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Common catfish

by Rowan Hooper

* Japanese name: Namazu
* Scientific name: Silurus asotus
* Description: The most common catfish in Japan, not to be mistaken for the mythical giant catfish god of the same name (Namazu) who is reputed to live in mud deep under Tokyo. The namazu catfish has a long, cylindrical scaleless body with a small dorsal fin and two pairs of “whiskers” — actually, sensory barbels — growing from around the mouth. It is dark brown or greenish-brown, with a yellow- or white-colored belly. It is a medium- to large-size fish growing from 30 to 50 cm long. Baby fish have a third pair of sensory barbels that fall off as they grow up.
* Where to find them: In rivers and lakes all over Japan, from Hokkaido and Honshu to Kyushu. It is a hardy little fish, able to survive in a wide variety of conditions, across a broad range of temperatures, hence it is distributed from the chilly parts of Hokkaido to the warmer southern and western parts of Japan. They may also be seen in holding tanks at restaurants, as they are sometimes eaten.
* Food: The namazu catfish is a carnivore, feeding on smaller fish, crustaceans such as freshwater shrimp and insect larvae. The mouth expands to a large size, and prey are sucked in to their doom.
* Special features: Namazu catfish are negatively buoyant, meaning that they naturally sink to the bottom of the river. Most fish float, but catfish have a small gas bladder and a heavy head, so they sink, which suits them fine for feeding. The barbels are sensory touch organs, allowing them to feel around on the bottom of the river for food, but they also house the taste organs. In other words, the barbels are like external tongues. Na,azu become sexually mature at two years, and they mate from May through July. Females spawn small (1.2mm diameter) eggs that are slightly sticky and attach themselves to stones or vegetation.

PHOTO COURTESY OF BIO-IMAGE NET