Winter is upon us, although early winter daytime in this part of the world is usually unpleasantly cold only in the early morning. Clear skies are the norm, and being out in the sun on a fifteen degree day (while warmly dressed, of course!) can almost make one forget the decay around them. Add some cloud cover, a northerly wind, and maybe some rain, however, and the countryside transforms into the Land of the Dead.
Just recently, I had the opportunity to take the kids to the Saitama Aquarium. This is a small and modest affair, dealing mostly with aquatic life (both native and introduced) in Saitama water systems. It is located in what amounts to the middle of nowhere (somehow, much of Saitama seems to be, err, planned that way), but admission is cheap and it’s easy to spend a few hours in and around the facility for the price of a single ticket.
For the kids, the highlight was probably feeding the large fish in the outdoor enclosures – Nile tilapia, American catfish, sturgeon, grass carp and the massive black carp, the latter two being quite content to stick their heads out of the water and be touched.
My little one was chuffed when he found a Japanese common catfish, which ate the fish pellets he offered it. I was pretty happy too, as this is one of my favourite freshwater fish, and the star of this post.
The Japanese common catfish or Amur catfish (Silurus asotus) is a comical-looking fish. It is found in Asia east of the Amur River down to northern Vietnam. In Japan, its distribution includes all the main islands except Hokkaido and the Ryukyu islands. Recent research suggests that the fish’s distribution in Japan was originally limited to the west of modern Shiga prefecture, and only later spread eastwards with human intervention.
The local name for the fish is namazu, believed to derived from nameraka (smooth or slippery). The original character from China was 鮎, but this is now used to designate the sweetfish or ayu, and the indigenous character 鯰 is now in use. Around Lake Biwa the regional name hekoki is also used.
The alternate common name is manamazu, used to distinguish it from two other catfish species – the Lake Biwa catfish (Silurus biwaensis) or biwako-onamazu (琵琶湖大鯰) and the rock catfish (Silurus lithophilus) or iwatokonamazu (岩床鯰) – both of which are endemic.
Amur catfish typically grow up to 60 cm long. Their dorsal, pectoral and tail fins are atrophied, and they lack scales, giving them an almost tadpole-like appearance. Adult fish have two pairs of barbels, while larval fish have three (which degenerate as the fish grows).
They live in rivers, lakes, ponds and even wet rice paddies, and have a fondness for muddy substrate. However, they have a low tolerance for water pollution.
Catfish are carnivorous, feeding on smaller fish, frogs, crustaceans and insects. Cannibalism is common among larval fish. (For this reason, aquarists are encouraged to keep catfish in individual enclosures)
These fish are generally nocturnal hunters, preferring to spend the daylight hours hidden in or under plants, driftwood or rocks. This was one reason I was surprised to see that individual in full sunlight taking commercial fish pellets.
The catfish’s barbels are used to help detect prey in dark conditions.
Amur catfish were once an important food item, especially for farmers, but their significance as a table fish has declined significantly. While some places are known for their catfish cookery, most people have never eaten catfish.
In fact, owing to the wild fish’s nocturnal habits and the lack of specimens in the supermarket, many people have never seen an actual catfish…
…Which it not to say that they are unfamiliar with them.
Amur catfish depictions – usually comic-art style – are common on signs warning against polluting river systems, but the most common association is with earthquake warnings. This is a two-fold association.
Folklore and mythology hold that earthquakes are caused by a giant catfish, O-namazu. The god Takemikazuchi (also known as Kashimanokami) holds the catfish still, but sometimes he dozes off and the catfish struggles violently, causing the earth to shake. Depictions of this became very common in the Edo era, especially after a major quake in 1855, and there is a whole class of ukiyoe called namazu-e (“catfish pictures”) devoted to this theme.
The other association is a theory that catfish are able to sense earthquakes before humans can, and that they may provide a key to early quake detection.