414 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



GROWTH AND DEVELOPMENT 



The smallest P. mncxdatns examined was 18.5 

 mm. (fig. 7). The presence of a minute first dor- 

 sal spine, absence of a palato-vomerine tooth 

 patch, and characteristic pigmentation served to 

 identify this species at this size. The secondary 

 caudal rays, 9 on the dorsal lobe and 10 on the 

 ventral lobe, have ossified and, by my definition, 

 this specimen was a juvenile. 



There are no major clianpes occurring until the 

 juvenile (fig. 4) goes to the bottom and transforms 

 (fig. 5). In the material tliat I examined, this 

 usually occurred between 40 and 60 mm. At 94.7 

 mm. (fig. 8) the juvenile has assumed the general 

 appearance of the adult. 



Body proportions 



Thirteen of the body dimensions measured on 

 66 specimens selected for size were chosen to de- 

 pict development of various body proportions. 

 Twenty-one of the 66 were of a series of 25 trans- 

 forming specimens, ranging from 49.5 to 73.5 mm., 

 taken with the aid of rotenone in less than 1 fathom 

 of water (table 2). Body depth was determined 

 for several additional 40- to 60-mm. pelagic speci- 

 mens to reveal more clearly the sudden increase 

 in this dimension in this size range. These orig- 

 inal measurements are plotted against standard 

 length in figures 9 through 21. The data suggest 

 the inflection in slope for body dimensions to coin- 

 cide with, or appear shortly after, the size range 

 in which the species changes habitats. 



For tJiree of the dimensions, head length (fig. 

 9), postorbital head length (fig. 10), and snout 

 to anal fin (fig. 11), the rate of increase is con- 

 stant from the smallest through the largest 

 specimens. 



For body depth a straight line can be fitted to 

 the data (fig. 12). In the 50- to 60-mm. size 

 range, however, the pelagic fonns are all below 

 the line, and the bottom-dwelling forms are above 

 the line (inset), suggesting sudden increase in this 

 dimension initially upon assumption of a bottom 

 habitat and a cessation of depth growth for pe- 

 lagic forms in this range. TIae resumption of the 

 initial rate of increase beyond this transforma- 

 tion period suggests this to be a temporary 

 phenomenon. 



Beyond 70- to 80-mm. the rate of increase of 

 eye diameter is constant and slightly lower than 

 the initial rate (fig. 13) . 



The data for the measurement, snout to spinous 

 dorsal fin (fig. 14), suggest one rate of increase 

 to about 50 mm. and a second slightly higher and 

 constant rate beyond about 60 mm.; but rather 

 than a simple inflection at 50 to 60 mm., there is 

 an upward shift, indicating a sudden increase in 

 this dimension in this range. 



The rate of increase for snout to soft dorsal 

 fiii (fig. 15) beyond an inflection at about 50 to 60 

 mm. is constant and slightly higher than the initial 

 rate. 



Figure 8. — Pseudupeneus mamilatus, 94.7 mm 



