Abstract. — The reproductive bi- 

 ology of red drum, Sciaenops ocel- 

 latus, in the northern Gulf of 

 Mexico is described from examina- 

 tion of 3,351 specimens sampled 

 from March 1986 through Septem- 

 ber 1992. The sex ratio of the 

 spawning population, as manifest 

 in purse seine collections, was es- 

 sentially 1:1. Gonosomatic indices 

 and ovarian histology demon- 

 strated an 8-9 week spawning sea- 

 son from mid August to early Octo- 

 ber. Both sexes achieved >50% 

 maturity at age 4; however, at 50% 

 maturity males were somewhat 

 smaller than females (660-670 mm 

 vs. 690-700 mm, 3.4-3.5 kg vs. 4.0- 

 4.1 kg). Simultaneous observations 

 of oocytes in all stages of matura- 

 tion throughout the spawning sea- 

 sons confirmed group-synchronous 

 oocyte maturation and multiple 

 batch spawning. Batch fecundity of 

 51 females (age 3-33 yr) ranged 

 from 0.16 million to 3.27 million 

 ova per batch (mean=1.54 million 

 ova) and was positively correlated 

 with fork length, gonad-free body 

 weight, eviscerated body weight, 

 and age. Seasonal spawning fre- 

 quencies estimated from the pro- 

 portion of mature females with 

 postovulatory follicles varied 

 widely from once every 3 days to 

 once every 80 days. More plausible 

 spawning frequencies (2-4 d) were 

 obtained if proportions of females 

 exhibiting oocyte yolk coalescence 

 and oocyte hydration, indicative of 

 imminent spawning, were included 

 in estimates of this variable. 



Reproductive biology of red drum, 

 Sciaenops ocellatus, from the 

 neritic waters of the 

 northern Gulf of Mexico* 



Charles A. Wilson 

 David L. Nieland 



Coastal Fisheries Institute, CCEER 



Wetland Resources Building, Louisiana State University 



Baton Rouge, LA 70803-7503 



Manuscript accepted 18 March 1994. 

 Fishery Bulletin 92:841-850. 



Red drum, Sciaenops ocellatus (fam- 

 ily: Sciaenidae), has been a prime 

 target species for both recreational 

 and commercial fishermen in the 

 northern Gulf of Mexico. As conflicts 

 over allocation of a purportedly de- 

 clining population escalated in the 

 mid 1980s, management of the red 

 drum offshore spawning stock be- 

 came an imperative. However, ba- 

 sic to the formulation of any man- 

 agement strategy is the need for 

 sound biological information, in- 

 cluding the various aspects of the 

 species' reproductive biology. Most 

 of the literature on red drum repro- 

 duction (see Murphy and Taylor 

 [1990] for a review) has been de- 

 rived from studies of juveniles and 

 itinerant adults in estuarine wa- 

 ters. Little is known of the repro- 

 ductive biology of adult "bull" red 

 drum that assemble into large 

 schools in the northern Gulf and 

 constitute the spawning stock for 

 the species in this area. 



Overstreet 1 first reported on vari- 

 ous aspects of the biology, including 

 reproduction, of schooling red drum 

 based on specimens gathered from 

 the purse-seine fishery for the spe- 

 cies. Fitzhugh et al. ( 1988) added to 

 this body of knowledge by describ- 

 ing ovarian development in speci- 

 mens similarly taken from the 

 purse-seine fishery. They further 

 provided the first documentation of 



feral red drum as group synchro- 

 nous, batch spawners (Wallace and 

 Selman, 1981) in which clutches of 

 newly matured ova are spawned 

 periodically throughout the spawn- 

 ing season. Thus all previous esti- 

 mates of red drum fecundity in the 

 wild, based on numbers of vitello- 

 genic oocytes present in the ovary, 

 were rendered invalid. 



The present study is a continua- 

 tion and an expansion of the work 

 begun by Fitzhugh et al. ( 1988) and 

 was undertaken in conjunction with 

 two studies of red drum age and 

 growth (Beckman et al., 1988; Wil- 

 son et al. 2 ). Our specific objectives 

 were 1) to verify the sex ratio of the 

 spawning population; 2) to ascer- 

 tain the duration of the spawning 

 season; 3) to determine age, length, 

 and weight at sexual maturity; and 



♦Contribution LSU-CFI-93-4 of the Coastal 

 Fisheries Institute, CCEER, Louisiana 

 State University. 



1 Overstreet, R. M. 1983. Aspects of the bi- 

 ology of the red drum, Sciaenops ocellatus, 

 in Mississippi. Gulf Res. Rep. (Suppl. 1), 

 p. 45-68. Gulf Coast Res. Lab., Ocean 

 Springs, MS. 



2 Wilson, C. A., D. L. Nieland, and A. L. 

 Stanley. 1993. Variation of year-class struc- 

 ture and annual reproductive output of red 

 drum Sciaenops ocellatus and black drum 

 Pogonias cromis from the northern Gulf of 

 Mexico. Final Report for 1991-1992 to U. 

 S. Department of Commerce, Marine Fish- 

 eries Initiative (MARFIN) Program, 

 NA90AA-H-MF724. LSU-CFI-93-3. 37 p. 

 and 16 figs. 



841 



