Hood and Johnson: Life history of Pagrus pagrus 



725 



Figure 1 



Sectioned sagittae from lA) a 5-year-old (345-mni-TL) and (B) a 10-year-old 

 (485-mm-TL) eastern Gulf of Mexico red porgy. The 5-year-old fish was caught in Sep- 

 tember 1996. and the 10-year-old fish was caught in April 1996. 



readers was high (869f ) for the second readings, one reader 

 read the remaining otoliths to determine age. Each of the 

 remaining otolith sections was read three times, and annu- 

 lus counts were accepted for ages only if at least two of the 

 three separate readings were the same. Age was considered 

 to be the count with the highest frequency of occurrence. 

 To validate annulus periodicity, marginal increments and 

 their medians were plotted by month for each age and com- 

 pared for consistent temporal patterns. 



Age in years was estimated as the number of opaque 

 rings; therefore, length at age included any growth that 

 occurred after the last opaque ring was formed. Length at 

 age between sampling sources was compared by using an 

 unbalanced two-way analysis of variance (SAS Institute, 

 Inc., 1985). Mean observed length at age was calculated 

 for males, females, and for all aged fish. Age and length 

 data were fitted to a von Bertalanffy growth model with 

 nonlinear regression (SAS Institute, Inc., 1985). We calcu- 

 lated an adjusted r-' for the resulting curve by using meth- 

 ods described by Helland ( 1987). 



We used age-frequency data from this study to estimate 

 mortality rates from Florida commercial and recreational 



length data for Florida. Because the number of red porgy 

 measured by the Trip Intei-view Program'' and MRFSS'^ 

 were low, we pooled the data from the most recent years 

 for which data were available. Length data from commer- 

 cial landings were obtained from the TIP'' from 1992 to 

 1994 and in 1996. Length data from recreational land- 

 ings were obtained from the MRFSS-^ and the National 

 Marine Fisheries Service's Headboat Survey" and were 

 pooled for years 1990-1996. Because red porgies are pro- 

 togynous hermaphrodites, we pooled sexed and unse.xed 

 fish to generate the catch cun'es. Instantaneous mortality 

 and sui-vivorship rates were estimated by the Chapman- 

 Robson method (Youngs and Robson, 1978). Age at full 

 recruitment was estimated from the catch curve as being 

 one year older than the age with the gi'eatest catch. 



" Trip Interview Progi-am (TIP). 1997. Unpubl. data. Florida 



Fish and Wildlife Conservation Commission, 100 Eigth Avenue. 



SE, St. Petersburg, FL .33701-5095. 

 " National Marine Fisheries Service Headboat Sui-vey. 1999. 



Unpubl. data. Beaufort Laboratory. 101 Pivers Island Rd.. 



Beaufort. NC 28516-9722. 



