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Fishery Bulletin 103(4) 



formation on reproductive biology is surprising given 

 the worldwide importance of mullet. In particular, there 

 have been very few studies where sexual differentiation 

 of immature striped mullet has been examined in con- 

 junction with histological confirmation of maturity stage 

 in reproductively capable adults. One notable exception 

 was the work of Stenger (1959), who although thorough 

 in histological confirmation of the male and female de- 

 velopmental stages in relation to length, did not take 

 age into consideration at differentiation or maturity. 

 More recent studies (Chang et al., 1995; Chang et al., 

 1999) have examined gonad histology and plasma sex 

 steroids during sex differentiation in young-of-the-year 

 striped mullet up to 12 months old, but these studies 

 did not provide any detail on fish length during devel- 

 opment and differentiation. Other studies have exam- 

 ined oocyte development and relative fecundity for the 

 reproductive assessment of female striped mullet but 

 did not examine reproductive development in males or 

 take into consideration an independent confirmation of 

 fish age (Greeley et al., 1987; Render et al., 1995). Few 

 studies have described the process of spermatogenesis 

 in striped mullet because most efforts on the propaga- 

 tion and enhancement of striped mullet reproduction 

 have concentrated on female development because of 

 their commercial value. Grier (1981) used striped mul- 

 let in describing the cellular organization of testes and 

 spermatogenesis as a model for synchronously spawning 

 fishes but did not describe size and age in relation to 

 spermatogenesis. 



Striped mullet are considered isochronal spawning 

 fishes (Greeley et al., 1987; Render et al, 1995). There 

 are only a few observations of offshore spawning activ- 

 ity (Arnold and Thompson, 1958), and eggs and larvae 

 have rarely been collected offshore (Anderson, 1958; Fi- 

 nucane et al., 1978; Collins and Stender, 1989). Collins 

 and Stender (1989) concluded that striped mullet spawn 

 in and around the edge of the continental shelf off the 

 coasts of North Carolina, South Carolina, Georgia, and 

 the east coast of Florida (an area often referred to as 

 the South Atlantic Bight), but may also spawn outside 

 the South Atlantic Bight (SAB). They also indicated a 

 protracted spawning season that extended from October 

 to April. This contrasts with the estimated spawning 

 season from previous studies (2-5 months from No- 

 vember through March) (Jacot, 1920; Broadhead, 1956; 

 Anderson, 1958; Arnold and Thompson, 1958; Stenger, 

 1959; Dindo and MacGregor, 1981; Greeley et al., 1987; 

 Render et al., 1995; Hettler et al., 1997). Female mul- 

 let were thought to mature at three years of age at a 

 size of 230 to 350 mm standard length (Thomson, 1951, 

 1963; Greeley et al., 1987). 



This study had three purposes: 1) to determine at 

 what size and age striped mullet become fully sexually 

 differentiated and to describe the morphological char- 

 acteristics of sexual differentiation in both male and 

 female striped mullet; 2) to determine the size and age 

 at first maturity for each sex; and 3) to describe the 

 timing and process of gametogenesis in relation to size 

 and age in both males and females in order to provide a 



histological baseline for the evaluation and reproductive 

 staging of striped mullet. 



Materials and methods 



Sampling and data collection 



Collections of striped mullet were conducted from Octo- 

 ber 1997 through December 2000. Collections were based 

 on a protocol of monthly random stratified sampling 

 conducted in the Cape Romain, Charleston Harbor, and 

 the ACE Basin estuaries in South Carolina (Fig. 1). The 

 Charleston Harbor estuarine system is made up of three 

 river systems: the Ashley, Cooper, and Wando rivers. In 

 addition, Charleston Harbor proper was sampled as a 

 separate stratum. The ACE Basin estuary is formed by 

 the confluence of the Ashepoo, Combahee, and Edisto 

 rivers and was sampled as a single estuary. One of the 

 problems initially encountered with sampling was the 

 ability to sample striped mullet throughout their estua- 

 rine salinity range. The primary sampling gear used 

 was a 184-meter trammel net with 356-mm stretch mesh 

 outside panels and a 64-mm stretch mesh inner panel. 

 Because striped mullet use the full range of estuarine 

 habitats and freshwater, the use of alternate gear was 

 necessary to obtain a representative sample of the popu- 

 lation within all salinity regimes. Specimens collected 

 with additional gear types in low salinity and freshwater 

 habitats supplemented those specimens sampled with a 

 trammel net. The additional gear types were an electro- 

 shock boat, cast nets, and gill nets. The electroshock boat 

 samples were obtained from the South Carolina Depart- 

 ment of Health and Environmental Control from the 

 major coastal river basins in South Carolina, including 

 freshwater portions of the Waccamaw, Black, Pee Dee, 

 Sampit, Santee, Cooper, Edisto, Ashepoo, Combahee, and 

 Broad rivers (Fig. 1). Cast nets were used primarily in 

 different portions of the Charleston Harbor estuary in 

 tidal creeks and in areas where the trammel net could 

 not be used effectively . The cast nets were 1.84 meters 

 in diameter and had 10-mm mesh. The gill net was a 

 200-meter net with 64-mm stretch mesh that was used 

 to test the efficiency of the trammel net sets. 



Standard morphological measurements were total 

 length (TL), fork length (FL), standard length (SL) 

 in mm, and body weight (BW) in grams (g). Any sub- 

 sequent mention of fish length in the remaining text 

 will be total length unless otherwise noted. Sagittal 

 otoliths were removed for estimating fish ages. A gross 

 examination of the gonads was used for initial sex and 

 maturity assessment. If the gonads were estimated to 

 weigh more than 1 g they were also weighed. A small 

 sample of gonad tissue was removed from the posterior 

 portion of the gonad where the lobes were joined and 

 was fixed in 10% neutral buffered formalin for histologi- 

 cal examination. The tissue samples used for histologi- 

 cal evaluation were taken from the posterior section of 

 the gonad because earlier developmental stages and 

 differentiation were more evident where the ductwork 



