830 



Fishery Bulletin 101(4) 



The paired i-test showed no significant difference between 

 the preserved oocytes and the predicted size of fresh oo- 

 cytes (t=-26.2, df=128, P=0.000). 



Discussion 



Fecundity in striped mullet from South Carolina correlated 

 highly with length and weight, but not with age. Oocyte 

 counts ranged from 4.47 x IQS to 2.52 x 10'' in 1998 for fish 

 ranging in total length from 331 mm to 600 mm, 2.13 x 10^ 

 to 3.89 X 10® in 1999 for fish ranging in total length from 

 332 mm to 588 mm, and 3.89 x 10^ to 3.01 x 10® in 2000 for 

 fish ranging in total length from 325 mm to 592 mm. These 

 fecundity levels correspond with general fecundity levels 

 (2.0 x 10'' to 14.0 X 10®) found in striped mullet in northeast 

 Florida (Greeley et al., 1987), the Gulf Coast (Render et 

 al., 1995) as well as studies in Europe and Asia (review by 

 Alvarez-Lajonchere, 1982). One marked difference in fecun- 

 dity between the present study and some in the literature 

 was the difference in oocyte density. Render et al. (1995) 

 found densities ranging from 798 to 2616 oocj^es/g ovary 

 weight, whereas densities in the present study ranged from 

 1710 to 14,817 oocytes/g ovary weight. However, although 

 fecundity increased with both total length and body weight 

 in 1998 and 1999, densities did not. The lower oocyte densi- 

 ties in the larger fish were most likely indicative of larger 

 oocytes. This feature is common in both synchronous and 

 asynchronous spawning fishes (Greeley et al., 1987; Render 

 et al., 1995; Fox and Crivelli, 1998; DeMartini and Lau, 

 1999). Because total length and body weight were more 

 highly correlated with increased fecundity, the larger speci- 

 mens would have made a greater individual reproductive 



o 

 O 



Males 

 Females 



M.^Y JUN JUL AUG SEP 



OCT NOV 



Month 



DEC JAN FEB MAR APR 



Figure 7 



Mean gonadosomatic index value by month for male and female striped 

 mullet from South Carolina estuaries from 1998 to 2000. n (number of fish 

 in sample) = 455. 



contribution during any given spawning season (Korhola 

 et al., 1996; Kaunda-Arara and Ntiba, 1997; DeMartini 

 and Lau, 1999). Making estimates of potential fecundity 

 from age alone was difficult because of the variability in 

 the size-at-age relationship; however, fecundity estimates 

 from total length or body weight appeared more reliable 

 and reflected values closer to the fecundity levels observed 

 in the present study. 



Previous studies have reported that female mullet be- 

 come reproductively mature at three years of age (Thom- 

 son, 1951; 1963; Stenger, 1959; Chubb et al., 1981; Render 

 et al., 1995). Greely et al. (1987) suggested that fecundity 

 specimens collected in northeastern Florida were as young 

 as two years at maturity. But, Greely et al. (1987) did not 

 age the striped mullet used in their study and inferred age 

 from a size-at-age growth schedule (Thomson, 1966). In 

 the present study, two-year-olds made up only a small per- 

 centage of the fecund fish in 1998 and 1999. However, the 

 results were different for the 2000 specimens in that there 

 was an almost equal distribution in the age frequency of 

 two-, three-, and four-year- olds. However, three- and four- 

 year-olds made up the greatest percentage of females with 

 advanced ovaries. Maturing fish were those undergoing ac- 

 tive vitellogenic development and were generally captured 

 in and around inlets or estuaries. Our study would suggest 

 that female striped mullet reach 50% maturity at age 2 and 

 100% maturity at age 3. Three- and four-year-olds made up 

 the majority of reproductively advanced fish in all years, 

 whereas less abundant older fish made less of a contribu- 

 tion towards total reproductive effort. 



There are several possible explanations accounting for the 

 wide age distribution in maturity stages; the most likely 

 is that fecundity is size related despite the highly variable 

 growth rates and the widely ranging size at 

 age in adult striped mullet. Size at maturity 

 has been found to range widely from 230 mm 

 standard length (Thomson, 1963; Greeley et 

 al., 1987; Tamaru et al, 1994) up to 410 mm 

 standard length (Thomson, 1963; 1966; Chubb 

 et al., 1981) for two- and three-year-old fish. 

 The lower end of this size range agrees quite 

 readily with the lower size range (291 mm 

 TL=239 mm SL) found in our study. In a con- 

 current study of maturity schedules related to 

 size and age in South Carolina striped mullet 

 (McDonough, unpubl. data), male striped mul- 

 let were found to mature at two years of age 

 and as small as 250 mm total length ( 190 mm 

 standard length). Other species of mullet have 

 been shown to mature over a wide range of siz- 

 es. The Pacific mullet (Mugil so-iuy) becomes 

 mature upon reaching approximately 430 mm 

 total length (Okumus and Bascinar, 1997). 



Monthly GSI levels clearly showed that 

 the time period of reproductive activity is 

 from October through April. Female striped 

 mullet in all reproductive developmental 

 stages were observed during the course of 

 our sampling, with the exception of stage-3 

 (hydrated oocytes) females and females with 



