Harter et a!.: Fish assemblages associated with grouper pits in the Gulf of Mexico 
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Figure 1 
Map of the Pulley Ridge mesophotic coral ecosystem off southwestern Florida in 
the Gulf of Mexico where video surveys were conducted with a remotely operated 
vehicle during 2012-2015. The polygon outlined in black represents the Pulley 
Ridge Habitat Area of Particular Concern. The extent of the survey area includes 
the entire area of available multibeam bathymetric imagery. 
ies have revealed deleterious effects of the invasion of 
lionfish on abundances and species richness of native 
fish through predation and competition (Albins and 
Hixon, 2008; Green et al., 2012; Albins, 2013). In ad- 
dition, studies of MCEs in the Bahamas found that 
predation by lionfish on herbivorous fish has caused 
a shift in the benthic fauna, and an increase in the 
proportion of algae to the proportion of corals (Lesser 
and Slattery, 2011). 
Because the grouper pits of Pulley Ridge have not 
been characterized previously, particularly since the in- 
vasion of lionfish, our objectives for this study were 1) 
to quantify and characterize fish populations associat- 
ed with grouper pits at Pulley Ridge, 2) to estimate the 
spatial distribution and abundance of key economically 
and ecologically important reef fish species, and 3) to 
examine the effect of lionfish on the abundance and 
composition of fish communities of the grouper pits. 
Materials and methods 
Data collection 
Information on the fish community in the grouper pits 
was collected annually from 2012 to 2015 by using 
underwater video cameras attached to remotely oper- 
ated vehicles (ROVs) that were deployed from the RV 
F. G. Walton Smith. Video surveys were conducted with 
2 different ROVs: the Phantom S-2 in 2012-2013 and 
the Mohawk in 2014-2015. Both vehicles are operated 
by the Undersea Vehicles Program of the University of 
North Carolina at Wilmington. To keep the ROV near 
the seafloor during dives, a “down weight” (145 kg) was 
tethered to its umbilical cable at a distance of 25-30 m 
behind the ROV. The configuration of the down weight 
allowed the ROV to traverse just above the seafloor (<1 
m) at a mean speed-over-ground of approximately 0.13 
m/s (range: 0.13 to 0.28 m/s). The precise location of 
the ROV was recorded constantly throughout each dive 
with a tracking system linked to the GPS of the RV F. 
G. Walton Smith. 
The Phantom ROV was equipped with a standard- 
definition Sony 10 color video camera (Sony Corp., Tokyo, 
Japan) with more than 460 lines of resolution, and the 
Mohawk ROV had a Mini Zeus II high-definition video 
camera (Insite Pacific Inc., Solana Beach, CA). Both 
cameras provided continuous video data recorded on 
external hard drives. On both ROVs, the camera typi- 
cally was angled down -30° to capture the view both 
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the National Marine Fisheries Service, NOAA. 
