Hightower et al.: Population dynamics and relative abundance for adult Sciaenops ocellatus 169 
In particular, red drum had a preference 
for surface current northward velocities 
greater than 0 m/s, with high prefer- 
ences for velocities greater than 0.1 m/s 
(Fig. 6, A, D, and G). Preferences for sur- 
face temperatures less than 22°C (Fig. 6, 
B, E, and H) and depths between 5 and 
17 m (Fig. 6, C, F, and I) were also appar- 
ent. These predictors were consistent 
across seasons. In general, the most suit- 
able habitat for red drum was predom- 
inately within state waters. A seasonal 
shift in predicted habitat suitability was 
detected, indicating that red drum prefer 
shallow (<10 m) habitats in the spring 
All fish (n=1174) and autumn and deep (>30 m) waters 
during the summer (Fig. 7). Coefficients 
of variance of the predicted relative 
abundance were low, but were highest in 
deep waters (Suppl. Fig. 2) (online only). 
Because all fish in the BRT analysis 
were larger than the estimated size at 
50% maturity (Fig. 3A), we are confident 
that these results do not confound local- 
ized spatial preferences with life history 
shifts in habitat use. 
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Discussion 
Our findings, based on a large sample 
size and broad size distribution, support 
results of previous studies indicating 
Female 202) Male (ae) that the red drum is a relatively long- 
| lived, slow-growing species in the GOM. 
20 40 Perhaps not surprisingly, our findings are 
Age (years) most similar to those of Bennetts et al. 
(2019); 3-parameter VBGF's were used in 
Figure 4 both studies to model sex-specific growth 
von Bertalanffy growth curves for red drum (Sciaenops ocellatus) sampled in from a similar number and size range of 
the north-central Gulf of Mexico from 2006 through 2018, (A) for sexes com- fish collected in Mississippi and Alabama. 
bined, including fish of unknown sex, and (B) for males and females sepa- However, the maximum age in our study 
rately. n=number of samples. is notably older than the maximum age 
reported by Bennetts et al. (2019) (36 years 
Table 1 
Mean estimates for parameters of the von Bertalanffy growth function, by sex, based on age data for red 
drum (Sciaenops ocellatus) collected from 2006 through 2018 during fishery-independent bottom longline 
and gill-net surveys in the north-central Gulf of Mexico. Parameters include mean asymptotic length (Z.,), 
Brody growth coefficient (K), and hypothetical age at which length equals 0 (¢)). The category for sexes 
combined includes fish of unknown sex. Standard errors of the mean (SE) are provided in parentheses. 
Sex L,, (mm) K (years ') ty (years) 
Combined 950.45 (2.35) 0.31 (0.01) —0.26 (0.03) 
Female 969.63 (3.42) 0.30 (0.01) —0.35 (0.05) 
Male 932.71 (3.78) 0.30 (0.01) —0.45 (0.06) 
