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Fishery Bulletin 117(3) 
that catch at the point of saturation is correlated with 
the density of American lobsters on the bottom. Satura¬ 
tion tended to occur when the rate of entry of lobsters into 
ventless traps became equal to their rate of escape, so lob¬ 
sters stopped accumulating in the trap, and the catch rate 
reached a plateau (Clark et al., 2018). Importantly, these 
data indicate that ventless traps probably saturate before 
they reach some upper physical capacity, or maximum 
number of lobsters the trap could hold. Therefore, ventless 
traps seem to provide a fairly accurate index of the num¬ 
ber of lobsters on the bottom, at least when the density of 
lobsters on the bottom is not very high (Watson and Jury, 
2013; Clark et al., 2015). 
Previously, Clark et al. (2018) determined, using video 
cameras mounted above traps, that the number of lob¬ 
sters within 1 m of both standard and ventless traps was 
less on day 2 of a 48-h soak than on day 1. Given that 
ventless traps typically capture >30 lobsters in the area 
studied by Clark et al. (2018) (i.e., same site used in the 
present study) during a 48-h soak (Fig. 1), the ventless 
traps may have accumulated enough lobsters to reduce 
the density of lobsters in the EFA surrounding the traps. 
In this study, we surveyed a much larger area around 
traps and found that there were no significant differ¬ 
ences in the densities of lobsters in the EFA after the 
traps were deployed for 24 h. These findings do not sup¬ 
port the hypothesis that ventless traps saturate because 
they accumulate enough lobsters to reduce the density in 
their vicinity. 
One reason why some American lobsters do not enter 
traps is that conspecifics already inside the traps keep 
them out (Richards et al., 1983). During 2 previous studies 
(Jury et al., 2001; Watson and Jury, 2013), time-lapse videos 
were used to investigate this phenomenon with standard 
lobster traps, and, in both cases, it was clear that lobsters 
in the kitchen portion of the trap, where lobsters enter and 
the bait is located, would often prevent other lobsters from 
entering. However, it should be noted that in all previous 
studies of this type the lobsters used for pre-stocking were 
large adults that might be more aggressive than the sub- 
legal lobsters that typically accumulate in ventless traps. 
In this study, ventless traps were pre-stocked with the 
same number, and size composition, of lobsters that were 
typically captured in ventless traps on day 1 of a soak, in 
the same location (see Clark et al., 2015), and despite this 
modification in protocol, pre-stocking traps still reduced 
catch. Also, the removal of the lobsters captured on day 1 
increased the number of lobsters captured on day 2, most 
likely because of reduced agonistic interactions. Moreover, 
when the lobsters captured and removed on day 1 of a 48-h 
soak were added to those captured on day 2, the total net 
catch was greater than that for traps that were deployed 
continuously for 48 h (Fig. 7). This result indicates that 
as a trap fills over the course of the soak time, fewer lob¬ 
sters enter, and more lobsters leave, leading eventually to 
a dynamic equilibrium in which catch plateaus. However, 
although it appears as if the reduction in the rate of entry 
is, in part, due to the presence of lobsters in the trap, loss of 
bait attractiveness also appears to play an important role. 
Bait attractiveness was reduced after 24 h, as indicated 
by a number of different results. First, catch of traps with 
1-day-old bait was significantly less than catch of identical 
traps deployed for 24 h with fresh bait (Fig. 4). Second, 
when scuba divers replaced old bait with fresh bait, there 
was an immediate increase in the rate of entries observed 
on video recordings made with the LTV system. This find¬ 
ing strongly indicates that the new bait was significantly 
more attractive than the old bait (Fig. 6). Moreover, traps 
that had new bait added after 24 h captured more lob¬ 
sters than control traps (Fig. 4). Finally, after 6-24 h, there 
was a significant reduction in the amount of amino acids 
released from Atlantic herring bait, even though the bait 
itself, in terms of weight, was mostly intact. These results 
are consistent with those of a previous study of the rate 
of leaching from mackerel bait (Lpkkeborg, 1990). There¬ 
fore, a change in the attractiveness of bait over time also 
plays a key role in lobster trap dynamics and the onset of 
ventless trap saturation. It should be noted that the initial 
amount and type of bait, along with environmental factors 
such as temperature and current velocity, will likely affect 
catch and trap saturation by altering the rate at which 
bait loses its attractiveness. 
The findings from this study have several practical impli¬ 
cations. First, ventless traps saturate after approximately 
24 h because of a combination of factors related to bait dete¬ 
rioration and behavioral interactions between lobsters that 
inhibit further entries and enhance escapes. Therefore, in 
areas with high densities of lobsters, soak times of ~24 h 
might be best for ventless trap surveys. However, longer 
soak times might be appropriate in areas where the density 
of lobsters is lower or where the size-frequency distribu¬ 
tion is different. Second, even though there is a correlation 
between catch in ventless traps and the density of lobsters 
on the bottom (Clark et al., 2015), the accuracy of catch in 
ventless trap surveys as an indicator of abundance might 
be affected in areas with higher densities of lobsters or, as 
mentioned previously, in habitats with a higher density of 
larger, more aggressive lobsters. In these areas, one possi¬ 
ble solution might be to use double-parlor ventless traps, 
which might saturate at a higher capacity, or after a longer 
soak time. Finally, it would be prudent to consider stan¬ 
dardization of the amount and type of bait used in ventless 
traps and to consider bait or bait delivery systems that do 
not deteriorate as fast as Atlantic herring, so that lobsters 
will continue to approach and enter traps at a high rate 
throughout a longer soak time. 
Acknowledgments 
We thank the staff at the UNH Coastal Marine Labo¬ 
ratory, including W. Howell, N. Rennels. and the late 
N. Carlson, as well as UNH students, J. Goldstein, 
N. Copp, H. Cheng, B. Dubofsky, and T. Langley and South¬ 
ern Maine Community College students under the super¬ 
vision of B. Tarbox. We also thank the Massachusetts 
Division of Marine Fisheries, J. Carloni, and T. Pugh. This 
work was supported by a faculty development grant from 
