638 



Fishery Bulletin 100(3) 



American shad in the diets of striped bass (Manooch, 1973; 

 Austin and Walter''), this absence may be due to current 

 low numbers of American shad in relation to other clupe- 

 ids. Correspondingly, American shad juveniles have the 

 potential to prey upon striped bass larvae (McGovern and 

 Olney, 1988). Competition for food may occur between the 

 early life stages of these two species as well. According to 

 several studies, larval and juvenile stages of striped bass 

 and American shad feed on similar prey items (Massmann, 

 1963; Markle and Grant, 1970; Setzler-Hamilton et al. 

 1981; Gardinier and Hoff, 1982; Crecco and Blake, 1983; 

 Johnson and Dropkin, 1997; Ross et al., 1997). Distinct 

 spawning locations of these species may act to minimize 

 competition between larval- and early juvenile-stage fish, 

 which use nursery locations downriver of spawning reaches. 

 There is also potential overlap in habitat use between the 

 juveniles of these species because both species occupy shal- 

 low nearshore waters. Some habitat overlap may be avoided 

 by differing inshore-offshore diel migration patterns. Amer- 

 ican shad occupy nearshore areas during daylight and move 

 offshore during night hours (Schmidt et al., 1988), whereas 

 striped bass have been observed to predominately occupy 

 nearshore habitats during both day and night hours (Boyn- 

 ton et al., 1981; Rudershausen and Loesch, 2000). 



Locations of striped bass spawning grounds on the 

 Pamunkey River in this study corresponded to those of 

 previous studies. Primary spawning reaches on the Pa- 

 munkey River were previously reported from 8-48 km 

 above West Point (Rinaldo, 1971); at approximately 27 km 

 (Pamunkey) and 14 km (Mattaponi) above the mouth of 

 each river (Tresselt, 19.52); and within the first 40 km of 



Austin, H. M., and J. F. Walter. 1998. Food habits of large 

 striped bass in the lower Chesapeake Bay and its tributaries 

 March 1997-May 1998. Final report to the Marine Recre- 

 ational Fisheries Advisory Board and Commercial Fisheries 

 Advisory Board, VMRC, 56 p. Contract number RF-97-08 and 

 CF09709-08. Virginia Institute of Marine Science, Gloucester 

 Point, VA 23062. 



tidal freshwater of both rivers (Grant and Olney, 1991). 

 In the our study, some striped bass eggs were collected on 

 the Pamunkey River upstream of previously reported loca- 

 tions, but in lower abundance than occurred downstream. 

 In the Mattaponi River, striped bass eggs were absent in 

 upstream locations, an observation in agreement with pre- 

 vious sui-veys (Tresselt, 19.52; Rinaldo, 1971; Grant and 

 Olney, 1991; McGovern and Olney, 1996). 



On both rivers, American shad were collected in higher 

 abundance upriver of previously reported primary ranges 

 by Massmann (1952). He observed peak egg abundance 

 from 96.2 to 111.0 rkm on the Pamunkey River and from 

 81.4 to 94.4 rkm on the Mattaponi River This is in part be- 

 cause we sampled farther upriver than Massmann. How- 

 ever, in those upriver reaches that both studies sampled, 

 eggs were found in higher abundance in 1997-99. Shifting 

 spawning habitats (possibly due to changes in population 

 structure and size, climate, or river discharge), sampling 

 deficiencies, unknown catchability differences between the 

 studies, or some combination of these factors may explain 

 these historical differences. As populations of American 

 shad fluctuate, the spawning area used will likely expand 

 or shrink. If restoration efforts are successful, the availabil- 

 ity of suitable spawning areas may become a limiting factor 

 to population growth. Further studies of habitat suitability 

 for spawning within this system are underway to elucidate 

 potential spawning reaches and optimal areas. 



Acknowledgments 



We thank David Evans, Herbert Austin, and Deborah 

 Bodolus for their reviews of this manuscript. We also 

 thank the staff of Vessel Operations at VIMS and Jim 

 Goins for their assistance with push-net design, Jason 

 Romine for his help in sorting samples, and numerous 

 associates for their assistance in the field. This research 

 was funded by the Wallop-Breaux Program of the U.S. 

 Fish and Wildlife Service through the Recreational Fish- 



