Climate change shrinks fish – Olhar Digital

A recent study from the University of Tokyo in Japan revealed that the weight of fish in the western North Pacific Ocean decreased in the 2010s due to rising water temperatures, which limited food supply.

The research, which looked at 13 species of fish, observed a reduction in individual weight and overall biomass during the 1980s and 2010s. Scientists linked the first weight loss to the increase in Japanese sardines, generating greater competition for food between species. .

In the 2010s, global warming appears to have intensified competition for food, as warmer, more nutrient-dense water could not easily reach the surface. These results have significant implications for fisheries and ocean resource management policies in the face of future climate change.

Mackerel is one of the fish species off the coast of Japan that has decreased in size. Credit: Martin Prochazkacz – Shutterstock

Global warming emerges as one of the biggest threats, directly impacting the east coast of Japan, which borders the western North Pacific Ocean, a vital marine region.

According to the Food and Agriculture Organization of the United Nations (FAO), in 2019, this area was responsible for almost 25% of global fish catches. However, the University of Tokyo study reveals drastic changes in the weight of fish in this region between the 1980s and 2010s.

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Fish weight and biomass

Professor Shin-ichi Ito and co-author Lin Zhen analyzed fish weight and biomass data from the Fisheries Agency and the Japan Fisheries Research and Education Agency. Fish weight refers to individuals, while biomass covers the total weight of a species or group in an area.

The study involved six fish populations of four species between 1978 and 2018, and 17 fish populations of 13 species from 1995 to 2018. In addition, seawater temperature data was analyzed between 1982 and 2014 to understand the impact of changes in the layers of the ocean.

The results indicate two periods of reduced fish weight, initially in the 1980s and again in the 2010s. The decline in the 1980s was attributed to the increase in Japanese sardines, intensifying competition for food.

Warming oceans make fish smaller off the coast of Japan. Credit: Divedog – Shutterstock

Climate change has warmed the oceans

Already in the 2010s, even with a moderate increase in the population of Japanese sardines and mackerel, research suggests that climate change, warming the ocean and reducing the supply of nutrients to the surface, were preponderant factors.

Shin-ichi highlights the importance of fisheries managers and policymakers understanding these changes to make decisions. He warns that fish stocks need to be managed differently, considering the increasing impact of climate conditions. If global warming is not controlled, fish quality could decline, highlighting the need for action to preserve ocean health.

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