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Fishery Bulletin 1 10(4) 
present on the reefs that we sampled, including 2 of the 
oldest fish (19 and 14 years old) that were caught on the 
2009 reefs. It is possible that larger, older red snapper 
become less dependent on particular reefs because of 
relief from predation pressure and may show greater 
movement among reef sites as they search for new prey 
resources (including young red snapper) on newly estab- 
lished reefs (Mudrak and Szedlmayer, 2012). However, 
although attraction is clear and accounts for both the 
initial recruitment of young fish and the presence of 
older red snapper, if attraction was the only function of 
artificial reefs, we would not expect a positive correla- 
tion between mean fish age and reef age. Instead, the 
age distribution of red snapper should be random or re- 
lated to the proximity of nearby reefs. Hence, this study 
provides evidence that both attraction and production 
are important ecological functions of artificial reefs for 
red snapper populations in the northern Gulf of Mexico. 
According to our study and several other studies, 
young fish (age-0 and age-1) will recruit to new habi- 
tat, usually small (1-7 m 3 ) artificial reefs (Gallaway et 
ah, 2009; Szedlmayer, 2011; Mudrak and Szedlmayer, 
2012). Many of these red snapper remain at such habi- 
tats for extended periods (up to several years; Szedl- 
mayer, 1997; Szedlmayer and Schroepfer, 2005; Schro- 
epfer and Szedlmayer, 2006; Topping and Szedlmayer, 
2011a, 2011b) and then begin to show greater movement 
as they become older and larger and are less vulner- 
able to predation (Gallaway et ah, 2009). For example, 
on the basis of a 72% residency rate per year from te- 
lemetry studies (Topping and Szedlmayer, 2011a), and 
a mean of 45 age-1 recruits to new (1-year-old) reefs 
in our study, there would be -18 age-5 red snapper 
per reef after 4 years. These estimates are similar to 
counts recorded for the 2006 reefs in our study, with 
a mean of 26 age-5 fish per reef (on the basis of pro- 
portions of age-5 red snapper among all fish captured 
from 2006 reefs, extrapolated to mean total densities 
on 2006 reefs). Also, these residency estimates based 
on telemetry are underestimates because the time that 
red snapper reside on a particular reef before being 
tagged is not included (Topping and Szedlmayer, 2011a). 
Laboratory and field studies indicate that these older 
age-5 red snapper may then competitively exclude and 
even cannibalize new recruits (Bailey et ah, 2001; Piko 
and Szedlmayer, 2007; Mudrak and Szedlmayer, 2012), 
and perhaps contribute to the association between fish 
age and reef age. However, attraction may continue 
to play an important role as older fish that are bet- 
ter able to fend off aggression and cannibalism move 
to favorable habitats that still harbor abundant prey 
resources (Ouzts and Szedlmayer, 2003; Szedlmayer 
and Lee, 2004). 
Several studies suggest that red snapper popula- 
tions have been overfished and that habitat limita- 
tion was not the most important controlling factor that 
contributed to declines in abundance (Schirripa and 
Legault, 1999; Patterson et al., 2001b; Cowan et al., 
2011). Clearly, there was significant fishing mortality 
of red snapper in the northern Gulf of Mexico (Gil- 
Figure 4 
Map showing proximity of publicly known reefs to reefs 
sampled in 2010 in our study of red snapper (Lutjanus 
campechanus ) on artificial reefs in the northern Gulf of 
Mexico. Note that the positions of the reefs sampled in 
our study were not released to the public. Study reefs: 
gray circles=reefs deployed in 2006; open circles=reefs 
deployed in 2009; and black circles = reefs deployed in 
2010. Publicly known reefs: black stars=reefs of army 
tanks deployed in 1994-1995; black triangles=reefs 
made of concrete pyramids deployed in 2007; black and 
white triangles=pyramid reefs deployed in 2004; open 
star=barge deployed as a reef in 1994. Dotted lines 
indicate depth contours at 5-m intervals. 
lig et al., 2000). However, if fishing mortality was the 
only limiting factor for red snapper and habitat was 
not important, we would not expect reef age to have 
significant effects on fish age (i.e., all reefs, whether 
fished or not, would show similar age distributions). 
Red snapper enter the fishery at around age 2 (mini- 
mum size: recreational=406 mm TL, commercial=330 
mm TL), and the catch consists predominately of 2- to 
4-year-old fish. These ages represented 59% (rc = 602) of 
the total catch in our study and indicate that fishing 
mortality was not limiting red snapper abundance on 
the reefs investigated in our study. 
One substantial difference between our study, which 
suggests habitat limitation, and previous studies, which 
