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Fishery Bulletin 95(4), 1997 
downstream may indicate movement of larger, older 
individuals into deeper, warmer waters of the 
mainstem Chesapeake Bay. Atlantic croaker’s sensi- 
tivity to low temperatures (Massmann and Pacheco, 
1960; Joseph, 1972) may further explain the move- 
ment of older and larger fish from the rivers into 
warmer Bay waters. 
Hatching-date distributions 
Our estimate of a protracted spawning season from 
early July 1987 to February 1998, with peak spawn- 
ing in September, is similar to earlier reports in stud- 
ies that used the presence of eggs or early larvae to 
estimate spawning. These studies suggest a pro- 
tracted spawning period from August through De- 
cember with peak spawning from August to October 
(Wallace, 1940; White and Chittenden, 1977; 
Johnson, 1978; Colton et al., 1979; Morse, 1980; 
Chittenden et al. 5 ). Although our observation that 
spawning may begin as early as July has not been 
reported elsewhere, ovaries containing postovulatory 
follicles recently have been observed in Atlantic 
croaker from the Chesapeake Bay as early as July 
(Barbieri et al., 1994). Furthermore, because sexu- 
ally mature adults do not begin to migrate out of the 
Chesapeake Bay until early July, and mainly in Au- 
gust and September (Wallace, 1940), limited spawn- 
ing of Atlantic croaker may occur in proximal coastal 
waters as suggested by Haven (1957). 
Growth 
When comparing temporal patterns in growth, it is 
best to analyze differences between groups by spawn- 
ing date, rather than by capture date; otherwise older 
fish are under represented because of their greater 
accumulated mortality (Campana and Jones, 1992). 
Temporal growth variability was observed when the 
data were analyzed both by capture date and spawn- 
ing date, although a 6% greater difference was ob- 
served when the data were analyzed by spawning 
date. 
Seasonal variability in the growth of larval and 
juvenile Atlantic croaker may result from higher 
water temperatures or increased food in July and 
August (or both) (Alden et al. 6 ) or from improved 
5 Chittenden, M. E., C. M. Jones, L. R. Barbieri, S. J. Bobko, and 
D. E. Kline. 1990. Initial information on the Atlantic croaker, 
a final report on development of age determination methods, 
life history-population dynamics information, and evaluation 
of growth overfishing potential for important recreational 
fishes. Final Rep. to Virginia Mar. Res. Comm. VMRC I, Va. 
Inst. Mar. Sci., College of William and Mary, Gloucester Point, 
VA, 88 p. 
survival of larger, faster-growing fish (Miller et al., 
1988; Isley and Grimes, 1996). Hatching dates of 
faster-growing, early-spawned fish coincided with 
peak mean surface water temperatures in July and 
August (26.3° and 26.7°C, respectively; U.S. Depart- 
ment of Commerce 7 ) and with peak plankton abun- 
dances in the Chesapeake Bay which typically occur 
in July (Alden et al. 6 ). Furthermore, hatching dates 
of slower-growing fish coincided with increased 
patchiness and falling plankton abundances which 
typically begin in September and October (Alden et 
al. 6 ). Warlen (1982) reported similar seasonal growth 
patterns for North Carolina Atlantic croaker larvae 
and speculated that slow growth observed in late- 
captured fish (mid- January to mid- April) might be 
attributed to colder ocean temperatures and low food 
availability in mid- to late-winter, or less likely, to 
smaller egg size of late-spawned larvae. 
Recently immigrated larvae collected in Virginia 
estuaries in this study were larger at age than North 
Carolina larvae. Monthly mean growth rates (mean 
SL/mean age) of estuarine collected larvae (26-65 d) 
in this study ranged from 0.26 to 0.40 mm/d and were 
considerably higher than weekly mean growth rates 
(0.16-0.27) for similar age (32-64 d) North Carolina 
larvae collected in estuarine waters (see Warlen 1982, 
Table 1). Because this study and Warlen’s (1982) were 
conducted in different years, we cannot eliminate the 
real possibility that these differences may be tempo- 
ral, year-to-year changes. Further inter-year studies 
within Virginia and North Carolina, showing consis- 
tent patterns of growth variability, are needed to con- 
clude that there are regional growth differences. How- 
ever, whether spatial or temporal, or a combination of 
both, within-season patterns among the two studies 
are similar, whereas growth rates themselves differ. 
Apparently, Atlantic croaker larvae immigrating 
into estuaries of Virginia and North Carolina can be 
categorized as early-spawned, fast growers or as late- 
spawned, slow growers. These seasonal growth dif- 
ferences, coupled with a spatially and temporally 
extended spawning season suggest that Atlantic 
croaker encounter variable environmental factors 
that may affect their survival. Identifying factors that 
may enhance survival or affect mortality rates of 
these spatially and temporal explicit groups are of 
major interest and are worthy of further study. 
6 Alden, R. W., Ill, R. S. Birdsong, D. M. Dauer, H. G. Marshall, 
and R. M. Ewing. 1992. Virginia Chesapeake Bay water qual- 
ity and living resources monitoring programs: executive report, 
1985-89. Applied Marine Research Laboratory, Old Domin- 
ion University, Norfolk, VA 23529, Report 849, 33 p. 
7 U.S. Department of Commerce, National Ocean Service, NOAA, 
Ocean and Lake Level Division Database, Rockville, MD 20874, 
June 1992. 
