Rudderfish / Guili
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Rudderfish / Guili
Kyphosus vaigiensis
Image from Coral Reefs CD
Guili are important traditional foodfishes caught primarily by talåya (cast net), spearfishing, and rod and reel. They have small mouths with small closely-set incisiform teeth (shaped like human front teeth). They feed primarily on plants, including the thin layer of green filamentous algae as well as on larger seaweeds. They also eat small bottom living animals and sewage. They are most numerous along the reef margin and steep rocky areas which are often wave-swept and dangerous. It takes great skill with the talåya to catch them. Young guili are commonly found far out at sea beneath floating debris.
There are three kinds of guili in the Marianas but only two are common. They are the highfin rudderfish (Kyphosus cinerascens) and the lowfin rudderfish (K. vaigiensis). They can be distinguished by the height of the soft-rayed portion of the dorsal (upper) fin. On the highfin rudderfish, this part is nearly twice as high as the spiny part of the dorsal fin and on the lowfin rudderfish, both parts are about equal in height.
All three guili have both light silvery-gray and dark color phases as well as a light-spotted phase occasionally seen underwater. Although the species of guili are not distinguished by local fishermen, the color phases are. The lighter phase is known locally as guili and the dark phase is known as guilen puengi (puengi is the Chamoru word for night or dark). Chamorus call small guili under about 10 inches (25 cm) "geppan" because they move rapidly about the upper portion of the reef. The highfin rudderfish reaches a length of about 19 inches (48 cm) and the lowfin rudderfish reaches a length of about 26 inches (66 cm).
Guam Comprehensive Wildlife Conservation Strategy, 9/27/2005
