Nagoya Aquarium Begins Joint Study on Sea Turtle Migration

Courtesy of the Port of Nagoya Public Aquarium / Jiji Press
Research team members stick a transmitter on a turtle in Nagoya on June 20.

NAGOYA (Jiji Press) — An aquarium in Nagoya has begun a joint study with foreign research institutions to uncover the mechanism behind the migration of loggerhead sea turtles in the Pacific Ocean.

Little is known about the exact route and mechanism of the endangered loggerhead’s migration from the coast of Japan, where the turtles hatch, to the west coast of North America.

In the project, 100 satellite-tagged juvenile loggerheads will be released into the ocean over four years. The first batch of 25 turtles, which were around the age of 2 years, was released into waters north of Hawaii last month.

It is the second time for the Port of Nagoya Public Aquarium to take part in a loggerhead migration tracking study. Previously, it released some 230 juvenile loggerheads from the coast of Japan and other locations as part of a project conducted from 1997 to 2013.

Most of the turtles traveled to the central North Pacific Ocean on the Kuroshio Current flowing along Japan’s east coast, but only six were confirmed to have reached the west coast of North America, due partly to the limited battery life of transmitters, which lasted for only about a year.

The project gave no clue as to why so many loggerheads live near the North American west coast, where nesting grounds have not been found.

Subsequent research has led to the theory that loggerheads migrate across the Pacific to the west coast when the El Nino phenomenon, in which the sea temperature rises near the equator, is observed. The six turtles were found to have arrived in the west coast in the years that saw the phenomenon.

Researchers began the new tracking study last month to test the hypothesis that a “corridor” opens up when sea water temperatures rise.

They plan to release 25 turtles every year for four years from the eastern end of the central North Pacific, where many turtles were found to have stayed in the last study, to check the relationship between their movements and seawater temperatures.

The locations of all released turtles can be observed in real time on the website Loggerhead STRETCH.

El Nino has been observed this year since spring, meaning that the 25 turtles released last month will arrive on the North American west coast sometime around next January if the hypothesis is correct.

“We don’t know how climate change affects living creatures,” said Masanori Kurita, director of the aquarium. “Uncovering the biology of loggerheads will lead to future conservation efforts.”