Powers et al : Age composition and distribution of Sciaenops ocellatus in offshore waters of the north central Gulf of Mexico 
289 
45 
Gonadosomatic Index (n=413) 
| | Intraperitoneal fat index (n=413) 
! Fulton condition index (n=446) 
Figure 5 
Mean monthly gonadosomatic index (GSI), intraperitoneal fat index (IPF), and 
Fulton condition indices for red drum ( Sciaenops ocellatus) sampled from the north 
central Gulf of Mexico between March 2008 and May 2010. Gonadosomatic and 
IPF indices are measures of condition where gonad weight (GSI) or fat content 
(IPF) is divided by total body weight then multiplied by 100 (Wilson and Nieland, 
1994; Craig et al., 1995). The Fulton condition index was calculated by dividing 
weight of the fish by TL 3 and multiplying by 100,000 (Ricker, 1975). 
Table 1 
Comparison of von Bertalanffy growth parameter esti- 
mates from red drum (Sciaenops ocellatus ) studies in the 
Gulf of Mexico. L oo =the asymptotic length, £ = the von Ber- 
talanffy growth coefficient, and f 0 =the theoretical age at 
which total length equals zero. TX=Texas; LA=Louisiana; 
MS = Mississippi; AL=Alabama; FL = Florida. 
Study 
Location 
k 
^0 
Current study 
AL 
Males 
923 
0.11 
-10.00 
Females 
965 
0.109 
-10.00 
Beckman 
TX, LA, 
et al. (1988) 
MS, AL 
Males 
909 
0.137 
-7.74 
Females 
1013 
0.088 
-11.29 
Murphy and 
FL 
934 
0.45 
0.029 
Taylor (1990) 
this species. Effective monitoring of the recovery of red 
drum stocks will require the development of fishery- 
independent indices that allow periodic examination of 
age composition — a strategy needed for many species 
under harvest moratorium. The most cost-effective 
approach to developing such monitoring is the expan- 
sion of existing fishery-independent surveys because 
of the limited economic incentive to evaluate nonex- 
ploited stocks. Using our bottom longline survey, which 
was designed to be an expansion of the NMFS Gulf of 
Table 2 
Parameters for von Bertalanffy growth function by 
survey type (combined, longline and Alabama Deep Sea 
Fishing Rodeo [ADSFRD and sex for red drum ( Sciaenops 
ocellatus) in the north central Gulf of Mexico. W=total 
sample size, L M =the asymptotic length, £=the von Ber- 
talanffy growth coefficient, and t 0 =the theoretical age at 
which total length equals zero. 
Data set 
N 
k 
*0 
Combined 
( both sexes) 
403 
993 
0.109 
-10.00 
Males 
166 
969 
0.110 
-10.00 
Females 
221 
1012 
0.109 
-10.00 
Longline 
(both sexes) 
227 
979 
0.108 
-10.00 
Males 
99 
954 
0.114 
-10.00 
Females 
114 
989 
0.113 
-10.00 
ADSFR 
(both sexes) 
176 
1037 
0.127 
-7.11 
Males 
67 
1009 
0.123 
-7.58 
Females 
106 
1046 
0.126 
-7.36 
Mexico bottom longline survey into nearshore waters, 
we illustrate the benefits of such an approach. 
Fishery-independent longline surveys proved to be 
an effective means of obtaining the data needed to 
calculate an abundance index for adult red drum in 
the nearshore waters of the ncGOM. Data from these 
