AGE AND GROWTH OF RED DRUM, SCIAENOPS OCELLATUS, 

 FROM OFFSHORE WATERS OF THE NORTHERN GULF OF MEXICO' 



Daniel W. Beckman, Charles A. Wilson, and 

 A. Louise Stanley^ 



ABSTRACT 



Otolith (sagitta) sections are used to accurately age red drum, Sciaejiops ocellatus. from the offshore 

 northern Gulf of Mexico. Marginal increment analysis indicated that annuli were formed during winter 

 and spring months. 



Ages of offshore schooling red drum ranged from 1 to 37 years. Age distributions indicated variability 

 in relative abundances of year classes, with the majority of fish sampled being over 10 years of age. 

 Male and female age distributions did not differ significantly. 



Growth differed significantly between males and females. The von Bertalanffy growth equation for 



males was L, = 909(1 - e ' 



"), and for females was L, = 1,013(1 - e"""**"*"'^'), where t is 



age (years) and L, is fork length (mm). 



The red drum, Sciaenops ocellatus, is a large sciae- 

 nid that inhabits temperate and subtropical near- 

 shore and estuarine waters from Massachusetts to 

 northern Mexico. Juveniles are most abundant in 

 estuarine waters and move from estuarine to near- 

 shore waters as they near maturity (Pearson 1929). 

 The primary spawning stock in the Gulf of Mexico 

 is thought to spawn in nearshore open waters (Over- 

 street 1983). 



The red drum is one of the most popular recrea- 

 tional and commercial fish species in the northern 

 Gulf of Mexico. Recent increase in demand for red 

 drum has escalated the controversy concerning its 

 management; however, little has been reported con- 

 cerning its growth and population structure. 



Age and growth-rate estimates of red drum have 

 only used immature fish from inshore estuarine 

 waters. Pearson (1929) and Wakeman and Ramsey 

 (1985) identified modes in length-frequency distribu- 

 tions and performed scale analysis to determine age 

 estimates. However, Wakeman and Ramsey (1985) 

 reported that scale annuli were unsatisfactory for 

 accurately estimating the age of red drum. Theil- 

 ing and Loyacano (1976) reported age estimates of 

 red drum from a South Carolina salt marsh im- 

 poundment based on otolith examination. Growth 

 rates of juveniles were reported by Roessler (1970), 

 Bass and Avault (1975), and Simmons and Breuer 

 (1962). 



'Publication 88-06 of the Coastal Fisheries Institute, Louisiana 

 State University, Baton Rouge, LA 70803-7503. 



^Coastal Fisheries Institute. Center for Wetland Resources, 

 Louisiana State University, Baton Rouge, LA 70803-7503. 



No age or growth rate estimates have been pub- 

 lished for adult red drum from offshore waters. Ac- 

 curate information on the age and growth of adult 

 red drum is necessary for determining population 

 dynamics and monitoring the population's response 

 to fishing pressure. Due to the reduction in growth 

 rate in larger individuals, which leads to size over- 

 lap between age classes, age estimation by cohort 

 analysis is not feasible. Otolith sections have 

 provided valid age estimates for many large, 

 long-lived fish species (Beamish and McFarlane 

 1987). 



The purposes of this study were to determine if 

 otoliths (sagittae) could be used to obtain valid age 

 estimates for red drum and to estimate grow^th rates 

 and determine the age structure of the oceanic 

 schooling population of red drum. 



MATERIALS AND METHODS 



Red drum (1,726 fish) were collected in Texas, 

 Louisiana, Mississippi, and Alabama offshore coastal 

 waters of the northern Gulf of Mexico from Sep- 

 tember 1985 through October 1987 by purse seine 

 (N = 1,428 from 67 sets) (Fig. 1), gill net (N = 

 134 from 9 sets), and hook and line (N = 164 

 from 12 dates). Samples captured by unknown gear 

 from February 1985 through June 1987 (AT = 96) 

 were included for marginal increment analysis 

 only. 



After fish were randomly sampled from landings, 

 they were measured (fork length) and weighed, and 

 their sex was determined. Sex identifications were 



Manuscript accepted August 1988. 

 FISHERY BULLETIN, U.S. 87:17-28. 



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