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Table l. — Some meristic characters in Scomber japonicus and S. scombrus young as determined in bone-stained (and two 

 X-rayed) specimens. Dj refers to the first dorsal fin; pterygiophore counts were made between successive neural spines, 

 starting in the second interneural space. ( — = count was indeterminate. X = X-rayed specimen. * = pterygiophore 

 series completed. M = mutilated, spine(s) lost in handling.) 



SL (mm) 



Scomber japonicus 

 Vertebrae 



D, spines D, pterygiophores 



Scomber scombrus 



SL (mm) 



Vertebrae 



D, spines D, pterygiophores 



6.7 



7.6 

 7.7 

 84 

 85 

 9.0 

 9 1 

 10.2 

 10.5 



11.7 

 11-9 

 12.4 

 13.8 

 14.0 

 165 

 17.7 

 20.2 

 22.1 

 24.7 

 26.3 



28 6X 

 333X 



7.6 



8.6 



9.3 



13 + • 



13 



between the two species in counts of 

 pterygiophores in anterior, successive interneural 

 spaces, the two species can be separated well be- 

 fore the total complement is attained. A count of 

 six pterygiophores in the 2d through 6th inter- 

 neural spaces, characteristic of S. japonicus, was 

 observed in bone-stained larvae as small as 11.7 

 mm and on radiographs at 20.2 mm; a count of six 

 or seven pterygiophores in the 2d through 50th 

 interneural spaces, characteristic of S. scombrus, 

 was observed in bone-stained larvae as small as 

 18.2 mm and on radiographs at 20.1 mm. 



In S. japonicus the first anal pterygiophore is 

 anterior to the first haemal spine while in S. 

 scombrus the first anal pterygiophore is posterior 

 to the first haemal spine (Matsui 1967). This was 

 observable in bone-stained iS. japonicus at 11.7 

 mm and in S. scombrus at 32.0 mm, and on radio- 

 graphs at 17.0 mm in S. japonicus and 32.0 mm in 

 S. scombrus. 



Body Proportions 



Larvae of the two species differ noticeably in 

 several body proportions. Scomber japonicus is 

 deeper bodied and has a greater preanus length 

 than S. scombrus. Measurements of body depth 

 (BD) and preanus length (PAL) were converted to 



percentages of standard length (SL) and the re- 

 sults were graphed (Figure 2). Although the sep- 

 aration of the two species by these characters is 

 not total, more than two-thirds of the larvae are 

 separable by BD measurements at lengths of 4 to 

 11 mm and by PAL measurements at 3 to 15 mm 

 long. Of these two characters the PAL difference is 

 more useful, as it is present over a greater size 

 range. 



Other morphological differences between the 

 two species have been reported by previous work- 

 ers. These contrasts were not considered strong 

 enough in the larvae from this study to warrant 

 elaboration. Padoa (1956) noted a larger eye, 

 shorter lower jaw, and shorter snout relative to 

 eye diameter in S. japonicus than in S. scombrus. 

 Dekhnik (1959) presented a brief and generalized 

 comparison of larvae of the two species. She re- 

 ported S. japonicus larvae are more advanced 

 than S. scombrus of the same length. Thus S. 

 japonicus are smaller than S. scombrus at hatch- 

 ing, at yolk and oil globule absorption, and at the 

 initial formation of caudal fin rays. These differ- 

 ences were not as striking in my specimens. In our 

 survey both species apparently hatched at about 3 

 mm long, and yolk and oil globules were absorbed 

 in both by a length of 4 mm. Caudal ray develop- 

 ment varied between species; in S. japonicus the 



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