jBdc-mackerel eggs Id varlom sUges of developmf nL a, b, and r. earl; embryoDlc period, being the stage 

 Immediatelj preceding blastopore closure; d, IntercDedlate period of embryoolc developmest : and f, late-period 

 egga wltb advanced embryos: e shows an egg as viewed from above; all other figures are lateral vlewB. 



I^trra, 10.0 mm. 



Figure 4. — Eggs and larvae of jack mackerel (figures 1 through 8 of 

 Ahlstrom and Ball, 1954). 



3.22 Larval phase 



Ahlstrom and Ball (1954) gave a (detailed 

 description of the development of jack mack- 

 erel larvae (fig. 4). Jack mackerel hatch in 

 a relatively undeveloped condition- -before the 

 mouth is formed, before the eyes are pigmented, 

 and before any fin formation. In preserved 

 material the larvae average 2.07 mm. (range 

 1.91 to 2.38) at hatching. During the yolk-sac 



stage the eyes may begin to develop pigment 

 in larvae as small as 2.2 mm. The jaws 

 develop rapidly and begin to ossify- -the upper 

 jaw in larvae between 3 and 3.5 mm. long, and 

 the lower, in larvae between 3.2 and 3.8 mm. 

 The following table gives the approximate 

 length at which the first spine or ray appears 

 and the approximate length at which the full 

 complement of spines or rays is attained for 

 each fin. 



