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Fishery Bulletin 102(3) 



19°C water. Their criteria have been used by others 

 to estimate rates of POF atrophy in other species and 

 thereby determine the percentage of a population un- 

 dergoing spawning over a discrete time period (Brown- 

 Peterson et al, 1988; Fitzhugh et al., 1993; Taylor et al., 

 1998; Macchi and Acha, 2000; Brown-Peterson and War- 

 ren, 2001; Nieland et al., 2002). However, even though 

 it has been demonstrated that the rate of POF atresia 

 depends largely on ambient water temperature (Fitzhugh 

 and Hettler, 1995), few (Brown-Peterson et al., 1988; 

 Macchi and Acha, 2000; Nieland et al, 2002) have taken 

 this into account when establishing the age of POFs for 

 SF estimations. Our diurnal sampling of reproductively 

 active spotted seatrout during warm water conditions en- 

 abled us to establish criteria to accurately estimate the 

 age of POFs throughout the spawning season. Further- 

 more, we verified our assessments by sampling around 

 the clock on two occasions to collect fish over the time 

 period immediately following a spawning event. 



Spotted seatrout ages 1-3 in SC spawned less fre- 

 quently than those from the Indian River Lagoon, Flor- 

 ida (Crabtree and Adams 7 ) but both studies showed 

 that older fish spawned more frequently than younger 

 animals. Our estimates for spotted seatrout aged 1-3 

 were 4.7, 4.2, and 4 days, respectively. Trout in these 

 age classes in Florida were reported to spawn once ev- 

 ery 4, 2.8, and 2.5 days, respectively. These differences 

 probably not only reflect the distinct biological environ- 

 ments of each region but also indicate potential discrep- 

 ancies in aging methods. No age-specific estimates of 

 SF are available for other areas in the species' range. 

 Brown-Peterson and Warren (2001) found SF among 

 spotted seatrout in Biloxi Bay, MS, to be significantly 

 lower than that of fish inhabiting the other two areas 

 included in their study. They suggested that Biloxi Bay 

 was a less conducive spawning habitat because of sev- 

 eral factors, including shoreline development and a 

 reduced amount of aquatic vegetation. However, because 

 we found that SF varied significantly among age classes 

 (age-3 fish spawned more frequently), the relative age 

 composition of fish sampled by Brown-Peterson and 

 Warren (2001) in the three estuaries might also have 

 played a critical role in the determination of SF. 



Batch fecundity 



The best approach for estimating BF is to use only oocytes 

 in FOM (Hunter et al., 1985; Brown-Peterson et al., 1988; 

 Brown-Peterson and Warren, 2001; Brown-Peterson et 

 al., 2002; Nieland et al., 2002; Lowerre-Barbieri et al. 8 ). 

 When it is not possible to obtain these, BF estimations 

 can and have been carried out in some species by using 

 the largest vitellogenic oocytes (Overstreet, 1983; Hunter 

 et al., 1985; Wieting 1989). These efforts have the poten- 

 i ill of being less accurate because isolating those oocytes 

 destined to be spawned is difficult if the latter have 

 not yet reached final maturation (Nieland et al., 2002). 

 Inevitably this scenario would result in a nonmeasurable 

 overestimation of female reproductive output. Brown- 

 Peterson et al. (1988) and Brown-Peterson and Warren 



(2001) used a modification of this approach to estimate 

 BF of spotted seatrout in Texas and Mississippi, respec- 

 tively. However, even though the potential existed for 

 overestimating BF, their estimates fell well below those 

 presented in the present study, as did those presented 

 by Nieland et al. (2002) for spotted seatrout ages 2-4 in 

 Barataria Bay, Louisiana. Mean BF for ages 1-3 (170 

 thousand, 226 thousand, and 274 thousand oocytes, 

 respectively) spotted seatrout in Indian River Lagoon, 

 Florida (Crabtree and Adams 7 ), also differed from those 

 reported here. Our estimate took into account that not 

 all age-1 females were mature at the beginning of the 

 season. Crabtree and Adams, 7 however, did not adjust 

 their estimate to reflect this discrepancy. Moreover, due 

 to differences in aging methods, their age-1 and 2 cohorts 

 possibly included ages 2 and 3, respectively. In addition, 

 in the Florida study as well as in ours, relatively few 

 numbers of older specimens were examined. 



The relationships between BF and length, weight, and 

 age in the present study were significant and predictive. 

 Of these, TL exhibited the most predictive relationship. 

 This fact may explain why age-1 and age-2 spotted 

 seatrout in Georgia had mean BFs considerably higher 

 than ours (175 thousand and 407 thousand, respectively; 

 Lowerre-Barbieri et al. 8 ): the size ranges for age-1 and 

 age-2 in the Georgia study were greater than ours. To- 

 tal length seems to be the most reliable predictor of BF 

 among spotted seatrout in Georgia and SC (Lowerre- 

 Barbieri et al., 8 this study) and in Louisiana (Nieland 

 et al., 2002). However, Crabtree and Adams 7 found that 

 BF related best to ovary-free weight among spotted 

 seatrout in Florida. We found ovary-free weight to be 

 the second best predictor of BF. Overall, it appeared 

 that TL and ovary-free weight were better predictors of 

 BF than age for this species (Brown-Peterson, 2003). 



As with SF, monthly egg production (MEP) estimates 

 for SC spotted seatrout varied throughout the season. 

 Because BF was not significantly different among 

 months for any of our age classes, the variation in 

 MEP resulted directly from the frequency of spawning. 

 Monthly egg production estimates for age-1 fish were 

 lowest in May and highest in June because SF was 

 lowest in May and highest in June. Spawning frequency 

 is a critical reproductive parameter because it seems 

 to dictate annual reproductive output (DeMartini and 

 Fountain, 1981; Brown-Peterson and Warren. 2001; 

 Crabtree and Adams 7 ); therefore, SF should be carefully 

 considered, particularly for managed species. 



Relative fecundity 



We found that relative fecundity (RF), the number of 

 oocytes per gram of somatic weight, did not show a sig- 

 nificant relationship with female size. This finding was 

 expected because dividing fecundity by ovary-free weight 

 standardizes the values independently of size. However, 

 this finding was in contrast to that of Brown-Peterson 

 and Warren (2001). They collected specimens during 

 the morning only, whereas we sampled ours throughout 

 the day. This procedure allowed us to examine ovaries 



