FISH 



Anchoa milchilli 



MACROZOOPLANKTON 

 Neomysis omericona 



MICROZOOPLANKTON 

 Copepodo 



EPIBENTHOS 

 Nereis succineo 

 ft Amphipodo 



IN FA UN A 

 Pectmoria gouldn 



ft Nemotoda 



UNIDENTIFIED REMAINS a 

 ORGANIC MATTERS 



TOTAL LENGTH (mm) 

 NUMBER OF STOMACHS 



K\\\\\\\H 



74-126 

 12 



Larimus 



foscialus 



FISHERY BULLETIN: VOL. 75, NO. 4 



rioo 



50 



14.1 10.0 



riOO 

 50 



1 8 8 



23.5 



i^^ ^ 



70- 183 

 34 



57-153 

 58 



56-199 

 64 



37-118 

 20 



73-202 

 73 



Cynosaon Bairdiella Micropogon 



regols chrysoura undulafus 



Menhcirrhus Leiostomus 

 saxatil/s xonthurus 



UJ 



o 



<r 

 ir 



Z> 

 O 



o 

 o 



z 



UJ 



o 



FIGURE 29. — Frequencies of occurence of various categories of food groups in stomachs of juveniles of six species of sciaenids from the 



York River and lower Chesapeake Bay estuary. 



phological characters are correlated with the 

 dietary differences. The premaxillary and dentary 

 teeth of both species are sharp and set in narrow 

 ridges or bands (Figure 22 A, B). Cynoscion regalis 

 has much larger teeth than L. fasciatus , especially 

 a pair of large canines at the tip of upper jaw in C. 

 regalis. These large sharp teeth are adaptations 

 for grasping larger swimming prey. Both species 

 have small sharp pharyngeal teeth (Figure 23 A, 

 B). The arrangement and size of the gill rakers 

 (Figure 24A, B) in L. fasciatus are much denser 

 and longer than those of C. regalis. These differ- 

 ences reflect the food contents in the stomachs of L. 

 fasciatus, which consisted of small crustaceans 

 collected by filtering. The stomach contents of C. 

 regalis consisted of large crustaceans and fishes 

 (Table 10). Larimus fasciatus has a much longer 

 two-looped intestine than the straight intestine of 

 C. regalis (Figure 25A, B; Table 7). The number of 

 pyloric caeca in L. fasciatus (10 or 11) is also 



higher than in C. regalis (4 or 5). These mor- 

 phological differences are probably correlated 

 with the size of food ingested. The cephalic pore 

 systems of C. regalis and L. fasciatus are not well 

 developed. Cynoscion regalis has only two mar- 

 ginal pores on the snout (Figure 26B) whereas L. 

 fasciatus has five minute marginal pores on the 

 snout and four pores on the underside of the lower 

 jaw (Figure 26 A). In addition, the more fusiform 

 C. regalis (Figure 28B) is adapted for fast swim- 

 ming and active predation. The robust, and pre- 

 sumably slower moving, L. fasciatus (Figure 28A) 

 shows adaptations characteristic of a plankton 

 grazing type of feeding. 



Bairdiella chrysoura has a slightly oblique ter- 

 minal mouth (Figure 20C) and a slightly protrusi- 

 ble upper jaw (Figure 20C). These features allow 

 the fish to feed directly in front of its body axis 

 along its swimming course. Its mouth opens as the 

 lower jaw drops anteroventrally and the premaxil- 



696 



