Syc and Szedlmayer: A comparison of size and age of Lut/anus campechanus with the age of artificial reefs in the Gulf of Mexico 
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O 2009 Reefs 
• 2010 Reefs 
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Distance (km) of public reefs to study reefs 
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Figure 5 
Comparison of mean age of red snapper ( Lutjanus campechanus ) 
caught in 2010 in our study of artificial reefs in the northern Gulf 
of Mexico with proximity to publicly known reefs <1.7 km from our 
sampled reefs, which were deployed in 2006, 2009, and 2010. Line 
is linear regression that showed no significant relation between 
red snapper age and distance to known reefs (Pearson’s correlation 
coefficients [r] = 0.026, P=0.88). 
suggested fishing mortality limitation, was the use of 
fishery-independent data rather than fishery-depen- 
dent data. Although other studies used mainly fishery- 
dependent data on red snapper caught by sport and 
commercial fishermen (Szedlmayer and Shipp, 1994; 
Baker and Wilson, 2001; Patterson et al., 2001a; Wilson 
and Nieland, 2001), we used fishery-independent meth- 
ods at unpublished artificial reef sites. These fishery- 
independent methods also allowed us to sample red 
snapper that were too small to be counted with fishery- 
dependent methods. In addition, fishing mortality at 
reef sites surveyed in our study was probably far more 
reduced than at known reefs because the locations of 
the artificial reefs that we sampled were unpublished 
and likely had limited access for fishing. 
Several alternative factors, aside from reef age, could 
have affected the size and age of red snapper caught on 
the artificial reefs examined in our study. Additional 
prey may be one important factor that created differenc- 
es in habitat value among reefs of different ages, and 
these differences may have resulted in larger, older fish 
at older reefs. If older reefs were providing more prey 
resources, we would expect that red snapper on these 
reefs would have higher growth rates, especially the 
relatively young (<10-year-old) individuals that have a 
nearly linear growth rate. Yet no significant differences 
in mean growth rates of red snapper were detected 
among the reefs sampled, despite their age differences. 
Even so, older reefs often have more well-developed 
epifaunal benthic communities that can influence habi- 
tat value (Redman and Szedlmayer, 2009), and this 
development might be expected for older artificial reefs 
like those in our study. If older reefs actually provide 
more prey resources or greater habitat complexity and 
shelter than younger reefs, attraction to these “better” 
reefs may account for some of the older ages and higher 
abundances of red snapper on older reefs. However, we 
still are left with the same conclusion: artificial reefs 
enhance red snapper production. One implication of our 
study is that habitat value may vary not only spatially 
(e.g., open versus structured habitats) but also tempo- 
rally (e.g., new versus older, more “developed” reefs). 
Therefore, we need to include a temporal component to 
habitat value, whereby new artificial reefs may need 
time to develop before they start to enhance production. 
Another factor that may have caused differences in 
the ages of fish among reefs was reef depth. The mean 
depth of the 2006 reefs was 30 m, but the mean depth 
of the 2009 reefs was 20 m, and there is some evidence 
that larger, older red snapper were more common in 
deeper offshore waters than in shallower nearshore wa- 
ters (Render, 1995; Mitchell et al., 2004). However, com- 
parisons of reefs with the same mean depth (30 m) and 
distance from shore (27 km) still showed significantly 
larger and older red snapper at the 2006 reefs than at 
the 2010 reefs. In addition, the distances among the 
reefs that were farthest apart were relatively smaller 
(14 km) than the distance across the continental shelf 
(110 km) where depth-related differences in size and age 
may be more apparent (Mitchell et al., 2004). 
