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BULLETIN OF THE BUEEAU OF FISHEBIES 



they grow to a length of 4 to 9 inches by autumn, fish of that size being common 

 in October, while general experience suggests a length of 8 to 12 inches by the 

 following spring. The growth of the older fish has not been followed, 8 nor is the 

 age at which the bluefish matures known. 



THE MARIPOSAS. FAMILY LAMPRID^E 



93. Opah (Lampris luna Gmelin) 



Moonfish; Jerusalem haddock 



Jordan and Evermann, 1896-1900, p. 954. 



Description. — The opah is notable for the large number of its ventral fin rays, 

 of which there are 14 to 17 (no mackerels, swordfishes, pompanos, bluefish, or 



Fig. 113.— Opah (Lampris luna) 



butterfish have more than 8) . There is only one (soft) dorsal fin. The flat, deep 

 (only about one and one-fourth times as long as deep) form of the opah, with the 

 moderately slender caudal peduncle (which is not keeled) and rather pointed snout, 

 suggests an enormous butterfish, but it is provided with very long falcate ventral 

 fins, whereas the butterfish lacks ventrals. The anal (38 to 41 rays) and dorsal 

 fins (53 to 55 rays) are relatively higher than in the latter, and its tail fin is but 

 slightly emarginate instead of deeply forked. The opah, furthermore, is toothless. 

 We may also note as characteristic that the mouth is very small, the pectorals 

 unusually long and pointed, with their bases horizontal instead of vertical, the 

 dorsal very high in front and deeply emarginate in outline, and the anal only about 

 half as long as the dorsal and of nearly even height from front to rear. Both the 

 dorsal and the anal fins extend back close to the base of the caudal, and both are 

 depressible in grooves. The scales are minute. 



• No growth studies based on the scales or on other exact methods have been undertaken for the bluefish. 



