5mm 



Figure 5.-22.7-mm SL (60 days posthatching) juvenile of Brevoortia smithi. 



pectoral fin base in some larvae as small as 4.5 mm 

 and was present in all larvae at 7.0 mm. The pig- 

 ment pattern associated with the pectoral 

 symphysis, heart area, and pectoral fin base was 

 retained until larvae were about 16.5 mm. 



At 9.0 mm, from one to three stellate 

 melanophores had developed internally and could 

 be seen through the otic capsules. A single, stellate 

 melanophore frequently was present over the 

 hindbrain at 10.0 mm, and some specimens had a 

 small melanophore just posterior to and dorsal to 

 the eye at that length. At about 12.0 mm, the pig- 

 mentation on the head began to increase substan- 

 tially. Melanophores appeared on both jaws, on the 

 side of the head, and over both midbrain and 

 hindbrain regions. The number of melanophores 

 increased as larvae grew, and numerous stellate 

 melanophores were present on the heads of the 

 larvae at 16.5 mm. Melanophores were especially 

 concentrated on the jaws and over the brain in 

 larvae larger than 16.5 mm. 



Gut and Trunk Region 



Newly hatched yellowfin menhaden had a few 

 tiny melanophores on the dorsal surface of the 

 trunk along the forebody. Within 12 h of hatching, 

 these melanophores apparently migrated ven- 

 trally because they disappeared on the dorsal sur- 

 face, but a series of malanophores was developing 

 along the gut region of larvae. 



Paired series of melanophores along the gut 

 margin, which are typical of clupeid larvae, were 

 present on yellowfin menhaden larvae of 4.5 mm 

 and longer. Distinct pairs, numbering from 8 to 16, 

 developed along the dorsolateral margin of the 

 foregut and less distinct pairs, numbering 9 to 14, 



occurred along the ventral margin of the hindgut. 

 These series were clearly visible until larvae were 

 about 17.0 mm; they were not present on 

 specimens longer than 18.0 mm. From one to three 

 stellate melanophores usually occurred near the 

 anus along the dorsal surface of the gut on larvae 

 longer than 4.5 mm. These were continuous with 

 an internal series of melanophores that were visi- 

 ble over the hindgut on most specimens longer 

 than 8.5 mm. The number in this series increased 

 from 6 to about 17 at 10.5 mm. Three or four 

 melanophores were associated with the developing 

 swim bladder in 10.0- to 12.0-mm larvae. A second 

 internal series of melanophores was associated 

 with developing vertebrae, but these were too in- 

 distinct to count accurately. 



Pigment developed along the sides of the trunk 

 of some yellowfin menhaden as small as 5.2 mm. 

 From 1 to 3 stellate melanophores were present on 

 some larvae between 5.5 and 7.0 mm, and this 

 number usually increased to as many as 10 for 7.0- 

 to 10.0-mm larvae. Some larvae up to 8.6 mm had 

 no lateral pigment on the trunk, but most 

 specimens, when examined closely, were observed 

 to have these melanophores. The number of lateral 

 melanophores increased greatly when larvae were 

 between 10.0 and 12.0 mm; some specimens of 

 those lengths had as many as 25 lateral 

 melanophores. When larvae were 14.0 mm or 

 longer, these melanophores became very 

 numerous, and most were located above the lateral 

 midline. A paired series of melanophores 

 developed along the dorsal midline, both anterior 

 and posterior to the dorsal fin, on specimens longer 

 than 16.5 mm. 



There are melanophores associated with the 

 developing fins. From 1 to 3 stellate melanophores 



670 



