188 



Fishery Bulletin 89(2). 1991 



Figure 1 



Spatial extent of observed striped bass egg occurrence, 

 Pamunkey and Mattaponi rivers, 1980 and 1983. Over 80% 

 of eggs occurred in solid black areas. Inset shows location in 

 Chesapeake Bay region. 



Figure 2 



Spatial and temporal abundance (numbers/100 m :i ) of striped bass eggs 

 and larvae in the Pamunkey River, 1980. River miles are nautical miles 

 above the York River mouth. 



were combined and preserved in 5-8% buffered for- 

 malin. Sampling in 1983 was intended to document only 

 egg occurrence; however, surveys on 4 and 11 May 

 1983 yielded some larval data. Surface and bottom 

 measurements of temperature, salinity, and dissolved 

 oxygen were made at each station. 



Whole collections were sorted for striped bass eggs 

 and Morone spp. larvae, except where large amounts 

 of detritus necessitated examining only one-half of the 

 collection. When bits and pieces of striped bass eggs 

 were found, only intact eggs and separated embryos 

 were counted. The area of peak spawning was defined 

 as those strata that cumulatively contributed >80% of 

 all eggs collected. Morone larvae lacking yolk material 

 and larger than 8.5 mm standard length were cleared 

 and stained for positive identification (Fritzsche and 

 Johnson 1980, Olney et al. 1983). 



Results 



York River System, 1980 and 1983 



Spawning extended approximately 40 km upstream 

 from the limit of brackish water in the Pamunkey River 

 in 1980 and 1983 and 27 km in the Mattaponi River in 

 1980. Peak spawning was recorded over 13km on the 

 Mattaponi River, while on the Pamunkey River it was 

 observed in two disjunct regions (miles 27-41 and 

 45-47) in both years (Fig. 1). In 1980, eggs were found 

 on initial surveys (April 16 and 18), indicating that 

 spawning activity had already begun (Figs. 2, 

 3). Peak egg densities (> 1/m 3 ) occurred on 22 

 and 25 April in the Pamunkey and Mattaponi 

 rivers, respectively. In 1983 (Fig. 4), sampling 

 on the Pamunkey River was initiated on 5 

 April, but few eggs were collected until 27 

 April, when peak densities for the season were 

 encountered. 



Abundance of larval striped bass was cen- 

 tered somewhat further upstream than eggs 

 on the initial 1980 surveys, and all were yolk- 

 sac larvae. Peaks in egg and larval abundance 

 coincided more closely on subsequent sampling 

 dates (Figs. 2, 3). Few larvae were collected 

 after the 8 and 9 May surveys of the Pamunkey 

 and Mattaponi rivers, none after 31 May. 



Modal length of larvae in both rivers was 

 5 mm NL (notochord length) and most were 

 yolksac larvae. All larvae captured after 16 

 May were 12 mm SL (standard length) or 

 larger. In 1983, all larvae from the surveys of 

 4 and 11 May (the only collections examined 

 for larvae) were yolksac larvae less than 6 mm 

 in length. 



