

It is the second juvenile Japanese spiny lobster from Hokkaido documented in academic literature following the one measuring about 7 cm found off the coast of the town of Shikabe, also in southern Hokkaido, in October the same year.

The known habitat of the marine crustacean was once limited to waters no farther north than Ibaraki Prefecture in the Kanto region.

However, the species’ range has shifted northward, with reports of growing populations off the northeastern Tohoku region, including Fukushima and Iwate prefectures.

Michiya Kamio, a professor of marine biology at Tokyo University of Marine Science and Technology, noted that rising seawater temperatures have changed the marine ecosystem in recent years, making it more difficult for “kombu” kelp to grow in Hokkaido.

“The appearance of the Japanese spiny lobster adds to the surprise,” Kamio said.

The crustacean, which also inhabits waters around the Korean Peninsula and Taiwan, has many closely related species with similar appearances.

The research team not only examined the specimen’s morphology but also analyzed its mitochondrial DNA base sequence to ensure accurate identification.

After hatching, Japanese spiny lobsters spend about a year drifting in the ocean as phyllosoma larvae and then pass through the puerulus larval stage before developing into juveniles.

The research team believes larvae carried to Hokkaido by ocean currents were able to grow into juveniles due to elevated water temperatures.

Around the site in Hakodate where the specimen was found, average monthly surface water temperatures ranged around 20 degrees from July to September of that year.

Researchers said the appearance of juveniles is likely influenced by the recent northward shift of the Kuroshio Current, in addition to the rise in seawater temperatures around Japan.

That said, no adult Japanese spiny lobsters have been reported in Hokkaido to date. Current water temperatures in the winter are considered too low for them to survive.

“If warming continues and seawater temperatures rise further, Japanese spiny lobsters could eventually establish themselves and begin reproducing in Hokkaido waters,” Kamio said.

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