Japanese eels, which are traditionally raised from glass eels in aquaculture farms, are now experiencing changes in their migration patterns due to the impact of global warming. The warming of ocean waters has caused a northward shift in the Kuroshio Current, resulting in a significant increase in the number of eel larvae reaching rivers in Hokkaido, well beyond their previously known northern limit at Aomori Prefecture.
In a collaborative effort, scientists from JAMSTEC, the University of Tokyo, and Hokkaido University employed numerical simulations on a supercomputer to trace the migration of eel larvae. These simulations modeled how particles representing the larvae moved from offshore areas near Taiwan, taking into account the effects of ocean currents, maritime environmental data, and even the swimming behavior of the young eels.
The study highlights that during the decade starting in 2014, the likelihood of eel larvae reaching Hokkaido increased dramatically—by nearly 20 times compared to figures from a previous decade. This shift is attributed to the warmer Kuroshio Current and its extension, factors driven by global climate changes, and suggests that new environmental conditions might support an increased presence of eels in northern territories.
Additionally, the research underscores the significance of understanding the conditions under which glass eels can thrive once they reach these new habitats. Scientists noted that continued studies are essential for determining the types of rivers that can support the growth of these larvae. Their findings aim to inform conservation measures, ensuring that even as these eels venture into new territories, strategies can be developed to protect this endangered species and secure sustainable eel resources for the future.