LIFE HISTORY, FEEDING HABITS, AND FUNCTIONAL 



MORPHOLOGY OF JUVENILE SCIAENID FISHES 



IN THE YORK RIVER ESTUARY, VIRGINIA 1 2 



Labbish N. Chao 3 and John A. Musick 4 



ABSTRACT 



Four abundant sciaenid fishes, Cynoscion regalis, Bairdiella chrysoura, Micropogonias undulatus, and 

 Leiostomus xanthurus, use the York River, Va., as a nursery ground and as an adult seasonal feeding 

 ground. In addition, six species of sciaenids, Menticirrhus saxatilis, M. americanus , Sciaenops ocellata, 

 Cynoscion nebulosus, Pogonias cromis, and Larimus fasciatus, are present in the estuary occasionally. 

 Yearling C. regalis were first caught in April and young-of-the-year in July or August. Yearling B. 

 chrysoura were first caught in March or April and young-of-the-year in July or August. Juvenile 

 Micropogonias undulatus and Leiostomus xanthurus maybe present in the York River all year-round. 

 Young-of-the-year L. xanthurus were first caught in April and M. undulatus were first caught in 

 August. Small M . undulatus ( <20 mm TL) were caught from August to June, which may indicate a 

 prolonged spawning season (or a late spawning stock). Emigration to the ocean was found in all the four 

 species during late fall or early winter. Water temperature and dissolved oxygen seemed to be the most 

 important factors in the spatial and temporal distributions of these four species in the York River. 

 Mouth position, dentition, gill rakers, digestive tract, pores and barbels, nares, and body shape of six 

 sciaenid species, Larimus fasciatus, C. regalis, B. chrysoura, M. undulatus, Menticirrhus saxatilis, and 

 Leiostomus xanthurus, were found to be important in locating and ingesting prey in the water column. 

 Stomach contents indicated that the food partitioning of these six species was closely correlated with 

 the species and their prey habitat. Larimus fasciatus, C. regalis, andB. chrysoura fed mainly above the 

 bottom, whereas Micropogonias undulatus, Menticirrhus saxatilis, and L. xanthurus fed on epifauna, 

 infauna, or both. Juvenile sciaenids are able to coexist in the same area because of differences in spatial 

 and temporal distribution, relative abundance, and food habits. 



Sciaenid fishes are among the most important in- 

 shore bottom fishery resources of the Atlantic and 

 Gulf of Mexico coasts of the United States (Roith- 

 mayr 1965; Joseph 1972; Gutherz et al. 1975). 

 Sciaenid fishes usually use the estuary as a nur- 

 sery ground and seasonal feeding ground. Among 

 the 14 species of sciaenids recorded from 

 Chesapeake Bay proper (Musick 1972), young-of- 

 the-year of 10 species were caught in the York 

 River system during this study. Leiostomus 

 xanthurus, Micropogonias undulatus, Bairdiella 

 chrysoura, and Cynoscion regalis were the most 

 abundant species. Menticirrhus saxatilis, M. 

 americanus, Sciaenops ocellata, C. nebulosus, 



l A portion of a dissertation submitted to the School of Marine 

 Science, College of William and Mary, Williamsburg, Va., in 

 partial fulfillment of the requirements for the degree of Doctor of 

 Philosophy in Marine Science, by the first author, May 1976. 



Contribution No. 816, Virginia Institute of Marine Science, 

 Gloucester Point, Va. 



3 Ichthyology Unit, Vertebrate Zoology Division, National 

 Museum of Natural Sciences, Ottawa, Ontario, Canada K1A 

 0M8. 



■•Virginia Institute of Marine Science, Gloucester Point. VA 

 23062. 



Manuscript accepted April 1977. 



FISHERY BULLETIN: VOL. 75, NO. 4. 1977. 



Pogonias cromis, and Larimus fasciatus were 

 caught only occasionally. 



Juvenile sciaenids, except the Atlantic croaker, 

 Micropogonias undulatus, usually entered the 

 York River in late spring and left in late fall. 

 During this period, sciaenid fishes dominated bot- 

 tom trawl catches in the York River (Colvocores- 

 ses 1975; Markle 1976). By yearly average, they 

 composed more than 50^ of the total catch by 

 weight and 18 to 289c by number of individuals. 

 The purpose of this study is to describe the coexis- 

 tence of the four most abundant juvenile sciaenids 

 in the York River system, Va., based upon relative 

 abundance, temporal and spatial distribution, 

 length frequency, apparent movements, and feed- 

 ing habits. Morphological structures related to 

 feeding habits and habitats were also studied. 

 Specimens of the banded drum, Larimus fasciatus, 

 and the northern kingfish, Menticirrhus saxatilis, 

 were included to show the range of variability in 

 the feeding habits of juvenile sciaenids. Bottom 

 trawl surveys conducted by the Virginia Institute 

 of Marine Science (VIMS) from January 1972 to 



657 



