FISHERY BULLETIN: VOL. 75, NO. 4 



of both species foraged into the bottom sand often, 

 especially when the substrate was freshly dug 

 from the beach. Foraging tapered off gradually, 

 especially in M. undulatus, apparently as the food 

 in the substrate decreased. Brine shrimp, Ar- 

 temia, were fed to these two species in the 

 aquarium. Both M. undulatus and L. xanthurus 

 were able to feed on brine shrimp just below the 

 water surface. Micropogonias undulatus fed on 

 the surface shrimp in an oblique to vertical posi- 

 tion. To feed on brine shrimp close to the surface, 

 L. xanthurus occasionally maneuvered in an 

 oblique upside-down position, with the dorsal fin 

 pointing toward the bottom to overcome the in- 

 ferior position of its mouth. 



Other accessory organs of feeding, such as the 

 nares and eyes, also reflect the feeding habits of 

 young sciaenid fishes. The numbers of nasal 

 laminae of the six species (Table 9) overlap, partly 

 due to ontogenetic changes; the absolute numbers 

 of nasal laminae increase as the fishes grow 

 larger. Generally, the bottom feeders, M. un- 

 dulatus and L. xanthurus, have more nasal 

 laminae than Larimus fasciatus, C. regalis, and B. 

 chrysoura (Table 9). Menticirrhus saxatilis has 

 relatively fewer nasal laminae than other benthic 

 feeders, but it has a pored mental barbel on the 

 lower jaw. This suggests that M. saxatilis depends 

 more on touch for foraging than other benthic 

 feeders. The relative eye size of M. saxatilis is 

 smaller than in other sciaenid fishes studied here 

 (Table 5). Larger eyes were found among the 

 pelagic feeders, L. fasciatus, C. regalis, and B. 

 chrysoura (Table 5). Allometrically, the relative 

 eye size of all these sciaenid fishes is larger in 

 young specimens and smaller in adults. For 

 benthic feeders, decrease in relative eye size with 

 growth is faster than for the pelagic feeders. The 

 relative roles of olfaction, touch, and vision in 

 feeding in young sciaenids studied may be 

 hypothesized as follows. The benthic feeders, Mi- 

 cropogonias undulatus, L. xanthurus, and Men- 

 ticirrhus saxatilis, depend more on their senses of 

 smell or touch or both to locate their prey. The 

 pelagic feeders, Larimus fasciatus, C. regalis, and 

 B. chrysoura, depend more on sight to catch their 

 prey, especially C. regalis and B. chrysoura which 

 prey on Anchoa mitchilli, an active small anchovy. 



Morphological differences in the feeding ap- 

 paratus, especially the mouth position, size, and 

 protrusibility, the form of teeth, and the gill raker 

 structure are limiting factors for the level of water 

 column and the size of the prey species which can 



be eaten by the fish. The pelagic feeders, L. fas- 

 ciatus, C. regalis, and B. chrysoura, almost com- 

 pletely lack any sedentary benthos in their diets 

 (Figure 29). Even among the bottom feeders, Mi- 

 cropogonias undulatus feeds more on epibenthic 

 polychaete species (Table 12) and Leiostomus 

 xanthurus feeds more on burrowing polychaete 

 species (Table 14). 



Morphological differences in the digestive tract, 

 the number of pyloric caeca, and the length of 

 intestine may be adaptations to more efficient use 

 of food. As is evident in Larimus fasciatus and 

 Leiostomus xanthurus, size of the food items is 

 important; Larimus fasciatus fed exclusively on 

 small crustaceans (small Mysidacea and Am- 

 phipoda), Leiostomus xanthurus fed mainly on 

 copepods (Table 14). Larimus fasciatus is mainly a 

 pelagic feeder and Leiostomus xanthurus is 

 mainly a benthic feeder. Both species have longer 

 intestines (Table 7) and more pyloric caeca (Table 

 8) than other species in their respective groups 

 (pelagic and benthic). 



Svetovidov reported a similar relationship be- 

 tween the number of gill rakers and size of food 

 items in Caspian shads (Nikolsky 1963). However, 

 he also found more pyloric caeca in shad that fed 

 on fishes than in species that ate small crusta- 

 ceans, a relationship opposite to that found here. 

 In feeding, the role of gill rakers is in ingestion and 

 the role of the pyloric caeca is in digestion. Al- 

 though there are morphological and numerical 

 correlations among the ingestive apparatuses and 

 digestive organs, they are highly adaptive and 

 may be variable among fishes. 



The so-called "selective feeding habits" of these 

 young sciaenids reported by many previous au- 

 thors (see citations of Tables 10-14) are not evi- 

 dent in the present study. Partitioning of food 

 among these young sciaenids depends more on the 

 habits of the prey species than on "selective pref- 

 erences" of the fishes. Juvenile sciaenids feed op- 

 portunistically in a limited depth range in the 

 water column, probably within or close to 2 m 

 above the bottom. Within this layer of the water 

 column, Larimus fasciatus, C. regalis, and B. 

 chrysoura feed in the upper portion of the water 

 column and M. undulatus, Leiostomus xanthurus, 

 and Menticirrhus saxatilis feed in the lower por- 

 tion of the water column to the bottom. Feeding 

 niche division and resulting dietary differences 

 among these species of sciaenids in the 

 Chesapeake estuary area are probably attribut- 

 able to differences in feeding behavior imposed 



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