Scientists alarmed by shift in eel migration patterns — here’s why it matters

Scientists in Japan who noticed a drastic shift in glass eel migration patterns sounded the alarm on an underlying issue.

What’s happening?

As reported by The Japan Times earlier this month, researchers from the Japan Agency for Marine-Earth Science and Technology, the University of Tokyo, and Hokkaido University published their findings in the international oceanography journal Ocean Dynamics. They determined that global warming is to blame for the Kuroshio Current shifting northward and increasing the number of glass eels in Hokkaido’s rivers in recent years.

Glass eels “mainly grow south of Japan’s Honshu main island” after they “hatch from eggs in waters west of the Mariana Islands and travel on the Kuroshio Current to estuaries on the coasts of Japan, Taiwan, and China in winter and early spring,” per the Times. The Kuroshio Current usually “flows northward along the Japanese archipelago,” but it is “shifting north” due to rising global temperatures caused by climate change.

The research team conducted a simulation of the movement of glass eels in waters surrounding Japan and found that “more glass eels reached rivers along the Pacific coast of Hokkaido in the decade through 2023 than in the decade through 2003,” the Times stated.

Why is this important?

Drastic shifts in animal behavior, like the glass eels’ fluctuating migration patterns, can often be attributed to significant changes to the environment. As ocean temperatures continue to rise because of climate change, researchers have found that fish are changing their hunting and feeding patterns, which could have dire results.

For example, fish in the Baltic Sea have adapted to warmer waters by consuming smaller, more abundant prey, which could significantly diminish the caloric intake they need to survive and lead to possible increases in extinctions.

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Rising temperatures could cause fish to migrate to areas where fishing pressure is high and regulations are minimal, which would leave them more vulnerable to human activities.

What’s being done about this?

Chang Yu-Lin, deputy senior scientist at JAMSTEC, told the Times he hopes these findings “would lead to securing Japanese eel resources over the long term.”

While there isn’t a quick fix for slowing the rise of ocean temperatures, these shifting migration patterns and animal behaviors show how crucial it is for global efforts to focus on reducing pollution and protecting marine ecosystems to ensure these species can thrive despite the challenges posed by a warming planet.

Reducing your contributions to carbon pollution is a great first step to help protect ocean life from ongoing climate change.

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