318 
Fishery Bulletin 1 12(4) 
Table 2 
Study site, aging structure, range of total lengths (TLs), age range, number of specimens sampled (n), and von Bertalanffy 
growth parameters of dusky groupers (Epinephelus marginatus ) examined in this study and in previous investigations. 
Ageing structures used were scales (Sc), sectioned otolith (So), and whole otolith (Wo). Von Bertalanffy growth parameters 
included L„, the mean theoretical maximum TL; to, the theoretical age at zero length; and K, the growth coefficient or the 
rate at which the curve approaches the asymptote. 
Reference 
Study site 
Aging 
structure 
TL range 
(nun) 
Age range 
(years) 
n 
(mm) 
K 
(years' 1 ) 
To 
(years) 
Rafail et al. (1969) 1 
Mediterranean Sea 
—Egypt 
Sc 
166-475 
1-7 
251 
800 
0.112 
-1.08 
Chauvet ( 1988) 2 
Mediterranean Sea 
— Tunisia 
Sc/Wo 
53-1180 
0-36 
270 
1144 
0.090 
-0.75 
Kara and Derbal (1995) 3 
Mediterranean Sea 
— Algeria 
Sc 
197-567 
1-7 
41 
785 
0.160 
-0.73 
Bouchereau et al. (1999) 4 
Mediterranean Sea 
— France 
Sc 
200-1200 
1-14 
22 
1359 
0.080 
-0.80 
Fennessy (2006) 5 
Southern Western Indian 
— FranceSouth Africa 
So 
95-1020 
1-16 
215 
1249 
0.090 
-1.43 
Renones et al. (2007 ) 6 
Western Mediterranean 
— Spain 
So 
66-1056 
0-61 
358 
955 
0.087 
-1.12 
Seyboth et al. (2011) 7 
Southern Western Atlantic 
— Brazil 
So 
260-800 
2-12 
108 
1249 
0.069 
-1.49 
Present study 
Southern Western Atlantic 
— Brazil 
So 
150-1160 
1-40 
190 
900 
0.129 
-1.45 
1 Rafail S. Z., W. L. Daoud, and M. M. Hilal. 1969. Long line Mediterranean fisheries studies west of Alexandria. GFCM 
Stud. Rev. 42, 16 p. 
2 Chauvet, C. 1988. Etude de la croissance du merou Epinephelus guaza (Linne, 1758) des cotes tunisiennes. Aquat. Living 
Resour. 1:277-288. 
3 Kara M. H., and F. Derbal. 1995. Morphometrie, croissance et mortality du Merou Epinephelus marginatus (Serranidae) des 
cotes de Test algerien. Cah. Biol. Mar. 36:229-237. 
4 Bouchereau J. L., P. Body, and C. Chauvet. 1999. Growth of the dusky grouper Epinephelus marginatus (Linnaeus, 1758) 
(Teleostei, Serranidae), in the natural marine reserve of Lavezzi Islands, Corsica, France. Sci. Mar. 63:71-77. 
5 See Fennessy, 2006. (In literature cited ’section.) 
6 See Renones et ah, 2007. 
7 See Seyboth et ah, 2011. 
trinsic feature of the studied population rather than 
a sampling effect related to emigration toward deeper 
offshore habitats. 
Dusky groupers from Carpinteiro Bank were older 
(mean age=7.4 years; maximum observed age=40 years) 
than fish from the inshore rocky jetties located in the 
mouth of Patos Lagoon in Rio Grande (mean age=5.0 
years; maximum observed age=12 years; Seyboth et 
al., 2011). Our study provides compelling evidence that 
younger (<7 years) dusky groupers from Carpinteiro 
Bank are also significantly larger than similar-age fish 
from the rocky jetties. Specifically, the sizes of offshore 
groupers at ages 3-6 are 11-19% larger than inshore 
dusky groupers — a finding that leads to the hypoth- 
esis that environmental quality at the deeper offshore 
habitat may be better than that at the shallow inshore 
habitats. 
In this study, we assume that differences on mean 
size-at-age between fish from the inshore and offshore 
habitats may be associated with differences in en- 
vironmental quality between both sites, and several 
types of evidence support this hypothesis. For example, 
freshwater runoff from the Patos Lagoon estuary is, 
perhaps, the most important physical factor that in- 
fluences the studied population, particularly during El 
Nino events, when freshwater discharge into the lagoon 
increases and pushes the estuarine plume over the in- 
shore zone (Garcia et ah, 2003), decreasing salinity and 
disturbing fish communities (Garcia et al., 2003; Garcia 
et al., 2004). The large variations in salinity periodi- 
cally experienced by the inshore population may cause 
osmotic stress, increasing the energy outlay required 
to maintain fish homeostasis (Schmidt-Nielsen, 2002). 
In contrast, the salinity variation at the offshore bank 
usually ranges from 26.8 to 36.6 (Moller 2 ), a level that 
is roughly a third of the salinity variability measured 
2 Moller, O. 2012. Unpubl. data. Laboratorio de Oceano- 
grafia Costeira e Estuarina, Institute de Oceanografia, Uni- 
versidade Federal de Rio Grande, CR 474, 96200-900, Brazil. 
