CHAO and MUS1CK: l.IFE HISTORY OF JUVENILE SCIAENID FISHES 



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FIGURE 26. — Anterior view of snout (captial letters) and ventral view of lower jaw (lower case letters) in juveniles of six species of 

 sciaenids: A, a, Larimus fasciatus; B, b, Cynoscion regalis: C, c.Bairdiella chrysoura; D, d, Micropogonias undulatus; E, e, Menticirrhus 

 saxatilis: F, f, Lewstomus xanthurus. 



pores plus six minute barbels at the tip of the lower 

 jaw (Figure 26D, d). Menticirrhus saxatilis has five 

 marginal pores and three upper pores on the 

 snout, and four mental pores and a short, rigid 

 barbel at the tip of the lower jaw (Figure 26E, e). 

 An apical pore is also present on the barbel of M. 

 saxatilis. The anterior margin of the snout (rostral 

 fold) in Larimus fasciatus and C. regalis is com- 

 plete without notches (Figure 26A, B). Bairdiella 

 chrysoura and Leiostomus xanthurus have a 

 slightly indented rostral fold (Figure 26C, F), al- 

 though the former has a terminal mouth and the 

 latter has an inferior mouth (Figure 26c, f). Both 

 M. saxatilis and Micropogonias undulatus have 

 deeply notched rostral folds (Figure 26D, E), corre- 

 lated with their inferior mouth positions. The 

 mental pores of Larimus fasciatus (Figure 26a) are 

 the smallest of these sciaenids. The barbels of M. 

 undulatus and Menticirrhus saxatilis may differ 

 in function as well as in number, because the 

 single barbel of M. saxatilis has a pore at the tip, 

 whereas barbels of Micropogonias undulatus do 

 not (Figure 26d, e>. The numbers and size of pores 

 increase from species to species as the feeding 

 niche tends toward the bottom; barbels are present 

 only in the bottom feeders. 



Nares 



Sciaenid fishes have two pairs of closely set nos- 

 trils. The anterior one is usually round; the pos- 

 terior one is oval and elongate (Figure 27). A flap 



of skin is sometimes also present along the poste- 

 rior margin of the anterior nostril in bottom feed- 

 ing species. The nasal cavity is generally oval 

 shaped with a cluster of olfactory laminae forming 

 a nasal rosette anteriorly. Larimus fasciatus has 

 the shortest nasal cavity from anterior to posterior 

 nostril (Figure 27A), and Leiostomus xanthurus 

 has the longest (Figure 27F). The shape of the 

 nasal rosettes and olfactory laminae are similar in 

 these six species of sciaenid fishes. The mean 

 number of laminae (averaging both sides per 

 specimen and rounding upwards) differs among 

 these species (Table 9) and is variable within a 

 species. The numbers of laminae are 11 to 14 in 

 Larimus fasciatus; 12 to 22 in C. regalis; 12 to 25 in 

 B. chrysoura; 10 to 31 in M. undulatus; 11 to 22 in 

 Menticirrhus saxatilis; and 16 to 30 in Leiostomus 

 xanthurus. Larimus fasciatus, C. regalis, and B. 

 chrysoura average fewer laminae than Micro- 

 pogonias undulatus, L. xanthurus, and Men- 

 ticirrhus saxatilis (Table 9). Within a species, the 

 number of nasal laminae seems higher in larger 

 specimens. The maximum number of nasal 

 laminae tends to be greater in bottom feeding 

 fishes. 



Other Morphological Characters 



Differences in body shape, mouth structure, food 

 specialization, and habitat preferences of fishes 

 may act to restrict interspecific competition 

 within a fauna (Keast and Webb 1966). The six 

 species of sciaenid fishes discussed here show a 



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