724 



Fishery Bulletin 98(4) 



on the GOM red snapper fishery (Anonymous''). The red 

 porgy fishery shifted from a predominately recreational 

 fishery to a predominately commercial fishery between 

 1988 and 1991 (Goodyear and Thompson' ). Owing to these 

 changing dynamics within the red porgy fishery, the Reef 

 Fish Stock Assessment Panel of the Gulf of Mexico Fish- 

 ery Management Council recommended that age, growth, 

 and reproduction studies be initiated for future stock 

 assessments (Anonymous^). Red porgy are protogynous 

 hermaphrodites and may be more susceptible to overfish- 

 ing than gonochoristic reef-fish species such as snappers 

 if size-selective fishing reduces the number of males avail- 

 able for spawning and thus limits the amount of sperm 

 available for fertilization (Bannerot et al., 1987; Koenig et 

 al., 1996). 



Existing age and growth data for this species in the 

 GOM are inadequate. Nelson (1988) used scales to age 

 red porgy collected from the Flower Garden Banks off 

 Texas in the early 1980s and reported a maximum age 

 of 6 years. This value is much lower than maximum 

 ages reported from other regions. Maximum ages, deter- 

 mined from scales, whole otoliths, and sectioned otoliths 

 have ranged from 13 to 18 years (Manooch and Hunts- 

 man, 1977; Vassilopoulou and Papaconstantinou, 1992; 

 Pajuelo and Lorenzo, 1996; Harris and McGovern, 1997; 

 Vaughan''). Nelson ( 1988) suggested that the reason he did 

 not observe fish as old as those observed by Manooch and 

 Huntsman ( 15 years; 1977) was that fishing had removed 

 older fish from the GOM. However, mortality rates in the 

 South Atlantic Bight (SAB) are now greater than those 

 reported by Nelson (1988) for the GOM, and SAB fish as 

 old as age 18 have recently been reported by Vaughan.-' 



Little information is available on the reproductive biol- 

 ogy of red porgy in the GOM. Female red porgy begin to 

 transform into males at 221 mm fork length; however, the 

 length at which females begin to mature in the GOM is 

 unknown because the smallest female sampled by Nelson 

 (1988) was 272 mm fork length and all females that he 

 examined were mature. Spawning occurs in the winter 

 and spring in the GOM, as has been reported for the 

 SAB, Canary Islands, and Mediterranean Sea (Manooch, 

 1976; Nelson, 1988; Vassilopoulou and Papaconstantinou, 

 1992; Pajuelo and Lorenzo, 1996), although Ciechomski 

 and Weiss (1973) reported, on the basis of larval collec- 

 tions, that red porgies may spawn in the Argentine Sea 

 during the summer (December and January). 



Basic life-history information is needed for use in assess- 

 ments of red porgy stocks in the GOM. Although Nelson 

 (1988) examined red porgy age, gi-owth, and reproduction 

 in the GOM; his study was limited by area ( Flower Garden 

 Banks off Texas), sample size (;? = 126), and aging struc- 



■* Anonymou.s. 1993. Final report of the reef fish stock assess- 

 ment panel. Gulf of Mexico Fishery Management Council. .3018 

 U.S. Highway 301 N, Suite 1000, Tampa, FL 33619-2266. 



■'' Vaughan, D. S. 1999. Population characteristics of the 

 red porg>- Pagrits pagrtis from the U.S. Southern Atlantic 

 Coast. Report prepared for the South Atlantic Fishery Man- 

 agement Council. National Marine Fisheries Sei-vice, Beaufort 

 Laboratory. 101 Fivers Island Road, Beaufort, NC 28516 



ture (scales). Accurate ages are needed to develop growth 

 models, develop age-length keys, and estimate total mor- 

 tality. In addition, the annual periodicity of ring deposi- 

 tion in otoliths has not been validated for red porgy in the 

 GOM. With the increasing reliance on estimates of spawn- 

 ing-potential ratios to describe a stock's condition, infor- 

 mation on maturation schedules and sex ratios are also 

 needed. The purpose of our study was to age eastern GOM 

 red porgy accurately in order to develop age-length keys 

 and growth models, to construct catch curves for deriving 

 estimates of total mortality, and to describe the reproduc- 

 tive biology of this species. 



Methods 



Collections 



Eastern GOM red porgy were sampled from headboat 

 and commercial catches between October 1995 and Sep- 

 tember 1996. Total length (TL), fork length (FL), and 

 standard length (SL) were measured to the nearest milli- 

 meter Whole weight and gutted weight were measured to 

 the nearest gram (g). The relationships between lengths, 

 weights, and logj,|-transformed total lengths and weights 

 were determined by least-squares regression (SAS Insti- 

 tute, Inc., 1985). Male and female regression lines of logjQ- 

 transformed total lengths and weights were compared by 

 using analysis ofcovariance (Snedecor and Cochran, 1971). 

 Length-frequency distributions were compared by sample 

 source and by sex by using the Kolmogorov-Smirnov test 

 for goodness of fit (Sokal and Rohlf, 1981). All length data 

 are reported as total length unless stated otherwise. 



Age, growth, and mortality 



Thin sections of otoliths (sagittae) were used to determine 

 the ages of fish. Otoliths were removed and stored dry 

 in culture wells. The left otolith was serially sectioned 

 across its anterior-posterior midpoint at 0.5-mm intervals 

 by making a transverse cut with an Isomet diamond saw. 

 Mounted sections were placed on a black field, illuminated 

 with reflected light, and examined with a binocular dis- 

 secting microscope. The magnified images of otolith sec- 

 tions were transmitted by means of video camera to a 

 video monitor The number of opaque zones and the radial 

 measurements from the core to the last opaque zone and to 

 the edge of the otolith (otolith radius. Fig. 1 ) were recorded 

 from the monitor by using a computer-driven, data-acqui- 

 sition software package (Optimas Corp., 1996). Marginal 

 increments were measured as the distance between the 

 last opaque zone and the edge of the otolith. 



To determine if zone counts were repeatable between 

 investigators, two readers independently examined sec- 

 tioned otoliths collected from fish collected during July and 

 August 1996 (n=241). After the first reading, readers exam- 

 ined the sections together and compared zone counts to form 

 a consensus about what constituted a zone. The two readers 

 then re-examined the sectioned otoliths independently, and 

 counts were compared again. Because agreement between 



