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Fishery Bulletin 102(3) 



seawater formalin) oocytes. We used a 

 video camera mounted on a Nikon SMZ-U 

 dissecting microscope and coupled to a PC 

 equipped with a frame-grabber and with 

 OPTIMAS- Image Analysis software (ver- 

 sion 6, Media Cybernetics, Bothell, WA). 

 Two readers independently measured the 

 diameter of approximately 30 preserved 

 oocytes in each of three subsamples from 

 27 ovaries. To test for uniformity of size 

 throughout the ovary, mean oocyte diame- 

 ters were compared between ovarian lobes 

 and among subsample locations within 

 each lobe by using two-way ANOVA. We 

 also compared mean oocyte diameters 

 among months and ages by using two- 

 way ANOVA. 



Annual fecundity 



Month 



Wiley (1996) demonstrated that spot- 

 ted seatrout in South Carolina estuaries 

 constitute a single population. Therefore, 

 we felt justified in calculating monthly 

 egg production (MEP) by multiplying the 

 monthly SF (of specimens taken along the 

 entire coast) by the mean monthly BF (of specimens from 

 Charleston Harbor). Because not all age-1 female trout 

 were mature at the beginning of the spawning season, 

 the fraction of mature age-1 females obtained from previ- 

 ous work in South Carolina (Wenner 6 ) was used to refine 

 the MEP estimate. Because the latter was calculated by 

 using SF obtained from data pooled across years, any 

 comparison of MEP among years was deemed invalid. 

 Kruskal-Wallis tests were used to determine whether 

 MEP varied among months for each age class. 



Monthly MEP estimates were summed to arrive at 

 an annual fecundity (AF) estimate for each age class. 

 Because the majority of individuals used in this study 

 were aged 1-3, AF was estimated only for these age 

 classes. We used linear regression to investigate the 

 relationship between AF and age and thus predict AF 

 for spotted seatrout aged 4 and 5. Using these predic- 

 tions and the relative abundance of each age class in 

 our samples, we estimated the contribution of each age 

 class to the annual egg production. 



All statistical analyses were conducted with the Sta- 

 tistical Package for the Social Sciences (version 9.0, 

 SPSS Inc., Chicago, ID. The level of significance for 

 all tests was 0.05. 



Results 



A total of 1038 spotted seatrout ranging in age from 

 1 to 5 was collected for this study. Because 97% of 

 these belonged to age classes 1-3 we report reproductive 

 parameters only for these ages. We examined a total of 

 941 mature and developing females, ranging in Length 

 from 248 mm to 542 mm TL, to determine spawning 



Figure 2 



Mean monthly gonadosomatic index iGSIl for spotted seatrout in South 

 Carolina for years 1991-2000 (circles). Mean water temperature for 

 1991-2000 i triangles). Error bars are standard errors, n = 1185. 



frequency (569, 285, and 87 for ages 1-3, respectively). 

 Of these, 135 specimens (12 from sportfishing tourna- 

 ments) were used to conduct oocyte counts (62, 52, and 

 21 for ages 1-3. respectively). These fish ranged in 

 length from 268 to 530 mm TL. Minimum size at first 

 maturity, as indicated by the presence of cortical alveoli 

 stage oocytes in histological sections, was 248 mm TL. 

 Size at 50'/c maturity was 268 mm, whereas 100'; matu- 

 rity was reached at 301 mm TL. Condition of females, as 

 indicated by Fulton's condition factor, diminished over 

 the course of the season (P<0.01, r 2 =0.24i. 



Seasonality 



Spawning in the Charleston Harbor area during the 

 study period began in mid to late April as indicated by 

 the presence of oocytes in late FOM or POFs in histo- 

 logical samples. During the study period, mean water 

 temperatures ranged from 16° to 34°C. Highest tem- 

 peratures were recorded during July and August for all 

 three years of the study. The lowest documented water 

 temperature when spawning began was 20°C. Cessation 

 of spawning occurred when water temperature was 28°C. 

 Mean monthly GSI for spotted seatrout captured along 

 the South Carolina coast since 1991 (Fig. 2) showed a 

 marked increase from 4.6 in April to 9.4 in May. Mean 

 GSI in June declined to 6.3 and remained around 5.0 in 

 July and August. A sharp decline was noted in Septem- 

 ber to 2.7, the lowest level for the season. Overall, mean 

 gonadosomatic index (GSI) values followed the seasonal 

 trend in water temperature (Fig. 2). Percent occurrence 

 of females in spawning condition as evidenced from 

 histological examination declined from approximately 

 87', in August to 12', in September. The percentage of 



