The Autumn Knife Fish: Why This Migratory Predator Is A Cultural Icon In Asia

Nature · Published 3 October 2026 Swipe more like this →

In short: Known as the autumn knife fish for its resemblance to a katana, the Pacific saury is a highly migratory pelagic species. Beyond its role as a seasonal culinary staple in Japan and Korea, this schooling fish has become a focal point of international commercial fishing and evolving sustainable maritime technology.

The Pacific saury, or Cololabis saira, is a slender, schooling fish characterized by its elongated body, dark green to blue dorsal surface, and silvery sides marked with bright blue blotches. Typically reaching lengths of 25 to 30 centimetres, these fish can grow up to 40 centimetres and weigh approximately 180 grams during the autumn months. They are highly migratory, inhabiting the North Pacific from the waters of China, Korea, and Japan across to the Gulf of Alaska and down to sub-tropical Mexico. They thrive in temperatures between 15 and 18 degrees Celsius, often found near the surface but capable of diving to depths of 230 metres.

Biologically, the saury is uniquely adapted to its environment. Lacking a stomach and possessing short, straight intestines, it feeds primarily on zooplankton such as krill, copepods, and amphipods. While they are oviparous, laying eggs attached to floating objects like seaweed, they are also preyed upon by tuna, squid, and marine mammals. Interestingly, their internal organs may contain harmless, worm-like parasites known as Rhadinorhynchus selkirki. Their nutritional profile is notable for high levels of n-3 unsaturated fatty acids and long-chain monounsaturated fatty acids.

Culturally, the fish holds significant weight. In Japan, it is a seasonal icon often served grilled with daikon oroshi, with many diners embracing the bitter taste of the intestines. In Korea, it is prepared in various ways, including as gwamegi, a half-dried winter delicacy. The commercial landscape has shifted significantly since 1950, when Japan accounted for nearly all the catch. Today, nations including Taiwan and China are major players. Taiwan, for instance, landed 40,000 metric tons in 2022. Modern efforts are underway to modernize this industry, with Taiwanese vessels transitioning to LED lighting to reduce their environmental impact.

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