Relying upon his prior observations and his limited knowledge of biology, including the Linnæan system of binomials, Lewis referred to the new species as an "anchovey," and compared it with "Clupea." Clupeidae (kloo-PEE-uh-dye)—Latin for herring—include shads, alewives, sardines and herrings, but not anchovies, which belong to the family Engraulidae (en-GRAU-luh-dee)—Greek for anchovy.
Anyway, the eulachon is neither of the above, but a smelt, representing the family Osmeridae (ahz-MEHR-i-dye), which is Greek for "odorous." Its own scientific binomial is Thaleichthys pacificus (thal-ee-ICK-this puh-SIFF-i-kuss), meaning "rich fish of the Pacific." It's also known as the Columbia River smelt, salvation fish, yshuh, swaive, chucka, and variations on the Clatsop word eulachon.
The eulachon is anadromous (an-ADD-dro-muss, from Greek, ana = back, and dromos = running). Every spring, along the Northwest Coast from central California to the Bering Sea, anadromous fish migrate in schools up freshwater rivers to reach the remembered redds (spawning beds) where they were born and reared, there to spawn a new generation, then die. Like other smelts, eulachons have been getting it on that way for about 40 million years, a timetested "rhythm method."
Just as Indians did for thousands of years, piscine gourmets still net eulachons in the spring when, at their fattest, they move into shallow waters—thus the name "fathom fish"—heading toward their sacrificial destiny. Otherwise, since larger fish such as salmon relish them, fisherpersons use them as bait.
Indians also dried them to burn as candles—thus the nickname candle fish—and to use them to barter along the "grease trail" to the Interior.
For Further Reading:
Andy Lamb and Phil Edgell, Coastal Fishes of the Pacific Northwest (Madeira Park, BC: Harbour Publishing Co. Ltd., 1986), 20-26.