CHAO and MUSICK: LIFE HISTORY OF JUVENILE SCIAENIDFISHES 



77° 00 



76° 40' 



STRATA: a,b,c,d,e,f,g,m,p. 



SUBSTRATA: north shoal 

 south shoal 

 channel ;•_'.: 



M-l, M-2.M-3 



P-I.P-2.P-3 



BEACH SEINE STATION 



37? 

 40' 



76°]40' 



FIGURE 1. — The trawl strata, substrata, and beach seine stations in the York River estuary, Va. Strata: A-G, M, and P. Substrata: 

 north shoal, channel, and south shoal. Substrata in Mattaponi River expressed as M-l, M-2, and M-3, in Pamunkey River as P-l, P-2, 

 and P-3. River distances from the mouth of York River (0 km) are indicated in kilometers. 



were made on cleared and stained specimens, ac- 

 cording to the methodology of Taylor (1967). 



The nomenclature used for the study fishes fol- 

 lows Chao (in press). Micropogonias must replace 

 Micropogon because the generic name Micropogon 

 was preoccupied by Boie (1826 in Aves). The 

 specific name chrysoura is used instead of chrys- 

 ura for Bairdiella because the spelling chrysourus 

 was used by the original author (Lacepede 

 1803:166). 



RESULTS AND DISCUSSION 



Hydrographic Description 



Water depth, temperature, salinity, and dis- 

 solved oxygen were measured with each sample 

 and are listed in the appendix section of Chao 

 (1976). The benthic environment was of particular 



importance to the present study. Mean values for 

 bottom temperature, salinity, and dissolved oxy- 

 gen in each stratum from May 1972 to August 

 1973 are summarized in Figure 2, to show sea- 

 sonal patterns in the York River estuary. 



Temperature 



The bottom water temperature of the York 

 River (Figure 2) was lowest in January and high- 

 est in July (1973) or August (1972). The gradual 

 increase of temperature from April to June and 

 the decrease from October to December are most 

 important to migratory fishes in the York River 

 (Markle 1976). In winter months (December- 

 February), the bottom temperature of the upper 

 portion of the York River was lower than that of 

 the lower portion. No apparent differences in 

 temperature were found among the shoal and the 



659 



