Complementary Testing of Off-Bottom Trawls to Target Georges Bank Haddock

Abstract

We tested two off bottom trawls (OBTs: OBT1 and OBT2) to harvest Georges Bank haddock along with redfish and pollock, while simultaneously avoiding overexploited fish stocks, mainly Atlantic cod, yellowtail flounder (Limanda ferruginea), and windowpane flounder (Scophthalmus aquosus).

Full text

Complementary Testing of Off-Bottom Trawls to Target Georges Bank Haddock
Final Report to NOAA Saltonstall-Kennedy Program
NOAA Grant Award # NA16NMF4270233
Amount of Grant: $299,083
Duration: 01/01/2017 to 12/31/2019
Report prepared by:
David M. Chosid and Mike Pol1
1MA Division of Marine Fisheries, 836 South Rodney French Blvd. New Bedford, MA 02744
September 26, 2020

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Principal Investigators:
David Chosid (Report author)
Marine Fisheries Biologist
Mass. Division of Marine Fisheries
836 South Rodney French Blvd.
New Bedford, MA. 02744
508-742-9724
David.chosid@mass.gov
Dr. Mike Pol
Senior Marine Fisheries Biologist
Mass. Division of Marine Fisheries
836 South Rodney French Blvd.
New Bedford, MA. 02744
508-742-9748
Mike.pol@mass.gov
Captain Mark Phillips
F/V Illusion
210 Atlantic Ave.
Greenport, NY 11944
516-361-3253
Mark.st.phillips@gmail.com
Collaborating Partners:
Dr. Pingguo He
School for Marine Science & Tech
706 S. Rodney French Blvd.
New Bedford, MA 02744
508-910-6326
phe@umassd.edu
Tor Bendiksen
Reidar’s Manufacturing, Inc.
9 Tarkiln Place
New Bedford, MA 02745
(508) 999-4616
Reidarstrawl@gmail.com
Mike Hillers
Simrad Fisheries
19210 33rd Ave W.
Lynnwood, WA 98036
206-601-2837
Mike.hillers@simrad.com
Coastal Enterprises, Inc.
30 Federal Street
Brunswick, ME 04011
207-882-7552
Swan Net
8300 Military Rd. South, 100
Seattle, Washington 98108
206-763-6139

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Withdrawn PIs
Steve Eayrs
Gulf of Maine Research Institute
350 Commercial St.
Portland, ME 04101
207-228-1659
Steve@gmri.org
Adam Baukus
Gulf of Maine Research Institute
350 Commercial St.
Portland, ME 04101
207-228-1691
abaukus@gmri.org
James. A. Odlin
Atlantic Trawlers Fishing
P.O. Box 288
Portland, ME. 04112
207 871 8050
jimodlin@maine.rr.com

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Executive Summary
The combined biomass of the Georges Bank haddock (Melanogrammus aeglefinus), Gulf of
Maine haddock, pollock (Pollachius virens), and redfish (Sebastes fasciatus) stocks currently
constitute more than 90% of the overall groundfish biomass observed in Northeast Fisheries
Science Center (NEFSC) spring surveys. Only a fraction of the available biological catch for
these species is captured (NEFSC, 2017). These valuable stocks are difficult to target without
capturing less healthy groundfish stocks such as Atlantic cod (Gadus morhua) and some flatfish
species. Specialized trawl gear has been implemented in the U.S. Northeast to reduce bycatch
while fishing, mainly for haddock, but the current status of Georges Bank Atlantic cod is so poor
that these designs proven to effectively reduce cod bycatch and implemented in special access
programs are still not sufficient to prevent exceeding quotas (Eayrs et al, 2020). However, the
partial effectiveness of these specialized trawls at reducing cod bycatch suggested to us that
raising the mouth of the trawl net even further off-bottom might decrease cod catch even more.
Further, none of the regulated groundfish trawl gears have successfully managed to completely
reduce seafloor contact, which could eliminate impacts to benthic habitat and possibly allow
access to grounds that were previously off-limits to fishermen. Reducing bottom contact would
also likely reduce fuel consumption and fishing costs. For these reasons, we tested two off-
bottom trawls (OBTs: OBT1 and OBT2) to harvest Georges Bank haddock along with redfish
and pollock, while simultaneously avoiding overexploited fish stocks, mainly Atlantic cod,
yellowtail flounder (Limanda ferruginea), and windowpane flounder (Scophthalmus aquosus).
These two nets were different in size and construction and were planned to be used on two
different fishing vessels to characterize a more diverse usage in the fishery. However, one of the
fishing industry participants was unable to complete the project so instead, all fieldwork was
conducted from a single groundfish vessel.
The OBT nets were built with very large meshes at the front end, made with “helix” twine, an
innovative twine that incorporates a thinner twine twisted along the surface of a thicker one to
produce lateral hydraulic forces, resulting in self-spreading of the meshes (Gloria: Self
Spreading, 2015; Kebede et al., 2020). Both nets were equipped with 5.1” square mesh codends
(matching the codends used by the Canadian groundfish fishery) and were spread using 3.0 m2
Gull Wing doors (Net Systems, AK, USA), configured to fish off-bottom. The OBT2 was a
much larger version of the net, with other design differences compared to the OBT1.
We conducted a gear tuning trip for each OBT net, primarily using acoustic mensuration sensors
and underwater video, to familiarize ourselves with the OBT nets and to establish optimal gear
configurations. An open codend was used during tuning trials and no catch was retained.
Following each tuning trip, we conducted a catch comparison trip comparing the previously
tuned OBT net against a Ruhle trawl (Beutel et al., 2008). The Ruhle trawl was equipped with a
standard 6.0” diamond mesh codend as a control and the doors were reconfigured to fish on
bottom. Paired catch comparisons were conducted between the OBT1 and the Ruhle trawl
through alternate towing procedures. Pairing was logistically not possible when testing the OBT2
v. the Ruhle trawl so instead, catch comparison results were pooled over that entire trip. During
catch comparison testing, the captain felt that the OBT nets were not remaining close enough to
the seafloor and added drop chains near the wingends for the majority of tows, creating some

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contact with the bottom.
The OBT1 tuning trip revealed that the footrope (also known as the fishing line) could maintain
the desired height of under one meter, even without additional drop chains, although frequent
attention to the vessel’s RPMs or adjustments of the amount of warp wire out were required to
maintain that height and optimal door spread. Close proximity of the footrope to the seafloor was
also identified during subsequent catch comparison testing of this net. Less attention to RPMs
were required after the addition of drop chains. There was no significant difference in RPMs
between the OBT1 and Ruhle trawl although tow speed was significantly different.
The OBT1 successfully maintained haddock catches while reducing several non-target species as
compared to the Ruhle trawl. Most notably, a significant reduction was identified for monkfish,
barndoor skates, and little skates and the OBT1 appeared to eliminate catch of all winter skate.
The lack of skates in the catch also implies less or no bottom contact of the footrope.
For the OBT2 tuning, the captain had difficulty setting out an amount of warp wire to achieve the
desired door spread and thus, establish the preferred angle of attack and net shape. This was
partially due to the large size of this net and the position of its doors (which were closer in depth
to the headline than for the OBT1) in relation to the relatively shallow depths we operated in.
The OBT2 operated more stably than the OBT1 but required significantly more RPMs than both
the OBT1 and Ruhle trawl. Also, probably due to the large size of the OBT2, more pelagic
species became captured in the net or enmeshed for unknown periods and, in some cases,
damaged parts of the net. It is unknown if operating in deeper areas would reduce this problem.
The OBT2, like the OBT1, also successfully maintained catches of haddock as compared to the
Ruhle trawl. The OBT2 also showed significant decreases in some bottom species compared to
the Ruhle trawl including monkfish and barndoor skates, like the OBT1, as well as a significant
decrease in winter skate, again implying less bottom contact.
We were unable to capture enough pollock or redfish to make a judgment on the OBTs’
effectiveness with these species. Also, bycatch reductions of some commercial species using the
OBT nets were difficult to assess as the OBTs and the Ruhle trawl are all designed to reduce
these species, like Atlantic cod. Therefore, either these nets retained a very small proportion of
these bycatch species or only few of these fish were present on the fishing grounds when we
conducted tests. In either case, the OBT nets generally showed less or no significantly different
impact to bycatch species compared to the Ruhle trawl.
No significant difference in fish lengths were identified for any species between the OBT nets
and Ruhle trawl which was unexpected due to the use of the smaller codends on the OBT nets.
The different shaped codend meshes may have accounted for the similar lengths for round fish,
such as haddock, which have difficulty passing through less-than-fully-opened diamond-shaped
meshes (as in the Ruhle trawl), effectively reducing escape through the meshes, but not for
flatfish which are more likely to pass through the diamond-shaped meshes (Graham, 2010). We
surmise that either fewer smaller fish entered the OBT nets or escape of smaller fish occurred
earlier in the OBT nets, before reaching the codends. Due to the extremely large size of the front

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meshes of the OBT nets, increased escape seems likely, but the combination of reasons is also
possible. Any fish escape earlier in the fishing process would reduce the physical interactions
and physiological fatigue which would likely reduce stress and mortality (Suuronen, 2005; Ryer,
2004).
While using the OBT nets, bottom contact was likely reduced but not eliminated, as indicated by
the reduction in bottom dwelling species in both designs as compared to the Ruhle trawl. This
outcome may be sufficient to open new areas for access, but perhaps not in all habitats where
disturbances are problematic for the ecosystem. Both OBT nets meet the regulation requirements
for fishing in areas that allow standard groundfish nets if fished with standard codends. The use
of smaller mesh codends in a commercial fishery would require fishing exemptions or changes to
regulations, which may be possible since bycatch was not adversely affected, and length
frequencies of fish were unchanged.
These results provide some encouragement for the continued development of off-bottom trawls
to fish for haddock. Further field research would be required to assess the OBTs’ capabilities at
catching pollock and redfish. The participating captain plans to continue to use both OBT nets,
with some adjustments.
Outreach is underway, but inhibited by the Covid-19 pandemic. We believe there is more to
learn from combining and comparing the data gained from the various fishing gear sensors and
we will continue to explore them for more insight into net performance.
Purpose
The New England groundfish fleet has been struggling recently, in part due to inadequate
revenues, with numbers of participating vessels declining over the last decades (Murphy et al.,
2014). Haddock (Melanogrammus aeglefinus), an abundant and healthy stock on Georges Bank,
could provide additional fishing opportunities but continues to be underexploited, with only 1%
of the allowable catch taken in recent years (Finley et al., 2019).
Haddock occupy a narrower range of habitats and less area compared to Atlantic cod (Gadus
morhua) (Colette and Klein-MacPhee, 2002), so limits to access to haddock fishing grounds can
severely inhibit haddock harvest. At the start of this project in 2016, Closed Areas I and II on
Georges Bank had excluded groundfish fishing from roughly 25% of the total area of the bank,
or about 10,900 km2 for more than twenty years (Link et al., 2005). Temporal restrictions were
also in place: from 2008 to 2010, the USA portion of the Eastern Georges Bank management
area was closed from May 1 to July 31 to vessels fishing with trawl gear. It is from the trawl gear
fleet, exclusively demersal otter trawls, that nearly all US haddock landings are derived (Finley
et al., 2019).
Area closures, temporal restrictions, and other management measures are in place, partially to
protect and to improve the health of groundfish stocks through effort reduction. Atlantic cod
stocks in particular are in poor condition, recently reaching all-time lows of 3-4% of target
biomass (NEFSC, 2015). As a result, cod quota is extremely limited and it follows that fisheries
that catch cod incidentally must be conducted cautiously to avoid quota exhaustion and

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expensive leasing or purchasing.
Access to haddock fishing grounds is permitted under special access programs using several
demersal otter trawl designs developed in the region to reduce bycatch of cod when targeting
haddock (Northeast Fishery Science Center, 2017). A relatively commonly used design, the
Ruhle trawl (a.k.a. rope trawl or Eliminator trawl) is constructed of very large meshes (240 cm)
at the front end, gradually reducing to 16.5 cm. In experimental trials, this design successfully
increased the bycatch ratio of haddock to cod from three haddock for each cod (3:1) to 20:1
(Beutel et al., 2008).
Vessels fishing with trawls with horizontal separator panels are also permitted in the special
access program. A separator trawl is a bottom-tending otter trawl with a netting panel across the
opening of the trawl that divides the trawl horizontally and consequently separates fish into
higher and lower groups (Nichols et al., 2001). Catch results from multiple studies of separator
trawls and some observations underwater suggest that haddock appear to enter an otter trawl
slightly higher than cod. A recent meta-analysis of these studies (Fryer et al., 2017) found this
separation of cod and haddock to be linked to the height of the panel off-bottom, with higher
panels increasing the degree of separation of haddock and cod. Another design, a rope separator
trawl, where the separator panel is constructed of ropes instead of netting, is also permitted in the
special access program (He et al., 2005).
We developed a haddock trawl design known as the Five-Point Trawl in the early 2000s (Chosid
et al., 2010). This net combined the virtues of cod separation via raising the footrope of the net,
with minimal contact with the seafloor. The only contact of the trawl net was from five chains
hanging from the fishing line that served to elevate the net approximately 1.5 m, as well as to
keep the net open, with headline heights to the seafloor as high as 10 m. In field trials, the net
fished as well as a net with a horizontal separator panel.
The current status of Georges Bank Atlantic cod is so poor that these designs proven to
effectively reduce cod bycatch and implemented in special access programs are not sufficient to
prevent exceeding quotas (Eayrs et al, 2020). However, the partial effectiveness of separator
trawls and the Five-Point Trawl at reducing cod bycatch suggested to us that raising the mouth of
the trawl net even further off-bottom might decrease cod catch even more. Therefore, testing of a
net to target haddock that fished completely off the seafloor appeared to be a logical progression
from this earlier work.
Modern trawling with bottom trawls began in the early 1900s (Gabriel, et al., 2005). Trawls that
fish completely off-bottom, including the doors, are known by several names: pelagic trawls,
midwater trawls, or off-bottom trawls. They are a relatively recent innovation, first used in 1948,
coinciding with, and relying upon, acoustic sensors to indicate their position (von Brandt, 1972).
The trawls differ in shape and design compared to demersal trawls and feature much larger
fishing circles and specially-designed pelagic doors to spread the net. They generally represent a
substantial increase in complexity in design, construction, and operation compared to demersal
trawls.

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Perhaps due to this complexity, commercial pelagic fishing for groundfish species is rare. It
occurs in the Baltic Sea for Atlantic cod (Madsen, 2007), and in the Bering Sea for Alaskan
pollock (Gadus chalcogrammus) (Erickson et al., 1996). Semi-pelagic and pelagic trawling for
haddock and other groundfish has been attempted in Norway in recent years but was abandoned
after target species were found to be too sporadic and unpredictable (S. Rosen, Institute for
Marine Research, pers. comm.).
An additional potential benefit of the development of pelagic trawls is eliminating bottom
contact from the trawl doors and reducing or eliminating other contact by the ground gear of the
net. Vessels using pelagic trawl gear would thus have broader access to fishing areas on Georges
Bank than bottom tending gears (NOAA Fisheries, 2020), and therefore more areas to find
sporadic, but highly concentrated haddock.
In this project, our goal was to test two candidate off-bottom trawls (OBTs) proposed by
fishermen and designed to harvest Georges Bank haddock along with redfish (Sebastes fasciatus)
and pollock (Pollachius virens), while simultaneously avoiding overexploited fish stocks, mainly
Atlantic cod, yellowtail flounder (Limanda ferruginea), and windowpane flounder
(Scophthalmus aquosus). The combined biomass of the Georges Bank haddock, Gulf of Maine
haddock, pollock, and redfish stocks currently constitute more than 90% of the overall
groundfish biomass observed in NEFSC spring surveys and only small fractions of their
respective annual catch limits are landed. (NEFSC, 2017). In addition to possibly increasing
access to these healthy stocks, because of their design, OBTs can eliminate impacts to benthic
habitat.
Our project objectives were:
• Share knowledge and experience among our team of regional fishermen and gear
scientists to evaluate two candidate off-bottom haddock trawls.
• Evaluate the ability of two OBTs to land abundant groundfish mainly including haddock,
redfish, and pollock while eliminating landings of Atlantic cod, yellowtail flounder, and
windowpane flounder, including comparisons of these nets to existing haddock trawls.
• Evaluate the ability of two OBTs to eliminate impacts by trawl gear on EFH.
• Comprehensively describe OBT geometry under a variety of operating conditions.
• Evaluate the applicability of OBTs to the groundfish fleet.
• Share results of OBT performance and experiences broadly to the wider fishing fleet and
other stakeholders.
Approach
This project tested two experimental net designs - the off-bottom trawl 1 and 2 (OBT1 and
OBT2) (Figure 1). For each experimental design, we conducted two at-sea field efforts: a gear
tuning trip followed by a catch comparison research trip. Due to the higher complexity of fishing
off-bottom, the gear tuning trips preceded comparisons of catch in order to understand and
control the geometry and performance of the experimental nets, gain familiarity with setting,
hauling, and fishing the gears, and to identify problems that could have otherwise been avoided
by on-shore adjustments. Gear tuning was not constrained by fish availability and therefore,

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tuning trips were conducted closer to port, reducing steam time at the start and end. Also, if a
problem occurred, such as a major tear in the net, repair work can be completed on land as
repairing these large nets are particularly challenging on the relatively small decks of a trawler.
Catch comparisons required working in areas further from shore in deeper waters where haddock
are available.
This approach differed from the original plan, which was modified after withdrawal of industry
co-PI Odlin, whose contributions were necessary for both experimental comparisons and
extensive industry testing of the OBT2 design. The withdrawal of his in-kind support for testing
made the original plan unfeasible. Using available resources from co-PI Phillips, the original
plan was revised and implemented after approval of Saltonstall-Kennedy Program staff.
Figure 1: Top-down chronological flow diagram of fieldwork as conducted.
All fieldwork was conducted on-board Capt. Phillip’s vessel, the F/V Illusion, a 25.3 m (83 ft),
745.7 kW (1000 hp) groundfish Western-rig commercial trawler with stern ramp and two net
reels.
Nets and Gear
Both OBT nets were built with meshes greater than 3.5 m in the front end, and made with 8 mm
color-coded “helix” twine, an innovative twine that incorporates a thinner twine twisted along
the surface of a thicker twine to produce lateral hydraulic forces, resulting in self-spreading of

10
the meshes (Gloria: Self Spreading, 2015; Kebede et al., 2020) (Figures 2 and 3). The direction
of the spreading force is altered by changing the rotation of the surface twine (clockwise or
counterclockwise). Colored threads within the twine identify their twist direction (red and green)
(Figure 2). Separate colors were further used to simplify construction and repair. Each of four
panels at the front end of the net was denoted by color: yellow on the bottom panel, blue on the
top, red on the starboard-side, and green on the port-side. Using this system helped ensure that
all twines in the same panel were producing spreading forces in the desired directions – all
outward to help expand the net.
The panels were formed from very large meshes at the front of the nets that were constructed in
an unusual manner. Each bar of each mesh was constructed from the appropriate type of twine,
cut to length, and swaged with loops at each end (Figure 2). The loops were joined by lashing
four of them together to form each diamond mesh (Figure 3).
Figure 2: Helix twine sections for the OBT1 from the bottom (yellow) panel with markings
delineating the direction of coils, clockwise (red; bottom) and counterclockwise (green; top).

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Figure 3: Four starboard (red) panel twines connected by eyes to form meshes for the OBT1.
From left to right – project collaborators Tor Bendiksen (Reidar’s Manufacturing), Captain
Mark Phillips (F/V Illusion), and Pingguo He (SMAST).
The net diagram in Figure 4 depicts the control net, the Ruhle trawl (Beutel et al., 2008). This net
used a PE 15.2 cm (6.0”) diamond-shaped mesh codend, double twine, 50 meshes deep and 60
meshes on the round with chaffing gear. We used 36.6 m (120 ft) ground cables and 73.2 m (240
ft) legs to connect the trawl doors and the wingends. The trawl has a 42.82 m headline with
fifteen, 8” floats and a 51.4 m, 3” cookie groundgear. Three kite panels (39.7 cm x 33.0 cm)
were located along the center of the headline to help provide lift to the headline.
The OBT nets were equipped at the back end with 13 cm (5.1”) square mesh-sized codends and
composed of braided 5.5 mm PE double twine, 150 bars deep, and 80 meshes on the round which
was compared against the control net’s standard 15.4 cm (6.0”) diamond mesh codend. The 13
cm mesh size was selected to emulate prior research by Capt. Odlin, and to match the Canadian
fishery across the Hague Line
1
(Finley et al., 2019); this mesh size was also easily obtainable
from netting manufacturers. Chaffing gear was used on all codends.
1
The mesh size in use in the Canadian fishery on Eastern Georges Bank has since decreased to
12.5 cm (4.9”).

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Figure 4: Net plan for a Ruhle trawl.
Meshes at the front end of all nets could not be measured using conventional gauges due to their
large openings. Meshes in the codends for the Ruhle trawl and OBT nets were measured during
the first comparative research trip wet, and inside the mesh from knot-to-knot using an Omega
Gauge following recommended procedures (Fonteyne, 2005); this procedure includes measuring
both cross dimensions for square meshes. The same codend was used on both OBT nets during
comparative research.
Nets were spread using 3.0 m2 Gull Wing doors (Net Systems, AK, USA), configured to fish
either on the bottom when pulling the Ruhle Trawl or off-bottom when pulling the OBT nets. A
detailed description of door configurations used during fieldwork is presented in Appendix 1.
Environmental data (wave height, wind speed, and weather conditions) were observed and

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recorded on all tows on all four trips. For each tow, set time (when trawl winches were locked in
place) and retrieval time (when winches began hauling) and location, depths at start, initial warp
wire set, and tow speed were recorded. For trips 2-4, we also recorded the depths at end of tows
and RPMs of the vessel soon after start of tows. Position and speed data were provided by the
vessel’s Northstar 6100 GPS. Depths during towing were acquired from a Simrad Fisheries ES70
split-beam sounder (38 and 200 kHz).
Riggings, structures, and positions of each gear type in the water column and presence of fish
around the gear on the two tuning trips were observed using three cameras: a GoPro Hero 3+
Black in a deep-water Sartek housing, and two low-light cameras: Deep Sea Power and Light
(DSP&L) Wide-I SeaCam and a DSP&L Low-Light SeaCam. The low-light cameras were used
without illumination to avoid creating an artificial light stimulus. The GoPro camera required
additional lighting at depth so two EBL-1200D Sartek LED lights with uniform lumen intensity
and a 60° light beam angle were used to provide illumination. Video from GoPro cameras was
recorded on SD cards. Video from the low-light cameras was recorded onto the FishCam unit, an
underwater recording system consisting of a single-board computer with custom software,
battery supply, recording media, sealed in a deep-water titanium housing (Integrity Systems,
Massachusetts, USA). Details of camera models used, placement locations, time of videos, and
viewing subjects are provided in Appendix 2.
Gear rigging and gear geometry were monitored and recorded using acoustic net sensors (Table
1). Distance between the trawl doors (door spread) of all nets was measured on all trips by a
Simrad Fisheries ITI (just Simrad for short; Seattle, Washington) acoustic net mensuration
system with a hull-mounted hydrophone. Additionally, on trips 2-4, we had access to a Simrad
headline sensor to obtain the headline height off the seafloor, and headline to footrope distance
(vertical opening). We were unable to automatically log Simrad data due to the age of the
system. As a result, logging on the first trip was by hand; for trips 2-4, we developed a semi-
automated logging system. Serial output from the F/V Illusion’s Simrad ITI system was viewed
in a command window on a Windows laptop connected to the ITI system via RS-232 using
PuTTY, a free and open-source terminal emulator, serial console, and network file transfer
application (developed by Simon Tatham, 1999; updated version used from 8/2019). The output
was in the form of individual comma-separated, sequential strings of numeric and text data
reported by each sensor. Time stamps and vessel position in latitude/longitude from the vessel
GPS and depth from the vessel’s echosounder in meters were also output as separate strings. The
output from the command window, encompassing the period the net was in the water, was
copied and pasted into text files, consisting of one or more tows, and named with the tow
number(s).

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Table 1: Net mensuration sensors used during each trip and for each net towed and their
associated measured geometries. Sensors listed in red provide a calculated geometry. The
number of tows that sensors were used are in parentheses.
A Notus net mensuration system (just Notus for short; Notus Electronics Ltd., St. John’s,
Newfoundland) with a portable hydrophone was used on trip 1 in addition to the Simrad system
(Table 1). Sensors were attached to the wingends of the net, the mid-points of the headline and
the footrope, and recorded the wing spread, the headline height from the seafloor, and the
vertical opening. Output from this system was logged to a laptop automatically by the
proprietary Notus Trawlmaster software.
Outputs from Simrad and Notus sensors were live-streamed during each tow using each
company’s proprietary software, and used by the captain to adjust the vessel’s speed, wire out,
and, between tows, gear configurations, to improve geometry and fishing performance. Using the
net mensuration live-feeds, the Captain attempted to keep the OBT nets’ footropes within one
meter from the seafloor.
RBR “Concerto” loggers (RBR Ltd., Canada) were mounted on both doors to measure depth and
accelerations in three dimensions (x, y, and z) on trips 1 and 3 (Table 1). Accelerations were
used to derive pitch and roll using standard formulas (see “Data Entry, Processing, and
Analyses” below). Door loggers were mounted so that both y-direction accelerations were facing
each other, towards the center of net. That is, doors tilting inward (roll) to the center would
register with the same sign (positive) for both loggers; tilting from parallel to the vessel direction
(pitch) would register as opposite signs. On some tows, RBR “Duet” loggers were mounted on
the headline and the footrope to measure depth and also height from the bottom (altitude) which
was corrected using the attitude (tilt) measurements (Table 1). RBR loggers were set to collect
data at one-second intervals.
Water temperatures were recorded by the RBR loggers and with calibrated TidBit loggers (Onset
Trip 1 Trip 3
Net OBT1 OBT1 Ruhle Trawl OBT2 OBT2 Ruhle Trawl
Door Depth RBR (10) RBR (6)
Door Spread Simrad (14) Simrad (14) Simrad (12) Simrad (3) Simrad (10) Simrad (9)
Door Attitudes RBR (10) RBR (6)
Headline Height
Notus (13) &
RBR (1)
Simrad (14) Simrad (4) Simrad (10)
Headline Depth RBR (7) RBR (11) RBR (11)
Vertical Opening Notus (9) Simrad (14) Simrad (4) Simrad (10)
Footrope Height
Notus (8) &
RBR (1)
Simrad (14) Simrad (4) Simrad (10)
Footrope Depth RBR (1) RBR (6) RBR (7)
Wing Spread Notus (12)
Bottom
Temperature
RBR (7)
RBR (4) &
Onset (16)
Onset (14) Onset (7) Onset (11) Onset (10)
Trip 2
Trip 4

15
Computers, Inc., Pocasset, Massachusetts) (Table 1). TidBit loggers were mounted on one or
both doors for each tow during the entire trips.
OBT1 Gear Tuning, Trip 1
The OBT1 (Figure 5) was modified by Reidar’s Manufacturing (New Bedford, MA) from an
existing net owned by Captain Phillips. The modified net was a four-seam midwater box trawl
with a 40.14 m headline and footrope and 28.41 m port and starboard side lines. The front end
was constructed of meshes made from the helix twine that decreases in mesh size towards the aft.
The largest helix twine bar lengths were 3.81 m (150”) at the wingends, graduating to 1.6 m
(64”) aft. The back-end of the trawl (the original net sections) was constructed of nylon twine
with five panels that reduce in mesh sizes and twine diameters towards the aft. The fishing circle
was 52 meshes around at 2.2 m (85”) sized meshes (4th sized meshes to the aft). No floats were
used on the headline of the OBT1. A canvas kite, 105 cm wide and 85 cm high, was attached
along a false headline to supplement lift generated by the helical twine. Adjustments to the top of
the kite were made using 10 links of a 11 mm long-link chain near the wingends of the net. The
kite was tested at different numbers of links during the tuning trip but was finally settled at three
links on tow 11 and remained this way for the remainder of trip 1 and for trip 2 (detailed gear
configurations are shown in Appendix 1). The footrope consisted of ½” chain. Steel bridles were
two legs (½” on top and ¾” on bottom) 36.6 m (120 ft) long leading to four legs (½” on the top
three legs and 5/8” on the bottom) also 36.6 m (120 ft) long.
The codend remained open during trip 1 (tuning trip) and no catch was retained.

16
Figure 5: OBT1 net plan

17
OBT1 Comparative Research, Trip 2
Comparative paired tows were conducted on this trip using the Ruhle trawl (Figure 4) and the
OBT1 (Figure 5), fishing over 24-hour periods. Two-hour duration tows were planned but were
increased when catches were light or shortened due to large catches or gear problems while
towing. Subsequent paired tow durations were matched to the extent possible. When paired, nets
were fished in an R-E-E-R (Ruhle (R) and experimental net (OBT1 - E)) alternating pattern for
approximately five days of comparative trials. The second tow of each pair was conducted along
roughly the same path although not directly on top of the prior tow’s path. Direction of paired
tows were at the discretion of the captain accounting for the lost time to return to the starting side
of the previous tow and the effects of different currents on the pair.
During the comparative research trips, all fauna in catches were identified and sorted. Most
species were weighed to the nearest 0.1 kg using a Marel M1100 (trip 2) or M2200 motion-
compensated bench scale (trip 4); or estimated quantitatively by weighing a subset of baskets.
For rare catches of some larger species, such as sharks, visual estimates were made. Midline
lengths of regulated groundfish species were measured to the nearest centimeter, with sub-
sampling of at least 100 fish lengths occurring as needed and available. Species of special
importance, such as protected species, were weighed, measured, or estimated quickly before
returning to sea when possible. Discarding did not occur while towing or during net retrieval or
deployment so that discarded catch would not end up in the active tow’s codend.
OBT2 Gear Tuning, Trip 3
The OBT2 was a Gloria Trawl 352 H2O design from Hampidjan (Iceland) (Figure 6). It was a
four-seam midwater trawl with a 96.6 m headline and footrope and 84.0 m port and starboard
side lines. As with the OBT1, the front end was constructed of meshes made from the helix twine
that reduced in mesh size towards the aft. The helix twine mesh lengths were 8.0 m (315.0”) at
the wingends and 4.0 m (157.5”) aft. The back-end of the trawl was constructed of nine panels of
either polyamide (PA), polyethylene (PE), or Magnet (MN, a type of PE) twine that reduced in
mesh sizes and twine diameters towards the aft. The fishing circle was 91 meshes around at 4.0
m (157.5”) sized meshes (2nd sized meshes to the aft). The ground gear was a 16 mm chain along
the footrope. Bridles were 18 mm Dynice (Dynema/Spectra) material and 60 m (196.9 ft) long
on the top and bottom. No additional flotation from floats or kites was used.

18
Figure 6: OBT2 net plan. The redfish belly panel (lower right) was an alternative, smaller mesh
in the lower belly panel and not used during this research.
The codend was the same as used on the OBT1 and, like before, for this gear tuning trip, the
codend remained open and no catch was retained.

19
OBT2 Comparative Research, Trip 4
On trip 4, we compared catches of tows between the Ruhle trawl (Figure 4) and the OBT2
(Figure 6) fishing over 24-hour periods. Two-hour duration tows were planned but were
increased when catches were light or shortened due to large catches or gear problems while
towing. A minimum of one hour was required to switch door configurations between the OBT2
and Ruhle trawl. For this reason and due to concerns for the crew’s safety while switching door
configurations at sea, paired tows were not practical. Instead, nets were switched before the first
tow of each day. We intended to perform the same number of valid tows for each net.
Catch processing and data collection procedures were identical to those followed for comparative
trip 2.
Data Entry, Processing, and Analyses
A customized Microsoft Access database was constructed for data entry, QA/QC, data
management and analyses. The database was used to manage all trip, tow, and species catch
weights and length frequency information. Other data, such as net mensuration data, were
imported into the Access database as tables, csv files, or as Microsoft Excel files.
Catch weights were adjusted by tow lengths (kg/hr) to equalize effort. Sub-samples were scaled
to the entire catch weight for analyses.
Catch weights of porbeagle sharks were visually estimated or derived from their total lengths
(when these data were collected) using calculations provided by the Northeast Fisheries Science
Center (https://www.nefsc.noaa.gov/nefsc/Narragansett/sharks/calc.html, accessed 06/2020).
Videos were collected in standard file formats and were spliced together by tow or other discrete
time event using Adobe CC Premiere. Some video became corrupted during retrieval from the
FishCam unit. In these cases, a variety of software tools were used to recover the files and
included FFmpeg (FFmpeg team), VideoRepair Tool (Grau GmbH Hardware & Software
Solutions), MediaInfo (developed by Jérôme Martinez, 2002), and HandBrake (HandBrake
Team). Video was reviewed using Adobe CC Premiere and VLC player (VideoLAN).
Simrad net mensuration text files were reshaped using the open-source data visualization and
analysis tool, R (R Core Team, 2018) so that each line had the prior time stamp appended to it.
The resulting data were then all saved into one comma-separated file. A second R script was then
used to separate each individual sensor output using its unique identifier into individual comma-
separated text files, named by the unique identifier for that sensor (e.g. IITDS, IIHFB). These
files were then imported by linking into the project database in Microsoft Access for QA/QC,
visualization, and analysis. Height of the footrope off the bottom was calculated from sensor data
during tows and in post-processing by subtracting the headline to footrope height from the
headline to seafloor height. When both distances reported the same value (i.e., the subtraction
equaled zero), it was assumed that the footrope was close to or contacting the seafloor.
Notus data, logged using Trawlmaster, was exported to an Excel file, and then imported into the
Access project database. Values of headline heights and vertical openings that exceeded 80 m,

20
the maximum depth encountered, were excluded from the data set as unrealistic. The mean
footrope heights off-bottom for tows were obtained by subtracting the mean vertical openings
from the mean headline heights.
Data from RBR loggers were off-loaded occasionally throughout trips to assess trawl
performance and at the end of each trip using the RBR Ruskin proprietary software, which was
also used to operate loggers. Analyses for RBR data were conducted with R.
Attitudes of RBR loggers mounted on fishing gear were provided as accelerations in the x, y, and
z directions. Roll and pitch were derived using the following equations provided by RBR Ltd.:
  
 

 
 

RBR Ltd. recommends limiting the denominator by values >0.025 (before the sign is applied)
due to the sensitivity limitations of the loggers’ accelerometers (pers. comm.).
No gravity vector exists in the x and y planes (the yaw component accelerations). Changes in
these planes cannot be stabilized by the internal gyroscopes and therefore produce large
variations in yaw. For this reason, yaw is not available.
Tilt is also calculated to determine the resulting angle based on the roll and pitch together. When
deployed on the headrope, the sensor’s tilt was used as a correction factor to determine the
vertical distance from the footrope to the seafloor using the Pythagorean theorem to remove any
deviation from the vertical.
  


Data from Simrad, Notus, and RBR were trimmed from the start of tows when the warp wire was
locked during the set to allow the gear to settle and stabilize, to the start of net retrieval. Onset
TidBit data were cropped five minutes after the start of tows based on prior experience to allow
the logger to acclimate to ambient temperatures.
Data visualization and analyses were conducted with R and Excel. Box and whisker plots
(McGill et al., 1978) were drawn using the 25th and 75th quantiles as lower and upper limits
(interquartile range, IQR) of the box, and a bar within the box representing the median of the
dataset. Whiskers are drawn to end at observed values at most 1.5 times the length of the IQR.
Points plotted beyond the whiskers are greater than 1.5 times the IQR and may be considered
outliers (Sokal and Rohlf, 2000). Outliers removed for readability are noted in figure captions.
Box widths are proportional to the square roots of the sample sizes within each grouping when

21
indicated in plots.
When alternate tows were possible (i.e. trip 2), catch rates (kg/hr) of regulated groundfish
species and dominant species were paired. To graphically compare catches by trawl gear, equal
catch plots were used for selected species. Each point on the equal catch plot represents a pair of
tows, with the x-coordinate indicating the catch rate for the tow using the control gear (the Ruhle
trawl) and the y-coordinate indicating the catch rate for the tow using the experimental gear
(OBT1). All pairs of tows where a species was present in at least one of the tows are included.
The equal catch plots include a line denoting equal catch rates in both gears.
For species that did not show a distinct pattern between the gear types in the equal catch plots,
data were checked for normality using Q-Q plots (used as reference and not reported here) and a
Shapiro-Wilk Test (p<0.05). The non-parametric Wilcoxon Signed-Rank Test was used to test
for significance of difference (p<0.05) between the catch rates in the two gears if the tests for
normality failed. For normal data, equal variance was first investigated (p<0.05) and then a
paired t-test was applied to check for significance between catches within gear types (p<0.05).
Two-sided tests were applied to haddock, redfish, and pollock (if caught in abundance) as the
experimental and control gear types were hypothesized to catch equally for these species; one-
sided tests were applied to species where reductions were anticipated.
For non-paired data (i.e. trip 4), catch data were pooled. Species caught within the general region
(Eastern Georges Bank) were identified and considered to be available to all tows. Zero catch
rates were applied to tows without that species. As with the paired data, Q-Q plots (again, used
as reference and not reported here) and a Shapiro-Wilk Test were used to check for normality
(p<0.05) in the catch rates, a Wilcoxon Rank Sum Test was used to test for significance of
difference (p<0.05) of non-normal data, and equal variance was investigated (p<0.05) for normal
data followed by the appropriate two-sided or one-sided t-test (p<0.05).
Mean catch/hour for each species was determined for pooled data and displayed using equal
catch plots showing all species for a region. Log10 scales were used for presentation purposes
and one was added to all catch rates to account for zeros on the log scale.
Length frequencies were compared using box and whisker plots for species whose mid-line
lengths were measured. Only commercially important groundfish species and those that were
considered important for this project are presented. Length-based differences by species were
explored for trip 2 paired data, using generalized linear mixed models (GLMMs) to fit low-order
(third or less) polynomials to the proportions of catch-at-length in the experimental net compared
to the total catch at length (Holst and Revill, 2009). Lengths of sufficient strength (i.e. where the
total count at length was >5) were used as a fixed effect, and haul was a random effect. Where
subsampling occurred, an offset (intercept term) equal to the proportion of the subsample was
used. A binomial link function was used to fit the most complex model, followed by decreasing
complexity. Model terms were assessed for differences from zero with Wald tests at a level of
p<0.05. GLMM analyses cannot be completed for the pooled data from trip 4.

22
Project Management
Actual tasks performed by individuals are listed in Table 2. Staffing changed as the project
evolved. All participants listed were PIs at some point over the course of the project except for
Aaron Whitman (GMRI), who was integral to the completion of the fieldwork. Steve Eayrs left
his position at GMRI and his duties were transferred to Adam Baukus. Baukus later switched
positions at GMRI and relevant duties were transferred to Aaron Whitman. James Odlin sold his
groundfish vessels that were integral to the original proposed project and opted to not continue
participation in the project. Fieldwork originally planned with Odlin’s involvement was
restructured to Captain Mark Phillips (F/V Illusion). Changes to this project’s design are detailed
in the section “Evaluation and Discussion: Modifications to Goals and Objectives”.
Table 2: List of participants and associated tasks. “OBT1”and “OBT2” refers to tasks only
associated with those gear types while “Both” refers to both gears. Outreach is on-going and is
therefore to be determined “tbd”.
Findings
Organizing meetings of project participants were held to initiate the project and to familiarize
participants with each other. Communication and job responsibilities, contracting, permitting
requirements, timing and locations for fieldwork, fishing equipment construction, and equipment
acquisitions were reviewed, revised, and discussed. Following the initial meeting, occasional
meetings were held at various locations to view progress of gear constructions and other
activities. Equipment was upgraded and repaired as necessary before, during, and after
fieldwork. Multiple participant meetings were held during and after fieldwork operations to
provide project updates and to strategize activities moving forward, especially to adapt project
Task
Mike
Pol
Steve
Eayrs
David
Chosid
Mark
Phillips
James
Odlin
Pingguo
He
Adam
Baukus
Aaron
Whitman
Project concept/proposal Both Both Both OBT1 OBT2 Both
Sampling design Both Both Both Both
Project coordination Both OBT2 Both OBT2
Gear and equipment purchases OBT2 Both OBT2 OBT2
Gear maintenance Both OBT2
Observer training
Permit acquisitions OBT2 Both
Vessel operation Both
Comparative testing OBT1 OBT2 Both
Video sampling Both
Sensor and net testing Both Both Both
Administrative invoicing Both
Data entry Both Both
Data analyses Both Both
Report writing Both Both
Outreach tbd tbd
Participants

23
activities after PI departures and changes.
Appropriate permits and authorizations were obtained during the project. A NMFS Letter of
Acknowledgement (LOA; DA17-065) was acquired on 8/3/17 to conduct research using a 5.1”
codend with the OBT1 to temporarily possess fish and to gain access to the Haddock Special
Access Program (SAP) area and Closed Areas 1 and 2. This LOA was later reissued on 6/6/18
(DA18-037; see “Evaluation and Discussions: Modifications to Goals and Objectives”) to extend
the time period. A third LOA was granted on 3/20/19 (DA19-009) to conduct similar research
with the OBT2.
Meshes were measured for both the control and experimental codends used during trips 2 and 4.
Square mesh dimensions (inside, knot-to-knot) for the codend were measured for a mean of
121.7 mm (S.E.=1.2 mm) and 118 mm (S.E.=1.4 mm), smaller than the nominal 129.5 mm
(5.1”) mesh size. The Ruhle trawl used diamond-shaped meshes in the codend of 150.5 mm
(S.E.=0.4 mm), which was slightly smaller than the expected 152.4 mm (6”) mesh size.
Four fieldwork trips were completed as planned in our revised statement of work. Dates of trips
and numbers of tows with each gear are presented in Table 3 along with descriptive statistics for
operational data: duration over the entire tow, speed, RPM, depth, and wire out near the start of
the tow. Trips 1 and 2 were completed as planned. Trip 3 ended sooner than desired due to
damage of the OBT2 net from a basking shark, despite the open codend. The damage was
extensive and was repaired at the dock. Trip 4 could not be delayed due to limiting time conflicts
among the PIs before the end of the grant and was ended one day early as the final day would
have resulted in landing on a Friday, when fish sales were not possible and any fish stored in the
hold would have lost value from decreasing quality.
Table 3: Trip and tow information (at start) for each trawl type. S.E. = one standard error.
Tuning trips (1 and 3) generally required shorter tow durations than comparative research trips
and occurred at shallower depths and therefore, needed less wire out (Table 3). All nets started
tows with a mean warp wire to depth ratio of approx. 3:1. Speed, RPM, and wire out were often
changed during tows to maintain net height, adjust the door spread, or to maintain the depth to
wire out scope as the depth changed. These changes are reflected in larger standard errors.
Speed was not significantly different for the OBT1 on trips 1 and 2 (Table 3). RPMs were not
collected on trip 1. Trip 2 revealed a significantly higher speed while using the OBT1 over the
Trip Date Left Date Returned Net Tows (#) mean S.E. mean S.E. mean S.E. mean S.E. mean S.E.
1 8/31/2017 9/2/2017 OBT1 17 0.6 0.1 3.4 0.1 41.5 3.2 123.7 4.8
OBT1 16 1.8 0.1 3.4 0.1 1316.4 20.4 83.1 3.8 240.8 10.7
Ruhle 14 1.9 0.1 3.0 0.1 1293.0 26.1 83.5 4.0 261.3 8.9
3 9/16/2019 9/18/2019 OBT2 7 0.3 0.1 3.4 0.1 1589.0 16.1 77.0 2.7 218.1 35.0
OBT2 11 2.1 0.2 3.3 0.1 1582.0 23.6 117.7 7.6 373.2 24.6
Ruhle 10 1.9 0.1 3.2 0.1 1299.0 13.4 107.5 7.6 322.8 18.2
2
8/9/2019
8/15/2019
4
9/20/2019
9/26/2019
Tow Duration
(hours)
Tow Speed
(knots)
Tow RPM
Tow Depth
(m)
Wire Out
(m)

24
Ruhle trawl but RPMs were not significantly different. This difference in speed is likely due to
lower drag while using the OBT1 allowing the captain to set a standard RPM (resulting in
different speeds). Wire out was also slightly significantly larger for the Ruhle trawl than the
OBT1, again adding to additional drag. Depth was not significantly different during this trip.
Speed and RPMs were not significantly different for the OBT2 on trips 3 and 4 (Table 3). The
Ruhle trawl required significantly fewer RPMs for its optimal door spread when compared
against the OBT2 on trip 4. While depth was not significantly different for these two nets, the
amount of wire out was significantly larger for the OBT2 also adding to drag and requiring more
RPMs to maintain speed.
Fieldwork was conducted in two general locations (Figure 7). For gear tuning, selected locations
were chosen based upon the minimum working depth required for the OBT nets (Table 3). Trip 1
was conducted at a location relatively close to port in southern New England waters with depth
workable for the OBT1 (mean: 41.5 m). Tuning for OBT2 during trip 3 occurred at deeper
depths (mean: 77.0 m) on Georges Bank (in the most southerly location). Even greater depths
were sought for comparative research trips in Georges Bank to obtain the proper door spreads
and for the nets to fish as expected. On trip 3, this depth proved to be insufficient to achieve the
desired spread of the OBT2.

25
Figure 7: Start point locations of tows during all trips. Trip 1= blue; trip 2= red; trip 3= green;
trip 4= purple. The key shows symbols for gear types used. Sections in green are regulated
closed areas.
Seventy-five tows were completed overall; all but 4 were considered to be valid (Table 4). Tow
18 on trip 2 using the OBT1 was aborted early due to battery failure in the Simrad headline
sensor, necessary to keeping the net stable and at the desired height. Tow 1 on trip 3 using the
OBT2 was aborted near the start as the net was too close to the bottom; the captain adjusted the
doors after this tow (Appendix 1). One tow for each net was not valid on trip 4. On tow 1 using
the OBT2, the captain sensed something had damaged the net during the tow. After the net was
brought on-board, large holes were found in the side panels and smaller holes in the top panel
towards the aft. On tow 20, using the Ruhle trawl, an estimated 15,900 kg (35,000 lbs) of spiny
dogfish (Squalus acanthias) were caught, too much weight to be safely brought up on deck. This
catch was released while the net streamed behind the vessel.

26
Table 4: Number of total tows and valid tows for each trip and net.
Thirteen catch comparison tows of the OBT1 and the Ruhle trawl were paired successfully by
gear type on trip 2. On trip 4, delays from adjustment of the gear rigging between the OBT2 and
Ruhle trawl and vice versa necessitated pooling of valid tows by gear type over the entire trip,
instead of pairing.
Fish were retained on deck and landed on comparative research trips 2 and 4; the codend
remained open on gear tuning trips 1 and 3. The captain targeted haddock during each
comparative research trip but did not avoid other species in order to show the difference in target
catches and non-target catches between compared nets.
Gear Modifications
Tuning trips (trips 1 and 3) were intended to work out appropriate rigging for each experimental
net. Despite this tuning, maintaining proper height off the bottom was challenging during
comparative research trips (trips 2 and 4). Consequently, based on previous experience with
pelagic trawls, Captain Phillips felt that both experimental nets required weight added near the
wingends to improve stability during comparative trips. For this reason, drop chains were added
forward of the wingends at the lower bridles for the OBT1 and to the triplates for OBT2 (Figure
8). Each chain link used was 4.4 kg for the OBT1 and 7.6 kg for the OBT2. The OBT2 chains
were attached via approximately 2 m length, 3/8” chains connected to the heavier chains. Tow-
by-tow details of the chain additions are provided in Appendix 1. The added drop chains often
showed shine post-tows, presumably from bottom contact. These events were not quantified and
only occasionally noted for evidence of the nets’ contact to the bottom.
Following these adjustments, net stability continued to be a concern, and minor adjustment of net
rigging, tow speed, wire out, and other variables continued throughout much of the field work.
Trip # Net Total Tows Valid Tows
1 OBT1 17 17
OBT1 16 15
Ruhle Trawl 14 14
3 OBT2 7 6
OBT2 11 10
Ruhle Trawl 10 9
2
4

27
Figure 8: Drop chains added to the OBT1 lower bridle (left) and the OBT2 triplate (right).
OBT1: Gear Tuning (Trip 1) and Catch Comparison (Trip 2)
OBT1 Video and Mensuration Results
Gear tuning of the OBT1 on trip 1 was partially achieved using underwater video collected
during 10 tows and viewed afterward to make adjustments on subsequent tows. We imaged the
OBT1 kite on the headline, the large meshes just behind the center chain sweep, and the chain
sweep in relation to the bottom (details of video files presented in Appendix 2). From the video,
a final position of the kite was set at three links (Figure 9). Visibility of the seafloor on the video
was used to determine the most effective operational configuration of the doors (Appendix 1).
An acceptable gear configuration was achieved on tow 11 of trip 1.
No underwater video of nets was taken during trip 2, which was dedicated to comparative trials
of the OBT1 v. the Ruhle trawl.

28
Figure 9: Underwater video snapshots of OBT1 looking at the kite rigged with a three-link
extension (left) and along the footrope while towing close to the seafloor (right).
Extensive data were collected for net geometry during the OBT1 tuning trip (trip 1) and the
OBT1 catch comparison (trip 2). We obtained door spreads from Simrad sensors from 14 tows
for trip 1 and 26 tows for trip 2 (Figure 10). Trip 1 door spreads were similar (boxes of box and
whisker plots overlap) for most tows, especially after tow 8. The trip’s median door spread was
about 64 m. Door settings were changed after the larger door spreads on tow 1 of this trip and
appeared effective at reducing spread. It is unknown why tow 16 had a larger door spread. The
OBT1 door spreads were much smaller in trip 1 than in trip 2, likely due to setting less wire out
due to the much shallower depth of trip 1 (Table 3).
Trip 2 median door spreads for the Ruhle trawl were generally larger than for the OBT1 (91.3 m
v. 82.5 m) but largely consistent within gear type. As noted above, persistent attention was
required to maintain a steady door spread while using the OBT1 by making small adjustments to
the RPMs, especially prior to the addition of drop chains. This level of attention was not required
while using the Ruhle trawl, perhaps due to bottom contact by the doors.

29
Figure 10: Door spreads (y-axis) by tow (x-axis) and trip (panels) from Simrad net mensuration.
Boxes are colored by net type (green=OBT1, blue=OBT2, pink=Ruhle trawl). Dashed lines are
the panel medians and colors of dashed lines match the associated net type. Box widths represent
the sample sizes within tows. Trip 1, tow 5 only had a single data point (23.8 m) and was
removed since it cannot be represented in box and whisker plots.
Roll and pitch of both trawl doors using OBT1were measured on trip 1 during 10 tows using
RBR loggers (Figure 11). On most tows, pitch and roll for both doors were not significantly
different from zero. The port door pitch and roll during tow 10 and the starboard door pitch
during tow 16 appeared to be different from the rest, although the medians were still close to
zero. We are unaware of what caused deviations in these tows, but as noted above, tow 16 also
showed abnormally large door spreads (Figure 10).

30
Figure 11: Pitch (forward or backward tilt) and roll (inward or outward tilt) angles (y-axis) of
port door (left, light blue) and starboard (stbd) door (right, pink) for tows (x-axis) during trip 1
while using the OBT1 from RBR loggers. Roll is shown at top and pitch at the bottom. The y-axis
is restricted to -5° to 5° and the outliers are removed for presentation purposes. Box widths
represent the sample sizes within tows.
Door depths using the OBT1 were also collected during 10 tows on trip 1 from RBR loggers
located on each door and on the footrope and headline (Figure 12). Median door depths ranged
from 34.7 – 41.5 m for the port door and 34.2 to 42.6 m for the starboard door and were
generally similar for both doors as shown by the overlapping boxes of box and whisker plots.
The maximum median difference between each door depth occurred on tow 12 at 4.9 m. For this
tow, the difference in door depths was as great as 7 m and persisted for more than 30 minutes
(within tow details provided in Appendix 3, Figure 29). Overall, whether the starboard or port
door was deeper was inconsistent between tows and within tows. It is unclear why this is the
case. Changes in depths of one door were usually accompanied by a similar change from the
other door and their depths were not usually significantly different by tow.

31
Figure 12: Door, footrope, and headline depths (y-axis) from trip 1 using RBR loggers for tows
(x-axis) using the OBT1. Panels show individual sensor values with outliers removed for scaling.
Dashed red lines are the panel medians. Box widths represent the sample sizes within tows.
Comparisons of door depths to headline and footrope depths for the OBT1 were possible due to
simultaneous deployment of the RBR loggers in three or more locations. The OBT1 headline
was measured to be about 6 m shallower than the doors (Figure 12). A vertical opening of OBT1
of approximately 15 m through simultaneous headline and footrope depth recorded on tow 14.
By comparing the relative depths of the doors, headline, and footrope recorded, the net is seen to
fish with the doors positioned about midway between the headline and footrope. This orientation
is more clearly visible in Appendix 3, Figure 29.
The headline and footrope were observed to vary in depth together, maintaining a mostly
constant opening, which suggests the net was off-bottom. That is, if the net was contacting the
bottom, the footrope would fluctuate with the topography, while the headline would more be
more consistent, resulting in a varying opening. Median height of the footrope from the seafloor
during tow 14, corrected for tilt, was 5.1 m (Figure 13). Maximum adjustment due to the tilt of
the logger was small (0.22 m).

32
Figure 13: Footrope height (m) from the seafloor (y-axis) of the OBT1 during tow 14 (x-axis) on
trip 1, corrected for tilt. Missing values indicate no data from the RBR logger’s sounder. The
dashed red line is the median.
Additional information on OBT1 wing spread, headline height, and vertical opening were
collected on 14 tows during trip 1 using Notus sensors (Figure 14). The first 11 tows were used
to try out different gear configurations; tows 11 and afterward were in the preferred OBT1 gear
arrangement. Median headline heights varied greatly from tow-to-tow, and were generally from
17-32 m. Tows 4 and 5 were unusual: tow 4 was only eight minutes long and was composed of
four data points; tow 5 had a much lower median headline height of 6.7 m for unknown reasons.
The headline height became somewhat more stable and consistent within and between tows after
tow 11 when the median vertical opening varied between 14-18 m. This opening is consistent
with heights derived from the RBR loggers (Figure 12). The vertical openings are more stable
than the headline heights for tows 12-17, with the exception of tow 15, which had a smaller
vertical opening (the box of the box and whisker plot does not overlap the adjacent boxes). Wing
spread measurements generally varied around 18 m for all tows except tow 6 which was slightly
less. Within-tow details of OBT1 net mensuration using the Notus system are provided in
Appendix 3, Figure 30.
Ranges (distance from Notus sensors to the hydrophone) from 14 tows were as expected and
gave further information on the net geometry regarding the distances from the wingends to the
headline through subtraction. Means and standard errors of ranges to the headline sensor and
wing sensors were 212.0 ± 0.5 and 199.8 ± 0.4, respectively.

33
Figure 14: Headline height, vertical opening, and wing spread (y-axis) for tows numbers (x-axis)
from trip 1, OBT1 from Notus net mensuration. Dashed red lines are the panel medians. Box
widths represent the sample sizes within tows.
Footrope height for each tow was calculated from Notus data when available as the difference of
the mean distances of the headline heights and mean vertical openings (Figure 15). The preferred
mean footrope heights (<2 m) was achieved during tows 12, 13, and 17.
Figure 15: Mean footrope height per tow from trip 1 for OBT1.
Headline heights collected from the vessel’s SIMRAD ITI system on trip 2 for tows using the
OBT1 were similar (overlapping boxes of box and whisker plots), with medians of about 12 m,
except for the first one using the OBT1, tow 4 (Figure 16, bottom row). Headline heights for
OBT1 measured using this system on this trip were lower than heights measured during the
tuning trip (trip 1) (Figure 14).
The vertical opening for OBT1 on trip 2 stabilized to about 12 m after tow 4 (Figure 16).
Footrope heights were often <1 m to the bottom for the OBT1, particularly later in trip 2,
suggesting that the footrope was often on or near the bottom. The vertical opening measured in
trip 2 was also smaller, and the footrope was likely closer to the bottom than in trip 1 (Figure
14).
Within tow details of the Simrad mensuration data over time are presented in Appendix 3, Figure
31.

34
Figure 16: Headline height, vertical opening, and footrope height (columns) for the OBT1 (blue
boxes) and OBT2 (pink boxes) on trip 2-4 (rows) for tow numbers (x-axis) for Simrad data.
Dashed red lines are the panel medians. Box widths represent the sample sizes within tows.
On trip 2, headline or footrope depths were collected during 15 tows from RBR loggers for the
OBT1 (Figure 17). Both depths were collected on tows 11 and 14 and showed a very consistent
net opening of about 12-13 m over the course of the tows, and a headline depth around 80 m.
Within tow details, provided in Appendix 3, Figure 32, captured two unusual events. At the start
of tow 6 on this trip, the depth of the net was reduced for a period due to a hang. An abrupt
reduction in the net’s depth occurred on tow 21 which likely coincided with a hard change in
direction of the vessel and a change in bottom depth.

35
Figure 17: Footrope (left) and headline (right) depths (y-axis) for OBT1, trip 2 from RBR
loggers by tow (x-axis). Dashed red lines are the panel medians. Box widths represent the
sample sizes within tows.
Tidbit temperature loggers were placed on doors for the OBT1 trips to record bottom
temperatures but the logger failed on trip 1 (Table 5). Bottom temperatures were gained from
seven trip 1 tows from the RBR Duet logger placed on the headline. Bottom temperatures varied
between trips 1 (mean of 15.0° C) and 2 (mean of 8.6° C) and were generally consistent within
these trips. The warmer bottom temperatures on both tuning trips may be related to shallower
depths and differing locations and regions.
Table 5: Temperature means, standard deviations, and standard errors during tows on each trip.
OBT1 Catch Results
OBT1 and Ruhle trawl catch comparisons during trip 2 resulted in catches greater than 3 kg of
twenty-two species and taxa (Table 6). Total weight of all species caught was 9,152 kg. Haddock
was the primary catch species, comprising 68.1% of the total weight captured. The next largest
catches by weight were short-fin squid, (7.5%), porbeagle sharks (6.6%), winter skate (5.7%),
monkfish (3.4%), spiny dogfish (3.0%), and barndoor skate (2.3%). Only 1.5 kg of Atlantic cod
were caught using the Ruhle trawl and none in the OBT1 net. Total flatfish catches in both nets
comprised 80.7 kg, mostly of grey sole. Aside from haddock, for the other species that this
project was intending to target, pollock were barely captured (0.8 kg) and redfish were not
caught during trip 2.
Trip # Logger
Logger
Placement
Mean
Standard
Deviation
Standard
Error
1 RBR Headline 15.0 0.7 0.0
2 TidBit Door 8.6 1.9 0.0
3 TidBit Door 12.8 3.5 0.3
4 TidBit Door 8.6 2.4 0.1
Temperature (°C)

36
The only large pelagic species caught was porbeagle sharks (Lamna nasus) - six in the Ruhle
trawl and three in the OBT1 (Table 6).
Table 6: Catch weights (kg) by species and net for trips 2 and 4. Species with total weights from
all trips <3 kg are excluded.
We compared mean catch rates for 14 valid tow-pairs on trip 2 by net type and species using
equal catch plots (Figure 18). Haddock catch rates were highly variable in both the OBT1 and
the Ruhle trawl, ranging up to 259 kg/hr. There were no tow-pairs where haddock was caught in
one net, but not in the other. For other species, most were clearly caught at higher rates with the
Ruhle trawl, as illustrated by points below the equal catch lines. The highest catch rate of any
non-target species in the OBT1 was about 5 kg/hr, while rates as high as about 70 kg/hr were
observed in the Ruhle trawl. Some species were caught at very low rates in both nets such as cod,
pollock, and yellowtail flounder.

37
Figure 18: Catch rates (kg/hr) for selected species (panel) by tow-pairs during trip 2. The y-axis
shows the catch rates for OBT1 and the x-axis shows the corresponding paired catch rates for
the Ruhle trawl.
Mean catch rates of haddock and American plaice were not significantly different in the OBT1

38
than the Ruhle trawl during trip 2 (Table 7). Mean catch rates of monkfish, grey sole, barndoor
skate, and little skate were significantly lower in the OBT1. Catch rates of other important
commercial species that had catches in the Ruhle trawl but zero catch in OBT1 included winter
flounder, Atlantic cod, American lobster, and winter skate and therefore, no tests needed to be
completed to demonstrate differences in catch by this gear type (Figure 18 and Table 6). Pollock
were not caught in the Ruhle trawl and were in low amounts in the OBT1 and yellowtail flounder
catches were also very low so tests for significance were not conducted on these commercially
important species.
Table 7: Test statistics for significance comparing species’ catches between the experimental
nets (either OBT1 for trip 2 or OBT2 for trip 4) and the Ruhle trawl. Tests are applied as
appropriate or not applicable “na” if not. “Sided” describes if tests are one-tailed or two-tailed.
Values in green are not significantly different (α=0.05); values in red show significant
differences. Gray values are species with a zero catch in at least one net.
Length frequency distributions show no significant differences between nets for all commercial
species measured in adequate numbers in trip 2 tow-pairs (Figure 19). Most individuals were
generally over the minimum legal sizes (MLSs) as illustrated by medians to the right of the lines
showing MLSs. In both nets, most haddock caught were 0-5 cm larger than the MLS. Sub-legal
yellowtail flounder were caught only in the Ruhle trawl and legal ones were caught in both;
American plaice above and below the MLS were caught in both nets. Only one pollock was
caught; it was below MLS and in the OBT1. Also, only one Atlantic cod, above MLS, was
caught in the Ruhle trawl. Lengths of porbeagle sharks were collected but are not reported here.
Monkfish lengths were not collected on this trip.
Species Sided
Wilcoxon
Signed-Rank
Welch Two
Sample t-test
Wilcoxon
Rank Sum
Welch Two
Sample t-test
Haddock two na 0.27 na 0.79
Monkfish one 0.01 na 0.04 na
Grey Sole one na 0.02 0.15 na
American Plaice one 0.18 na 0.18 na
Barndoor Skate one 0.01 na 0.01 na
Winter Skate one 0.03 na
Little Skate one 0.00 na
No catch in either net
Trip 2 (paired)
No catch in OBT1
Trip 4 (pooled)

39
Figure 19: Lengths (x-axis) of species (panel) by gear type (y-axis) for trip 2. The red line is the
minimum legal size for each species. Box widths represent the sample sizes within gear type.
Only haddock were caught in sufficient quantities during trip 2 to examine length-dependent
differences using a GLMM (Figure 20). A 2nd order polynomial model was selected as the best
fit and no significant difference in proportion at any length between the two nets was found.

40
Figure 20: Best fit model (black line), confidence region (gray area) and observed proportions-
at-length (open circles) (top) and length frequency distributions (bottom) for haddock lengths (x-
axes) in the OBT1 and the Ruhle trawls during trip 2. All data are shown but points outside the
gray region in the top panel were not used in the GLMM. Dotted green lines are the MLS of
haddock.
OBT2: Gear Tuning (Trip 3) and Catch Comparison (Trip 4)
OBT2 Video and Mensuration Results
Attempts to collect underwater video of the OBT2 footrope above the seafloor on trip 3 were not
successful due to parting of the cable between the Wide-I low-light camera and the FishCam
recording device during the first video deployment (tow 4). No video was acquired on this trip.
A limited amount of video with a view from the footrope was captured on trip 4, which was
primarily intended for comparative testing of OBT2 v. the Ruhle trawl. The GoPro Hero3 Black
camera and flood lights were deployed on tow 1 only. Despite intermittent failure of one or both
lights, observable video shows the OBT2 footrope traveling over and near the seafloor bottom
following a brief period where the bottom is not visible (likely while the net is still setting). Near
the seafloor, fish were observed reacting along the pathway (Figure 21). Video confirmed that

41
the net could remain stable while close to the seafloor.
Figure 21: Snapshot of video from trip 4, tow 1 showing a red hake in front of the OBT2
footrope.
Door spread data for OBT2 were obtained for three tows for trip 3 and 19 tows for trip 4 from
Simrad sensors (Figure 10). Data from trip 3 were limited by failure of the headrope sensor and
fewer tows due to damage to the twine from basking shark catches. An initial median door
spread of 75.8 m on trip 3, tow 3 led to adjustments to the upper attachment points on the trawl
doors (top tow pads, see Appendix 1). A smaller median spread of about 64 m resulted for the
subsequent tows (4 and 7). During trip 4, median OBT2 door spreads were highly variable, in the
range of 65.6 - 83.8 m.
Differences between OBT2 door spreads in trips 3 and 4 may be due to the difference in depths
(and wire out) between trips (Table 3). Median door spreads while using the Ruhle trawl ranged
from 92.2 - 108.1 m, generally about 25 m larger than door spreads of the OBT2 (Figure 10).
The Ruhle trawl also demonstrated considerable variability in door spreads between tows.
Trawl doors depths towing the OBT2 were collected during 6 tows on trip 3 using RBR loggers
(Figure 22). Unexpectedly, doors were often at different depths from each other and between and
within tows, varying from tow medians of 33.8 – 66.2 m for the port door and 40.1 – 67.8 m for
the starboard door. Tow 4 had the largest difference of median depths between doors at 12.1 m.
Which door was deeper was not consistent between tows. Within-tow data displayed different
patterns on different tows: a constant large difference of depths for each door during tow 4, much
more than in other tows; little or no difference during tows 5 and 7; and inconsistent differences
between door depths in tow 2, 3, and 6 (Appendix 3, Figure 33).

42
Figure 22: Door depths (y-axis) for port (left) and starboard (right) doors for OBT2 on trip 3
from RBR loggers by tow number (x-axis). Dashed red lines are the panel medians. Box widths
represent the sample sizes within tows.
We attempted to measure roll and pitch angles for both doors on tuning trip 3 during six tows
using RBR loggers. Following review of the port-side door data with RBR Ltd. after the trip, it
was determined that this logger was likely damaged prior to usage and was providing false
readings. For these reasons, door attitude results are not presented for trip 3.
Headline heights for the OBT2 (four tows on trip 3 and 10 tows on trip 4; Figure 16) were
collected from the vessel’s SIMRAD ITI system. Headline heights on trips 3 and 4 were
surprisingly inconsistent with each other. The final trip 3 tuning tow for OBT2 showed a
headline height of about 16 m. On trip 4, headline height was relatively unstable until tow 9,
when the height stabilized at about 20 m following addition of weights to the wingends.
Similarly, vertical openings varied between and within trips 3 and 4 but stabilized in the second
half of trip 4 to about 20 m. Footrope heights were often <1 m or zero to the bottom for the
OBT2, particularly later in trip 4. Within tow details of these net mensuration results are
provided in Appendix 3, Figures 34 and 35.
Depths of the OBT2 headline and footrope were obtained during trip 4 from RBR loggers
(Figure 23). The median headline and footrope depths were 87.5 m and 95.1 m respectively and
vertical opening was very consistent within and between tows. The minimum and maximum
median difference of depths between those loggers (for tows where both headline and footrope
depths are collected) were 18.3 m and 22.9 m respectively, further supporting a net opening of
about 20 m as reported by Simrad results in Figure 16. For most tows, depths of both sensors
remained relatively stable. More outliers were produced during tow 15, especially for the
footrope and we are unsure what may have affected the net’s geometry. Within tow details of
these net mensuration results are provided in Appendix 3, Figure 36.

43
Figure 23: Footrope (blue) and headline (pink) depths (y-axis) of the OBT2 on trip 4 from RBR
loggers by tow number (x-axis). Dashed lines are the medians, colored by location. Box widths
represent the sample sizes within tows and sensor.
Tidbit temperature loggers were placed on doors for the OBT2 trips (Table 5). Bottom
temperatures varied between trips 3 (mean of 12.8° C) and 4 (mean of 8.6° C). The two tuning
trips and the two comparative trips with the different nets were similar, perhaps reflecting their
similar depths. Trip 3 also had the larger variance in temperatures compared with all other trips.
OBT2 Catch Results
Catches from trip 4 were similar in species composition to trip 2 but differed in weights (Table
6). Little skates were an exception – none were seen on trip 4. The total catch weight for this trip
was 21,480 kg, including species <3 kg caught, and was dominated by one tow using the Ruhle
trawl (tow #20) that was released before being brought on board for operational and safety
reasons. We estimated a bit less than 16,000 kg of spiny dogfish were caught on that tow, with
some skates, about 1.25 baskets of flatfish, and some silver hake mixed in. Catch from this tow
was not otherwise quantified. Aside from that one big tow, only 72.3 kg of spiny dogfish were
caught during all other tows during this trip. Excluding this tow, the largest contributors to the
total weight were winter skates (29.6% of the total weight), monkfish (23.1%), haddock (16.7%),
barndoor skate (10.3%), porbeagle sharks (6.1%), and winter flounder (2.7%). For the other
species that this project was intending to target, pollock were barely captured (11 kg in both nets
total) and redfish were not caught.
Catches of large pelagic species were observed during trip 4 (Table 6). Three common dolphins
were captured on trip 4 in the OBT2 (60 cm length on tow 2 and 72 & 72 cm lengths on tow 11)
and weights were visually estimated as no reliable length-weight conversions were available.
Porbeagle sharks were caught on this trip – four in the OBT2 and two in the Ruhle trawl.
For trip 4 catches, all valid tows came from the same geographical region and were pooled by net
(Figure 7). Pooled species’ catch rates (kg/hr) were compared by net for visualization of
differences (Figure 24). For haddock, catch rates were very similar between nets, about 20-25
kg/hr. For most non-target species, the mean and median catch rates were lower with the OBT2

44
or were very low such as for white hake. Catch rates were also compared using box and whisker
plots and, except for monkfish, which were caught in greater rates in the Ruhle trawl, and some
of the those species caught in low numbers, no significant differences in catch rates were evident
by overlapping boxes of box and whisker plots (Figure 25).
Figure 24: Mean catch rates (kg/hr) pooled over all valid tows for selected species during trip 4.
The y-axis shows the mean catch rates for OBT2 and the x-axis shows the corresponding mean
catch rates for the Ruhle trawl. Data are jittered on the y-axis to reduce overlap of species’
names. Axes use a log10 scale.

45
Figure 25: Catch rates (log10 kg/hr)(x-axis) for trip 4 for species (panels) by net type (y-axis;
OBT2=blue, Ruhle trawl=pink).
In trip 4, despite the overlapping boxes in Figure 25, significant differences in total catch rates
were identified using the Wilcoxon Rank-Sum test between the OBT2 and Ruhle trawl for
barndoor skate and winter skate (Table 7). Monkfish catches were also found to be significantly
different, matching the results from Figure 25. No significant differences were found for
American plaice and haddock (the only species using the Welch Two Sample t-test on trip 4),
similar to the trip 2 catch results. Also similar to trip 2, pollock and yellowtail flounder catches
were very low overall so tests for significance are not reported (Figures 18 and 24). Gray sole,
which showed no significant difference between the nets in trip 4, was the only species to
demonstrate different results than in trip 2. It was caught at significantly greater rates in the
Ruhle trawl than the OBT1.
Length frequencies show no significant differences for all measured commercial species for trip
4 (Figure 26). Haddock were largely over the MLS in both the Ruhle trawl and the OBT2,
similar to the results from trip 2 (Figure 19). All other species measured were also generally over
the MLSs (whole monkfish do not have an MLS). Other species whose lengths were measured
but are either not commercially important or did not have a sufficient numbers of lengths
collected are not displayed here and include silver and white hake, short-fin squid, porbeagle
sharks, fourspot flounder, and common dolphins.

46
Figure 26:Mid-line lengths (x-axis) of measured species (panel) by gear type (y-axis) for trip 4.
The red line is the minimum legal size for each species. Whole monkfish have no minimum legal
size. Box widths represent the sample sizes within gear type.
Evaluation and Discussion
In this project, our goal was to test two candidate off-bottom trawls (OBTs) proposed by
fishermen and designed to harvest Georges Bank haddock along with redfish and pollock, while
simultaneously avoiding overexploited fish stocks, mainly Atlantic cod, yellowtail flounder, and
windowpane flounder.
Our project objectives were:
• Share knowledge and experience among proponents (our team of regional fishermen and
gear scientists) to evaluate two candidate off-bottom haddock trawls.
• Comprehensively describe OBT geometry under a variety of operating conditions.
• Evaluate the ability of two OBTs to eliminate impacts by trawl gear on EFH.
• Evaluate the ability of two OBTs to land abundant groundfish mainly including haddock,
redfish, and pollock while eliminating landings of Atlantic cod, yellowtail flounder, and
windowpane flounder, including comparisons of these nets to existing haddock trawls.
• Evaluate the applicability of OBTs to the groundfish fleet.
• Share results of OBT performance and experiences broadly to the wider fishing fleet and
other stakeholders.
The sections below describe our success in accomplishing this goal and objectives. Our team
developed and acquired two different OBTs, constructed with innovative twines and techniques,
and successfully obtained the necessary permits, equipment, and staffing to test them. When our
original plan did not work out due to factors beyond our control, our team successfully pivoted,
persevered, and accomplished the planned testing, resulting in experience, rigging and catch
data for both trawls. Sufficient data were collected to make informed decisions about moving

47
forward with these nets.
Modifications to Goals and Objectives
The project underwent major changes due to the departures of P.I.s Steve Eayrs, James Odlin,
Mark Szymanski, and Adam Baukus. Odlin’s vessels, the F/V Teresa Marie IV and F/V
Harmony were tasked to conduct a large portion of the testing, including all the original industry-
focused work using the OBT2 (Figure 27) under the direction of GMRI personnel. We were able
to restructure the project so that all work followed the revised flow (Figure 1).
Figure 27: Original flow diagram for the science-focused work, led by MA DMF, and the
industry-focused work, let by GMRI.
An Exempted Fishing Permit (EFP) request was submitted and approved to conduct the industry-
focused work. Under the restructured project, we did not use the EFP and instead requested and
obtained an extended LOA to conduct additional comparative research on the F/V Illusion using
the OBT2.
A no-cost, one-year extension was granted on 10/24/17 followed by a second extension and
modifications to the project, granted on 12/21/18, so that further research could be conducted
using the small mesh codend in the OBT2 as well. Program income (fish sales) from this award
were used to pay for PI Chosid’s personnel costs needed to conduct this additional research.
Industry-focused work was going to utilize a Simrad FS70 system loaned by Simrad Fisheries for
high quality imagery of the OBT2 fishing circle. A coaxial cable was obtained to live-feed the
FS70 imagery to the F/V Teresa Maria IV. Atlantic Trawlers had committed a dedicated third-
wire winch to operate the cable while towing. Since the F/V Teresa Maria IV was no longer able
to participate, the winch also became unavailable. An alternate winch to equip the cable to use on

48
the F/V Illusion was not found. Instead, we used the vessel’s existing Simrad ITI system and
RBR loggers, as described above.
Paired tows were not possible during trip 4 comparative research as originally planned due to the
time required to switch nets and door configurations between the Ruhle trawl and OBT2 net on
the F/V Illusion. Instead, nets were used approximately daily and data were pooled.
Performance of Experimental Gears
In demersal trawling, it is possible to set the net and fish for hours with minimal or no
adjustment to the speed or wire out, and without any live feeds of data from the net. In contrast,
fishing off-bottom nets required frequent attention and adjustment to speed and wire out. For
both OBTs, we deployed multiple sensors that provided real-time and subsequent information on
net location and geometry and partnered with a captain experienced with midwater trawling. For
OBT1, it was necessary for the captain to continually monitor the net so he could adjust vessel
speed and wire out to maintain the targeted door spread and net height off-bottom. Further, he
judged that crew, despite extensive experience demersal fishing, could not relieve him at the
helm, and this arrangement to some degree inhibited our ability to test the nets, as breaks were
required for the captain to rest. The frequency of adjustments was lessened with the addition of
drop chains near the wingends. However, even with the benefit of dedicated tuning trips,
constant attention and changes to the rigging were often required within or between tows and
trips to attempt to stabilize the geometry of the nets and their location off-bottom.
Did the off-bottom nets remain off-bottom? It was often difficult to know where the net was in
relation to the bottom during the tow. We planned to have the latest SIMRAD net sensors on
some trips, which would have provided a much clearer image and data of the net mouth. This
information, supplemented with video and RBR loggers, had to be adjusted to the F/V Illusion’s
equipment after the departure of Odlin. Without the newer sensor, we could not meet the goal of
“comprehensively” describing the nets’ geometries. By necessity, we used the F/V Illusions’
older SIMRAD ITI system for OBT2 as well as OBT1, but nevertheless, according to underwater
video footage (Figure 9) and Notus net mensuration data (Figure 15) during trip 1, maintaining
the OBT1’s footrope at the desired height of under one meter, even without additional drop
chains, was possible. Further, on trip 2, prior to the addition of drop chains, comparatively stable
OBT1 headline and footrope heights were observed on some tows (Figure 16) while some post-
drop chain tows often revealed a footrope that was close to or touching bottom. The smaller
vertical openings in trip 2 than in trip 1 (Figures 14 and 16) coincide with the larger door spreads
in trip 2 (Figure 10).
Different challenges were faced with the geometry of the OBT2 net, although we once again
relied on the SIMRAD ITI system and a mixture of acoustic video and other sensors. This net, a
Gloria Trawl, was intended by Odlin for use in the Gulf of Maine for, in part, redfish, which are
typically deeper than haddock. Since we operated at these shallower depths of Georges Bank and
southern New England, more familiar to Phillips, the captain found it especially difficult to set
out the amount of warp wire to achieve the desired door spread of about 80 m (Figure 10) and
thus, establish the preferred angle of attack and net shape (Figure 16).

49
The challenge of achieving the desired door spread may also have been due to the position of the
doors in relation to the headline. The OBT2 was designed to have the doors at the same depth as
the headline, unlike the OBT1 where the doors are designed to fish approximately equidistant in
depth between the headline and footrope. According to the captain, when the doors are centrally
located (like for the OBT1), additional warp wire could be released and more easily achieve the
proper door spread. Alternatively, working deeper (>100 fa) would require less scope, and the
door positions at the top of the trawl (like for the OBT2) would spread more optimally. The
captain felt that the OBT2 may be better suited to targeting redfish in deeper water. Unlike while
using the OBT1, the captain did not have to constantly monitor and adjust the RPMS to maintain
door spreads for the OBT2.
The relationship between the position of the doors in the water column and the net may account
for the similar mean vertical openings of the net between trips 3 and 4 (Figure 16) while the
mean door spreads changed considerably (Figure 10), along with the mean depths (Table 1).
Further field research using net mensuration sensors or modeling of the fishing gear may be
required to better understand these complex relationships both within the water column and with
drop chain ground contact.
Significantly higher RPMs were needed during tows for the OBT2 than the OBT1 and Ruhle
trawl likely due to the large difference in sizes of the OBT2 net and the greater amount of warp
wire required (Table 3). The lack of floats and less ground gear and off-bottom doors of the
OBT2 likely creates less drag, but it also had a much larger fishing circle and the helix twine all
added drag (Kebede et al., 2020). Added drop chains to the OBT2 likely contributed to increased
frequency of bottom contact and increased drag.
Impacts to EFH were not eliminated for either OBT net due to the use of drop chains but were
likely substantially reduced compared to typical demersal haddock trawls.
The size of the OBT2 may have contributed to contact with a number of marine mammals and
large pelagics during trips 3 and 4. This result may simply be a factor of the extremely large
opening of this net (Figure 16) overlapping the habitat of these species. Further, the large size of
the net and its design may have made it difficult for the mammals to find and/or successfully
manage an escape. This interaction is troubling due to the status of these large pelagics and
protected status of marine mammals. However, more porbeagle sharks were captured in the
Ruhle trawl than in the larger opening OBT1 (during trip 2) demonstrating the complexity of
avoiding some large pelagic species. All incidental marine mammal takes were reported by the
vessel’s captain in accordance with his MMPA requirement.
Another challenge with the OBT2 was the rather small diameter twine in its back end (Figure 6).
This twine was prone to breakage from large species’ interactions including mammals and large
sharks. Considerable time was spent repairing broken meshes in these areas during research trips.
The captain thought that replacing the existing twine with higher strength Spectra line would
improve its durability.
The suite of net sensors, other than the Simrad ITI sensors, were somewhat unfamiliar to the

50
captain, sometimes unreliable, or did not provide a live-feed. Similarly, our video collection
methods obtained very useful information for tuning the OBT1 kite and verifying near-bottom
net orientation of both OBT nets but are impractical for use during commercial deployment. A
comprehensive, reliable, and familiar net mensuration system capable of imaging or providing
headrope, footrope, and bottom locations seem invaluable for commercial practice of the OBT
nets. The loss of Odlin’s extensive in-kind testing inhibited our objective of obtaining geometry
under a “variety of operating conditions”. While we cannot claim to have comprehensive
knowledge, we still have learned a great deal about how to fish and to monitor these nets using a
mix of live feedback from net mensuration equipment and loggers and video that were reviewed
post tows. Additional information may be gained through further investigation into the Simrad
data, which will require matching time codes from multiple data streams and attempting to match
times and events from other sensors and video.
For both experimental nets, despite the tuning trips, additional adjustments were necessary
during the comparative trips. This difference may have been due to changes in tides and currents,
deeper fishing depths, and other factors. With additional practice, it may have been possible to
maintain the OBT1 at the desired shape and height off the bottom without the drop chains.
Dissemination of Catch Results and Data
Catch results for both nets showed some positive outcomes that are consistent with fishing off-
bottom. The OBT1 successfully maintained haddock catches while reducing several non-target
species as compared to the Ruhle trawl (Tables 6 and 7 and Figure 18). Most notably, a
significant reduction was identified for monkfish, grey sole, barndoor skates, and little skates.
The OBT1 appeared to eliminate any catch of winter skate: a total of 522.2 kg of winter skate
were caught in the Ruhle trawl, and none were caught in the OBT1. Skates are often considered a
time-consuming, low value species and can reduce the quality of more valuable species by
causing abrasion damage in the codend. Their absence also implies less bottom contact of the
footrope.
The OBT2, like the OBT1, successfully maintained catches of haddock as compared to the Ruhle
trawl although catches were in smaller quantities (Tables 6 and 7 and Figure 24). The OBT2 also
showed significant decreases in some bottom species compared to the Ruhle trawl (monkfish and
barndoor skates, like the OBT1, as well as a significant decrease in winter skate) again implying
less bottom contact of the experimental gear.
American plaice were not significantly reduced in either OBT net when compared against the
Ruhle trawl (Table 7) but were caught in relatively low numbers in all nets (98.0 kg total, Table
6 and Figures 18 and 24).
Grey sole demonstrated different results between the two comparative research trips (Table 7).
Grey sole were significantly reduced using the OBT1 but not the OBT2. This species was also
caught in relatively low numbers (132.2 kg total), and results are therefore not strongly
supported, especially during trip 2 (Table 6 and Figures 18 and 24).
No significant difference in fish lengths were identified for any species (Figures 19, 20, and 26)

51
which was unexpected due to the use of two different sized codends (15.2 cm (6”) nominal in the
Ruhle trawl vs. 13.0 cm (5.1”) nominal in the OBT nets). These nets also used two different
shaped codend meshes (diamond in the Ruhle trawl and square in the OBT nets) which may
account for the similar lengths for round fish, such as haddock, which have difficulty passing
through less-than-fully-opened diamond-shaped meshes but not for flatfish which are more likely
to pass through the diamond-shaped meshes (Graham, 2010). We surmise that either fewer
smaller fish entered the OBT nets or escape of smaller fish occurred earlier in the OBT nets,
through the extremely large meshes and before reaching the codends. Fish escape earlier in the
fishing process would reduce the physical interactions and physiological fatigue which would
likely reduce stress and mortality (Suuronen, 2005; Ryer, 2004).
We were unable to capture enough pollock or redfish to make a judgment on the OBTs’
effectiveness with these species, due in part to loss of testing opportunities from changes in
project PIs. Loss of these opportunities also inhibits our ability to assess greater applicability for
the groundfish fleet. During the extensive industry-based testing in the original plan, fishermen
would have had an opportunity to learn how to handle the OBT2 under a wide variety of
conditions and provide innovation and insight into simpler handling and monitoring. Captain
Phillips has continuing interest in OBT nets and wished to continue fishing and refining them.
We adjusted catch weights by effort in terms of tow duration (catch/hour). The OBT1 was towed
at a faster mean speed than the Ruhle trawl while maintaining the mean RPMs so the totalvswept
areas (or volumes) of the OBT1 tows would be greater (Table 3). We expected differences in
swept areas simply due to the differences in trawl sizes, as experimental nets were intentionally
designed to be bigger than the Ruhle trawl. While swept area could be used as an alternative
catch modifier, adjustments for duration are more common. Further analysis can consider swept
area as well.
Requests for data from this award can be directed to Principal Investigator, David Chosid, at
david.chosid@mass.gov. Requests granted for this data will be accompanied by this statement:
“These environmental data and related items of information have not been formally disseminated by
NOAA and do not represent and should not be construed to represent any agency determination,
view, or policy.” NOAA may at its own discretion, use information from the Data/Information
Sharing Plan to produce a formal metadata record and include that metadata in a catalogue to indicate
the pending availability of new data. All data is available at this time and if requested, will be
provided free of charge or at minimal, the cost to reproduce.
Any pre-publication manuscripts of scholarly nature produced as a result of the findings and/or data
from this award, will first be submitted to the NOAA Institutional Repository at
http://library.noaa.gov/repository after acceptance, and no later than upon publication, of the
paper by a journal. MA DMF acknowledges that NOAA will produce a publicly-visible catalog
entry directing users to the published version of the article; and that after an embargo period of
one year after publication, NOAA shall make the manuscript itself publicly visible, free of
charge, while continuing to direct users to the published version of record.

52
Conclusions
This project initially intended to conduct comparative research with the OBT1 net and Ruhle
trawl in various locations in Georges Bank targeting haddock, redfish, and pollock. After the
project was restructured and our time at sea and number of trips were more limited than
originally planned, we decided to conduct both comparative research trips (using OBT1 and
OBT2) in a more limited area in Georges Bank targeting only haddock. We had intended to
compare the Ruhle trawl and the two experimental nets, which we expected to fish without
bottom contact, to potentially open fishing areas closed to gears with bottom contact. The
additions of drop chains near the wingends likely meant that the OBT nets touched bottom in
some manner. Since the trawl doors and ground gear were off-bottom, the OBT nets likely
reduced but did not eliminate seafloor contact, as indicated by the reduction in bottom dwelling
species in both designs. This outcome may be sufficient to open new areas for access, but
perhaps not in all habitats. Recently, interest in these nets was investigated by fishermen as a
way of targeting haddock that were reportedly displaced off-bottom by sediment suspended by
storms.
The OBT1 net was a challenge to fish properly, with a stable, desired shape and height off-
bottom. Frequent adjustment to the vessel’s RPMs were required to maintain these qualities.
While adding drop chains at the lower bridles reduced RPM adjustments and kept the net closer
to the bottom, other tows without the extra weight demonstrated good shape and height from
bottom without the undesired contact caused by the additions.
The OBT2 net was found to be potentially more suitable for deeper water, targeting redfish on
Georges Bank. The combination of the limited depths that we worked in, and the construction of
the net, made it susceptible to interaction with and damage from large pelagic species. Higher
RPMs and thus greater fuel consumption were required to operate the OBT2 over the OBT1 and
Ruhle trawl.
With the drop chains, bottom contact was reduced but not completely eliminated using the OBT
nets versus a Ruhle trawl. The lack of apparent contact of the doors and ground gear, maintaining
haddock catches, and reducing non-target catches are all positive developments. Both OBT nets
meet the regulation requirements for fishing in areas that allow standard groundfish nets if fished
with standard codends. The use of smaller mesh codends in a commercial fishery would require
fishing exemptions or changes to regulations.
It appears that the nets cannot be fished confidently without live feedback on the position of the
net in the water column. This project demonstrated that it was possible to fish reasonably well
with an outdated system. Further exploration of net performance and adoption by fishing vessels
may require the use of a third wire winch, a cable, and updated electronics to successfully
keeping the net in good configuration and off-bottom, and may allow elimination of the drop-
chains and all bottom contact.
Both OBT nets demonstrated that they could catch the same amount of haddock as the Ruhle
trawl while reducing most non-target species. This result validated Capt. Phillips’s confidence
that the already low bycatch in the Ruhle trawl could be reduced further. The Ruhle trawl has

53
been proven to exclude Atlantic cod catch and catches of this species were very low during trials.
We found that the OBT nets caught less cod than the Ruhle trawl during testing, although
insufficient data was collected to demonstrate a statistical difference. Interestingly, despite both
OBT nets using a smaller codend mesh size than the Ruhle trawl, the OBT nets did not lead to
higher catches (and discards) of small fish or even increases in less desirable, smaller, but
marketable haddock.
All species that were significantly reduced in the OBT nets such as skates, monkfish, and
flounders (Table 7) are bottom oriented. Their reduction, without significant changes to length
frequencies, suggests individuals of these species were either passed over by the OBT nets or the
fish passed through the large meshes in the bellies of the OBT nets which are even larger than
the very large meshes found in the Ruhle trawl. Haddock, on the other hand, are known to follow
the meshes without passing through them and are often higher in the water column, and our
similar comparative catch results provide some confirmation of this behavior (Main and
Sangster, 1981). Other than haddock, no species were caught in commercial amounts more in the
OBT nets than the Ruhle trawl (Table 6); haddock were caught in greater weights in the OBT
nets but not significantly.
Further field research would be required to assess the OBTs’ capabilities at catching pollock and
redfish as well as these nets’ performances during high catch situations.
The Captain plans to continue using both the OBT nets, likely with added weights near the
wingends. For the OBT2, he feels that a smaller sweep chain can be used than the one that came
equipped on the net, which may allow him to achieve an improved door spread and wing spread.
These OBT nets will be shared with other fishermen interested in trying them and MA DMF has
offered to provide further assistance as needed and as possible.
Our objective was to share news of OBT performance broadly to the wider fishing fleet and other
stakeholders. While we had hoped to have greater outreach via Odlin’s fleet, and although our
results are not as robust as we had hoped, we feel they are generally positive and a good
direction for trawl fishing for haddock. MA DMF plans to continue presenting the results from
this work to industry and the scientific community. We planned to share our results at the 2020
ICES conferences (Bergen, Norway) which has now been cancelled due to the Covid-19 virus
emergency. Future meetings will be sought to present our work.
We believe there is more to learn from combining and comparing the various sensor streams and
will continue to explore them for more insight into net performances.
Acknowledgements
This study was funded by the 2016/17 NOAA Saltonstall-Kennedy Funding Award
NA16NMF4270233. M. Pol and D. Chosid received separate salary support under Award
NA15NMF4070137 from NOAA Fisheries Service, in cooperation with the Interjurisdictional
Fisheries Act. The statements, findings, conclusions, and recommendations are those of the
authors and do not necessarily reflect the views of NOAA Fisheries. We would like to thank the
crew of the F/V Illusion for field operations. Steve Eayrs and Adam Baukus (GMRI) were

54
originally PIs to this project and contributed greatly to the experimental design and operations of
the project. Aaron Whitman, also from GMRI, greatly assisted in the fieldwork, lent research
equipment, and data collection. Dr. Pingguo He and Chris Rillahan (SMAST) contributed to the
development of the OBT designs and the project’s experimental design. Dr. He also assisted in
review of this report. Additional acknowledgements go to Mike Hillers (Simrad Fisheries) for
participation in planning of field trials, lending equipment, and assistance in logging ITI data,
Reidar’s Manufacturing for gear design consultation, Brad Schondelmeier (MA DMF) for
observer data queries, and Bob Conrad and Dan Farnham (captain and owner of the F/V Gabby
G) for loaning us a Simrad headline ITI sensor (trips 2-4) and Gullwing doors (trip 4).
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opening trawl to improve utilization of quota of Atlantic cod (Gadus morhua) in the
groundfish fishery of New England. Fishery Bulletin. 118 (2):171-183.
Erickson, D.L., Perez-Comas, J.A., Pikitch, E.K., and Wallace, J.R. 1996. Effects of catch size
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cert/documents/ref/CSAS_Res_Doc_2000_082.pdf.
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Link, J. S., Almeida, F., Valentine, P., Auster, P., Reid, R., and Vitaliano, J. 2005. The Effects of
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Direct Observations from a Towed Underwater Vehicle. Scottish Fisheries Research
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Suuronen, P. 2005. Mortality of fish escaping trawl gears. FAO Fisheries Technical Paper. No.
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239 pp.

57
Appendix 1 – Gear Configurations
Figure 28: 3m2 Gull Wing door diagram reference.

58
Table 8: OBT1 and OBT2 Gear configurations during all trips and tows. The “Valid” column indicates tows that
were not considered valid (“N”). “Top Tow Pad”, “Lower Tow Pad”, “Lower Pad Position”, “Bail Box Bracket”,
and “Tow Bail Position” refer to the door settings used (see Figure 28). Kite links refer to the number of links used
to pull the top of the kite inward or let it out. Catch and haddock weights/hour (“AdjCatch Weight” and
“AdjHaddock Weight”) are provided as reference.
Trip Haul Net Valid
Top Tow
Pad
Lower
Tow Pad
Lower
Pad
Position
Bail Box
Bracket
Tow Bail
Position
Kite
Links
Wingend
Triplate
Chains (kg)
AdjCatch
Weight
(kg/hr)
AdjHaddock
Weight
(kg/hr)
Other Mods
1 1 OBT1
D D 4 5 A 5 0
1 2 OBT1
E C 4 6 A 3 0
1 3 OBT1
E C 4 6 A 7 0
1 4 OBT1
E C 4 5 A 7 0
1 5 OBT1
E C 4 5 A 6 0
1 6 OBT1
E C 4 5 A 6 0
1 7 OBT1
E C 4 5 A 6 0
1 8 OBT1
E C 4 5 A 4 0
1 9 OBT1
E C 4 5 A 2 0
110 OBT1
E C 4 5 A 2 0
111 OBT1
E C 4 5 A 3 0
112 OBT1
E C 4 5 A 3 0
113 OBT1
E C 4 5 A 3 0 Pulled in center bridle 6.5"
114 OBT1
E C 4 5 A 3 0
115 OBT1
E C 4 5 A 3 0
116 OBT1
E C 4 5 A 3 0
117 OBT1
E C 4 5 A 3 0
2 2 OBT1
C D 4 5 A 3 0 0.1 0.0
2 4 OBT1
C D 4 5 A 3 0 0.0 0.0
2 6 OBT1
C D 4 5 A 3 0 4.5 4.0
2 7 OBT1
C D 4 5 A 3 0 70.7 65.1
210 OBT1
C D 4 5 A 3 0 48.1 9.5
211 OBT1
C D 4 5 A 3 22 85.9 20.3
214 OBT1
C D 4 5 A 3 22 119.7 112.5
215 OBT1
C D 4 5 A 3 22 171.9 164.5
218 OBT1 N
C D 4 5 A 3 22 9.2 8.5
220 OBT1
C D 4 5 A 3 22 176.7 91.5
221 OBT1
C D 4 5 A 3 22 34.5 14.8
224 OBT1
C D 4 5 A 3 22 264.4 261.9
225 OBT1
C D 4 5 A 3 22 23.5 21.1
228 OBT1
C D 4 5 A 3 22 216.8 200.7
229 OBT1
C D 4 5 A 3 22 341.3 332.8
230 OBT1
C D 4 5 A 3 22 302.0 294.7
3 1 OBT2 N
? ? 4 6 B 0 Original pad positions unknown
3 2 OBT2
C D 4 5 B 0
3 3 OBT2
C D 4 5 B 250
3 4 OBT2
D D 4 5 B 250
3 5 OBT2
C C 4 5 B 250
3 6 OBT2
C C 3 5 B 250
3 7 OBT2
D C 4 5 A 250
4 1 OBT2 N
D C 4 5 A 0 0.0 0.0
4 2 OBT2
D C 4 5 A 0 25.5 0.0
4 3 OBT2
D C 4 5 A 250 22.5 0.7
4 4 OBT2
D C 4 5 A 121.2 5.1 0.0
4 9 OBT2
D C 4 5 A 250 29.5 20.3 Removed 34.7 kg from each door
410 OBT2
D C 4 5 A 250 146.1 37.3
411 OBT2
D C 4 5 A 250 85.0 35.4
412 OBT2
D C 4 5 A 250 111.5 71.5
413 OBT2
D C 4 5 A 250 32.7 30.1
414 OBT2
D C 4 5 A 250 44.8 15.8
415 OBT2
D C 4 5 A 250 29.7 10.1

59
Appendix 2 – Video and Images
Table 9: Video descriptions and camera details.
DMF ID Name Film Title Camera
Camera
location
Date Start
Start
Time
End Date
End
Time
Comments
17MADMF1425
OFF BOTTOM TRAWL,
TOW 6
Wid e-I
SeaCam
HEADROPE
CENTER
9/1/2017 7:48 9/1/2017 8:27
On headr ope star board si de looking a ft at kite. Kite was s et 6
li nks out. Video sta rt and end times are a ctuall y the star t and
end of tow. Video dis connected on set out.
17MADMF1426
OFF BOTTOM TRAWL,
TOW 7
Wid e-I
SeaCam
HEADROPE
CENTER
9/1/2017 9:19 9/1/2017 10:05
On headr ope star board si de looking a ft at kite. Kite was s et 6
li nks out. Video star t and end times are a ctuall y the star t and
17MADMF1427
OFF BOTTOM TRAWL,
TOW 8
Wid e-I
SeaCam
HEADROPE
CENTER
9/1/2017 11:02 9/1/2017 11:46
On headr ope star board si de looking a ft at kite. Kite was s et 4
li nks out. Video star t and end times are a ctuall y the star t and
17MADMF1428
OFF BOTTOM TRAWL,
TOW 9
Wid e-I
SeaCam
HEADROPE
CENTER
9/1/2017 13:09 9/1/2017 13:29
On headr ope star board si de looking a ft at kite. Kite was s et 2
li nks out. Video star t and end times are a ctuall y the star t and
17MADMF1429
OFF BOTTOM TRAWL,
TOW 10
Wid e-I
SeaCam
HEADROPE
CENTER
9/1/2017 14:02 9/1/2017 14:30
On headr ope star board si de looking a ft at kite. Kite was s et 2
li nks out. Video star t and end times are a ctuall y the star t and
17MADMF1430
OFF BOTTOM TRAWL,
TOW 11
Wid e-I
SeaCam
HEADROPE -
CENTER
9/1/2017 9/1/2017
On i nside center headrope l ooking aft at meshes . Kite was set
3 li nks out.
17MADMF1431
OFF BOTTOM TRAWL,
TOW 12
Low-Light
SeaCam
HEADROPE -
CENTER
9/1/2017 18:53 9/1/2017 19:50
On i nside center headrope l ooking aft at meshes . Kite was set
3 li nks out. Video s tart an d end times a re actuall y the start
and end of tow.
17MADMF1432
OFF BOTTOM TRAWL,
TOW 15, ORI GINAL
ASPECT
Low-Light
SeaCam
FOOTROPE 9/2/2017 9:30 9/2/2017 10:15
On i nside center footrope cha in looki ng down and aft a t
bottom and meshes. Ki te was s et 3 li nks out. Video sta rt and
end times ar e actua lly the star t and end of tow.
17MADMF1433
OFF BOTTOM TRAWL,
TOW 15, NEW ASPECT
Low-Light
SeaCam
FOOTROPE 9/2/2017 9:30 9/2/2017 10:15
This is a a djusted i mage from 17MADMF1432 . On i nside
center footrope chai n looki ng down and aft at bottom and
meshes. Kite was set 3 li nks out. Video star t and end times a re
actua lly the star t and end of tow.
17MADMF1434
OFF BOTTOM TRAWL,
TOW 16
Low-Light
SeaCam
FOOTROPE 9/2/2017 11:04 9/2/2017 11:55
Camera on fo otrop fac ing star board si de down chai n sweep to
see chai n and bottom. Twine on chai n in vi deo shows actual
center of footrope (chai n). Kite was s et 3 li nks out. Video sta rt
and end ti mes are a ctuall y the star t and end of tow.
17MADMF1435
OFF BOTTOM TRAWL,
TOW 17
Low-Light
SeaCam
FOOTROPE 9/2/2017 12:29 9/2/2017 13:24
Camera on fo otrop fac ing star board si de down chai n sweep to
see chai n and bottom. Twine ion ch ain i n video shows a ctual
center of footrope (chai n). Kite was s et 3 li nks out. Video sta rt
and end ti mes are a ctuall y the star t and end of tow.
20MADMF1515
F/V ILLUSION ARRIVING
FOR OFF BOTTOM
TRAWL, TRIP 4
Gal axy
S8+
phone
PIER 9/20/2019 22:28 9/20/2019 22:28
18 s econd vi deo of the Il lusi on coming into por t at ni ght, near
Tichon , New Bedford.
20MADMF1514
OFF BOTTOM TRAWL,
TRIP 4, TOW 3 ,
HAULING IN OBT1
GoPro
Hero 3+
Black
DECK 9/22/2019 9/22/2019 9:30
20MADMF1513
OFF BOTTOM TRAWL,
TRIP 4, TOW 3 , SETTING
OUT OBT1
GoPro
Hero 3+
Black
DECK 9/22/2019 9/22/2019 7:29
20MADMF1512
OFF BOTTOM TRAWL,
TRIP 4, TOW 1
GoPro
Hero 3+
Black
FOOTROPE 9/21/2019 9/21/2019
Started arou nd 17:04. That's when the tow began. Flas hlights
stopped i nto the tow but one turned on a gai n later.

60
Table 10: Image descriptions.
Folder
File Names
Image Description
GloriaTrawl
IMG_25571.jpg
OBT2 bundled up in canvas
GloriaTrawl
IMG_25581.jpg
OBT2 bundled up in canvas
GloriaTrawl
IMG_25591.jpg
Additional chains for weight
GloriaTrawl
IMG_25601.jpg
OBT2 bundled up in canvas
Meeting20170202
P2020001.JPG
Meeting with Mike Pol, Steve Eayrs, Mike Hillers, and Mark Phillips at Boston DMF office.
Meeting20170605
20170605_130952.jpg
OBT1 twisted twines.
Meeting20170605
20170605_131025.jpg
OBT1 twisted twines.
Meeting20170605
20170605_131102.jpg
Eyes of yellow twisted twines, both coils
Meeting20170605
20170605_131251.jpg
OBT1 twisted twines.
Meeting20170605
20170605_132636.jpg
Mark Phillips and Tor Bendiksen inspecting attachments of four, red twisted twines.
Meeting20170605
20170605_132641.jpg
Mark Phillips, Pingguo He, and Tor Bendiksen inspecting attachments of four, red twisted twines.
Meeting20170605
20170605_143534.jpg
Meeting with Mark Phillips, Tor Bendiksen, and Pingguo He at Reidar's Manufacturing.
Meeting20170605
20170605_143535.jpg
Meeting with Mark Phillips, Tor Bendiksen, and Pingguo He at Reidar's Manufacturing.
Meeting20170605
20170605_143538.jpg
Meeting with Mark Phillips, Tor Bendiksen, and Pingguo He at Reidar's Manufacturing.
Meeting20170605
20170605_143549.jpg
Meeting at Reidar's Manufacturing with Mark Phillips, Mike Pol, Tor Bendiksen, and Pingguo He.
Meeting20170605
20170605_143554.jpg
Meeting at Reidar's Manufacturing with Mark Phillips, Mike Pol, Tor Bendiksen, and Pingguo He.
Meeting20170605
20170605_143556.jpg
Meeting at Reidar's Manufacturing with Mark Phillips, Mike Pol, Tor Bendiksen, and Pingguo He.
Meeting20170804
P8040001 (2).JPG
Steve Eayrs, Aaron Williams, and other GMRI staff inspecting OBT1
Meeting20170804
P8040001.JPG
Mike Pol inspecting OBT1 on pavement to n et drum.
Meeting20170804
P8040002 (2).JPG
Steve Eayrs inspecting OBT1
Meeting20170804
P8040002.JPG
Steve Eayrs, Aaron Williams, Tor Bendiksen, and other GMRI staff discussing OBT1
Meeting20170804
P8040003.JPG
Mike Pol inspecting OBT1 on pavement to net drum.
Meeting20170804
P8040004 (2).JPG
Chosid, Eayrs, Whitman inspecting OBT1
Meeting20170804
P8040004.JPG
Tor Bendiksen, Eayrs, Whitman inspecting OBT2
Meeting20170804
P8040005 (2).JPG
Chosid, Eayrs, Whitman inspecting OBT1
Meeting20170804
P8040005.JPG
Pol, Bendiksen, Eayrs, Whitman, and one other GMRI staff inspecting OBT1
Meeting20170804
P8040006 (2).JPG
Attachments on blue twisted twines (both coils) to gores.
Meeting20170804
P8040006.JPG
Pol, Bendiksen, Eayrs, Whitman, and one other GMRI staff inspecting OBT1
Meeting20170804
P8040007 (2).JPG
Wingend.
Meeting20170804
P8040007.JPG
Bottom (yellow), top (blue), and port (green) panels of OBT1.
Meeting20170804
P8040008 (2).JPG
Bottom (yellow), top (blue), and port (green) panels of OBT1.
Meeting20170804
P8040008.JPG
Bottom (yellow), top (blue), and port (green) panels of OBT1.
Meeting20170804
P8040009 (2).JPG
Front end of the OBT1.
Meeting20170804
P8040009.JPG
Starboard (red) panel construction of OBT1
Meeting20170804
P8040010.JPG
Bottom (yellow), top (blue), and port (green) panels of OBT1.
Meeting20170804
P8040011 (2).JPG
Connection of 4 twisted twines in the lower belly, 2 in each direction.
Meeting20170804
P8040011.JPG
Starboard (red) panel construction of OBT1
Meeting20170804
P8040012 (2).JPG
Bottom (yellow), top (blue), and port (green) panels of OBT1.
Meeting20170804
P8040012.JPG
Hanging starboard (red) twines during construction.
Meeting20170804
P8040013 (2).JPG
Bendiksen, Eayrs, Whitman, and other GMRI staff discussing OBT1.
Meeting20170804
P8040013.JPG
Starboard (red) panel construction of OBT1
Meeting20170804
P8040014 (2).JPG
Bendiksen, Eayrs, Whitman, Chosid, and other GMRI staff discussing OBT1.
Meeting20170804
P8040014.JPG
Starboard (red) panel construction of OBT1
Meeting20170804
P8040015.JPG
Bendiksen, Eayrs, Whitman, Chosid, and other GMRI staff discussing OBT1.
Meeting20170804
P8040016 (2).JPG
Bendiksen, Eayrs, Whitman, Chosid, and other GMRI staff discussing OBT1.
Meeting20170804
P8040016.JPG
Twine sections of the starboard (red) panel.
Meeting20170804
P8040017.JPG
Bendiksen and Chosid discussing OBT1.
Meeting20170804
P8040018 (2).JPG
Bendiksen and Chosid discussing OBT1.
Meeting20170804
P8040019 (2).JPG
Bendiksen and Eayrs inspecting OBT1.
Meeting20170804
P8040019.JPG
Bendiksen showing gullwing doors.
Meeting20170804
P8040020 (2).JPG
Bendiksen inspecting OBT1.
Meeting20170804
P8040020.JPG
Gullwing door.
Meeting20170804
P8040021 (2).JPG
Starboard (red) panel construction of OBT1
Meeting20170804
P8040021.JPG
Gullwing door.
Simrad
20181019_130212.jpg
F/V Illusion's back of Simrad computer.
Simrad
20181019_130229.jpg
F/V Illusion's Simrad controller.
Simrad
IMG_25561.jpg
Wire for Simrad system.
Trip1_TuningTrials
20170831_185954.jpg
Stern deck shot with OBT1 net.
Trip1_TuningTrials
20170831_190027.jpg
Stern deck shot with OBT1 net.
Trip1_TuningTrials
P8310001.JPG
Adding SIMRAD sensor to stbd Gullwing door.
Trip1_TuningTrials
P8310002.JPG
Adding SIMRAD sensor to port Gullwing door.
Trip1_TuningTrials
P8310003.JPG
Net reel.
Trip1_TuningTrials
P8310004.JPG
Groundgear and conveyer belt.
Trip1_TuningTrials
P8310005.JPG
Conveyer belt from other side.

61
Trip1_TuningTrials
P8310006.JPG
MA DMF storage case (black with white lid)
Trip1_TuningTrials
P8310007.JPG
Top tow pad door adjustment.
Trip1_TuningTrials
P8310008.JPG
Top tow pad door adjustment.
Trip1_TuningTrials
P8310009.JPG
Crewman setting door position.
Trip1_TuningTrials
P8310010.JPG
Crewman setting door position.
Trip1_TuningTrials
P8310011.JPG
Setting OBT1.
Trip1_TuningTrials
P8310012.JPG
Setting OBT1.
Trip1_TuningTrials
P8310013.JPG
Setting OBT1.
Trip1_TuningTrials
P8310014.JPG
Setting OBT1.
Trip1_TuningTrials
P8310015.JPG
Setting OBT1.
Trip1_TuningTrials
P8310016.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310017.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310018.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310019.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310020.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310021.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310022.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310023.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310025.JPG
Attaching the SIMRAD ITI headline sensor to OBT1 during set out.
Trip1_TuningTrials
P8310026.JPG
Setting OBT1.
Trip1_TuningTrials
P8310027.JPG
Setting OBT1.
Trip1_TuningTrials
P8310028.JPG
Setting OBT1.
Trip1_TuningTrials
P8310029.JPG
Setting OBT1.
Trip1_TuningTrials
P8310030.JPG
Setting OBT1.
Trip1_TuningTrials
P8310031.JPG
Setting OBT1.
Trip1_TuningTrials
P8310032.JPG
Kite at surface.
Trip1_TuningTrials
P8310033.JPG
Mark Phillips at stern observing OBT1 structure.
Trip1_TuningTrials
P8310034.JPG
Mark Phillips at stern observing OBT1 structure.
Trip1_TuningTrials
P8310035.JPG
Setting OBT1.
Trip1_TuningTrials
P8310036.JPG
Setting OBT1.
Trip1_TuningTrials
P8310037.JPG
Setting OBT1.
Trip1_TuningTrials
P8310038.JPG
Setting OBT1.
Trip1_TuningTrials
P8310039.JPG
Crewman fixing the pull master.
Trip1_TuningTrials
P8310040.JPG
Crewman on outrigger.
Trip1_TuningTrials
P8310041.JPG
Hauling tow 1.
Trip1_TuningTrials
P8310042.JPG
Hauling tow 1.
Trip1_TuningTrials
P8310043.JPG
Hauling tow 1.
Trip1_TuningTrials
P8310044.JPG
Hauling tow 1.
Trip1_TuningTrials
P8310045.JPG
Hauling tow 1.
Trip1_TuningTrials
P8310046.JPG
Adjustment to bottom tow pad door arrangement.
Trip1_TuningTrials
P8310047.JPG
Adjustment to top tow pad door arrangement.
Trip1_TuningTrials
P8310048.JPG
Adjustment to top tow pad door arrangement.
Trip1_TuningTrials
P8310049.JPG
Adjustment to door bails.
Trip1_TuningTrials
P8310050.JPG
Adjustment to door bails.
Trip1_TuningTrials
P8310051.JPG
Inside wheelhouse of the F/V Illusion
Trip1_TuningTrials
P8310052.JPG
Inside wheelhouse of the F/V Illusion
Trip1_TuningTrials
P8310053.JPG
Inside wheelhouse of the F/V Illusion
Trip1_TuningTrials
P8310054.JPG
Retrieving tow 2.
Trip1_TuningTrials
P8310055.JPG
Retrieving tow 2.
Trip1_TuningTrials
P8310056.JPG
Retrieving tow 2.
Trip1_TuningTrials
P8310057.JPG
Chosid and Phillips adding Notus vertical opening slave to lower belly before tow 4.
Trip1_TuningTrials
P8310058.JPG
Chosid and Phillips adding Notus vertical opening slave to lower belly before tow 4.
Trip1_TuningTrials
P8310059.JPG
Chosid and Phillips adding Notus vertical opening slave to lower belly before tow 4.
Trip1_TuningTrials
P8310060.JPG
Chosid and Phillips adding Notus vertical opening slave to lower belly before tow 4.
Trip1_TuningTrials
P8310061.JPG
Chosid and Phillips adding Notus vertical opening slave to low er belly before tow 4.
Trip1_TuningTrials
P8310062.JPG
Chosid and Phillips adding Notus vertical opening slave to lower belly before tow 4.
Trip1_TuningTrials
P8310063.JPG
Notus vertical opening slave on lower belly before tow 4.
Trip1_TuningTrials
P9010064.JPG
Attaching FishCam recording unit on OBT1.
Trip1_TuningTrials
P9010065.JPG
Wire for FishCam along OBT1.
Trip1_TuningTrials
P9010066.JPG
Attaching FishCam recording unit on OBT1.
Trip1_TuningTrials
P9010067.JPG
Deploying OBT1 with FishCam.
Trip1_TuningTrials
P9010068.JPG
Removing FishCam after tow 7.
Trip1_TuningTrials
P9010069.JPG
Removing FishCam after tow 7.
Trip1_TuningTrials
P9010070.JPG
Crewman cutting chain for kite adjustment.
Trip1_TuningTrials
P9010071.JPG
Crewman cutting chain for kite adjustment.
Trip1_TuningTrials
P9010072.JPG
Sensor sleeve in Gullwing door.
Trip1_TuningTrials
P9010073.JPG
Crewman adding attachment for RBR logger on door.
Trip1_TuningTrials
P9010074.JPG
Attaching FishCam recording unit on OBT1 prior to tow 8.

62
Trip1_TuningTrials
P9010075.JPG
Crewman adding attachment for RBR logger on door.
Trip1_TuningTrials
P9010076.JPG
Crewman adding attachment for RBR logger on door.
Trip1_TuningTrials
P9010077.JPG
Attaching FishCam recording unit on OBT1 prior to tow 8.
Trip1_TuningTrials
P9010079.JPG
Phillips attaching RBR logger on stbd door.
Trip1_TuningTrials
P9010080.JPG
Phillips attaching RBR logger on stbd door.
Trip1_TuningTrials
P9010081.JPG
SIMRAD sensor and temp monitor on door. Attachment for RBR logger near SIMRAD sensor.
Trip1_TuningTrials
P9010082.JPG
Attachment for RBR logger near SIMRAD sensor.
Trip1_TuningTrials
P9010083.JPG
RBR logger on door.
Trip1_TuningTrials
P9010084.JPG
Phillips attaching RBR logger on door.
Trip1_TuningTrials
P9010085.JPG
RBR logger on door.
Trip1_TuningTrials
P9010086.JPG
RBR logger setting out on headrope on tow 8.
Trip1_TuningTrials
P9010087.JPG
RBR logger setting out on headrope on tow 8.
Trip1_TuningTrials
P9010088.JPG
Dolphins.
Trip1_TuningTrials
P9010089.JPG
Dolphins.
Trip1_TuningTrials
P9010090.JPG
Dolphins.
Trip1_TuningTrials
P9010091.JPG
Dolphins.
Trip1_TuningTrials
P9010092.JPG
Dolphins.
Trip1_TuningTrials
P9010093.JPG
Dolphins.
Trip1_TuningTrials
P9010094.JPG
Dolphins.
Trip1_TuningTrials
P9010095.JPG
Dolphins.
Trip1_TuningTrials
P9010096.JPG
Dolphins.
Trip1_TuningTrials
P9010097.JPG
Removing low-light camera from OBT1 after tow 9
Trip1_TuningTrials
P9010098.JPG
Removing low-light camera from OBT1 after tow 9
Trip1_TuningTrials
P9010099.JPG
Removing low-light camera from OBT1 after tow 9
Trip1_TuningTrials
P9010100.JPG
Attaching low-light camera to OBT1 for tow 10
Trip1_TuningTrials
P9010101.JPG
Attaching low-light camera to OBT1 for tow 10
Trip1_TuningTrials
P9010102.JPG
Low light camera, FishCam recording unit, and Notus headrope sensor.
Trip1_TuningTrials
P9010103.JPG
Low light camera and FishCam recording unit.
Trip1_TuningTrials
P9010104.JPG
Attaching FishCam before tow 10
Trip1_TuningTrials
P9010105.JPG
Setting tow 10
Trip1_TuningTrials
P9010106.JPG
Setting tow 10
Trip1_TuningTrials
P9010107.JPG
Setting tow 10
Trip1_TuningTrials
P9010108.JPG
RBR logger and rig for footrope placement.
Trip1_TuningTrials
P9010110.JPG
RBR logger and rig for footrope placement.
Trip1_TuningTrials
P9010111.JPG
Removing FishCam after tow 12
Trip1_TuningTrials
P9010112.JPG
Removing FishCam after tow 12
Trip1_TuningTrials
P9010114.JPG
Fish there were stuck in net from tow 13.
Trip1_TuningTrials
P9020115.JPG
Phillips adding Notus footrope sensor to OBT1.
Trip1_TuningTrials
P9020116.JPG
Phillips adding Notus footrope sensor to OBT1.
Trip1_TuningTrials
P9020117.JPG
Phillips adding Notus footrope sensor to OBT1.
Trip1_TuningTrials
P9020118.JPG
Adding RBR logger on rig to footrope.
Trip1_TuningTrials
P9020119.JPG
Adding RBR logger on rig to footrope.
Trip1_TuningTrials
P9020120.JPG
Adding RBR logger on rig to footrope.
Trip1_TuningTrials
P9020122.JPG
Adding RBR logger on rig to footrope.
Trip1_TuningTrials
P9020123.JPG
Adding RBR logger on rig to footrope.
Trip1_TuningTrials
P9020124.JPG
Adding RBR logger on rig to footrope.
Trip1_TuningTrials
P9020126.JPG
Setting tow 14.
Trip1_TuningTrials
P9020128.JPG
Retrieving data from RBR loggers.
Trip1_TuningTrials
P9020129.JPG
Setting low-light camera for tow 15.
Trip1_TuningTrials
P9020130.JPG
Setting low-light camera for tow 15.
Trip1_TuningTrials
P9020131.JPG
Setting low-light camera cable for tow 15.
Trip1_TuningTrials
P9020132.JPG
Setting low-light camera cable for tow 15.
Trip1_TuningTrials
P9020133.JPG
Setting low-light camera for tow 15.
Trip1_TuningTrials
P9020134.JPG
Setting FishCam recording unit for tow 15.
Trip1_TuningTrials
P9020135.JPG
Setting FishCam recording unit for tow 15.
Trip1_TuningTrials
P9020136.JPG
Setting tow 15 with FishCam recording unit.
Trip1_TuningTrials
P9020137.JPG
Bridles off stern.
Trip1_TuningTrials
P9020138.JPG
Bridles off stern.
Trip1_TuningTrials
P9020139.JPG
Mike Auriemma, assistant researcher (MA DMF).
Trip1_TuningTrials
P9020140.JPG
F/V Illusion conveyer belt.
Trip1_TuningTrials
P9020141.JPG
Kitchen area.
Trip1_TuningTrials
P9020142.JPG
Galley.
Trip1_TuningTrials
P9020143.JPG
Lazerette.
Trip1_TuningTrials
P9020144.JPG
Hallway to bunks.
Trip1_TuningTrials
P9020145.JPG
Phillips in the wheelhouse.
Trip2_OBT1vRuhleTrip
P8100056.MOV
Inspecting codend meshes.
Trip2_OBT1vRuhleTrip
P8120082.MOV
OBT1 in the water while Captain and crew make adjustments made near reel.
Trip2_OBT1vRuhleTrip
P8090006.JPG
Gullwing doors hoisted onto vessel.

63
Trip2_OBT1vRuhleTrip
P8090007.JPG
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090008.JPG
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090009.JPG
OBT1 hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090010.JPG
OBT1 hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090011.JPG
Vessels at pier near Trio in New Bedford.
Trip2_OBT1vRuhleTrip
P8090001.JPG
Behind the F/V Illusion wheelhouse.
Trip2_OBT1vRuhleTrip
20190809_121121.jpg
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090002.JPG
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090003.JPG
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090004.JPG
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090005.JPG
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
20190809_121436.jpg
Gullwing doors hoisted onto vessel.
Trip2_OBT1vRuhleTrip
20190809_121438.jpg
OBT1 hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090012.JPG
OBT1 hoisted onto vessel.
Trip2_OBT1vRuhleTrip
P8090013.JPG
Deck of F/V Illusion.
Trip2_OBT1vRuhleTrip
P8090014.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090015.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090016.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090017.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090018.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090019.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090020.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090021.JPG
Leaving New Bedford for trip 2.
Trip2_OBT1vRuhleTrip
P8090022.JPG
DOF vessel at sea.
Trip2_OBT1vRuhleTrip
P8090023.JPG
DOF vessel at sea.
Trip2_OBT1vRuhleTrip
20190809_163711.jpg
At the gate after loading vessel from trip 2.
Trip2_OBT1vRuhleTrip
P8090024.JPG
Scenic.
Trip2_OBT1vRuhleTrip
P8090025.JPG
Whitman and crewman on deck.
Trip2_OBT1vRuhleTrip
P8100026.JPG
Crewman adjusting groundgear.
Trip2_OBT1vRuhleTrip
P8100027.JPG
Crewman adjusting groundgear.
Trip2_OBT1vRuhleTrip
P8100028.JPG
Crewman adjusting groundgear.
Trip2_OBT1vRuhleTrip
P8100029.JPG
Whitman on deck.
Trip2_OBT1vRuhleTrip
P8100030.JPG
Crewmen adjusting groundgear.
Trip2_OBT1vRuhleTrip
P8100031.JPG
Crewmen adjusting groundgear.
Trip2_OBT1vRuhleTrip
P8100032.JPG
Crewmen adjusting groundgear.
Trip2_OBT1vRuhleTrip
P8100033.JPG
Stbd Gullwing door.
Trip2_OBT1vRuhleTrip
P8100034.JPG
Phillips at port Gullwing door.
Trip2_OBT1vRuhleTrip
P8100035.JPG
Whitman on deck.
Trip2_OBT1vRuhleTrip
P8100036.JPG
Whitman on deck.
Trip2_OBT1vRuhleTrip
P8100037.JPG
Whitman on deck.
Trip2_OBT1vRuhleTrip
P8100038.JPG
Ruhle trawl in the water and crewman on deck.
Trip2_OBT1vRuhleTrip
P8100039.JPG
Ruhle trawl in the water and crewmen on deck.
Trip2_OBT1vRuhleTrip
P8100040.JPG
Ruhle trawl in the water and crewmen on deck.
Trip2_OBT1vRuhleTrip
P8100041.JPG
Ruhle trawl in the water and crewmen on deck.
Trip2_OBT1vRuhleTrip
P8100042.JPG
Ruhle trawl in the water and crewmen on deck.
Trip2_OBT1vRuhleTrip
P8100043.JPG
OBT1 across deck. SIMRAD headline sensor in panel on headline.
Trip2_OBT1vRuhleTrip
P8100044.JPG
Whitman inspecting OBT1.
Trip2_OBT1vRuhleTrip
P8100045.JPG
Whitman attaching RBR logger onto footrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100046.JPG
Whitman attaching RBR logger onto footrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100047.JPG
Whitman attaching RBR logger onto footrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100048.JPG
Whitman attaching RBR logger onto footrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100049.JPG
Whitman attaching RBR logger onto footrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100050.JPG
Whitman attaching RBR logger onto headrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100051.JPG
RBR logger on headrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100052.JPG
RBR logger on headrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100053.JPG
RBR logger on headrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100054.JPG
RBR logger on headrope of OBT1.
Trip2_OBT1vRuhleTrip
P8100055.JPG
Legs of net.
Trip2_OBT1vRuhleTrip
P8100056.JPG
Codend meshes.
Trip2_OBT1vRuhleTrip
P8100057.JPG
Gulfstream flounder from tow 3.
Trip2_OBT1vRuhleTrip
P8110058.JPG
Retrieving OBT1 on tow 7.
Trip2_OBT1vRuhleTrip
P8110059.JPG
Retrieving OBT1 on tow 7.
Trip2_OBT1vRuhleTrip
P8110060.JPG
Retrieving OBT1 on tow 7.
Trip2_OBT1vRuhleTrip
P8110061.JPG
Retrieving OBT1 on tow 7.
Trip2_OBT1vRuhleTrip
P8110062.JPG
Catch from tow 7.
Trip2_OBT1vRuhleTrip
P8110063.JPG
Catch from tow 7.
Trip2_OBT1vRuhleTrip
P8110064.JPG
Catch from tow 7.
Trip2_OBT1vRuhleTrip
P8110065.JPG
Catch from tow 7.

64
Trip2_OBT1vRuhleTrip
P8120066.JPG
Catch and porbeagle captured on tow 10.
Trip2_OBT1vRuhleTrip
P8120067.JPG
Catch and porbeagle captured on tow 10.
Trip2_OBT1vRuhleTrip
P8120068.JPG
Porbeagle captured on tow 10.
Trip2_OBT1vRuhleTrip
P8120069.JPG
Porbeagle captured on tow 10.
Trip2_OBT1vRuhleTrip
P8120070.JPG
Porbeagle being returned to sea.
Trip2_OBT1vRuhleTrip
P8120071.JPG
Porbeagle being returned to sea.
Trip2_OBT1vRuhleTrip
P8120072.JPG
Porbeagle being returned to sea.
Trip2_OBT1vRuhleTrip
P8120073.JPG
Porbeagle being returned to sea.
Trip2_OBT1vRuhleTrip
P8120074.JPG
Porbeagle being returned to sea.
Trip2_OBT1vRuhleTrip
P8120075.JPG
Wingend chain for OBT1.
Trip2_OBT1vRuhleTrip
P8120076.JPG
Wingend chain for OBT1.
Trip2_OBT1vRuhleTrip
P8120077.JPG
Top and bottom tow pad setting of Gullwing door.
Trip2_OBT1vRuhleTrip
P8120078.JPG
Top and bottom tow pad setting of Gullwing door.
Trip2_OBT1vRuhleTrip
P8120079.JPG
Codend of OBT1.
Trip2_OBT1vRuhleTrip
P8120080.JPG
Whitman and crew attaching RBR logger to headrope.
Trip2_OBT1vRuhleTrip
P8120081.JPG
Whitman and crew attaching RBR logger to headrope.
Trip2_OBT1vRuhleTrip
P8120083.JPG
Setting tow 11 with OBT1.
Trip2_OBT1vRuhleTrip
P8120084.JPG
Attaching chains to OBT1 wingends on tow 11.
Trip2_OBT1vRuhleTrip
P8120085.JPG
Attaching chains to OBT1 wingends on tow 11.
Trip2_OBT1vRuhleTrip
P8120086.JPG
Setting OBT1 with wingend chains.
Trip2_OBT1vRuhleTrip
P8120087.JPG
Porthole to kitchen.
Trip2_OBT1vRuhleTrip
P8120088.JPG
Catch from tow 11 with porbeagle.
Trip2_OBT1vRuhleTrip
P8120089.JPG
Porbeagle from tow 11.
Trip2_OBT1vRuhleTrip
P8120090.JPG
Porbeagle from tow 11.
Trip2_OBT1vRuhleTrip
P8120091.JPG
Porbeagle and catch from tow 11.
Trip2_OBT1vRuhleTrip
P8120092.JPG
Returning porbeagle to sea from tow 13.
Trip2_OBT1vRuhleTrip
P8120093.JPG
Returning porbeagle to sea from tow 13.
Trip2_OBT1vRuhleTrip
P8130094.JPG
Porbeagle and catch from tow 17.
Trip2_OBT1vRuhleTrip
P8130095.JPG
Porbeagle and catch from tow 17.
Trip2_OBT1vRuhleTrip
P8130096.JPG
Porbeagle and catch from tow 17.
Trip2_OBT1vRuhleTrip
P8130097.JPG
Laptop station collecting SIMRAD data in wheelhouse.
Trip2_OBT1vRuhleTrip
P8130098.JPG
Wheelhouse of F/V Illusion.
Trip2_OBT1vRuhleTrip
P8130099.JPG
Wheelhouse of F/V Illusion.
Trip2_OBT1vRuhleTrip
P8130100.JPG
Wheelhouse of F/V Illusion.
Trip2_OBT1vRuhleTrip
P8130101.JPG
Wheelhouse of F/V Illusion.
Trip2_OBT1vRuhleTrip
P8130102.JPG
Wheelhouse of F/V Illusion.
Trip2_OBT1vRuhleTrip
P8130103.JPG
Three porbeagles from tow 19.
Trip2_OBT1vRuhleTrip
P8130104.JPG
Three porbeagles from tow 19.
Trip2_OBT1vRuhleTrip
P8130105.JPG
Porbeagle damages with blue straps around one causing injury.
Trip2_OBT1vRuhleTrip
P8130106.JPG
Size reference for blue straps.
Trip2_OBT1vRuhleTrip
P8130107.JPG
Size reference for blue straps.
Trip2_OBT1vRuhleTrip
P8140108.JPG
Catch and porbeagle from tow 27.
Trip2_OBT1vRuhleTrip
P8140109.JPG
Catch and porbeagle from tow 27.
Trip2_OBT1vRuhleTrip
P8140110.JPG
Catch and porbeagle from tow 27.
Trip2_OBT1vRuhleTrip
P8140111.JPG
Catch and porbeagle from tow 27.
Trip2_OBT1vRuhleTrip
P8140112.JPG
Catch and porbeagle from tow 27.
Trip2_OBT1vRuhleTrip
P8140113.JPG
Pol collecting length data on a haddock.
Trip2_OBT1vRuhleTrip
P8140114.JPG
Pol collecting length data on a haddock.
Trip2_OBT1vRuhleTrip
P8140115.JPG
Pol collecting length data on a haddock.
Trip2_OBT1vRuhleTrip
P8140116.JPG
Pol collecting length data on a haddock.
Trip2_OBT1vRuhleTrip
P8140117.JPG
Catch from tow 28.
Trip2_OBT1vRuhleTrip
P8140118.JPG
Catch from tow 28.
Trip2_OBT1vRuhleTrip
P8140119.JPG
Catch from tow 28.
Trip2_OBT1vRuhleTrip
P8140120.JPG
Catch from tow 28.
Trip2_OBT1vRuhleTrip
P8140121.JPG
Fish guts on hull after dressing.
Trip2_OBT1vRuhleTrip
P8140122.JPG
Baskets of catch from tow 29.
Trip2_OBT1vRuhleTrip
P8140123.JPG
Baskets of haddock from tow 29.
Trip2_OBT1vRuhleTrip
P8140124.JPG
Baskets of shortfin squid and mixed species from tow 29.
Trip2_OBT1vRuhleTrip
P8140125.JPG
Baskets of shortfin squid and mixed species from tow 29.
Trip2_OBT1vRuhleTrip
P8140126.JPG
Chain shine after tow 30.
Trip2_OBT1vRuhleTrip
P8140127.JPG
OBT1 across deck with crewman.
Trip2_OBT1vRuhleTrip
P8140128.JPG
OBT1 across deck with crewman.
Trip2_OBT1vRuhleTrip
P8140129.JPG
Pol with haddock catch from tow 30.
Trip2_OBT1vRuhleTrip
P8140130.JPG
Pol and crewman with haddock catch from tow 30.
Trip2_OBT1vRuhleTrip
20190815_165913.jpg
Pol and Whitman on deck of the F/V Illusion post trip 2.
Trip2_OBT1vRuhleTrip
20190815_165920.jpg
Pol and Whitman on deck of the F/V Illusion post trip 2.
Trip2_OBT1vRuhleTrip
20190815_170520.jpg
Dockside worker and crewman near the wheelhouse on the F/V Illusion post trip 2.
Trip2_OBT1vRuhleTrip
20190815_170522.jpg
Pol, dockside worker, and crewman near the wheelhouse on the F/V Illusion post trip 2.

65
Trip2_OBT1vRuhleTrip
20190815_170618.jpg
Research crew and fishing crew from trip 2 on the F/V Illusion post trip 2.
Trip2_OBT1vRuhleTrip
20190815_170623.jpg
Research crew and fishing crew from trip 2 on the F/V Illusion post trip 2.
Trip2_OBT1vRuhleTrip
20190815_170636.jpg
Research crew and fishing crew from trip 2 on the F/V Illusion post trip 2.
Trip2_OBT1vRuhleTrip
20190815_170640.jpg
Research crew and fishing crew from trip 2 on the F/V Illusion post trip 2.
Trip3_Tuning_Images
20190916_144023.jpg
Lower pad connection on Gull Wing door.
Trip3_Tuning_Images
20190916_144026.jpg
Gull Wing door.
Trip3_Tuning_Images
20190916_144941.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_144950.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_144952.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_145019.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_145022.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_145024.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_145040.jpg
Capt. Phillips adjusting rigging.
Trip3_Tuning_Images
20190916_150430.jpg
Gull Wing door backstrop connection.
Trip3_Tuning_Images
20190916_150438.jpg
Gull Wing door backstrop connection.
Trip3_Tuning_Images
P9170001.JPG
OBT2 codend on drum.
Trip3_Tuning_Images
P9170002.JPG
Capt. Phillips with OBT2 codend on drum.
Trip3_Tuning_Images
P9170004.JPG
Extension of the OBT2.
Trip3_Tuning_Images
P9170005.JPG
RBR logger mounted in Gull Wing door.
Trip3_Tuning_Images
P9170006.JPG
Bail position of Gull Wing door.
Trip3_Tuning_Images
P9170007.JPG
TidBit mounted on Gull Wing door.
Trip3_Tuning_Images
P9170008.JPG
Lower pad connection on Gull Wing door.
Trip3_Tuning_Images
P9170009.JPG
Upper pad connection on Gull Wing door.
Trip3_Tuning_Images
P9170010.JPG
Upper pad connection on Gull Wing door.
Trip3_Tuning_Images
P9170011.JPG
OBT2 on deck with headrope sensor.
Trip3_Tuning_Images
P9170012.JPG
Twine and gore of OBT2
Trip3_Tuning_Images
P9170013.JPG
OBT2 on drum.
Trip3_Tuning_Images
P9170014.JPG
OBT2 on drum.
Trip3_Tuning_Images
P9170015.JPG
Capt. Phillips working on footrope of OBT2
Trip3_Tuning_Images
P9170016.JPG
Footrope of OBT2.
Trip3_Tuning_Images
P9170017.JPG
Footrope of OBT2.
Trip3_Tuning_Images
P9170018.JPG
Capt. Phillips working on OBT2
Trip3_Tuning_Images
P9170019.JPG
Capt. Phillips working on OBT2
Trip3_Tuning_Images
P9170020.JPG
Crew repairing twine on OBT2
Trip3_Tuning_Images
P9170021.JPG
Crew repairing twine on OBT2
Trip3_Tuning_Images
20190917_055807.jpg
Scenic portside.
Trip3_Tuning_Images
20190917_055814.jpg
Scenic portside.
Trip3_Tuning_Images
P9170022.JPG
Capt. Phillips repairing twine on OBT2
Trip3_Tuning_Images
P9170023.JPG
Capt. Phillips repairing twine on OBT3
Trip3_Tuning_Images
P9170024.JPG
Crew inspecting OBT2
Trip3_Tuning_Images
P9170025.JPG
Crew inspecting OBT2
Trip3_Tuning_Images
P9170026.JPG
Lower pad of starboard Gullwing door
Trip3_Tuning_Images
P9170027.JPG
Upper pad of starboard Gullwing door
Trip3_Tuning_Images
P9170028.JPG
Lower pad of port Gullwing door
Trip3_Tuning_Images
P9170029.JPG
Upper pad of port Gullwing door
Trip3_Tuning_Images
P9170030.JPG
Bail position of starboard Gull Wing door and RBR logger.
Trip3_Tuning_Images
P9170031.JPG
Bail position of starboard Gull Wing door and RBR logger.
Trip3_Tuning_Images
20190917_071640.jpg
Capt. Phillips in wheelhouse at hauling station.
Trip3_Tuning_Images
20190917_071641.jpg
Capt. Phillips in wheelhouse at hauling station.
Trip3_Tuning_Images
20190917_071648.jpg
Capt. Phillips in wheelhouse at hauling station.
Trip3_Tuning_Images
20190917_071704.jpg
Looking aft in the wheelhouse.
Trip3_Tuning_Images
20190917_071713.jpg
Wheelhouse with laptop for Simrad logging.
Trip3_Tuning_Images
20190917_071723.jpg
Capt. Phillips in wheelhouse at hauling station.
Trip3_Tuning_Images
P9170032.JPG
Retrieving tow 2.
Trip3_Tuning_Images
P9170033.JPG
Retrieving tow 2.
Trip3_Tuning_Images
P9170036.JPG
Setting tow 3.
Trip3_Tuning_Images
P9170037.JPG
Setting tow 3. Attaching drop chains to triplate.
Trip3_Tuning_Images
P9170038.JPG
Drop chains prior to tow 3.
Trip3_Tuning_Images
P9170039.JPG
Drop chains prior to tow 3.
Trip3_Tuning_Images
P9170040.JPG
Drop chains prior to tow 3.
Trip3_Tuning_Images
P9170041.JPG
Drop chains prior to tow 3.
Trip3_Tuning_Images
P9170035.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170042.JPG
Looking for shine from tow 3 on Gullwing door.
Trip3_Tuning_Images
P9170043.JPG
Looking for shine from tow 3 on Gullwing door.
Trip3_Tuning_Images
P9170044.JPG
Looking for shine from tow 3 on Gullwing door.
Trip3_Tuning_Images
P9170045.JPG
Switching upper pad position on Gullwing door prior to tow 4.
Trip3_Tuning_Images
P9170046.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170047.JPG
Drop chain from tow 3.

66
Trip3_Tuning_Images
P9170048.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170049.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170050.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170051.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170052.JPG
Retrieving tow 3. Trap trawl entangled in net.
Trip3_Tuning_Images
P9170053.JPG
Retrieving tow 3. Trap trawl entangled in net.
Trip3_Tuning_Images
P9170054.JPG
Retrieving tow 3. Trap trawl entangled in net.
Trip3_Tuning_Images
P9170055.JPG
Retrieving tow 3.
Trip3_Tuning_Images
P9170056.JPG
Retrieving tow 3. Trap trawl entangled in net.
Trip3_Tuning_Images
P9170057.JPG
Trap caught during tow 3.
Trip3_Tuning_Images
P9170058.JPG
Trap caught during tow 3. Vent blocked with zip tie.
Trip3_Tuning_Images
P9170059.JPG
Trap caught during tow 3. Vent blocked with zip tie.
Trip3_Tuning_Images
P9170060.JPG
Trap tags.
Trip3_Tuning_Images
P9170061.JPG
Trap tags.
Trip3_Tuning_Images
P9170062.JPG
Trap tags.
Trip3_Tuning_Images
P9170063.JPG
Trap tags in trap.
Trip3_Tuning_Images
P9170064.JPG
Trap tags.
Trip3_Tuning_Images
P9170065.JPG
Trap tags.
Trip3_Tuning_Images
P9170066.JPG
Trap caught during tow 3. Vent blocked with zip tie.
Trip3_Tuning_Images
P9170067.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170068.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170069.JPG
Retrieving tow 4. Drop chains at triplate.
Trip3_Tuning_Images
P9170070.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170071.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170072.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170073.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170074.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170075.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170076.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170077.JPG
Retrieving tow 4.
Trip3_Tuning_Images
P9170078.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170079.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170080.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170081.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170082.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170083.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170084.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170085.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170086.JPG
Retrieving codend from tow 4. Basking shark in codend.
Trip3_Tuning_Images
P9170087.JPG
Basking shark in codend.
Trip3_Tuning_Images
P9170088.JPG
Basking shark escaping codend.
Trip3_Tuning_Images
P9170089.JPG
Basking shark escaping codend.
Trip3_Tuning_Images
P9170090.JPG
Basking shark escaping codend.
Trip3_Tuning_Images
P9170091.JPG
Basking shark swimming away.
Trip3_Tuning_Images
P9170092.JPG
Basking shark swimming away.
Trip3_Tuning_Images
P9170093.JPG
Basking shark swimming away.
Trip3_Tuning_Images
P9170094.JPG
Basking shark swimming away.
Trip3_Tuning_Images
P9170095.JPG
Basking shark swimming away.
Trip3_Tuning_Images
20190917_150442.jpg
Diagram of 3.5m^2 Gullwing door diagram.
Trip3_Tuning_Images
20190917_150823.jpg
Wheelhouse.
Trip3_Tuning_Images
20190917_150827.jpg
Wheelhouse laptop station.
Trip3_Tuning_Images
20190917_150834.jpg
Wheelhouse.
Trip3_Tuning_Images
20190918_063813.jpg
Repairing twine in OBT2 damaged from basking shark after tow 6.
Trip3_Tuning_Images
20190918_063814.jpg
Repairing twine in OBT2 damaged from basking shark after tow 6.
Trip4_ComparisonTrials
P9210001.JPG
Capt. Phillips attaching GoPro camera and Sartek lights to OBT2 footrope.
Trip4_ComparisonTrials
P9210002.JPG
Capt. Phillips attaching GoPro camera and Sartek lights to OBT2 footrope.
Trip4_ComparisonTrials
P9210003.JPG
GoPro camera and Sartek lights on OBT2 footrope.
Trip4_ComparisonTrials
P9210004.JPG
GoPro camera and Sartek lights on OBT2 footrope.
Trip4_ComparisonTrials
P9210005.JPG
Setting out OBT2, tow 1. Capt Phillips inspecting
Trip4_ComparisonTrials
P9210006.JPG
Setting out OBT2, tow 1. RBR logger on headline.
Trip4_ComparisonTrials
P9210007.JPG
Setting out OBT2, tow 1. Close up of port side helix twine.
Trip4_ComparisonTrials
P9210008.JPG
Setting out OBT2, tow 1.
Trip4_ComparisonTrials
P9210009.JPG
Setting out OBT2, tow 1. Triplate.
Trip4_ComparisonTrials
P9210010.JPG
Setting out OBT2, tow 1.
Trip4_ComparisonTrials
P9210012.JPG
Bow of the F/V Illusion.
Trip4_ComparisonTrials
P9210013.JPG
Deck of the F/V Illusion.
Trip4_ComparisonTrials
P9210014.JPG
Stern view.
Trip4_ComparisonTrials
P9210015.JPG
Stern view.

67
Trip4_ComparisonTrials
P9210016.JPG
Deck of the F/V Illusion.
Trip4_ComparisonTrials
P9210017.JPG
Repairing small meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210018.JPG
Repairing small meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210019.JPG
Repairing small meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210021.JPG
Crew inspecting OBT2.
Trip4_ComparisonTrials
P9210022.JPG
Crew inspecting OBT2.
Trip4_ComparisonTrials
P9210023.JPG
Crew inspecting OBT2.
Trip4_ComparisonTrials
P9210024.JPG
Simrad sensor and RBR logger on OBT2 headline.
Trip4_ComparisonTrials
P9210020.JPG
Repairing small meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210025.JPG
Starboard side red helix meshes from OBT2.
Trip4_ComparisonTrials
P9210026.JPG
Starboard side red helix meshes with opposite coils from OBT2.
Trip4_ComparisonTrials
P9210027.JPG
Repairing meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210028.JPG
Repairing meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210029.JPG
Repairing meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210030.JPG
Repairing meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210032.JPG
Repairing meshes in OBT2 after tow 1.
Trip4_ComparisonTrials
P9210033.JPG
OBT2 triplates
Trip4_ComparisonTrials
P9210034.JPG
OBT2 triplates
Trip4_ComparisonTrials
P9210035.JPG
OBT2 triplates
Trip4_ComparisonTrials
P9210036.JPG
Adding chains to OBT2 triplates
Trip4_ComparisonTrials
P9210037.JPG
Outrigger.
Trip4_ComparisonTrials
P9210038.JPG
Scenic moon.
Trip4_ComparisonTrials
P9220039.JPG
Common dolphin in codend after OBT2 tow 2.
Trip4_ComparisonTrials
P9220040.JPG
Releasing common dolphin in codend after OBT2 tow 2.
Trip4_ComparisonTrials
P9220041.JPG
Indicating tow 2.
Trip4_ComparisonTrials
P9220042.JPG
Common dolphin from OBT2 tow 2.
Trip4_ComparisonTrials
P9220043.JPG
Common dolphin from OBT2 tow 2.
Trip4_ComparisonTrials
P9220044.JPG
Common dolphin from OBT2 tow 2.
Trip4_ComparisonTrials
P9220045.JPG
Common dolphin from OBT2 tow 2.
Trip4_ComparisonTrials
P9220046.JPG
Shine on drop chains after OBT2 tow 3.
Trip4_ComparisonTrials
P9220047.JPG
Preparing drop chains.
Trip4_ComparisonTrials
P9220048.JPG
Drop chains.
Trip4_ComparisonTrials
P9220049.JPG
Setting OBT2.
Trip4_ComparisonTrials
P9220050.JPG
Attaching drop chains to OBT2.
Trip4_ComparisonTrials
P9220051.JPG
Indicating tow 4.
Trip4_ComparisonTrials
P9220052.JPG
Wheelhouse plotter, sounder, and Simrad readout.
Trip4_ComparisonTrials
P9220053.JPG
Fish marks on sounder.
Trip4_ComparisonTrials
P9220054.JPG
Indicating tow 5.
Trip4_ComparisonTrials
P9220055.JPG
Kite on Ruhle trawl
Trip4_ComparisonTrials
P9220056.JPG
Setting up Ruhle trawl.
Trip4_ComparisonTrials
P9220057.JPG
Lower pad configuration on Gullwing door.
Trip4_ComparisonTrials
P9220058.JPG
Upper pad configuration on Gullwing door.
Trip4_ComparisonTrials
P9220059.JPG
Bail adjustment on Gullwing door.
Trip4_ComparisonTrials
P9220060.JPG
Bail adjustment on Gullwing door.
Trip4_ComparisonTrials
P9220061.JPG
Tow 5 on data sheet.
Trip4_ComparisonTrials
P9220062.JPG
Setting out tow 5 Ruhle trawl.
Trip4_ComparisonTrials
P9220063.JPG
Catch from tow 5, Ruhle trawl.
Trip4_ComparisonTrials
P9220064.JPG
Weight additions on doors prior to tow 6.
Trip4_ComparisonTrials
P9220065.JPG
Weight additions on doors prior to tow 6.
Trip4_ComparisonTrials
P9220066.JPG
Indicating tow 6.
Trip4_ComparisonTrials
P9220067.JPG
Porbeagle shark caught on tow 6.
Trip4_ComparisonTrials
P9220068.JPG
Porbeagle shark caught on tow 6.
Trip4_ComparisonTrials
P9220069.JPG
Porbeagle shark caught on tow 6.
Trip4_ComparisonTrials
P9220070.JPG
Porbeagle shark caught on tow 6.
Trip4_ComparisonTrials
P9220071.JPG
Upper pad Gullwing door position.
Trip4_ComparisonTrials
P9220072.JPG
Upper pad Gullwing door position.
Trip4_ComparisonTrials
P9230073.JPG
Dinner.
Trip4_ComparisonTrials
P9230074.JPG
Retrieving tow 8, Ruhle trawl
Trip4_ComparisonTrials
P9230075.JPG
Retrieving tow 8, Ruhle trawl
Trip4_ComparisonTrials
P9230076.JPG
Retrieving tow 8, Ruhle trawl
Trip4_ComparisonTrials
P9230077.JPG
Catch from tow 8.
Trip4_ComparisonTrials
P9230078.JPG
Catch from tow 8.
Trip4_ComparisonTrials
P9230079.JPG
Drop chains on deck.
Trip4_ComparisonTrials
P9230080.JPG
Drop chains on deck.
Trip4_ComparisonTrials
P9230081.JPG
Drop chains on deck.
Trip4_ComparisonTrials
P9230082.JPG
Data sheet of tow 9.
Trip4_ComparisonTrials
P9230083.JPG
Crewman on deck next to portside door.
Trip4_ComparisonTrials
P9230084.JPG
Starboard side door showing bail configuration.

68
Trip4_ComparisonTrials
P9230085.JPG
Crewman adjusting weights on starboard side door.
Trip4_ComparisonTrials
P9230086.JPG
Crewmen on deck prior to tow 9.
Trip4_ComparisonTrials
P9230087.JPG
Crewman on deck retrieving tow 9.
Trip4_ComparisonTrials
P9230088.JPG
Crewmen on deck retrieving tow 9.
Trip4_ComparisonTrials
P9230089.JPG
Shine on drop chains from tow 9
Trip4_ComparisonTrials
P9230090.JPG
Shine on drop chains from tow 9
Trip4_ComparisonTrials
P9230091.JPG
Crewman on deck retrieving tow 9.
Trip4_ComparisonTrials
P9230092.JPG
Crewman on deck retrieving tow 9.
Trip4_ComparisonTrials
P9230093.JPG
Retrieving tow 9. RBR logger on footrope.
Trip4_ComparisonTrials
P9230094.JPG
Fishing vessel Nobska to stern.
Trip4_ComparisonTrials
P9230095.JPG
Fishing vessel Nobska to stern.
Trip4_ComparisonTrials
P9230096.JPG
Porbeagle in codend, tow 9.
Trip4_ComparisonTrials
P9230097.JPG
Two porbeagles on deck from tow 9.
Trip4_ComparisonTrials
P9230098.JPG
Two porbeagles on deck from tow 9. Aaron Whitman measures lengths
Trip4_ComparisonTrials
P9230099.JPG
Two porbeagles on deck from tow 9. Aaron Whitman measures lengths
Trip4_ComparisonTrials
P9230100.JPG
Two porbeagles on deck from tow 9.
Trip4_ComparisonTrials
P9230101.JPG
Two porbeagles on deck from tow 9.
Trip4_ComparisonTrials
P9230102.JPG
Two porbeagles on deck from tow 9.
Trip4_ComparisonTrials
P9230103.JPG
Two porbeagles on deck from tow 9.
Trip4_ComparisonTrials
P9230104.JPG
Two porbeagles on deck from tow 9. Rope around caudal to return shark to sea.
Trip4_ComparisonTrials
P9230105.JPG
Two porbeagles on deck from tow 9.
Trip4_ComparisonTrials
P9230001.JPG
Data sheet of tow 10.
Trip4_ComparisonTrials
P9230002.JPG
Drop chain after tow 10.
Trip4_ComparisonTrials
P9230003.JPG
OBT2 on drum after tow 10.
Trip4_ComparisonTrials
P9230004.JPG
Codend from tow 10.
Trip4_ComparisonTrials
P9230005.JPG
Tow 10 catch in codend.
Trip4_ComparisonTrials
P9230006.JPG
Tow 10 catch on deck.
Trip4_ComparisonTrials
P9240007.JPG
Retrieving OBT2 tow 11.
Trip4_ComparisonTrials
P9240008.JPG
Retrieving OBT2 tow 11.
Trip4_ComparisonTrials
P9240009.JPG
Retrieving OBT2 tow 11.
Trip4_ComparisonTrials
P9240010.JPG
Tow 11 codend catch.
Trip4_ComparisonTrials
P9240011.JPG
Tow 11 catch. Two common dolphins.
Trip4_ComparisonTrials
P9240012.JPG
Tow 11 catch. Two common dolphins.
Trip4_ComparisonTrials
P9240013.JPG
Tow 11 catch. Two common dolphins.
Trip4_ComparisonTrials
P9240014.JPG
Tow 11 catch. Two common dolphins.
Trip4_ComparisonTrials
P9240015.JPG
Tow 11 catch. Common dolphin
Trip4_ComparisonTrials
P9240016.JPG
Data sheet showing tow 12.
Trip4_ComparisonTrials
P9240017.JPG
Catch from tow 12. Haddock
Trip4_ComparisonTrials
20190924_120921.jpg
Tow 13 fish marks and GPS coordinates.
Trip4_ComparisonTrials
20190924_120924.jpg
Tow 13 fish marks and GPS coordinates.
Trip4_ComparisonTrials
20190924_121525.jpg
Tow 13 fish marks, GPS coordinates, Simrad data.
Trip4_ComparisonTrials
20190924_121531.jpg
Tow 13 fish marks, GPS coordinates, Simrad data.
Trip4_ComparisonTrials
20190924_121534.jpg
Tow 13 fish marks.
Trip4_ComparisonTrials
P9240018.JPG
Crew retrieving tow 13.
Trip4_ComparisonTrials
P9240019.JPG
Data sheet indicating tow 13.
Trip4_ComparisonTrials
P9240020.JPG
Crew retrieving tow 13.
Trip4_ComparisonTrials
P9240021.JPG
Aaron Whitman on deck.
Trip4_ComparisonTrials
P9240022.JPG
David Chosid on deck.
Trip4_ComparisonTrials
P9240023.JPG
Opening tow 13 codend.
Trip4_ComparisonTrials
P9240024.JPG
Tow 13 catch. Haddock.
Trip4_ComparisonTrials
P9240025.JPG
Sampling station.
Trip4_ComparisonTrials
P9240026.JPG
Sampling station.
Trip4_ComparisonTrials
P9240027.JPG
Vessel conveyer.
Trip4_ComparisonTrials
P9240028.JPG
Sampling station.
Trip4_ComparisonTrials
P9240029.JPG
Crew retrieving tow 14.
Trip4_ComparisonTrials
P9240030.JPG
Data sheet indicating tow 14.
Trip4_ComparisonTrials
P9240031.JPG
Crew retrieving tow 14.
Trip4_ComparisonTrials
P9240032.JPG
Crew retrieving tow 14.
Trip4_ComparisonTrials
P9240033.JPG
Crew retrieving tow 14.
Trip4_ComparisonTrials
P9240034.JPG
Crew retrieving tow 14.
Trip4_ComparisonTrials
P9240035.JPG
Crew retrieving tow 14 codend.
Trip4_ComparisonTrials
P9240036.JPG
Crew retrieving tow 14 codend.
Trip4_ComparisonTrials
P9240037.JPG
Tow 14 codend catch. Porbeagle shark.
Trip4_ComparisonTrials
P9240038.JPG
Tow 14 codend catch. Porbeagle shark.
Trip4_ComparisonTrials
P9240039.JPG
Tow 14 codend catch. Porbeagle shark.
Trip4_ComparisonTrials
P9240040.JPG
Tow 14 codend catch. Porbeagle shark.
Trip4_ComparisonTrials
P9240041.JPG
Tow 14 codend catch. Porbeagle shark.
Trip4_ComparisonTrials
P9240042.JPG
Retrieving tow 15.

69
Trip4_ComparisonTrials
P9240043.JPG
Retrieving tow 15. Porbeagle shark.
Trip4_ComparisonTrials
P9240044.JPG
Retrieving tow 15. Porbeagle shark.
Trip4_ComparisonTrials
P9240045.JPG
Retrieving tow 15. Porbeagle shark.
Trip4_ComparisonTrials
P9240046.JPG
Retrieving tow 15. Porbeagle shark.
Trip4_ComparisonTrials
P9240047.JPG
Retrieving tow 15. Porbeagle shark. Line around caudal to return to sea.
Trip4_ComparisonTrials
P9240048.JPG
Upper pad Gullwing door position prior to tow 16.
Trip4_ComparisonTrials
P9240049.JPG
Upper pad Gullwing door position prior to tow 16.
Trip4_ComparisonTrials
P9240051.JPG
Crewman on deck prior to tow 16.
Trip4_ComparisonTrials
P9240052.JPG
Upper pad Gullwing door position prior to tow 16.
Trip4_ComparisonTrials
P9240053.JPG
Changing door weights prior to tow 16.
Trip4_ComparisonTrials
P9240054.JPG
Changing door weights prior to tow 16.
Trip4_ComparisonTrials
P9240055.JPG
Crew changing door rigging for tow 16.
Trip4_ComparisonTrials
P9240056.JPG
Captain Phillips changing door weights prior to tow 16.
Trip4_ComparisonTrials
P9240057.JPG
Data sheet indicating tow 16.
Trip4_ComparisonTrials
P9250058.JPG
Tow 17 catch. Porbeagle.
Trip4_ComparisonTrials
P9250059.JPG
Tow 17 catch. Porbeagle.
Trip4_ComparisonTrials
P9250060.JPG
Tow 17 catch. Porbeagle.
Trip4_ComparisonTrials
P9250061.JPG
Tow 17 catch. Porbeagle.
Trip4_ComparisonTrials
P9250062.JPG
Monkfish from tow 17.
Trip4_ComparisonTrials
P9250063.JPG
Monkfish from tow 17.
Trip4_ComparisonTrials
P9250064.JPG
Datasheet for tow 18.
Trip4_ComparisonTrials
P9250065.JPG
Catch from tow 17.
Trip4_ComparisonTrials
P9250066.JPG
Crew with catch from tow 17.
Trip4_ComparisonTrials
P9250067.JPG
Data sheet indicating tow 19.
Trip4_ComparisonTrials
P9250068.JPG
Retrieving tow 19.
Trip4_ComparisonTrials
P9250069.JPG
Retrieving tow 19.
Trip4_ComparisonTrials
P9250070.JPG
Codend from tow 19.
Trip4_ComparisonTrials
P9250071.JPG
Catch from tow 19.
Trip4_ComparisonTrials
P9250072.JPG
Data sheet indicating tow 20.
Trip4_ComparisonTrials
P9250073.JPG
Retrieving tow 20.
Trip4_ComparisonTrials
P9250074.JPG
Retrieving tow 20.
Trip4_ComparisonTrials
P9250075.JPG
Retrieving tow 20.
Trip4_ComparisonTrials
P9250076.JPG
Retrieving tow 20.
Trip4_ComparisonTrials
P9250077.JPG
Retrieving tow 20.
Trip4_ComparisonTrials
P9250078.JPG
Retrieving tow 20 codend. Dogfish tow.
Trip4_ComparisonTrials
P9250079.JPG
Retrieving tow 20 codend. Dogfish tow.
Trip4_ComparisonTrials
P9250080.JPG
Aaron Whitman inspecting tow 20.
Trip4_ComparisonTrials
P9250081.JPG
Retrieving tow 20 codend. Dogfish tow.
Trip4_ComparisonTrials
P9250082.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250084.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250085.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250086.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250087.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250088.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250089.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250090.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250091.JPG
Captain Phillips cutting codend to release dogfish on tow 20.
Trip4_ComparisonTrials
P9250092.JPG
Retrieving tow 20.
Trip4_ComparisonTrials
P9250093.JPG
Retrieving tow 20 codend.
Trip4_ComparisonTrials
P9250094.JPG
Retrieving tow 20 codend.
Trip4_ComparisonTrials
P9250095.JPG
Retrieving tow 20 codend.
Trip4_ComparisonTrials
P9250096.JPG
Retrieving tow 20 codend.
Trip4_ComparisonTrials
P9250097.JPG
Retrieving tow 20 codend.
Trip4_ComparisonTrials
P9250098.JPG
Capt. Phillips on deck.
Trip4_ComparisonTrials
P9250099.JPG
Scenic.
Trip4_ComparisonTrials
P9250100.JPG
Scenic.
Trip4_ComparisonTrials
P9250101.JPG
Scenic.
Trip4_ComparisonTrials
P9250103.JPG
Scenic.
Trip4_ComparisonTrials
P9250104.JPG
Data sheet indicating tow 21.
Trip4_ComparisonTrials
P9250105.JPG
Retrieving tow 21 codend.
Trip4_ComparisonTrials
P9250106.JPG
Tow 21 catch.
Trip4_ComparisonTrials
P9250107.JPG
Tow 21 catch.

70
Appendix 3 – Supporting Material
Figure 29: Depths (m, y-axis) of the headline (pink), footrope (blue), starboard door (red), and
port door (green) over time (x-axis) by tow (panels) of the OBT1during trip 1 from RBR loggers.

71
Figure 30: OBT1 headline heights, vertical openings, and wing spreads (y-axis) over time (x-
axis) for tow numbers (panels) from Notus sensors on trip 1, represented by blue, pink, and
green lines respectively.

72
Figure 31: Vertical openings, headline heights and footrope heights (blue, pink, and green
points, y-axis) of OBT1 on trip 2 from Simrad sensors over time (x-axis) for tows(panels).

73
Figure 32: Depths (m, y-axis) of headline (pink) and footrope (blue) over time (x-axis) by tow
(panels) during trip 2 using the OBT1 from RBR loggers.

74
Figure 33: Depths (m, y-axis) of starboard door (pink) and port door (blue) over time (x-axis) by tow
(panels) using OBT2 during trip 3 from RBR loggers.
Figure 34: Distances (m) of vertical openings, headline heights, and footrope heights (y-axis,
blue, pink, and green) over time (x-axis) by tows(panels) for the OBT2 on trip 3, OBT2 using
Simrad sensors.

75
Figure 35: Distances (m) of vertical openings, headline heights and footrope heights (y-axis,
blue, pink, and green) over time (x-axis) by tows(panels) for the OBT2 on trip 4 using Simrad
sensors. Vertical opening data points may be obscured by overlapping headline height points.

76
Figure 36: Footrope (blue) and headline (pink) depths (m, y-axis) over time (x-axis) by tow
(panels) during trip 4 on the OBT2(bottom) from RBR loggers.