Potts and Manooch Estimated ages of Pagnis pagnis 



87 



-M&H: Southeastern US 



 H&M 79-81 Soulheaslern US 

 • HSM ee 90 Soulheaslern US 



 H&M 91-94 Soulheaslern US 

 P&M Soulheaslern US 

 P&L Canary Islands 

 V&P Easlern Medilerranean 

 S&K Azores 



C&R North Buenos Aires 

 C&R South Buenos Aires 

 H&J Eastern Gull ol Mexico 

 N: Western Gull ol Mexico 



1 3 5 7 9 11 13 15 17 

 Age (yr) 



Figure 3 



Comparison of von BertalanfTy growth curves from various locations 

 in the Atlantic Ocean: M&H = Manooch and Huntsman 1 1977); H&M = 

 Harris and McGovern (1997) from three separate data year sets; 

 P&M = Potts and Manooch (this studyi; P&L = Pajuelo and Lorenzo 

 11996); V&P = Vassilopoulou and Papaconstantinou (1992); S&K = 

 Serafim and Ki'ug ( 1995); C&R = Cotrina and Raimondo ( 19971 from 

 two study areas; H&J = Hood and Johnson (2000); N = Nelson 

 (1988). 



100 



1 3 5 7 9 11 13 15 17 



Age (yr) 



-»-M &H -iic -P&M - Fishe ry-dependent data 



Figure 4 



Comparison of the von Bertalanffy growth curve 

 from Manooch and Huntsman (1977) using 

 headboat data versus the resulting growth 

 curves from headboat and commercial fisheries 

 data from this study. 



have been due to heavy fishing on the population, the small 

 sample size of older age fish, or differences in assigned ages 

 due to the structure used for aging, because the comparison 

 of ages determined from otoliths was very close. 



Harris and McGovern (1997) and Hood and Johnson 

 (2000) have put forth the theory that heavy fishing pres- 

 sure may cause a shift in the size and age structure of a 

 population to smaller, slower growing fish. Our study does 

 not support this theory. Cotrina and Raimondo ( 1997 ) dem- 

 onstrated the differences in growth of red porgy caught 

 from two areas off Argentina. Because we feel that our 

 samples encompassed the full range of red porgy along 

 the southeastern United States., our data more truly rep- 

 resents that population than the data from Harris and 

 McGovern's (1997) study. We also feel that the perceived 

 changes in length at age reported in Harris and McGov- 

 ern's (1977) study may be confounded by the changes in 

 sampling strategy of the MARMAP program between 1979 

 and 1994 (e.g. sampling gear used, locations of sampling, 

 personnel, etc). Differences in growth of red porgy in the 

 Gulf of Mexico between Hood and Johnson's (2000) study 

 and Nelson's (1988) study may certainly be affected by 

 the different locations the samples came from for the two 

 studies. We suggest that further investigation into sample 

 design and effects of habitat, temperature, fishing pres- 

 sure, weather, fishing gear, etc. on fish populations is need- 

 ed to help resolve differences between these studies. 



The von Bertalanffy growth parameters L . and K are 

 integral components of stock assessment models. Samples 

 for age determination should be representative of the tar- 

 get population (i.e. entire geographic range, all habitats, 

 and all gear types used in the fisheries). Because back- 

 calculated length-at-age information was unavailable to 



us from all previous studies, we compared the various 

 von Bertalanffy growth curves with direct comparisons of 

 length at age (Fig. 3). The growth curve of red porgy es- 

 timated by Manooch and Huntsman (1977), L, = 763(1 - 

 g-uo96i( -1- 1 88i)_ jg similar to our equation for all samples. 

 Our calculated von Bertalanffy equation with fishery-de- 

 pendent samples only was almost identical to that of Ma- 

 nooch and Huntsman (1977): L, = 774(1 - g-ooaa/ * i96i) 

 (Fig. 4). Although aging structures for the two studies 

 were very different, ages were validated in both studies, 

 and overall size ranges were similar 



In comparison with our study and that of Manooch and 

 Huntsman (1977), the growth curves estimated by Harris 

 and McGovern ( 1997) from their 1979-94 data had L, val- 

 ues ranging from 411 to 451 mm TL. Red porgy in their 

 study exhibited theoretical growth only from 58 to 69 mm, 

 between ages 5 and 11. Red porgy from our study (all data 

 combined) and Manooch and Huntsman's ( 1977) study the- 

 oretically grew from 164 mm to 172 mm, between ages 5 

 and 11. Also, the growth coefficients (0.27 to 0.34: 1979-94 

 data) from Harris and McGovern's ( 1997) data seemed high 

 for red porgy in relation to those reported in other red por- 

 gy age and growth studies (Table 4) (Manooch and Hunts- 

 man, 1977; Vassilopoulou and Papaconstantinou, 1992; Se- 

 rafim and Krug, 1995; Pajuelo and Lorenzo, 1996; Cotrina 

 and Raimondo, 1997; Hood and Johnson, 2000). 



Studies using fishery-independent sources for red porgy 

 showed smaller L^. and higher A' values than those from 

 most studies where a combination of commercial, recre- 

 ational, or fishery-independent samples were used (Table 4). 

 The differences in growth curves are likely a result of 

 smaller fish in the fishery-independent samples and a con- 

 sequent truncated upper-length range. Although Hood and 



