Brown et al.: Simple gear modifications for bycatch reduction in a shrimp trawl fishery 
375 
Figure 1 
Illustration of a typical shrimp vessel equipped with 4 trawl nets. 
Double-rigged vessels like this one were used during the trials con¬ 
ducted in 2015 and 2016 in Pamlico Sound, North Carolina. Control 
and experimental gear were placed in the outside positions (i.e., Net 
#1 or Net #4). Note that try nets were not used in this study. Image 
source: Scott-Denton et al. (2012). 
Trawl body 
Figure 2 
Illustration of the components of a trawl net. Several modifications 
of the trawl net typically used in the shrimp fishery were tested for 
this study aboard commercial vessels in Pamlico Sound and near¬ 
shore waters off North Carolina during 2015-2017. Image source: 
Scott-Denton et al. (2012). 
minimized or eliminated the use of try nets to mitigate 
potential effects from their use (Eayrs, 2012; Figs. 1 and 2). 
To coincide with the peak shrimp seasons, testing was con¬ 
ducted during June-July 2015, July-September 2016, and 
July 2017 in Pamlico Sound and from August through 
November 2017 in the nearshore waters of North Carolina 
(Fig. 3). All paired tows were performed under normal 
fishing conditions. 
Observers were hired and trained to collect data under 
NCDMF protocols and met or exceeded National Marine 
Fisheries Service (NMFS) guidelines (NMFS 12 ). 
Two observers were assigned to each trial. Per¬ 
sonnel from the Beaufort Laboratory, NOAA 
Southeast Fisheries Science Center, trained 
observers to handle, transport, identify, resus¬ 
citate, tag, and release protected sea turtles in 
accordance with federal standards of the U.S. 
Endangered Species Act. 
Prior to formal field trials, tows were made to 
calibrate the nets on each side of the vessel to 
ensure that the nets fished evenly. To reduce 
the potential for side bias, protocol required 
that experimental and control modifications be 
switched periodically from one side to the other 
side to achieve an equal number of success¬ 
ful tows on each side of the vessel. Specifically, 
only the gear modifications being tested (i.e., 
BRDs and TEDs with reduced bar spacing) were 
switched while the body of the net remained to 
mitigate any net effect. Gear specification data 
were collected for both experimental and control 
nets and included fabrication costs, head rope 
length, mesh size of wing and codend, TED type, 
TED bar spacing, BRD type, and location, dura¬ 
tion, and time of day of tow. 
At the request of industry collaborators, data 
were collected for whole hauls (i.e., catches were 
not subsampled). Specifically, industry collabora¬ 
tors were concerned about the public perception 
of sampling a portion of the catch versus obtain¬ 
ing a census of harvest from each tow. Follow¬ 
ing each paired tow, the catches from each net 
(experimental and control) were counted and 
weighed separately in their entirety. Because of 
the volume of catch, organisms were not identi¬ 
fied to species; instead, catches were grouped into 
shrimp and finfish categories for counting and 
weighing. In 2015, the total weight (in kilograms) 
of shrimp and finfish were recorded. In 2016 and 
2017, smaller catches allowed further categoriza¬ 
tion that included groups for penaeid shrimp, fin¬ 
fish, non-shrimp invertebrates, sharks and rays, 
and miscellaneous organisms. 
Description of control and experimental gears 
All control and experimental nets were built to 
have identical head rope length, footrope length, 
and net bodies. The control net configuration for 
this project consisted of a shrimp otter bottom (2-seam) 
trawl with a state fisheye, a TED with 10.16-cm bar spac¬ 
ing, and a 3.81-cm stretched mesh codend (Fig. 4). This 
configuration was considered the most typical gear 
12 NMFS (National Marine Fisheries Service). 2010. Characteri¬ 
zation of the US Gulf of Mexico and southeastern Atlantic otter 
trawl and bottom reef fish fisheries: observer training manual, 
186 p. Galveston Lab., Southeast Fish. Sci. Cent., Natl. Mar. 
Fish. Serv., NOAA, Galveston, TX. [Available from website.] 
