National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
a- established in 1881 ■*?. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Experimental analyses of the mechanisms leading 
to American lobster [Homarus americanus) 
ventless trap saturation 
3 International Center for Coral Reef Research and Restoration 
Mote Marine Laboratory 
24244 Overseas Highway 
Summerland Key, Florida 33042 
Abstract—Ventless lobster traps are 
now widely used to assess the abun¬ 
dance of American lobsters (Homarus 
americanus). However, catch in vent¬ 
less traps plateaus after 24 h (trap 
saturation), possibly influencing abun¬ 
dance estimates. This study addressed 
3 mechanisms that may cause vent¬ 
less trap saturation: 1) traps retain so 
many lobsters that, over time, fewer 
lobsters are available to catch; 2) as 
lobsters accumulate in traps, they 
inhibit entry of additional lobsters and; 
3) bait quality deteriorates over time 
and loses its attractiveness. We found 
that 1) the number of lobsters in the 
vicinity of traps did not change after 
a 24-h soak; 2) stocking traps with 
lobsters before deployment lowered 
subsequent catch, while removing the 
lobsters captured after 24 h led to an 
increase in catch after 48 h; 3) when 
fresh bait was added to traps that had 
been fished for 24 h, entry rate imme¬ 
diately increased; 4) if “old” bait was 
used, catch after 24 h was less than 
in traps fished with fresh bait; and 5) 
amino acid attractants in bait declined 
after the first 6-24 h. Thus, ventless 
traps appear to saturate due to a com¬ 
bination of loss of bait attractiveness 
and the interactions between lobsters 
as they accumulate in traps. 
Manuscript submitted 6 September 2018. 
Manuscript accepted 25 July 2019. 
Fish. Bull. 117:211-219 (2019). 
Online publication date: 15 August 2019. 
doi: 10.7755/FB.117.3.8 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Winsor H. Watson III (contact author) 1 
Elizabeth Morrissey 2 
Stephanie Sykes 1 
Abigail S. Clark 3 
Steven Jury 4 
Email address for contact author: win@unh.edu 
1 Department of Biological Sciences 
School of Marine Sciences and Ocean Engineering 
University of New Hampshire 
46 College Road 
Durham, New Hampshire 03824 
2 Marine Institute 
Memorial University of Newfoundland 
155 Ridge Road 
St. John's, Newfoundland, Canada A1C 5R3 
4 Department of Biology 
Saint Joseph's College 
278 Whites Bridge Road 
Standish, Maine 04084 
The American lobster (Homarus amer¬ 
icanus) represents one of the most 
lucrative fisheries in the United States 
and Canada, and, therefore, effec¬ 
tive management is imperative. This 
requires accurate monitoring of the 
abundance of lobsters, of all sizes and 
sexes, so that declines and distribution 
shifts, such as the changes that have 
recently occurred in Southern New 
England (ASMFC 1 ), can be detected 
and management options can be con¬ 
sidered. However, one of the challenges 
inherent in using the standard traps 
1 ASMFC (Atlantic States Marine Fisheries 
Commission). 2010. Recruitment failure in 
the Southern New England lobster stock, 
30 p. [Available from website.] 
employed by the industry to assess 
resident lobster populations is that 
they are designed to capture the larger 
adults; thus, many of the animals that 
enter them ultimately escape, espe¬ 
cially those that are sublegal (Jury 
et ah, 2001; Barber and Cobb, 2009; 
Boutson et al., 2009; Weiss, 2010; Stur¬ 
divant and Clark, 2011; Broadhurst, 
et ah, 2014). 
To address this problem, and improve 
the quality of the data used for stock 
assessments, in 2006 the coast-wide 
ventless trap survey was initiated 
(see ASMFC, 2015, for details). Vent¬ 
less traps retain most of the sublegal 
lobsters that would otherwise escape 
because the escape vents that are typ¬ 
ically present in standard (vented) 
