162 
Fishery Bulletin 11 6(2) 
Table 1 
Summary of the 6 trials in which a video surveillance system attached to lobster traps was used to investi¬ 
gate trap saturation in ventless (3 trials) and standard traps (3 trials) deployed off New Hampshire (Wallis 
Sands) during 2010-2012. The total number of hours of recorded video excludes nighttime footage because 
the lobster-trap video system recorded behavior of American lobsters (Homarus americanus) only during 
the day (-0900-1700 or 1900 h). Density represents the number of lobsters on the bottom during each trial. 
The final catch values in traps were calculated on the basis of the number of entries and escapes observed 
in videos. 
Trial 
Trap type 
Start date 
End date 
Total hours 
recorded 
Density 
(individuals/m 2 ) 
Final catch 
(no. of lobsters) 
1 
Standard 
09/24/2010 
09/25/2010 
15.8 
0.136 
3 
2 
Standard 
06/28/2011 
06/29/2011 
24.4 
0.053 
0 
3 
Standard 
07/18/2012 
07/19/2012 
19.3 
0.054 
1 
4 
Ventless 
09/14/2010 
09/15/2010 
19.5 
0.136 
14 
5 
Ventless 
08/06/2011 
08/07/2011 
15.7 
0.100 
28 
6 
Ventless 
08/25/2011 
08/26/2011 
15.3 
0.140 
27 
cape vents in the parlor; the remaining 72% escaped 
from the kitchen, where the bait was located, through 
one of the 2 entrances. Although the exit of sublegal- 
size lobsters through the escape vent is advantageous 
for sustaining lobster populations, it is clear that catch 
in standard traps does not always correlate well with 
either the abundance or size composition of lobster 
populations on the bottom (Courchene and Stokes- 
bury, 2011; Watson and Jury, 2013; Clark et ah, 2015). 
Ventless traps, which lack escape vents (Estrella and 
Glenn 3 ), help to alleviate this problem and, for this 
reason, are being used in assessments by some state 
fisheries management agencies (MADMF 2 ). 
Recently, Clark et al. (2015) showed that ventless 
traps provide a better representation of American lob¬ 
ster density and size composition than standard traps. 
Although the time it took for ventless traps to satu¬ 
rate, or reach a point where catch plateaued (16-24 h), 
was similar at different lobster densities surrounding 
the experimental traps, the maximum catch was cor¬ 
related with the greatest lobster density surrounding 
the traps. In other words, traps saturated at a level of 
catch that was much less at low densities of lobsters 
than at higher densities; therefore, ventless traps were 
saturating not because they had reached a theoretical 
maximum capacity but for reasons that have yet to be 
determined. The major goal of this investigation was 
to use underwater video surveillance techniques to ob¬ 
serve and quantify the behavior of American lobsters 
in and around ventless and standard traps in order 
to gain a better understanding of the mechanisms un¬ 
derlying trap saturation, defined as a plateau in catch 
over time, in both trap types. 
Video surveillance makes it possible to study ani¬ 
mals in their natural habitats without the interference 
3 Estrella, B. T., and R. P. Glenn. 2006. Lobster trap escape 
vent selectivity. Mass. Div. Mar. Fish., Tech. Rep. TR-27, 15 
p. [Available at website.] 
of humans (Mallet and Pelletier, 2014). For example, 
Jury et al. (2001) attached a video recording system 
to a standard lobster trap and noted the behaviors of 
American lobsters in and around a trap for up to 48 
h. The data from that study indicated that many of 
the lobsters that enter traps ultimately escape. Sub¬ 
sequently, other investigators used similar methods to 
observe the behavior around traps of commercially im¬ 
portant marine crustaceans, including the Caribbean 
spiny lobster (Panulirus argus ; Weiss et al., 2006), Jap¬ 
anese rock crab ( Charybdis japonica; Vazquez Archdale 
et al., 2007), Dungeness crab ( Cancer magister ; Barber 
and Cobb, 2009), and blue crab ( Callinectes sapidus ; 
Reichmuth et al., 2011). 
Despite these advances, the mechanisms that cause 
saturation in crustacean traps are still not fully un¬ 
derstood. The most generally accepted explanation is 
that trap saturation is due, in part, to the competitive 
and agonistic interactions between conspecifics inside 
and outside a trap (Richards et ah, 1983; Miller, 1990; 
Addison, 1995; Jury et al., 2001; Barber and Cobb, 
2009; Ovegard et ah, 2011). For example, pots used to 
catch Dungeness crab are believed to saturate because 
of agonistic interactions between entering crabs and 
approaching crabs (Barber and Cobb, 2009). Similar 
territoriality has been observed in and around lobster 
traps (Richards et al., 1983; Addison, 1995; Jury et ah, 
2001). Prestocking standard traps with American lob¬ 
sters caused a reduction in entry rate and therefore 
catch (Richards et al., 1983; Addison, 1995; Watson 
and Jury, 2013). These findings, combined with those 
of Jury et al. (2001), suggest that saturation of stan¬ 
dard traps is at least partially a function of increased 
agonistic interactions between lobsters in and around 
traps—interactions that reduce the rate of entry as 
traps accumulate lobsters. However, if agonistic inter¬ 
actions were the only cause of saturation, then traps 
would be expected to reach this plateau sooner at high¬ 
er densities. Clark et al. (2015) observed that the catch 
