epihyal in Scomber , but less than one -third as 

 long as the epihyal in Rastrelliger ; 12 to 28 

 first dorsal fin interneurals in Scomber , 11 

 (rarely 10) in Rastrelliger ; the first haemal 

 spine somewhat flattened and bent backward 

 in Scomiber but flattened with the middle hooked 

 and the distal part nearly vertically directed 

 in Rastrelliger . 



Matsui recognized only three species of 

 mackerels with 31 vertebrae and 5 finlets in 

 the genus Scomiber (including Pneumato- 

 phorus ). These include S^. scombrus Linnaeus, 

 S. japonicus Houttuyn, and S. australasicus 

 Cuvier. S. scombrus differs from the others 

 in having nnore heavily ossified bones, in hav- 

 ing no swim bladder, and in having the first 

 haemal spine anterior to the first interhaemal 

 bone. He saw no reason for recognizing 

 Pneumatophorus for the other two species. He 

 summarized 12 characters for comparison of 

 the three species, the most distinguishing of 

 which, other than the absence of a swim blad- 

 der in scombrus , is the number and arrange- 

 ment of the interneurals under the first dorsal 

 fin--21 to 28 in S. scombrus , 15 to 21 in S. 

 australasicus, and 1 2 to 15 in S. japonicus . He 

 showed these arrangements by a representa- 

 tive diagram in his figure 7. 



used are blue mackerel, greenback mackerel, 

 striped mackerel, and Americanmackerel. 



1.3 Morphology 



1.31 External morphology 



Dorsal IX-I, 9 to 13-IV to VI; anal I-I, 9 to 

 11 -IV to VI; pectoral 17 to 19; caudal 17; 

 pelvic I, 5; first dorsal fin rather high, re- 

 ceived entirely into a groove when depressed, 

 widely separated from the much lower second 

 dorsal; scales small, easily lost; two very 

 small keels on each side of the caudal peduncle. 

 Color: dark green to blue above with metallic 

 reflections shading into iridescent silvery on 

 the sides and below; a series of about 30 wavy, 

 dark streaks run vertically down the back to 

 just below the lateral line (fig. 1). 



Matsui (1967) differentiated three popula- 

 tions of S. japonicus in the temperate zones of 

 the Pacific Ocean and the west and east Atlantic 

 Ocean (table 1). 



The Pacific mackerel off the coast of North 

 America are not known to mix with any of the 

 other populations designated above. Racial 

 differences were investigated in this group by 

 Fry and Roedel (1949) in tagging experiments -- 



Figure 1. — Scomber japonicus (= Pneumatophorus dlego ) Houttuyn (adapted from frontispiece. Fitch, 1951). 



1.22 Taxonomic status 

 See above. 



1.23 Subspecies 

 See above. 



1.24 Standard common names 



The name officially sanctioned by the State 

 of California for purposes of keeping records 

 is Pacific mackerel. Other names variously 



see 3.51 below--and by Roedel (1952) in a 

 racial study. 



For the racial study, Roedel examined speci- 

 mens from six geographic regions: British 

 Columbia, southern California, northern Baja 

 California (Soledad Bay), central Baja Cali- 

 fornia (Sebastian Vizcaino Bay), the Cape San 

 Lucas region including sections of the Pacific 

 and Gulf coasts of the peninsula, and the Gulf 

 of California. 



