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Fishery Bulletin 105(4) 



brain except for an unpigmented midline through the 

 midbrain and anterior half of the nape. Internal pig- 

 ment was also visible at the base of the midbrain near 

 the nape and external pigment increased slightly on the 

 forebrain and disappeared on the snout (Fig. 2). 



Postanal ventral melanophores (pvm) became visible 

 late during the embryonic development (day 51) along 

 the ventral midline at 80% BL. By day 65, the pvm 



series extended anteriorly to 50% BL. At time of hatch- 

 ing, the completed series consisted of a light irregular 

 line of melanophores at 50% BL, larger and more closely 

 spaced melanophores at 60-80% BL, and ended 1-2 

 myomeres anterior to the terminus of the dorsal midline 

 series (Fig. 3). 



The internal and external lateral pigment series were 

 the last two pigments to appear. On day 62, internal 



Figure 2 



Drawing of two Atka mackerel (Pleurogrammus monopterygius) embryos with egg diameters of 2.5-2.8 mm after 11 weeks 

 of development at 6.15°C (areas of pigment: fb = forebrain, mb = midbrain, np = nape, dm = dorsal midline, and pvm = 

 postanal ventral melanophores; morphological features: n = nares, 1 = lens, e = eye, and m = myomere). 



Figure 3 



Drawing of a 10.9 mm Atka mackerel {Pleurogrammus monopterygius) larva one day after hatching (areas of pigment: 

 fb = forebrain, mb = midbrain, o = opercular, g = gut. dm = dorsal midline, id = internal dorsal, iv = internal ventrolateral, 

 pvm = postanal ventral melanophores, ed = e.xternal dorsolateral, and ev = external ventrolateral; morphological features: 

 s = snout, Ij = lower jaw, pf = pectoral fin, a = anus, cp = caudal peduncle, and nt = notochord). 



