473 



Abstract— We describe reproduc- 

 tive dynamics of female spotted sea- 

 trout (Cynoscion nebulosus) in South 

 Carolina (SC). Batch fecundity iBFl. 

 spawning frequency (SF), relative 

 fecundity (RF), and annual fecundity 

 (AF> for age classes 1-3 were esti- 

 mated during the spawning seasons of 

 1998, 1999, and 2000. Based on histo- 

 logical evidence, spawning of spotted 

 seatrout in SC was determined to take 

 place from late April through early 

 September. Size at first maturity was 

 248 mm total length (TL); 50% and 

 100% maturity occurred at 268 mm 

 and 301 mm TL, respectively. Batch 

 fecundity estimates from counts of 

 oocytes in final maturation varied 

 significantly among year classes. One- 

 year-old spotted seatrout spawned an 

 average of 145.452 oocytes per batch, 

 whereas fish aged 2 and 3 had a mean 

 BF of 291,123 and 529,976 oocytes, 

 respectively. We determined monthly 

 SF from the inverse of the proportion 

 of ovaries with postovulatory follicles 

 (POF) less than 24 hours old among 

 mature and developing females. Over- 

 all, spotted seatrout spawned every 

 4.4 days, an average of 28 times 

 during the season. A chronology of 

 POF atresia for water temperature 

 >25°C is presented. Length, weight 

 (ovary-free), and age explained 67%, 

 65%, and 58% of the variability in 

 BF, respectively. Neither RF (number 

 of oocytes/g ovary-free weight) nor 

 oocyte diameter varied significantly 

 with age. However. RF was signifi- 

 cantly greater and oocyte diameter 

 was smaller at the end of the spawn- 

 ing season. Annual fecundity esti- 

 mates were approximately 3.2, 9.5, 

 and 17.6 million oocytes for each age 

 class, respectively. Spotted seatrout 

 ages 1-3 contributed an average of 

 29%, 39%, and 21% to the overall 

 reproductive effort according to the 

 relative abundance of each age class. 

 Ages 4 and 5 contributed 7% and 4%, 

 respectively, according to predicted 

 AF values. 



Reproductive dynamics of female spotted seatrout 

 (Cynoscion nebulosus) in South Carolina* 



William A. Roumillat 



Marine Resources Research Institute 



South Carolina Department of Natural Resources 



217 Ft. Johnson Rd 



Charleston, South Carolina 29412 



E-mail address roumillatbiSrnrd.dnr.state.sc.us 



Myra C. Brouwer 



South Atlantic Fishery Management Council 

 One Southpark Center, suite 306 

 Charleston, South Carolina 29407 



Manuscript submitted 13 May 2002 

 to Scientific Editor's Office. 



Manuscript approved for publication 

 19 March 2004 by the Scientific Editor. 



Fish. Bull. 102:473-487 (2004). 



The spotted seatrout iCynoscion neb- 

 ulosus) is an estuarine-dependent 

 member of the family Sciaenidae. Spot- 

 ted seatrout are year-round residents 

 of estuaries along the South Atlantic 

 coast and spawning takes place inshore 

 and in coastal areas (McMichael and 

 Peters, 1989; Mercer 1 ; Luczkovich 

 et. al. 2 ). As in many other sciaenids, 

 spawning in this species occurs in 

 the evening (Holt et al, 1985). Male 

 spotted seatrout have the capacity to 

 produce "drumming" sounds that are 

 caused by the contraction of the swim- 

 bladder by specialized muscles that 

 are seasonally hypertrophied from the 

 abdominal hypaxialis muscle mass 

 (Fish and Mowbray, 1970; Mok and 

 Gilmore. 1983). Direct involvement of 

 sound production with spawning has 

 been shown for this and other sciae- 

 nids (Mok and Gilmore, 1983; Saucier 

 et al., 1992; Saucier and Baltz, 1993; 

 Luczkovich et al. 2 ). 



We have collected information on 

 the spawning behavior of spotted sea- 

 trout in coastal South Carolina since 

 1990 (Saucier et al., 1992; Riekerk 

 et al. 3 ). Spawning aggregations were 

 located by listening for drumming 

 sounds from late afternoon until 

 -2300 h with passive hydrophone 

 equipment. Spawning activity was 

 subsequently verified through collec- 

 tions of newly spawned eggs and by 

 the rearing of the larvae in the labo- 

 ratory (Saucier et al., 1992). 



Spotted seatrout are group-synchro- 

 nous spawners with indeterminate fe- 



cundity and the protracted spawning 

 season extends from April through 

 September along the South Atlantic 

 and Gulf of Mexico coasts (Overstreet, 

 1983; Brown-Peterson et al.. 1988; 

 McMichael and Peters, 1989; Saucier 

 and Baltz, 1993; Brown-Peterson and 

 Warren, 2001; Brown- Peterson et al., 

 2002; Nieland et al.. 2002, Brown- 



* Contribution 539 from the Marine 

 Resources Research Institute of the 

 South Carolina Department of Natu- 

 ral Resources, Charleston. SC 29422- 

 2559. 



1 Mercer. L. P. 1984. A biological and 

 fisheries profile of spotted seatrout. 

 Cynoscion nebulosus. Special Scien- 

 tific Report 40, 87 p. North Carolina 

 Department of Natural Resources and 

 Community Development, Division of 

 Marine Fisheries. Morehead City, NC 

 28577. 



2 Luczkovich, J. J.. H. J. Daniel III and M. 

 W. Sprague. 1999. Characterization of 

 critical spawning habitats of weakfish. 

 spotted seatrout and red drum in Pamlico 

 Sound using hydrophone surveys. Final 

 report and annual performance report F- 

 62-2 and F-62-2, p 65-68. North Caro- 

 lina Department of Environment and 

 Natural Resources, Division of Marine 

 Fisheries, Morehead City, NC 28557. 



3 Riekerk. G. H. M„ S. J. Tyree, and W. 

 A. Roumillat. 1997. Spawning times 

 and locations of spotted seatrout in the 

 Charleston Harbor Estuarine System 

 from acoustic surveys. 21 p. Final 

 Report to Charleston Harbor Project, 

 Bureau of Ocean and Coastal Resources 

 Management, South Carolina Depart- 

 ment of Health and Environmental Con- 

 trol, 1362 McMillan Ave., Charleston, 

 SC 29405. 



