1911 Encyclopædia Britannica/Opah
OPAH (Lampris luna), a pelagic fish, the affinities of which are still a puzzle to ichthyologists. The body is compressed and deep (more so than in the bream) and the scales are minute. A long dorsal fin, high and pointed anteriorly, runs along nearly the whole length of the back; the caudal is strong and deeply cleft. The ventral spine is also elongated, and all the fins are destitute of spines. The pelvic fins are abdominal in position, long and pointed in shape, and the pelvic bones are connected with the caracoids. These fins contain numerous (15–17) rays, a feature in which the fish differs from the Acanthopterygians.
In its gorgeous colours, the opah surpasses even the dolphins, all the fins being of a deep scarlet. The sides are bluish green above, violet in the middle, red beneath, variegated with oval spots of brilliant silver. It is only occasionally found near the shore; its real home is in the Atlantic, especially near Madeira and the Azores, but many captures are recorded from Great Britain, Ireland and Scandinavia; it strays as far north as Iceland and Newfoundland, and probably southwards to the latitudes of the coast of Guinea. It is rare in the Mediterranean. The name opah, which is now generally used, is derived from the statement of a native of the coast of Guinea who happened to be in England when the first specimen was exhibited (1750), and who thought he recognized in it a fish well known by that name in his native country. From its habit of coming to the surface in calm weather, showing its high dorsal fin above the water, it has also received the name of "sun-fish," which it shares with Orthagoriscus and the basking shark. It grows to a length of 4 or 5 ft. and a weight exceeding 100 lb, and is highly esteemed on account of the excellent flavour of its flesh.