Target Species: Topmouth Culter and Redfin Culter

Family: Cyprinidae (carps)

Redfin Culter

Scientific name: Chanodichthys erythropterus

Synonyms: Culter aokii, Culter brevicauda, Culter erythropterus, Culter ilishaeformis, Culter sieboldii, Culter tientsinensis, Culterichthys erythropterus, Cultrichthys erythropterus, Erythroculter erythropterus, Erythroculter ilishaeformis

Common names: redfin culter, predatory carp, skygazer

Habitat: Lakes, ponds, reservoirs, larger slow-flowing rivers.

Distribution: Map

Size range: Up to 100 cm, but more commonly 30-50 cm.

Topmouth Culter

Scientific name: Culter alburnus

Synonyms: Culter brevicauda, Culter recurviceps, Erythroculter aokii, Erythroculter ilishaeformes

Common names: topmouth culter, president fish, aruzay

Habitat: Lakes, ponds, reservoirs, larger slow-flowing rivers.

Distribution: Map

Size range: Up to 35 cm.

Angling tactics: Casting small spoons, spinners and plugs (minnow and shrimp imitations). Fly fishing with streamers.

Few species have been more challenging to research than the wily culters. This struck me as odd, since both the topmouth and redfin culter warrant mentions on several local fly fishing blogs, but little information is available in the English language literature mentioning them. Thanks to the Google page translation tool, I was able to pull together a bit more information to share here.

The difficulty in tracking down comprehensive information is compounded by confusing classification and naming that can lead one to wonder if the names “redfin” and “topmouth” refer to one or two different species. The scientific name Erythroculter ilishaeformis has been applied to both in various sources. They look similar, with upturned mouths not usually associated with members of the carp family. In fact they bear a slight resemblance to herring or a relative of the tarpon. The redfin culter can be distinguished by its slightly more pronounced dorsal “hump” behind the head. It has also been known to grow considerably larger than its cousin the topmouth culter.

Hang on to your hats, fellow fish nerds. A little digging revealed that these fish are not as closely related as one might think. The redfin is not really a true culter, belonging instead to the genus chanodichthys. Both are members of the subfamily Cultrinae. Culter, by the way, is Latin for “knife.”

Both species are found throughout east Asia, primarily in subtropical China and Taiwan. Of the two, the topmouth is probably the more famous of the two in Taiwan owing to its place in local political lore. It is said that the topmouth became a favorite dish of former ROC president Chiang Kai-shek after he sampled it on an early visit to Sun Moon Lake. Since that visit, the topmouth earned the nickname “president fish” and has become a staple for the Sun Moon Lake tourism industry. The lake still supports a healthy population, which is fished both commercially and for sport.

Both the topmouth and redfin are known to be voracious predators, sometimes at the expense of other carp species whose fry they often feed upon. Freshwater crustaceans and insects round out their diet. They feed most actively at dawn and dusk, often in large schools, before moving to deeper water by midday. Culters are ambush predators, preferring to attack their prey from below rather than pursue it for great distances.