MULLIDAE OF THE WESTERN NORTH ATLANTIC 



433 



As young M . aunttu.s were tukeu in inuiibers hy 

 dip net through 46 mm., but all specimens 47.2 

 mm. and larger were taken only by bottom trawl 

 (table 8), it appears tliat the species can termi- 

 nate its pelagic existence and descend to the bot- 

 tom when it reaches a size of approximately 4.5 

 mm. It was at this size that the species changed 

 markedly in appearance, as shown in the photo- 

 graph (fig. 25), in which the upper fish is a 47.2- 

 mm. specimen taken at Seahorse Reef (Cedar 

 Keys), Fla.. by trawl; the lower fish is a pelagic 

 45.8-mm. specimen dip netted otf Yucatan. This 

 metamorphosing 47.2-mm. M. auratus was the 

 only specimen in the size range from 46 to 66 nun. 

 available for examination, and it was the only 

 specimen with wliich a direct comparison could 

 be made witli a pelagic form of similar size. 

 However, on the basis of this one specimen, M. 

 aurahi-s does undergo a metamorphosis, but the 

 change of appearance is not so marked as in P. 

 maculatus. The graphs of body dimensions for 

 M. auratus (figs. 9 through 21) do not indicate 



UKuked or abrupt changes in dimensions iit 4."> 

 mm. except in snout length and head length, but 

 these niiglit become evident if more specimens of 

 the size 50-70 mm. were examined (see Body 

 Proportions, M. auratus). 



No juveniles were taken in the deeper waters 

 of the Gulf of Mexico in spite of the thorough 

 work by the U.S. Fish and Wildlife Service ves- 

 sels in this area in recent years. This could indi- 

 cate either that juveniles prefer shallower waters 

 or that the adults do not spawn in or close to deep 

 water. Some small specimens were taken off the 

 Atlantic coast in deep water, but a comparison of 

 the water depths at locations of capture of tiie 

 three species on which I have comparative data 

 (tables 2, 7; and 12, p. 435) shows that those 

 depths for F. ni acuta fii-s and U. parinis tend to be 

 greater than tliose for .1/. auratus. A pelagic ex- 

 istence of shorter duration could explain the 

 chunkier shape as oijposed to the long, slender 

 shape of pelagic juveniles of P. mucuJatus. 



Figure 



-.Juvenile JIiiIIks 



auratus. I'pprr. 47.2-mm. iiielamorpliosed, Irawled 

 Lower. 45.8-iam. dip netted specimen. (BLBG) 



siieciiiien ilMI.M 3105). 



