During its larval life, Elagatis bipinnulata is 

 planktonic. Some larvae and juveniles become as- 

 sociated with the pelagic sargassum community 

 (Dooley, 1972) and are carried along the Florida 

 Current and Gulf Stream. 



Banded rudderfish, 



Seriola zonata (Mitchill) 



Figure 3 



Literature 



Larvae of Seriola zonata have not been previ- 

 ously described. Early juveniles of the banded 

 stage were described by Nichols (1946), Ginsburg 

 (1952), and Mather (1958). Lutken (1880) illus- 

 trated an unhanded 20-mm juvenile. 



As noted earlier, larvae ofSeriola dumerili were 

 described by Hildebrand and Cable (1930) and 

 Sanzo (1933). Japanese workers have described 

 life history series of three species of Seriola. The 

 most detailed study of development from eggs to 

 juveniles was made on Seriola quinqueradiata 

 [Uchida, Dotu et al. (1958), Uchida in Uchida, 

 Imai et al. (1958), Mitani (1960), and Mito (1961)]. 

 Larvae and juveniles of two other Japanese 

 species, S. aureovittata and S. purpurascens were 

 covered by Uchida in Uchida, Imai et al. (1958). 



Distinguishing Features 



Seriola larvae resemble most those of Elagatis 

 bipinnulata in size, body structure, and pigmenta- 

 tion. Unlike £. bipinnulata, however, there is no 

 supraoccipital crest; the spines of the dorsal fin are 

 of unequal length, the anterior and posterior ones 

 being shorter; and the preopercular spines have 

 smooth sides until the transition period when the 

 longest spine develops 1 to 2 denticles. The larvae 

 transform at about 13 mm. They are deep-bodied 

 and robust. The head is massive and slightly de- 

 pressed, and the eyes protrude slightly from the 

 orbit at the dorsal side. 



Early larvae of Seriola zonata (3-7 mm) are dif- 

 ferentiated from those of other species of Seriola 

 by the presence of 5 to 6 large melanophores on the 

 middorsal line at the base of the dorsal fin (Figure 

 3 B). These large melanophores which are apposed 

 to the myomeres stand out among the more 

 numerous and smaller pigment spots on the back 

 and sides. In older larvae these melanophores be- 

 come embedded in the muscles and covered by 



FISHERY BULLFTIN: VOL 72. NO. 2 



superficial melanophores. When the full comple- 

 ment of dorsal fin rays is formed at about 8 mm, 

 larvae of S. zonata are distinct in having 35 to 40 

 soft rays in the second dorsal fin, the highest sec- 

 ond dorsal fin ray count of all species of Seriola. 

 All dorsal fin rays are sharply visible even in un- 

 stained specimens. 



The first interhemal spine of the first ventral 

 pterygiophore is only slightly enlarged and does 

 not press against the first hemal spine. 



Morphology 



Maximum body depth at 3.6 mm is 30% of the 

 standard length. It increases to 37% at initial 

 notochord flexion and does not change 

 significantly during larval and transition periods. 

 In early juveniles, the body depth is never less 

 than 30% of the standard length (Table 4). 



Head length is 33% of standard length in the 

 smallest larva (3.6 mm) and attains a maximum of 

 43% at 7.0 mm. Thereafter, head length decreases 

 gradually, with an average of 35% in early 

 juveniles 18.0 mm in length. Depth of head is 91% 

 of the head length at 3.6 mm and attains a max- 

 imum of 122% at 5 mm. Thereafter, head depth 

 decreases slightly and is never less than 89% of 

 the head depth throughout the larval and juvenile 

 periods. The dorsal profile of the snout is slightly 

 concave at 3.6 mm but becomes straight at about 5 

 mm and then convex in the older larvae and 

 juveniles. 



The eyes are round and large, and the orbit 

 diameter increases in relation to head length. Rel- 

 ative orbit diameter ranges from 28 to 36% of the 

 head length in larvae and transforming specimens 

 and gradually increases in early juveniles. A low 

 orbital crest with a weak spine is present in the 

 early larvae and is resorbed at metamorphosis. 



Marginal and lateral surface preopercular 

 spines are present. The marginal angle spine 

 which is the longest develops 1 or 2 denticles on its 

 dorsal side in transforming larvae and early 

 juveniles. All preopercular spines gradually 

 diminish in size and become overgrown by the 

 expanding preopercle. 



Scales along the posterior end of the lateral line 

 in front of the caudal peduncle are formed at 20 

 mm. Subsequently, the scales along the anterior 

 portion of the lateral line ossify, followed by those 

 on the head and sides of the body. 



The slender gut is coiled in a single loop in 

 larvae up to 10 mm long. The number of loops 



422 



