to 6 

 O 



w 



z 

 llJ 



I 

 I- 



o 



5 



y = -09340llx 



•X*^ ^o^*" y-0.35f006x 



ft* oo 



l^^ 



20 30 40 50 60 



FORK LENGTH (mm.) 



70 



80 



Figure 5. — Recession of gape height (solid circles) and gape width (open circles) on 

 fork length of young Atlantic menhaden. Circles represent means of a group of 

 measurements; regression lines were computed from measurements of 124 fish. 



of organisms that the fish might ingest would 

 increase from about 0.6 mm. in a 19-mm. larva 

 to about 7.0 mm. in a 75-mm. juvenile. 



Teeth 



Teeth are prominent in larvae but largely 

 absent in juveniles. Maxillary teeth of larvae 

 are in a single row on the anterior margin of 

 the bone (table 6). Each tooth is 30 to 40 /«. 

 long, irregularly shaped, but usually pointed, 

 and has a wide base (fig. 6). These teeth in- 

 crease in number in prejuveniles, become par- 

 tially embedded in tissue, and form two or 

 three overlapping rows on the flank of the 

 maxillary. After metamorphosis, maxillary 

 teeth apparently are nonfunctional and eventu- 

 ally disappear. 



Dentary teeth occur as slightly recurved con- 

 ical projections, each 25 to 30 /n long, on the 

 medial anterior edge of the bone (fig. 7) . These 

 teeth are conspicuous in larvae and prejuve- 

 niles but disappear in juveniles (table 6). 



Specialization of the mouth structures in re- 

 lation to actual food consumed by young At- 



Table 6. — Tooth counts of young Atlantic menhaden 



• Average of counts on two specimens. 



lantic menhaden is indicated. The large termi- 

 nal mouth and recurved marginal teeth in lar- 

 vae are adapted for the capture and retention 

 of zooplankters. Dentition would seem to be 



500 



U.S. FISH AND WILDLIFE SERVICE 



