Watson et al.: Experimental analyses of the mechanisms leading to lobster ventless trap saturation 
215 
mixed for 1 h on a shaker table in a temperature-controlled 
bath (20°C). The soaked bait and particulates were then 
allowed to settle for 15 min, and duplicate 15-mL aliquots 
of the supernatant were removed and frozen at -20°C for 
future analyses. The bait remaining after this 1-h period 
was weighed and then placed inside a bait bag and trans¬ 
ferred to a ventless lobster trap that had the entries cov¬ 
ered to minimize possible feeding on the bait by lobsters 
or other organisms too large to fit through the trap mesh. 
These traps were deployed in the field in Casco Bay, Maine 
(15°C, salinity of 32), for periods of 3, 6, and 24 h, and then 
the bait from each trap was weighed. After each time inter¬ 
val of soaking in the field, each bait bag with remaining 
bait was placed into 1 L of temperature-controlled, clean 
artificial seawater and shaken in the lab for another hour, 
after which duplicate leachate aliquots were removed and 
frozen. Thus, for each of the 4 bait samples tested, we had 
the wet weight of the bait and a leachate sample for 4 time 
periods: 0-1 h, 3-4 h, 6-7 h, and 24-25 h. For amino acid 
analyses, leachate samples were sent to SGS Analytical 
Services (Brookings, SD) for standard analyses via liquid 
chromatography-mass spectrometry. 
it appears that the reduction in the number of lobsters in 
the EFA of a trap, due to their accumulation in a ventless 
trap, is probably not a primary cause of trap saturation. 
Influence of lobsters in a trap on the entry 
of additional lobsters 
Catch in pre-stocked traps versus control traps deployed for 24 h 
Pre-stocked traps captured significantly fewer additional 
lobsters than traps that were not pre-stocked (Fig. 3; 
Mann-Whitney U test: P=0.002). An average of 12.2 new 
lobsters entered the pre-stocked traps in 24 h, while 7.8 of 
the marked lobsters used for pre-stocking escaped, yielding 
a net increase in catch of only 4.4 lobsters (SD 3.7). This 
indicates that lobsters in ventless traps influence the sub¬ 
sequent entry of additional lobsters, as has been observed 
for standard traps (Jury et al., 2001). When taken together 
with the fact that a number of the pre-stocked lobsters 
escaped, it appears as if, at some point during a soak, as 
traps fill, a dynamic equilibrium between entries and 
escapes is reached, which plays an important role in caus¬ 
ing catch to plateau, or saturate, in ventless traps. 
Results 
Density of lobsters around traps before and after a 24-h soak 
There was no significant difference between the density of 
lobsters in the vicinity of ventless traps before and after a 
soak of 24 h (Fig. 2; 2-tailed Wilcoxon test: n- 5, P=0.125). 
Even when the density of lobsters determined by scuba 
surveys was at its highest, there were more lobsters 
around the trap after 24 h than just after the trap was set. 
Therefore, with the possible exception of times of the year 
when, or locations where, densities of lobsters are very low, 
7 / 15/13 7 / 25/13 7 / 30/13 8 / 05/13 8 / 14/13 
Date 
Figure 2 
The abundance of American lobsters (Homarus ameri- 
canus) in the vicinity of a trap prior to, and after, a soak of 
24 h. Traps were deployed in 2013 off Wallis Sands State 
Beach in New Hampshire. There was no significant differ¬ 
ence (n- 5, P=0.125) in the density of lobsters before, and 
after, a trap had been deployed for 24 h. Therefore, traps 
did not reduce the number of lobsters in the area sur¬ 
rounding the traps significantly enough to influence catch 
on day 2 of a 48-h soak. Gray bars represent day 1, and 
black bars represent day 2. 
Removal of captured lobsters after 24 h of a soak influences 
catch after 48 h Traps (n=9) deployed for 24 h captured an 
average of 25.7 lobsters (SD 6.1). After these lobsters were 
removed from the traps and the same traps were rede¬ 
ployed without changing the bait for a second 24 h, they 
captured significantly fewer lobsters in the second 24-h 
soak period (13.7 individuals [SD 8.6]; Mann-Whitney 
U test: P-0.004). Moreover, if the number of lobsters cap¬ 
tured during each of the 2 days are added together, a net 
total of 39.3 lobsters (SD 12.9) were caught in the equiva¬ 
lent of a 48-h soak. This was significantly more than the 
40 
“ 35 High pre-stock 
CQ 
Day 1 pre-stock Day 2 total catch Day 1 pre-stock Day 2 total catch 
Experiment 
Figure 3 
The effect of pre-stocking traps on subsequent catch. 
When traps (n=6) were pre-stocked with -28 American 
lobsters (Homarus americanus ) on day 1 (high pre-stock), 
the traps captured few additional lobsters after a soak of 
24 h (day 2). When traps (n-3) were pre-stocked with only 
10 lobsters (low pre-stock), they caught ~9 more lobsters 
during the next 24 h, for a total of -19. Error bars in this 
figure denote standard errors of the mean. 
