Hightower et al.: Population dynamics and relative abundance for adult Scia@enops ocellatus 167 
BL study 
area 
State-federal 
boundary 
Figure 2 
Map of the study area in the north-central Gulf of Mexico showing catch per unit of effort (CPUE) 
of red drum (Sciaenops ocellatus) for the bottom longline (BL) surveys conducted in spring, sum- 
mer, and autumn during 2006-2018. Size of circles is proportional to CPUE, defined as the num- 
ber of fish per 100 hooks per hour. The symbol x indicates effort with no catch of red drum. The 
dashed line that follows the coastline indicates the boundary between state and federal waters. 
an additional 709 red drum captured in gill nets were ana- 
lyzed; therefore, a total of 1181 red drum were used for age 
and growth analyses. Of these fish, 392 red drum were 
female, 369 fish were male, and 420 fish were of unknown 
sex. The female-to-male ratio was 1.06:1.00 and did not 
differ significantly from a 1:1 ratio (y7=0.70, df=1, P=0.40). 
Total lengths of red drum were 80-1102 mm (Fig. 3B). The 
average TL of all fish examined (those caught with bottom 
longlines and gill nets combined) was 619.13 mm (SE 8.22). 
Results from Kolmogorov-Smirnoy tests indicate that 
females were significantly longer (D=0.20, P<0.01) and 
heavier (D=0.18, P<0.01) than males. 
Age 
Ages were assigned to 1178 red drum. Otoliths from 
the remaining 3 fish (0.25% of all red drum from which 
otoliths were taken) were deemed unreadable and were 
omitted from further analysis. Four fish had no length 
measurements and were also omitted from further anal- 
ysis. The between-reader percent agreement was 93.46%, 
and the between-reader average percent error was 4.52%; 
these estimates are largely driven by differences in the 
margin codes assigned to age-0 fish. Whole ages ranged 
from 0 to 36 years, and fractional ages ranged from 0.37 to 
36.53 years. The maximum age of both sexes was 36 years; 
however, results of Kolmogorov-Smirnov tests indicate 
that fractional age distributions differed significantly by 
sex (D=0.15, P<0.01). The mean ages of females and males 
were 11.72 and 9.90 years, respectively. 
Growth and mortality 
The VBGF for all age data combined (including females, 
males, and fish of unknown sex) is as follows: 
L, = 950.45(1 — e 0 3*¢- ©926)) (Rig, 4A), (6) 
For the sex-specific data, the model version that allowed 
L,, and t) to vary by sex best fit the data. This model ver- 
sion was followed closely by the version in which L,, and 
K vary (difference in AIC values [AAIC] between these 
2 models: 1.7) and the version that allowed all parameters 
to vary (AAIC for the best fit version and this version: 1.7). 
On the basis of predictions from the best-fit model, females 
