830 



Fishery Bulletin 97(4), 1999 



To determine the precision of vermilion snapper 

 otolith opaque zone counts, otoliths collected during 

 the first four months of sampling (n=200) were read 

 independently by two investigators. After the first 

 reading, readers examined the sections together and 

 compared counts to form a consensus about what 

 constituted an opaque zone. The two readers then 

 re-examined the sectioned otoliths independently, 

 and counts were compared again. Because agreement 

 between readers was 100%, one reader read the re- 

 maining otoliths to determine age. Each of the re- 

 maining otolith sections was read three times, and 

 opaque zone counts were accepted for ages only if at 

 least two of the three separate readings were the 



same. To validate annulus periodicity, marginal in- 

 crements and their medians were plotted by month 

 for each age and compared for consistent temporal 

 patterns. 



Age in years was estimated as the number of 

 opaque zones. Therefore, length at age included any 

 growth that occurred after the last opaque ring was 

 formed. Mean length at age was calculated for males, 

 females, and all aged fish. Age and observed length 

 data were fitted to a von Bertalanffy growth model 

 by using a nonlinear regression (SAS Institute, Inc., 

 1985). Growth curves were fitted separately for 

 males, females, and all aged fish. The estimated pa- 

 rameters for male and female curves were compared 

 by using likelihood-ratio tests 

 (Kimura, 1980; Cerrato, 1990). We 

 calculated an adjusted r-^ for the re- 

 sulting curves by using methods 

 described by Helland (1987). 



We used age-frequency data from 

 this study to estimate mortality 

 rates from the commercial and rec- 

 reational length data. Because the 

 numbers of vermilion snapper mea- 

 sured in fishery sampling programs 

 were low, we pooled the most recent 

 years where data were available. 

 Length data from commercial land- 

 ings were obtained from the TIPS*^ 

 from 1992 to 1994, and in 1996. 

 Length data fi-om recreational land- 

 ings were obtained from the MRFSS- 

 and pooled for years 1990-96. Instan- 

 taneous mortality and survivorship 

 were estimated by the Chapman- 

 Robson method (Youngs and Rob- 

 son, 1978). Age at full recruitment 

 was estimated from the catch curve 

 as the next oldest age from the age 

 with the greatest catch. 



Reproductive analyses were based 

 on gonad weights and a histological 

 examination of gonadal tissue. Whole 

 gonads were weighed to the near- 

 est 0.1 g, fixed in 10% buffered for- 

 malin for approximately one week, 

 rinsed in water, and then trans- 

 ferred to 70% ethanol. A sample was 

 taken from the middle of the pre- 



Figure 1 



Sectioned saggitae from (A) a 2-year-old (204-mm-TL) and (B) a 10-year-old 

 ( 184-m-TL) vermilion snapper. Both fish were caught in the eastern Gulf of 

 Mexico in July 1996. 



•^ TIPS (Trip Interview Program). 1997. 

 Florida Department of Environmental Pro- 



tection, 100 8th Avenue, S. 

 burg, FL. Unpubl data. 



E., St. Peters- 



