Powers et al.: Age composition and distribution of Sciaenops ocel/atus in offshore waters of the north central Gulf of Mexico 
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Figure 1 
(A) Sampling locations and (B) catch per unit of effort (fish-100 hooks -1 hour -1 ) for red drum ( Sciaenops ocel- 
latus) collected between 2006 and 2010 during the bottom longline surveys. (C) Transect lines and (D) locations 
of sightings of red drum from the aerial surveys. 
Iy = C y Py, (D 
where c v = the estimate of mean CPUE for positive 
catches only for year y; and 
p Y = the estimate of mean probability of occur- 
rence during year y. 
Both c y and p y were estimated with generalized linear 
models (GLMs). Data used to estimate abundance for 
positive catches (c) and probability of occurrence (p) 
were assumed to have lognormal and binomial distri- 
butions, respectively. The final standardized index is 
the product of the back-transformed year effects from 
the two above mentioned GLMs. All GLMs were com- 
puted with year and month as factors. The standard 
error and coefficient of variation were estimated with 
a jackknife routine on factors with greater than two 
positive observations. Models were run by using the R 
programming environment, vers. 2.10.KR Development 
Core Team, 2009). 
We complemented the red drum distribution data col- 
lected by bottom longline with data from aerial survey 
sightings for red drum conducted from August 2008 
through March 2010. Aerial transect surveys were 
conducted with a Piper Apache PA-23 aircraft. The 
design covered the ncGOM from the shoreline to 20 
