International Wildlife Encyclopedia - Vol. 19

International Wildlife Encyclopedia - Vol. 19

International Wildlife Encyclopedia - Vol. 19

International Wildlife Encyclopedia - Vol. 19



A popular food fish, the sweetfish bears physical similarities to both the salmon and the trout.

THE SWEETFISH, OR SWEETMOUTH, is known to the Japanese as the ayu except when it is living in landlocked waters, in which case it is known as koayu. It is probably best known as the fish that is caught using cormorants. Although the cormorants and the cormorant fishers are familiar in traditional eastern pictures, carvings, and prose, the fish itself is mentioned far less regularly in such sources. Yet the flesh of the sweetfish is considered by many to be delicious. It is an important commercial fish in Japan and has been widely studied.

The fish, which grows up to 28 inches (70 cm) long, has much the same shape as a salmon, and has prominent jaws extending well back behind the moderately large eyes, a feature that is common to the salmon as well. Sweetfish also have an adipose (fatty) fin near the tail end of the body, with a relatively large dorsal fin situated near the middle of the back.

Ceremonial fishing

The use of cormorants for fishing in China and Japan dates from at least the 12th century. It was practiced in other countries as well, for example in England, although to catch different fish.

In Japan in the 12th century, fish caught in the Nagano River were sent to the Emperor Yoritomo. In 1890 parts of the Nagano River were set aside for the emperor and the fishing was continued there as an imperial ceremony.

The principle of fishing using a cormorant is to slip a ring over the neck of the bird and put it into the water with a cord tied to the ring. The bird catches a fish but cannot swallow it, due to the ring around its neck. It is then drawn into the boat, and its neck is gently squeezed so the fish is ejected; the cormorant is then sent out to catch more fish. At the end of the session the fishers reward the bird with some of the less valuable fish it has brought back.

Combing food from rocks

Most sweetfish are caught in rivers and in landlocked stretches of water, while others are bred captively in ponds. The first teeth of the very young fish are conical, which helps them catch and eat plankton, such as water fleas and copepods. When the young fish is about 1½ inches (3.8 cm) long, it grows a second set of teeth on the outer edges of the jaws. These teeth have comblike edges and are used for nibbling small algae . . .

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