Catfish of the Month Right Arrow January 2005 • Article © Heok Hee Ng, uploaded January 01, 2005



Namazu, Amurmalle (Denmark), Chinese Catfish, Japanese Catfish - Silurus asotus   Linnaeus, 1758

It's a new year and what better way to start the first month of the year than with an article featuring the First Catfish, S. asotus. Why First Catfish? This is because S. asotus is the first catfish species to be described in Linnaeus' "Systema Naturae", the father of all taxonomic works. This first formal description of a catfish is exceedingly brief and reads: "Silurus pinna dorsali unica, cirris 4" (or "A Silurus with one dorsal fin and four barbels").

Silurus asotus
From Seibold's "Fauna Japonica".

Perhaps less widely known than its more familiar European cousin, the wels (Silurus glanis), S. asotus is one of the most widely distributed of all East Asian catfishes, being found throughout much of Japan, China, Taiwan, Korea and eastern Siberia. S. asotus looks like S. glanis at first glance, but differs from it in having only two (vs. four) mandibular barbels and fewer anal-fin rays (74-86 vs. 90-95). Like all members of the genus, S. asotus are solitary, lurking predators, spending much of the day hiding amongst vegetation or in crevices (maybe sometimes to ambush passing fishes) and coming out at night to actively hunt prey (seemingly by tracking their wakes). They are fairly easy fish to maintain (at least in terms of water conditions, but definitely not in terms of tank space), although like many silurids, they are sensitive to high ammonia/nitrates.

S. asotus is widely sold and cultured as a food fish in east Asia, and perhaps because of this, much is known of the spawning behavior of this species. Like many other east Asian Silurus species, the spawning behavior of S. asotus consists of a fixed series of stereotyped behaviors (in what is known as a "rigid reaction chain"). First the male chases the gravid female, who selects a suitable place to deposit her eggs. Once the nesting site is found, the female stops and the male swims in front of, or beyond the female's head. The male proceeds to curl his caudal peduncle alongside her head and enfolds her head with it, vibrating his tail at the same time. In some spawning instances, the male slips backwards until his abdomen and tail encircles the female's abdomen (at other instances, the caudal peduncle and tail remain firmly wrapped around the female's head). Wherever he is enfolding (the head or the abdomen), the male then begins to apply pressure, squeezing the female while vigorously shaking his head. The female begins thrashing her body and shifts the male rearwards, before throwing him off with a quick flip of the back and a turn. The pair then circles the nest site several times, before moving on to the next site and repeating the performance. It is not clear when the eggs and the sperm are released, but this apparently occurs at the moment the female throws off the encircling male.

Japanese illustrationThe large size and the aggressive nature of the fish have spawned much folklore around it, none more so than in Japan, where this is probably their largest freshwater fish species. The Japanese folklore that surrounds S. asotus is rich and diverse, and one article is simply not enough to cover all of it (in fact, catfishes in Japanese folklore have been the subject of several scholarly works, including at least one book). Some of the other lore will be covered in a later article dealing specifically with this topic, but one of the most evocative tales, which is narrated below, stems from the mid-eighteenth century and involves giant catfish and earthquakes.

The Namazu (the Japanese name for Silurus) is a giant catfish that lives in subterranean waters deep beneath the earth. On its head rests the kaname-ishi, a giant stone that resides in a shrine in the city of Kashima (near Tokyo) [because of its geographic location, the stone is often erroneously referred to as the Kashima stone]. The purpose of the stone is to pin the catfish still, but the weight of the stone alone is not sufficient for that. The Kashima Deity (Kashima daimyojin) must assist by pushing down on the kaname-ishi. The Kashima Deity sometimes falls asleep, is distracted, or has to leave for a meeting (in which case the deity Ebisu fills in, but Ebisu is frequently lax). Whatever the case, these lapses in vigilance cause the pressure on the namazu to be relaxed, giving it some freedom of movement. The thrashing of the namazu would result in an earthquake, the intensity of which depended on the vigor of its movements. Eventually, the earthquakes would subside and it was deemed that the Kashima Deity was back in control of things. The image (left) shows the Kashima Deity back in control of the Namazu after his temporary lapse, and all the lesser namazu (aftershocks) bow down in submission.

At the time of publication, it might at first seem insensitive to run with this particular catfish species for this month given it's folklore links with the monumental tragedy unfolding around mother natures show of force in the Indian Ocean; yet to hide from such widespread devastation is perhaps a greater wrong and, as webmaster, I'd like to conclude Heok Hee's article with truly heartfelt sentiment that's hard to carry off using the online medium. I'm sure all readers will understand that this is our way of standing shoulder to shoulder with the many hundreds of thousands of people directly affected by the worst natural disaster in living memory.

They are all in our thoughts.


Copyright information for the images used in this article can be found on the species' full Cat-eLog page.

Jump to next section Cat-eLog Data Sheet
Scientific NameSilurus asotus  Linnaeus, 1758
Common Name(s)Namazu
Amurmalle (Denmark), Chinese Catfish, Japanese Catfish
Type LocalityAsia.
Synonym(s)Parasilurus asotus, Parasilurus japonicus, Silurus bedfordi, Silurus cinereus, Silurus dahuricus, Silurus japonicus, Silurus punctatus
PronunciationSee loo russ - ass ott us
EtymologyFrom the Greek silouros which is the name of the fish. 
Jump to next section Species Information
Size 1000mm or 39.4" SL. Find near, nearer or same sized spp.
IdentificationElongated, cylindrical body. 2 pairs of barbels (mandibular and maxillary). Small dorsal fin, anal fin connected with caudal fin. Dark brown to greenish yellow-brown back, light yellow to yellowish white belly. Average adult size is around 300~500mm. Fry have a second pair of mandibular barbels that fall off spontaneously when the fish reach a length of 60-70 mm TL.
General RemarksAn important food fish. Can often be seen in holding tanks in restaurants in China. Also used in Chinese medicine.
Just as Siluris glanis was the prototypical catfish in early Western civilization, S. asotus was the prototypical catfish in early Chinese civilization. Its original Chinese name "Nian", is now the root of the term ("Nianke") for the order Siluriformes and of the common name ("Nianyu") for all catfish.
Jump to next section Habitat Information
DistributionChina, Taiwan, Japan, Korea, Mongolia and Russian Far East.
China Waters (click on these areas to find other species found there)
Japan Waters (click on these areas to find other species found there)
Taiwan Waters (click on these areas to find other species found there)
Mongolia Waters (click on these areas to find other species found there)
Korea Waters (click on these areas to find other species found there)
Show it on a map (Click the map-icon to show/hide map of species distribution)
IUCN Red List StatusLeast Concern
pH6.0 - 8.0
Temperature5.0-26.0°C or 41-78.8°F (Show species within this range)
Other ParametersA hardy fish that can survive and thrive in a wide variety of water conditions, notably including wide variations in temperature.
Jump to next section Husbandry Information
FeedingCarnivore. In the wild, eats smaller fish, crustaceans and insects.
CompatibilityNot recommended as an aquarium fish due to its large adult size and propensity to eat other fish.
BreedingSexually mature at two years. Spawns in May through July. Eggs are slightly sticky, yellowish green or green and spherical in shape, measuring 1.1 - 1.2 mm in diameter.
Jump to next section Further Information
ReferencesSystema Nat. ed. 10v. 1 - pp304
Registered Keepers(1) Silurus, (2) cochito, (3) EmpowerMaui (k: 3).

Click on a username above to see all that persons registered catfish species. You can also view all "my cats" data for this species.
Breeding ReportsNone.
Articles
Search Planet CatfishSearch Planet Catfish for more on Silurus asotus
Look up AquaticRepublic.comLook up Silurus asotus on AquaticRepublic.com
BBCode (for use in linking to this page from forum posts)
Link (for use in linking to the species from anywhere on the web)
Look up FishbaseLook up Silurus asotus on Fishbase
QR iconGet or print a QR code for this species profile, or try our BETA label creator.
Hits13598 hits.
Last Update2013 Jul 19 00:00 (species record created: 2005 Jan 01 11:22)

Hits: 13598

Back to Catfish of the Month index.