Climate change is causing fish to shrink: Japanese study


A new study reveals that fish in the western North Pacific Ocean are getting smaller due to climate change-driven shifts in their food supply.

What the scientists found: A University of Tokyo study published in the journal Fish and Fisheries analyzed medium-term data on the weight of 13 fish species over a 33-year period (1995-97 to 2018) and long-term data on the weight of four fish species over a 40-year period (1978 to 2018). The Japanese researchers found two distinct periods where the fish were lighter: the 1980s and the 2010s.

Major factors identified: The scientists noted that the culprit behind the weight decline in the 1980s appears to be a surge in the population of Japanese sardines. With more sardines competing for resources, other fish species had less food available, leading to stunted growth. Meanwhile, researchers attribute the weight decrease in the 2010s mostly to climate change. Stronger ocean stratification, caused by warming waters, reportedly limited the flow of nutrients from deeper layers to the surface and similarly reduced the food supply for fish.

Why it matters: The shrinking of fish in the western North Pacific, a critical fishing ground, represents a broader disruption to the marine ecosystem. Countries known for their seafood culture, like Japan, may need to address the escalating impact of global warming on marine life. The scientists noted that further research is needed to understand the long-term effects of climate change and competition on fish populations.

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Call to action: Study author Shin-ichi Ito, a professor at the University of Tokyo, emphasized the necessity of innovative management approaches to sustain fish populations in a press release.

“Fish stocks should be managed differently than they were before, considering the increasing impact of climate-induced conditions. The situation fish experience is much more severe than decades ago. If we cannot stop global warming, the quality of fish may decline. So, we need to take action so that we can enjoy a healthy ocean and delicious fish.”

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