200 



Fishery Bulletin 98(1) 



Almeida, 1997; Zhao etal., 1997; Goodyear and Schir- 

 ripa^), thus trends in growth can be indicators of 

 population stability. Additionally, nothing is known 

 about trends in sex ratio. Recent studies along the 

 southeast Atlantic coast and in the Gulf of Mexico 

 have documented sharp decreases in the proportion 

 of males in other grouper, gag (Mycteroperca microl- 

 epis) and scamp (M. phenax), populations (Coleman 

 et al, 1996; McGovern et al., 1998). This and other 

 factors have led to reduced genetic diversity in the 

 gag population along the southeast coast, a cause for 

 serious concern, although the ramifications are not 

 clearly understood (Chapman et al., 1999). 



Little is known about the reproductive biology of 

 snowy grouper off the Carolinas because the only pre- 

 vious study ( Moore and Labisky, 1984 ) was conducted 

 in the Florida Keys. Using a histological technique, 

 Moore and Labisky (1984) showed that the snowy 

 grouper is a protogynous hermaphrodite; females 

 reach sexual maturity at ages 3-5 and change to 

 males as early as age 6. The objectives of the present 

 study were 1) to compare individual growth rates, 

 population age structure, and sex ratio between two 

 periods, 1979-85 and 1993-94, and 2) to determine 

 reproductive seasonality, size and age at maturity, 

 and size and age at sex change for snowy grouper off 

 the Carolinas. 



Materials and methods 



Specimen acquisition 



Snowy grouper were obtained from commercial boats, 

 research vessels, and headboats, primarily off North 

 Carolina and South Carolina (Table 1). All speci- 

 mens were collected between 31°09'N and 34°44'N 

 at depths of 42-302 m. Only seven specimens were 

 caught south of 32°04'N. Fishery-independent sam- 

 ples were collected during cruises of the MARMAP 

 (Marine Resources Monitoring Assessment and Pre- 

 diction) program with bottom longlines. Kali poles 

 (an off-bottom longline; Russell et al., 1988), snap- 

 per reels, rods and reels, and chevron traps (Collins, 

 1990). Specimens caught with longlines were col- 

 lected primarily off South Carolina, whereas speci- 

 mens caught with snapper reels were collected off 

 South Carolina in the 1980s and primarily off North 

 Carohna in the 1990s (Fig. 1). Total length (mm) was 

 measured for all specimens and all length measure- 

 ments in the text refer to total length (TL). 



During 1993-94, samples from the commercial 

 fishery usually included the total catch of snowy 

 grouper from a vessel or a random subsample; on 

 three of 20 occasions, the catches from vessels that 

 landed fish in South Carolina were subsampled to 

 collect otoliths from small and large specimens. No 

 documentation on sampling design was available for 

 fishery-dependent samples that were collected with 

 snapper reels during 1979-85. 



Age and growth 



The left sagitta, and the right sagitta when time 

 permitted, was removed and stored dry prior to 

 processing. Each otolith was embedded in paraffin 

 ( 1979-85) or Araldite epoxy resin ( 1993-94) and sec- 

 tioned along a dorsoventral plane through the focus 

 with a single high-concentration diamond wheel on a 

 Buehler Isomet low-speed saw. Otolith sections were 

 mounted on glass slides with Crystalbond thermo- 

 plastic or Accu-mount 60, covered with cedar wood 

 oil, and examined under a dissecting microscope 

 ( 10-63x) with reflected and transmitted light. 



We examined otoliths from 1937 specimens and used 

 the age determinations (/!=326) of Waltz'* for speci- 

 mens collected with snapper reels from 1979 to 1985. 

 The width of the translucent zone along the margin of 

 the section was measured to assess the periodicity of 

 increment formation. Increments were counted inde- 

 pendently by two readers for 1853 of 1937 specimens. 

 In older fish, all increments could not be counted along 

 one axis in many specimens. Counting commenced on 

 one of three axes (ventral, ventromedial, or adjacent 

 to the sulcus acousticus) and shifted to another axis by 

 following an increment to the new axis. If counts dif- 

 fered, both readers examined the otolith by projecting 

 the image onto a TV monitor The otolith was rejected 

 if agreement could not be reached. 



A small portion ( /; = 129 ) of the 1937 otoliths that we 

 examined were used for an earlier MARMAP study 

 (Waltz"*). Age assessments were compared to deter- 

 mine if annual increment structure was being inter- 

 preted in a similar manner. The specimens selected 

 for the comparison were collected with longlines or 

 Kali poles on research cruises during 1982-85. Age 

 data from specimens collected with these two gear 

 types were combined because they were fished simul- 

 taneously in the same area and were deployed with 

 the same hook type and bait. 



The sagittae of three young-of-the-year (YOY) 

 specimens were hand-polished to thin (approx. 5pm) 



■* Goodyear, C. P., and M. J. Schirripa. 1993. The red grouper 

 fishery of the Gulf of Mexico, Report MIA92/93-75. Miami Lab- 

 oratory, Southeast Fisheries Science Center, National Marine 

 Fisheries Service, 75 Virginia Beach Dr, Miami, FL 33149. 



■• Waltz, W. 1986. The size and age of snowy grouper (Ep/nep/i- 

 elus niveatus) in the South Atlantic Bight. MARMAP Analytical 

 Report, 16 p. S. Carolina Department of Natural Resources, 

 PO. Box 12559, Charleston, SC 29422. 



