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Fishery Bulletin 117(3) 
catch in nearby ventless traps that were deployed 
for 48 h without the removal of lobsters (28.9 indi¬ 
viduals [SD 9.4]; Mann-Whitney U test: P= 0.035). 
These data indicate that 1) bait is less attractive 
after 24 h and 2) lobsters already in a trap influ¬ 
ence the entry of new lobsters, so if they are 
removed, more lobsters will enter the trap. 
Loss of bait attractiveness 
Traps deployed for 24 h with fresh or old bait Vent¬ 
less traps (n= 33) that were fished for 24 h with 
“fresh” bait captured significantly more lobsters 
(unpaired Atest: P<0.006) than ventless traps 
(n= 29) fished with bait that had been previ¬ 
ously used for 24 h in a different set of traps (i.e., 
1-day-old bait) (Fig. 4A). These results indicate 
that the old bait was less attractive than the new 
bait. It should be noted that, although this old bait 
had been in a trap for 24 h, much of the Atlantic 
herring, by weight, was still intact (on average, 
62% of the bait by wet weight remained). 
Old bait Fresh bait Bait added Control 
Figure 4 
The effect of bait “age” on catch per unit of effort. (A) Twenty-nine 
traps were deployed for 24 h with bait that had already been used 
in different traps in the same location for 24 h (old bait), and 33 
other traps were deployed for 24 h with the same amount of fresh 
bait. The traps with fresh bait captured significantly more Amer¬ 
ican lobsters (Homarus americanus) (P< 0.006). (B) Control traps 
(n=34) were deployed for 48 h with the same bait. Experimental 
traps (n=34, bait added) were hauled after 24 h, the bait in each 
trap was replaced with fresh bait, and then the traps were rede¬ 
ployed for an additional 24 h. The traps with added bait caught sig¬ 
nificantly more lobsters (P=0.027). Error bars in this figure denote 
standard errors of the mean. 
Traps deployed for 48 h Ventless traps 
(n= 34) were deployed for 24 h and then 
the bait was replaced with new bait, and 
the traps were redeployed, without 
removing any of the captured lobsters, 
for a second 24 h. These traps with bait 
added captured a mean of 21.0 lobsters 
after the initial 24 h and 13.9 lobsters 
during the second 24 h, for a total of 34.9 
lobsters after the total soak time of 48 h 
(Fig. 4B). This was significantly more 
than control traps (a=27) captured; con¬ 
trol traps were fished over the same time 
period, but without new bait added after 
the initial 24 h (unpaired t-test: P<0.05) 
(Fig. 4B). Interestingly, the experimental 
traps with added bait captured -50% 
fewer lobsters on day 2 than on day 1 in 
virtually every experiment, even though 
fresh bait was added, a result that was 
likely due to the influence of the lobsters 
retained from day 1 on the subsequent 
entry of new lobsters. Therefore, while 
loss of bait attractiveness appears to 
play a role in reducing the catch of lob¬ 
sters during day 2 of a 48-h soak, other 
factors, such as the behavioral interac¬ 
tions between lobsters, also influence 
saturation of ventless traps. 
Alanine 
Arginine 
Aspartic acid 
Glutamic acid 
Glycine 
Histidine 
Isoleucine 
Leucine 
Lysine 
Phenylalanine 
Serine 
Threonine 
Tyrosine 
Remaining bait (%) 
Figure 5 
Bait degradation over time, by proportion of remaining weight (%) and relative 
concentration (%) of amino acids. Although wet weight of the bait (n=4, frozen 
salted Atlantic herring, Clupea harengus), was relatively unchanged over a 
24-h simulated trap deployment, the concentrations of multiple amino acids 
rapidly decreased due to leaching. Note that the initial increase in weight is 
due to rehydration of the salted herring. Error bars in this figure denote stan¬ 
dard errors of the mean. 
Soak time (h) 
Attractants leaching from bait To estimate the leaching of 
possible bait attractants from Atlantic herring within the 
first 24 h of trap deployment, we measured changes in the 
concentrations of various amino acids over time in simu¬ 
lated trap deployments (Fig. 5). Although the weight of the 
Atlantic herring that were used as bait was essentially 
unchanged after 24 h (note that lobsters were not allowed 
to feed on baits during the soak time; for details, see the 
“Materials and methods” section), the amino acid concen¬ 
trations decreased by 30-80% after just 6 h and then 
decreased even further after 24 h. As a result, under the 
conditions tested, salted Atlantic herring after 24 h had 
