FISHERY BULLETIN: VOL. 82, NO. 4 



the third and is interposed between the fourth 

 ceratobranchial and pharyngobranchial. It may 

 be described as a curved bone with the angle 

 formed by the lateral and medial arms being 

 much more acute in Grammatorcynus than in 

 Acanthocybium or Scomberomorus. A dorsal pro- 

 cess arises from the middle of the bone and 

 attaches to the third epibranchial. 



Pharyngobranchials. — There are four pharyn- 

 gobranchials attached basally to the epibranchial 

 of their respective gill arch. The first is long and 

 slender, articulates dorsally with the prootic, and 

 is frequently called the suspensory pharyngeal 

 (Iwai and Nakamura 1964b). The elongate second 

 pharyngobranchial bears a patch of teeth. The 

 third is the largest element in the series; it has a 

 broad patch of teeth on its ventral surface, a 

 broad posterior end, and tapers to a narrow 

 anterior end. The third pharyngobranchial of 

 Scomberomorus is much more elongate than 

 those of Acanthocybium and Grammatorcynus. 

 The fourth pharyngobranchial also bears a ven- 

 tral tooth plate, has a rounded posterior end, and 

 has an elongate strut (pharyngobranchial stay) 

 mesially which overlaps the third pharyngo- 

 branchial. This stay is much more elongate in 

 Scomberomorus than in Acanthocybium and 

 Grammatorcynus. 



Gill Rakers. — The hypobranchial, ceratobran- 

 chial, and epibranchial of the first gill arch sup- 

 port a series of slender, rigid gill rakers. The 

 longest gill raker is at or near the junction of the 

 upper and lower arches, between the ceratobran- 

 chial and epibranchial. There is a correlation 



between numbers of gill rakers, gap between gill 

 rakers, and size of food items, as Magnuson and 

 Heitz (1971) have clearly shown for a number of 

 species of Scombridae. The number of gill rakers 

 is easily countable and is a useful taxonomic 

 character in Spanish mackerels as well as among 

 other groups of the Scombridae. 



Acanthocybium differs from Grammatorcynus , 

 Scomberomorus , and the other genera of Scom- 

 bridae by completely lacking gill rakers. Three 

 species of Scomberomorus have greatly reduced 

 numbers of gill rakers (Table 5): multiradiatus 

 (1-4, sometimes only a single gill raker present, 

 at the junction of the upper and lower arches), 

 commerson (1-8), and queenslandicus (3-9). One 

 species, concolor, stands out from the rest of the 

 genus in having many gill rakers, 21-27. Gram- 

 matorcynus has more gill rakers (19-24) than 17 

 species of Scomberomorus but fewer than S. 

 concolor. There is a correlation between number 

 of gill rakers and number of jaw teeth (Tables 3, 

 4) in Scomberomorus. The species with the fewest 

 gill rakers, S. multiradiatus, also has the fewest 

 jaw teeth (x 8.0 on the upper jaw, 7.8 on the lower 

 jaw) and the species with the most gill rakers, S. 

 concolor, has the most teeth (x 22.2, 19.7). 



AXIAL SKELETON 



This section is divided into four parts: vertebral 

 number, vertebral column, ribs and intermuscu- 

 lar bones, and caudal complex. 



Vertebral Number 

 Vertebrae may be divided into precaudal (ab- 



TABLE 5. — Total number of gill rakers on the first arch in Acanthocybium , Grammatorcynus , and the species of Scomberomorus. 



Species 



1 



7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 



N 



S brasiliensis 

 S. ca valla 

 S. commerson 

 S. concolor 

 S. guttatus 

 S koreanus 

 S lineolatus 

 S. maculatus 

 S. multiradiatus 

 S. munroi 

 S. niphonius 

 S. plurillneatus 

 S queenslandicus 

 S. regalis 

 S. semifasciatus 

 S sierra 

 S sinensis 

 S. tritor 



Acanthocybium 

 Grammatorcynus 



1 37 28 27 12 



2 12 10 



30 



30 22 



1 



3 11 13 1 



7 24 



3 9 

 1 



12 



4 



4 

 3 



1 1 11 9 5 



53 25 

 5 4 



9 

 3 



3 1 

 16 27 



37 22 11 



2 



11 



1 

 18 14 

 10 15 



1 

 3 

 1 



7 

 7 



13 



2 



8 



18 11 



4 19 13 



15 33 22 

 1 1 



1 2 10 10 9 



9 17 8 



129 

 66 



110 

 39 



123 

 27 

 29 

 67 

 27 

 8 

 38 

 34 

 34 

 46 

 32 

 82 

 16 

 41 

 30 

 43 



13.8 



9.3 



4.3 



24.2 



11.1 



13.2 



10.5 



13.0 



2.5 



10.8 



12.5 



13.0 



6.2 



15.4 



9.8 



15.1 



12.6 



13.3 







21.1 



594 



