476 



Fishery Bulletin 102(3) 



Table 2 



Criteria used for microscopic staging of C. nebulosus day-0 postovulatory follicles iPOFsl in water temperatures above 25°C. 

 Measurements represent longest axis of POFs. 



POF chronology fin hours) 



Description 



0-4 



5-8 



9-12 



13-24 



Regular arrangement of granulosa-cell nuclei proximal to the basement membrane and 

 obvious multiple layering as described by Hunter and Macewicz 1 1985 ). 200-300 ^m i Fig. 4Ai. 



Early signs of atresia, loss of the obvious layering, hypertrophy of granulosa cells, and a 

 general compaction with an investment of blood vessels. 180-250 jum (Fig. 4B). 



Well-defined lumen separating the internal granulosa cells from the outer wall of granulosa 

 cells encompassed by theca. 150-200 jum (Fig. 4C). 



Lumen reduced primarily by loss of granulosa tissue and proximity of peripheral layers. 130- 

 175 ^m (Fig. 4, DandE). 



the year were aged by the addition of 1 year to the count 

 of the number of annuli on the thin sections. In April or 

 May, if the section had a large marginal increment, one 

 was also added to the annular count. If the marginal 

 increment was small or if the ring was detectable on the 

 edge of the otolith section, age was equal to the number 

 of annuli. 



Seasonality 



Spawning season for spotted seatrout in South Carolina 

 was determined by using two techniques. The gonadoso- 

 matic index (GSI) was calculated as 



(GW/OFWT) x 100, 



where GW = gonad weight (g); and 

 OFWT = ovary-free weight (g). 



For years prior to this study (1991-97), mean monthly 

 GSI was obtained for all females by using data from 

 the South Caroline Department of Natural Resources 

 inshore fisheries archives (Wenner 6 ). Reproductive sea- 

 sonality among female spotted seatrout throughout the 

 year was also examined by using histology (Table 1). 



The first evidence of oocytes in final oocyte matura- 

 tion (FOM) as evidenced by lipid and yolk coalescence; 

 Brown-Peterson et al., 1988) or the occurrence of post- 

 ovulatory follicles (POFs) defined the beginning of the 

 spawning season. To determine the cessation of spawn- 

 ing, the percent occurrence of females in spawning 

 condition (ripe and repeat spawners) and those in post- 

 spawning condition (spent and resting) were obtained 

 for the months of August and September. To investigate 

 the condition of females, we examined Fulton's condition 

 factor (Ricker, 1975) over the spawning season using 

 linear regression. 



6 Wenner, C. 2002. Unpubl. data. Marine Resources Re- 

 search Institute, Marine Resources Division, South Carolina 

 Department of Natural Resources, 217 Ft. Johnson Rd., 

 i harleston, SC 29412. 



Spawning frequency 



We obtained samples for spawning frequency ( SFi deter- 

 mination from 1 May through 31 August 1998, 1999 

 and 2000. Although samples were routinely collected 

 throughout the year, only from early May through late 

 August did we capture enough animals in the appro- 

 priate reproductive state for SF estimation. Spawning 

 frequency was calculated as either the inverse of the 

 proportion of ovaries with day-0 POFs (Hunter and 

 Macewicz, 1985; Brown-Peterson et al., 1988) or with 

 oocytes in FOM (Brown-Peterson et al., 1988; Liso- 

 venko and Adrianov, 1991) among mature and develop- 

 ing females. 



We designated two distinct morphological features 

 of POFs based on time of specimen capture and water 

 temperature. We interpreted the largest, least atro- 

 phied POFs to be <24 h old and termed them "day-0" 

 POFs (Hunter and Macewicz, 1985). The presence 

 of day-0 POFs in the ovary indicated that spawning 

 had occurred the previous night. The second category 

 comprised smaller POFs, which primarily consisted of 

 closely packed granulosa cells determined to be >24 h 

 old. 



To complete the chronology of POF atresia we under- 

 took round-the-clock sampling on 27-28 June and 26 

 July 2000. During these efforts, sampling continued 

 beyond routine hours to encompass the period between 

 dusk and dawn. The histological samples obtained al- 

 lowed for the calibration of criteria used to age POFs 

 (Table 2). To determine whether SF varied among 

 months and age classes, Kruskal-Wallis tests were 

 used. Because both factors (month and age) were fixed 

 (model 1). it was not possible to test for their interac- 

 tion by using a two-way parametric ANOVA without 

 replication. 



As a result of targeting fish for batch fecundity esti- 

 mates (see below), we had available numerous specimens 

 with oocytes in FOM with which to establish monthly 

 SF. However, we knew that these specimens were dis- 

 appearing from our shallow sampling sites into deeper 

 spawning areas as the day progressed (Riekerk et al. 3 ), 



