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Fishery Bulletin 114(3) 
the seafloor itself. Imagery-based surveys have fewer 
direct impacts on the seafloor and its inhabitants and 
have the advantage of covering large areas efficiently. 
Early studies were performed with cameras mounted 
on a rigid stationary pyramid-shaped platform that 
was lowered from a vessel to the seafloor (Stokesbury, 
2002). More recently the HabCam system has been de- 
veloped, which is a towed camera sled tethered to a 
ship, and it can photograph long stretches of the sea- 
floor (Rosenkranz et ah, 2008). In 2010, the National 
Marine Fisheries Service (NMFS) formally expressed 
the need to develop and apply new approaches to stock 
assessment of sea scallop in the Mid-Atlantic Bight 
(NMFS, 2010). A recent NOAA-sponsored workshop 
(NOAA®) gathered numerous researchers engaged in 
seabed imaging to highlight the development of a va- 
riety of imaging platforms, and among their findings, 
the potential value of autonomous imaging platforms 
was recognized for future survey efforts. The present 
study is a an application of those recommendations by 
extending previous smaller scale camera studies with 
the use of autonomous underwater vehicles (AUVs) in 
Iceland (Singh et ah, 2013 and 2014) to a larger spatial 
scale study through surveys conducted within the Mid- 
Atlantic Bight. 
AUVs have been shown to be an effective platform 
for mapping benthic habitat (Tolimieri et ah, 2008; 
Forrest et ah, 2012; Raineault et ah, 2012; Seiler et 
ah, 2012; Raineault et ah, 2013) by coupling images 
obtained by underwater camera with highly accurate 
preprogrammed navigation. In this study, we used an 
AUV to assess sea scallop shell height and abundance, 
as well to estimate biomass in the shallow (< 40 m) 
open scallop fishing grounds within the Mid-Atlantic 
Bight. Because shallow grounds are not typically with- 
in the scope of the annual NMFS survey, this study 
offers unique findings of the sea scallop populations in 
such areas. Moreover, our results show that an AUV is 
a suitable platform for collecting images as part of the 
sea scallop stock assessment process. Our goal in this 
pilot study was to test and show the feasibility of the 
AUV platform by using synchronous commercial dredg- 
ing samples to illustrate the efficacy of the underwater 
camera system for what could be scaled up to be a use- 
ful tool for a full stock assessment process. 
Materials and methods 
Field sampling 
The Mid-Atlantic Bight is the shallow portion of the 
continental shelf that extends from Cape Hatteras, 
NC, to Cape Cod, MA. Our study area was selected to 
fulfill the needs of the Mid-Atlantic Fishery Manage- 
® NOAA. 2014. Undersea Imaging Workshop: workshop re- 
port; Red Bank, N.J., 14-15 January, 34 p. New Jersey Sea 
Grant Consortium, NOAA, Fort Hancock, NJ. [Available at 
website.] 
ment Council’s Research Set-Aside (RSA) program to 
survey heavily fished inshore scallop grounds (<40 m 
depth) that are not regularly monitored. All of the AUV 
surveys reported here were conducted in the New York 
Bight (NYB) and Long Island (LI) regions during July 
2011 (Fig. 1). 
As part of their survey sampling design, the Na- 
tional Marine Fisheries Service uses a 30x30 minute 
latitude/longitude grid system. Our AUV surveys were 
executed at randomly selected sites within each block 
area of an 8-block grid. They involved photographically 
surveying at least 37,500 m^ of seafloor at two or more 
sites within each grid. Sites were either chosen from 
recent NMFS survey sites for scallop stocks or were 
randomly chosen from within each grid to meet the 
predetermined total area. All of the surveys were con- 
ducted within 70 km of the coast of Delaware, New Jer- 
sey, or New York, and the water depths sampled ranged 
from 20 to 50 m (Table 1), which is within the normal 
habitable zone for the sea scallop (Merrill®; Hart and 
Chute, 2004). Extensive details of the sampling design 
were compiled in the master’s thesis for the pilot study 
(Walker, 2013) and were reviewed and approved by both 
an internal and external panel of scientists selected by 
NMFS as part of the final project review process. 
Survey design 
At each site, we deployed the AUV on a preplanned 
path that ranged from 3 to 16 kilometers of contigu- 
ous survey trackline. Surveys lasted up to 3 hours, an 
operational limit imposed by the life of a single battery 
pack. The AUV was programmed in a terrain-following 
mode with a commanded altitude of 2.2 m. Postprocess- 
ing analysis of the survey logs showed that the AUV 
remained within a 16 cm standard deviation of the 2.2 
m commanded altitude, a deviation that is consistent 
with previous studies in which the same vehicle sys- 
tem has been used (e.g., Forrest et ah, 2012; Raineault 
et ah, 2012). Precise navigation of the vehicle is ac- 
complished by using a DVL-aided (Doppler Velocity 
Log) INS (Inertial Navigation System), which has been 
shown in the literature to provide a positional drift 
rate of 0.5 m/h (Patterson et al., 2008) or 0.1% of dis- 
tance traveled (Rankey and Doolittle, 2012). Compari- 
son of known targets (such as stationary man-made ob- 
jects on the seafloor) in side-scan sonar imagery from 
repeated passes showed positional precision of within 2 
m from one survey to the next — a level that is consis- 
tent with results from other published benthic habitat 
mapping studies conducted with this same vehicle sys- 
tem (e.g., Forrest et al., 2012; Raineault et al., 2013). 
Because this was a pilot study, several trackline 
designs were tested to determine the most effective 
geometric design for image and acoustic sampling. The 
survey design that we used most often comprised a se- 
ries of parallel boustrophedon lines, commonly known 
® Merrill, A. S. 1971. The sea scallop. In Annual report for 
1970, p. 24-27. Am. Malacol. Union Inc. 
