The filefish is closely related to the triggerfish, however, the chunky first spine on the dorsal fin is positioned above the eye, and further back in triggers. The Hawaiian name ō‘īli (“sprout” or “come up”) probably refers to the dorsal spine which they commonly raise up.
The Fantail filefish is said to be the most common filefish species in Hawaiian waters, it’s comparatively rare on reefs most of the time and not often seen in large numbers.
photos courtesy Sandi Strickland
However, perhaps just a couple of times a decade, something very strange happens and becomes part of Hawaiian folklore.
Vast numbers appear on Hawai‘i’s reefs and undergo a population explosion, going from being a relative rarity among the reef’s fish fauna to being the most abundant fish species around. They gather in the shallows of the islands and become so numerous inshore that they spill into deeper habitats.
Yet this phenomenon doesn’t happen often. It was particularly notable in 1944, 1975 and 1982-1987 when millions gathered, but, as yet, scientists don’t really know precisely why it occurs when it does.
Many are picked off by predators, such as frigate birds, or die – apparently naturally – and large numbers wash ashore, pile up on local beaches and rot in the sun.
Early Hawaiians are said to have believed that the appearance on the shores of all these dead fish prophesied the death of a great king or chief.