COMMUNITY AND TROPHIC ORGANIZATION OF NEKTON UTILIZING 

 SHALLOW MARSH HABITATS, YORK RIVER, VIRGINIA 1 



Stephen M. Smith, 2 James G. Hoff, 2 Steven P. O'Neil, 3 

 and Michael P. Weinstein 3 



ABSTRACT 



Nekton were collected by trawl and Wegener ring at each of two stations within tidal creeks and at 

 adjacent shoal stations in the polyhaline and oligomesohaline zones of the York River estuary, Virginia. 

 Species richness was significantly higher (P < 0.05) in Goalders Creek (oligomesohaline) compared 

 with Blevins Creek (polyhaline) and may reflect the general absence of stenohaline marine "southern" 

 taxa which seasonally occupy the tidal creeks of warm-temperate estuaries. In general, diversity was 

 low in both creeks with dominance mainly shared by two species, Leiostomus xanthurus and Anchoa 

 mitchelli. Trinectes maculatus also was abundant at the Goalders Creek shoal station, about 200 m 

 outside of the creek mouth. A detailed analysis of the distribution of L. xanthurus indicated that after 

 recruitment ceased, this species was largely resident in the creeks for several months, only emerging in 

 the fall (October). Furthermore, emigration from Blevins Creek occurred earlier than at the upstream 

 locality. Of the "transient" marine species encountered, L. xanthurus seemed to be the most tidal creek 

 dependent. However, this may be due partly to the collection methodology employed. 



Diet composition of six dominant species comprising >98% of the total number of individuals 

 collected indicated that all were essentially trophic opportunists feeding on a wide variety of food items. 

 Ontogenetic shifts in diet were also observed for the five most abundant species. Lack of dietary 

 specialization and the consequently large degree of diet overlap in all species may reflect the nonlimit- 

 ing nature of food abundance in the primary nurseries, however a seasonal change in relative fullness 

 values may indicate periodic food scarcity. 



The structural and functional role of shallow es- 

 tuarine habitats has received increasing attention 

 in the past few years. Although widely recognized 

 as primary nurseries, two of these habitats, 

 marshes and seagrass meadows, have only re- 

 cently come under scrutiny in the lower Chesa- 

 peake Bay Much of the impetus for these efforts 

 was derived from priorities established by the 

 Chesapeake Bay Program (Environmental Pro- 

 tection Agency 1979). As a result, areas covered 

 with submerged aquatic vegetation (SAV) were 

 investigated between 1977 and 1981. The role of 

 SAV as primary nurseries, especially for blue 

 crabs, Callinectes sapidus, was confirmed (Orth 4 ). 

 It was suggested (and, in some cases, demon- 

 strated experimentally) that a principal function 

 of vegetated habitats was that of predation re- 



'Contribution No. 1160, Virginia Institute of Marine Science. 



2 Virginia Institute of Marine Science and School of Marine 

 Science, College of William and Mary, Gloucester Point, VA 

 23062. 



3 Virginia Institute of Marine Science and School of Marine 

 Science, College of William and Mary, Gloucester Point, Va.; 

 present address: Lawler, Matusky and Skelly Engineers, 1 Blue 

 Hill Plaza, Pearl River, NY 10965. 



4 R. J. Orth, Marine Scientist, Virginia Institute of Marine 

 Science, Gloucester Point, VA 23062, pers. commun. May 1982. 



Manuscript accepted January 1984. 

 FISHERY BULLETIN: VOL" 82, NO. 3, 1984. 



fugium for the early life stages of many species 

 (Heck and Thoman 1981; Lascara 1981; see also 

 Nelson 1979 and Coen et al. 1981). Although sea- 

 grass meadows were contrasted with immediately 

 adjacent unvegetated areas, their value compared 

 with tidal salt marshes was not established. 



To place the utilization of SAV and tidal creeks 

 by the immature life stages of dominant species 

 into better perspective, Weinstein and Brooks 

 (1983) undertook a direct comparison of these 

 areas along a contiguous marsh-seagrass ecosys- 

 tem on the eastern shore of Virginia. Two results of 

 their study were the observations that the domi- 

 nant finnsh in the area — spot, Leiostomus 

 xanthurus — was nearly four times more abun- 

 dant in the tidal creek throughout the study 

 period, and that larger juvenile and adult blue 

 crabs made nearly equal use of both habitats. A 

 further outcome of this study was the obvious need 

 for additional inventories of shallow waters of the 

 lower Chesapeake Bay with regard to the relative 

 value of different habitats to resident species. 



For this reason we have extended our program to 

 include a survey of habitat utilization by nekton 

 occupying oligohaline and polyhaline tidal creeks 



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