Frequently, we hear that it is getting harder to catch fish in the sea. There are a variety of reasons for diminished catches, including overfishing by large fishing boats, water pollution, and the loss of coastal fishing grounds due to landfill. However, we should also include global warming as one of the reasons behind dwindling fish stocks.

Global warming caused by carbon dioxide and other factors has raised the temperature of the sea surface in the waters around Japan by between 0.7 to 1.6°C. As the water temperature increases, it becomes lighter, making it harder for the water at the sea surface level to mix with the cooler water below. Consequently, the deep water, which is nutrient rich, is less able to rise near the sea surface, making it difficult for plankton to grow. Some researchers believe this can explain the decline in stocks of fish that rely on plankton as a food source.

Fish live in areas of the ocean where there is food and a comfortable living environment. Each fish has its own comfortable temperature zone, and as the sea surface temperature rises due to global warming, the areas where fish live will also change. For example, Spanish mackerel, previously found in the warmer waters of Kyushu and the Seto Inland Sea, are now caught farther north due to the rise in sea surface temperatures surrounding Japan.

In 2006, an article published in the American scientific journal Science claimed that, "By 2048, there will be no more edible fish in the ocean.” The causes were attributed to overfishing, ocean pollution, and global warming. The oceans are responsible for absorbing the heat of global warming and its rise. However, this leads to an ongoing gradual rise in seawater temperature. If the seawater temperature continues to rise at current rates, the areas of the ocean where fish can thrive will be dramatically reduced. Meaning, eventually there will be no more fish to catch.

Today, an increasing number of people around the world are eating fish. However, wild-caught fish catches have remained flat for a long time. Soon, these total catch numbers will start on a downward trend. Fish is an indispensable part of Japan's food culture. But, if this trend continues, it may become difficult to pass on this culture to future generations.

episode 11
No More Fish to Eat