426 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



COMPARISON OF SPECIES 



The five common species of Caranx in the 

 Atlantic off the United States are compared with 

 respect to selected characters— comparisons of 

 dentex and lugubris with these are less complete. 

 Regression lines for selected characters show 

 trends of differences between the species, but in 

 most instances they are not applicable to taxo- 

 nomic separation because of the overlapping of 

 individual measurements. Descriptions and com- 

 parisons apply to the size ranges given for each 

 species. 



Comparison of a series of morphometric char- 

 aracters of larval carangids morphologically similar 

 to Caranx showed a converging of body propor- 

 tions around 4 to 5 mm. standard length. Only 

 species of Decapterus and Selar were compared, 

 but gross study of other larger carangid larvae 

 and juveniles indicated that species of Trachurus, 

 Chloroscombrus, and Hemicaranx would follow the 

 same trend. No suitable meristic characters were 

 discovered to separate the genera at this size. 

 A treatment of the larvae of most of the species in 

 the family would be necessary to assure generic 

 and specific separation below 5 mm. standard 

 length, and the majority of these are undescribed. 

 Consequently, the series of crysos and of the form 

 referred to as Caranx sp. {"lotus and/or hippos") 

 were begun with specimens of 5.4 mm.; but a 

 3.8-mm. specimen that is suspected to be crysos 

 and a 4.9-mm. specimen that may belong to 

 the "latus and/or hippos" group are illustrated. 

 A 6.0-mm. form is the smallest one referred to 

 bartholomaei, but an 8.1-mm. specimen is the 

 smallest definitely identified bartholomaei. The 

 smallest ruber is 12.4 mm. The smallest latus is 

 16.1 mm., but a specimen between 12.7 and 13.0 

 mm. is tentatively referred to this species. The 

 smallest hippos is 15.3 mm., but a specimen of 

 12.7 mm. is tentatively referred to this species. 

 The series of specimens between 5.4 and 8.3 mm. 

 labeled "latus and/or hippos" represents either 

 latus or hippos, or both species. The smallest 

 dentex and only lugubris available for examination 

 were 87 mm. and 242 mm., respectively. 



The largest sizes examined were crysos, 267 

 mm.; ruber, 230 mm.; bartholomaei, 315 mm. (a 

 damaged specimen) and 243 mm.; latus, 146 mm.; 

 hippos, 830 mm.; dentex, 132 mm.; and lugubris, 

 242 mm. 



CHARACTERS 



Numbers preceding discussions of meristic 

 characters are the counts or ranges found in the 

 seven species combined. All body lengths are 

 given in standard length unless otherwise noted. 



Scales on chest.— All species have fully scaled 

 chests except hippos which has a patch of scales 

 anterior to the pelvics on an otherwise scaleless 

 chest (fig. 85). 



Dorsal spines.— VIII and I. Rarely 6 or 7 

 spines were counted in the first dorsal fin, and on 

 such specimens the position of the missing spine 

 or spines could usually be determined. The third 

 spine averages the greatest length of the first 

 dorsal-fin spines on specimens more than 30 to 

 40 mm. standard length; below this size it is 

 exceeded in length only by the fourth spine. 

 The interspinous membrane that connects the 

 eighth and ninth spines persists to larger sizes in 

 crysos and bartholomaei (to about 90 mm.) than in 

 the other three species (about 75 to 80 mm.). 



A composite graph of the regression lines for 

 third dorsal spine length on standard length of 

 the five common species is shown in figure 3. 

 The species can be adequately compared between 

 20 mm. and 80 mm. C. crysos apparently lias 

 the fastest, spine growth rate and ruber the slowest 

 (0.13-mm. and 0.10-mm. increase in spine length, 

 respectively, per 1.0 mm. increase in standard 

 length) . C. latus apparently averages the greatest 

 spine length at comparable body lengths and 

 ruber the least. 



Anal spines.— \l and I. The second spine is 

 longer than the first in all species, except hippos 

 below 20.4 mm., in which the first spine is the 

 longer. For specimens less than 10 mm., a differ- 

 ence in lengths of the second anal spine is illus- 

 trated between crysos and bartholomaei in figure 4 ; 

 specimens of the "latus and/or hippos" series over- 

 lap these two. The interspinous membrane con- 

 necting the second and third spines is lost at the 

 smallest size in hippos (about 25 mm.) and at the 

 largest size in crysos (about 45 mm.) . 



Dorsal soft-rays.— C. latus, hippos, and lugubris 

 are separable from bartholomaei, dentex, and ruber 

 by the smaller number of dorsal rays; crysos over- 

 laps these two groups (fig. 1). The first soft-ray 

 is generally the longest soft-ray of the dorsal fin 

 on specimens above 30 to 40 mm. standard 

 length; below this approximate size it is usually 

 exceeded in length only by the second soft-ray. 



