FEEDING HABITATS OF SPOT, LEIOSTOMUS XANTHURUS , IN 



POLYHALINE VERSUS MESO-OLIGOHALINE 



TIDAL CREEKS AND SHOALS^ 



Steven P O'Neil^ and Michael P. Weinstein^ 



ABSTRACT 



Young-of-year spot, Leiostomus xanthurus, were collected by otter trawl within tidal creeks and on 

 adjacent shoals in polyhaline and meso-oligohaline zones of the York River, Virginia. Total densities 

 of spot at Blevins Creek, a polyhaline system, were twice that of the meso-oligohaline Goalders Creek. 



Stomach content analysis confirmed previous studies of the generally opportunistic feeding strat- 

 egy of juvenile spot. However, distinct differences in food utilization were observed between creeks 

 and among creek and shoal stations. In addition, prey utilization differences due to habitat generally 

 paralleled seasonal distribution patterns of dominant macrobenthos reported for the area. 



Two major ontogenetic groups were distinguished. Small spot {<30 mm SL) consumed more plank- 

 tonic food items (calanoid copepods) than the larger size classes, which fed on more benthic prey and 

 displayed greater overlap in diet. Small spot tended to be selective; larger spot were more opportunis- 

 tic. 



Tidal salt marshes and their associated drainages 

 are recognized primary nurseries for spot, Leio- 

 stomus xanthurus, (Herke 1971; Parker 1971; 

 Weinstein 1979; Currin et al. 1984). Shortly after 

 recruitment, young spot tend to concentrate in 

 tidal creeks, and by late spring densities in these 

 creeks are often several times higher than in 

 nearby seagrass habitats or shoal areas (Wein- 

 stein and Brooks 1983; Smith et al. 1984). Once 

 recruited to tidal creeks, spot seem to take up 

 residence, w^ith limited movement out of (or be- 

 tween) marshes until the fall mass exodus (Wein- 

 stein 1983; Weinstein and Brooks 1983; Currin et 

 al. 1984; Weinstein et al. 1984; Weinstein and 

 O'Neil 1986). 



The role of marsh nurseries as predation 

 refuges versus feeding areas is currently under 

 debate (Boesch and Turner 1984). As suggested 

 by the studies of Vince et al. (1976), it is likely 

 that the marsh serves in both capacities. Qualita- 

 tive and quantitative data on food availability 

 and quality and on differences among habitats 

 will be necessary to resolve the food versus refuge 

 question. Ultimately, these data should be sup- 

 ported by experimental studies on growth rates 



iVirgmia Institute of Marine Science Contribution No. 1419. 



2Virginia Institute of Marine Science, Gloucester Point, VA 

 23062. 



3Virginia Institute of Marine Science, Gloucester Point, VA 

 23062; present address: Lawler, Matusky & Skelly Engineers, 

 One Blue Hill Plaza, Pearl River, NY 10965. 



Manuscript accepted July 1987. 



FISHERY BULLETIN: VOL 85, NO 4, 1987. 



versus the quality of food resources in different 

 habitats (Weisberg and Lotrich 1982). We report 

 here on one of the steps in the process, a descrip- 

 tive comparison of gut contents of spot collected in 

 tidal creeks and shoal areas in marshes of two 

 salinity regimes, meso-oligohaline and poly- 

 haline. 



Although the food habits of spot have been pre- 

 viously studied, most investigators captured spot 

 in openwater habitats, not in the primary nurs- 

 eries (Parker 1971; Stickney et al. 1975; Chao and 

 Musick 1977; Sheridan 1979). Only Hodson et al. 

 (1981) studied food utilization of spot in tidal 

 creeks. Their population, however, was restricted 

 mainly to small fish (<40 mm) capable of exploit- 

 ing the small creek rivulets and susceptible to 

 capture by block net. This study expands the ef- 

 fort of Hodson et al. (1981), and includes the en- 

 tire seasonal residency period for spot in tidal 

 creeks of the York River estuary, VA. A survey of 

 food utilization was conducted in 1983 for all 

 young-of-year size classes occupying two tidal 

 creeks and nearby river shoals at widely sepa- 

 rated salinities. Specific objectives of this effort 

 were to 1 ) describe food utilization of juvenile spot 

 in each habitat, 2) document any sequential onto- 

 genetic changes in food utilization, and 3) com- 

 pare the overall food utilization of spot residing in 

 tidal creeks or adjacent shoals dissimilar in salin- 

 ity. It was anticipated that feeding differences 

 would reflect the availability and types of food in 



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