436 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



GROWTH AND DEVELOPMENT 



Juvenile M. auratuf: were easily distinguished 

 from other young western North Atlantic Mul- 

 lidae by the combined charactei's of a minute first 

 dorsal spine and the characteristic tooth patch 

 formed by tlie fusion of tlie vomerine and palatine 

 bones (fig. 31). This patch was evident on all 

 specimens over 14 mm. The absence of teeth in 

 the upper jaw, a useful character in identification 

 of the adults, is reevaluated under the section 

 designated "teeth." 



Larval M. auratus, 9.5-9.8 mm., are illustrated 

 in figure 26. Except for incomplete ossification 

 of the secondary caudal rays, the larvae liad 

 reached tlie juvenile stage. 



At a size of 45.8 mm. (fig. 25, lower) the juve- 

 niles have acquired the barbels characteristic of 

 the family, and the stripes on the first dorsal fin, 

 characteristic of the adult, have appeared. 



The transition from a pelagic to a bottom-living 

 appearance (fig. 25, upper) takes place at approxi- 

 mately 47 mm. The pelagic juvenile coloration is 

 lost, the adult coloration is acquired, and the body 

 becomes more robust. 



Figure 27 sliows a 78.0-mm. specimen taken by 

 bottom trawl, and at tliis size it had assumed tlie 

 adult appearance. 

 Body Proportions 



Thirteen of the body dimensions measured on a 

 total of 49 specimens chosen at random except for 

 size selection are plotted against standard length 

 in figures 9 through 21. 



The rate of increase in dimension of body part 

 is constant tlii'oughout tlie size range of specimens 

 examined for postorbital head length, snout to 

 anal fin, body depth, snout to soft dorsal fin, ven- 

 tral lobe of caudal fin, dorsal lobe of caudal fin, 

 and interorbital space (figs. 10, 11, 12, 15, 16, 17, 

 and 18, respectively). For barbel length, there is 

 little if any change in dimension between 15 and 

 25 mm., after wliich there is an increase, and the 

 rate of increase remains constant to the largest 

 size (fig. 19). For head length and snout length 

 an inflection occurs at about 45 mm., and the rate 

 beyond tliis size is constant and slightly liiglier 

 than below 45 mm. (figs. 9 and 20). For distance 

 ivom snout to spinous doreal fin, an inflection 

 occurs at about 130 mm., with the rate of increase 



Figure 26. — Larval Mulltts auratus. Top: 9.5 mm., ventral view; middle: O.S mm., lateral view 



dorsal view. Dip netted by GUI personnel. ( BLBG ) 



bottom : 9.6 mm., 



