Clark et al.: Underwater video surveillance of catch saturation in lobster traps 
163 
Figure 1 
Photographs of the lobster-trap video 
(LTV) system used to investigate trap 
saturation in ventless and standard 
traps deployed off New Hampshire (Wal¬ 
lis Sands) during 2010-2012. A) View of 
the LTV system mounted on a standard 
lobster trap, placed underwater, at the 
study site. B) Close-up view of the LTV 
system, which includes a camera mount¬ 
ed in an underwater flashlight housing 
that was connected to another water¬ 
proofhousing containing a digital video 
recorder (DVR) and batteries. Note that 
the DVR is not visible. 
in lobster traps consistently plateaued after 16 to 24 
h for both high and low densities of lobsters. Thus, 
other factors that potentially influence trap saturation 
in both standard and ventless traps were the focus of 
our study. 
Our objective was to identify factors that affect the 
saturation of lobster traps. The behavior of American 
lobsters was observed by using a modification of the 
lobster-trap video system that had been incorporated 
into previous studies conducted off New Hampshire 
(Jury et al., 2001; Watson and Jury, 2013). We hypoth¬ 
esized that changes in the entry rate in relation to the 
escape rate over the period of a soak would cause catch 
in traps to plateau. 
Materials and methods 
Study site 
All data from video surveillance of traps were collected 
from 2010 to 2012 at a study site (0.8x2.5 km) just off¬ 
shore of Wallis Sands State Beach in Rye, New Hamp¬ 
shire (for details, see Clark et al., 2015). This location 
was chosen because previous trap studies were con¬ 
ducted there to take advantage of the predominantly 
sandy bottom, which made it easier to obtain accurate 
estimates of the density of American lobsters during 
dive surveys and to observe lobsters around the traps 
by using our digital video system. Additionally, few 
commercial lobstermen fished in this area throughout 
our study. 
Trapping trials and dive surveys 
Between June and September of 2010-2012, 6 trials (3 
with standard traps and 3 with ventless traps) were 
completed (Table 1). During these 6 trials, the densities 
of American lobsters were similar, all of the traps were 
deployed for 2 d, and high-quality video recordings of 
lobster activity were obtained. Traps were baited at the 
beginning of each trial with 3-4 frozen Atlantic her¬ 
ring (Clupea harengus ; >0.2 kg in total) from the same 
source (Little Bay Lobster Co. 4 , Newington, NH). 
Dive surveys (n=8) were performed a week before 
or after the 6 trapping trials to estimate densities of 
lobsters and to determine the size composition of the 
lobster population in the area fished with traps. The 
methods for the dive surveys are described in Clark et 
al. (2015). Briefly, 2 scuba divers swam along 4 tran¬ 
sects (30-60 mx4-6 m, depending on visibility), one 
transect in each of the cardinal directions. Before trap 
deployment, lobsters were counted to estimate lobster 
densities. After each trial, lobsters were collected by 
divers to determine size composition of the lobster pop¬ 
ulation. Divers handled lobsters only during the sur¬ 
veys that were conducted after each trial or after the 
traps were hauled. Handling the lobsters before trap 
deployment would have potentially caused lobsters to 
move out of the area during the trials, a change that 
would, thereby, have altered the density of lobsters. 
The data from these surveys were converted to den¬ 
sity estimates, as the number of individuals per square 
meter, for analyses. For the lobsters that were brought 
to the surface, carapace length (CL) and sex were re¬ 
corded before the lobsters were returned to their area 
of capture. The mean CL of the lobsters measured dur¬ 
ing the dive surveys was 46.4 mm (standard error of 
4 The mention of trade names or commercial products through¬ 
out this article is for identification purposes only and does 
not imply endorsement by the National Marine Fisheries 
Service, NOAA. 
