258 



Fishery Bulletin 92(2), 1994 



30 



20 



10 



I I Type A 

  TypeB 

 W TypeC 



o 



z 



LU 



o 

 cc 



LU 



o 



a: 



LU 

 Q. 



20 



15 



the range (0.68-1.18 mm) given 

 by Merriman and Sclar (1952) 

 for Block Island Sound, New 

 York. While the range in sizes 

 for silver perch and weakfish re- 

 ported in this study agree with 

 past research, overlaps in these 

 ranges preclude the sole use of 

 egg size for identification. 



Neither Joseph et al. (1964), 

 Olney (1983), nor the present 

 study identified eggs of C. nebu- 

 losus or M. saxatilis in samples 

 collected in lower Chesapeake 

 Bay. Fable et al. (1978) described 

 laboratory-spawned eggs of C. 

 nebulosus from a single female 

 and reported a mean diameter of 

 0.77 mm (range 0.70-0.85 mm). 

 Although based upon a limited 

 sample size, Fable et al.'s data 

 indicate that eggs of C. nebu- 

 losus could be confused with 

 eggs of B. chrysoura; however, no 

 eggs in our limited sample of 

 this size range (n=12) were ge- 

 netically identified as C. nebu- 

 losus. A possible explanation for 

 the lack of eggs of C. nebulosus 

 in the present study may be the 

 tendency for adults to spawn in 

 or around vegetated areas 

 (Brown, 1981). The absence of 

 eggs of Menticirrhus spp. in this 

 genetic analysis may be ex- 

 plained by our exclusion of eggs 

 with greater than three oil glob- 

 ules. Additionally, Menticirrhus 

 saxatilis reportedly spawns off 

 front beaches and possibly off- 

 shore (deSylva et al., 1962); con- 

 sequently, circulation in the bay may prevent eggs 

 of this species from entering the survey area or they 

 may be transported to areas that were not sampled 

 in our study. 



The identification of species-specific restriction 

 fragment patterns for spring-spawning sciaenids is 

 based on the assumption that there is limited in- 

 traspecific variation of the diagnostic restriction 

 fragment patterns. Recent studies of the population 

 genetics of spotted seatrout, black drum, and weak- 

 fish (Graves et al., 1992; Gold et al., 1993) indicate 

 that these species exhibit low intraspecific mtDNA 

 variability. Furthermore, no variation of the Hi n dill 

 fragment pattern was found in a survey of mtDNA 



23 APR 1991 



19 MAY 1991 



20 



10 



65 0.75 0.85 0.95 1.05 1.15 



29 APR 1991 



0.65 75 085 95 1.05 1.15 



22 MAY 1991 



30 



25 



10 



65 75 85 95 1 05 1 15 



9 May 1991 



065 0.75 085 0.95 1 05 1.15 



28 MAY 1991 



20 



15 



65 75 85 95 1.05 1.15 



065 0.75 0.85 0.95 1.05 1.15 



OUTSIDE EGG DIAMETER (mm) 



Figure 2 



Frequency distributions of outside egg diameters of sciaenid eggs collected 

 over six weeks during spring 1991 in lower Chesapeake Bay. 



isolated from 25 adult B. chrysoura (L. Daniel, 

 unpubl. data). Consequently, the common restriction 

 fragment patterns used to distinguish species in this 

 study were deemed suitable for use in identifications. 



Variability in egg-size distributions with changing 

 salinity and over the spawning season were not exam- 

 ined in this study. Consequently, exact size groupings 

 may only be applicable to the particular salinity re- 

 gime (19-25 ppt) that we sampled. However, samples 

 were taken throughout peak spawning for black drum 

 and silver perch and may encompass the ranges that 

 occur for these species in lower Chesapeake Bay. 



Results of our genetic analysis suggest that iden- 

 tifications of eggs of spring-spawning Sciaenidae in 



