On December 7, a horrifying sight was witnessed around the waters of Japan: a mass death of fish. A massive shoal of dead sardines and mackerel off the coast of Hakodate City covered about a kilometer of beach. The incident was also an unfamiliar experience for local residents, and the city of Hakodate advised residents not to take fish due to the unknown cause. According to the Asahi Shimbun, the amount of dead fish could be over 1000 tons. Takashi Fujioka, a researcher at the Hakodate Fisheries Research Institute, speculated that this could be due to lack of oxygen or pursuit by predators.
Analyze similar cases and causes at home and abroad
A similar sardine mass mortality event occurred in Jinhae Bay, Gyeongnam last fall. The National Oceanic and Atmospheric Administration blamed a lack of oxygen, but said further investigation is needed to determine the exact cause. In addition, some countries have raised concerns about the discharge of contaminated water from the Fukushima nuclear plant. In China, social media users are raising questions about whether the incident could be linked to the discharge of polluted water.
The mysterious history of sardines and the volatility of their catch
Sardines have shown remarkable catch fluctuations in the past. In the 1920s, there was a great sardine harvest off the coast of Hamgyong Island, resulting in a “gold rush” for sardines. By the early 1940s, however, fishing catches had plummeted, forcing many entrepreneurs into bankruptcy. Sardines, which began to be caught again in the 70s, peaked in the 80s and plummeted in catch by the early 2000s. However, in the 2010s, catches began to increase again and the “national fish” began to gain traction again.
Cyclical fluctuations in sardine catches and their ecological implications
Sardines are known to have large fluctuations in their catch on a cycle of about 20 to 50 years. These fluctuations may be related to rotation with other fish species. For example, when the catch of sardines decreases, the catch of saury or mackerel tends to increase. The exact cause of this phenomenon is still unknown, and it’s also unclear where the sardines go during their decline. The current theory is that it follows a giant ocean current that circles the Pacific Ocean.
