Gary Stauffer (Compiler)

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

NOAA Technical Memorandum NMFS-SPO-65

October 2004

NOAA Protocols for Groundfish

Bottom Trawl Surveys of the

Nation’s Fishery Resources

March 16, 2003

U.S. Department of Commerce

Donald L. Evans, Secretary

National Oceanic and Atmospheric Administration

Vice Admiral Conrad C. Lautenbacher, Jr., USN (Ret.)

Under Secretary for Oceans and Atmosphere

National Marine Fisheries Service

William T. Hogarth, Assistant Administrator for Fisheries

NOAA Technical Memorandum NMFS-SPO-65

October 2004

Compiled under the direction of:

Gary Stauffer

Leader of Trawl Survey Protocol Development

Alaska Fisheries Science Center

NOAA Protocols for Groundfish

Bottom Trawl Surveys of the

Nation’s Fishery Resources

March 16, 2003
Suggested citation:

Stauffer, Gary (compiler). 2004. NOAA Protocols for Groundfish Bottom Trawl Surveys of the

Nation’s Fishery Resources. U.S. Dep. Commerce, NOAA Tech. Memo. NMFS-F/SPO-65, 205 p.

A copy of this report may be obtained from:

RACE Division, F/AKC1

NMFS, NOAA

7600 Sand Point Way NE

Seattle, WA 98115

Or online at:

http://spo.nmfs.noaa.gov/tm/
iii

Table of Contents

INTRODUCTION .............................................................1

NOAA FISHERIES TRAWL SURVEY PROTOCOLS ................................3

Protocol 1: Length Measurement of Trawl Warps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Protocol 2: Use of Autotrawl Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Protocol 3: Survey Operational Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Protocol 4: Trawl Construction and Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Protocol 5: Changes to Regional Trawl Survey Protocols . . . . . . . . . . . . . . . . . . . . . . . . 8

RECOMMENDATIONS FOR ADDITIONAL WORK TO IMPLEMENT PROTOCOLS ....9

Wire Rope Specifications and Measurement Standards . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Survey Standardization Working Group (SSWG) ............................9

Training in Trawl Construction and Repair Verification . . . . . . . . . . . . . . . . . . . . . . . . . . 9

WORKSHOP PARTICIPANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

REGIONAL PROTOCOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Appendix 1 - Alaska Fisheries Science Center Standard Operating Protocols . . . . . . . . 17

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Protocol 1: Warp Measurement Standardization. . . . . . . . . . . . . . . . . . . . . . . . . 19

Protocol 2: Auto-trawl Standardization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Protocol 3: Operations Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Protocol 4: Trawl Construction and Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
iv

Appendix 2 - Northwest Fisheries Science Center Standard Operating Protocols . . . . . 81

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Protocol 1: Warp Measurement Standardization. . . . . . . . . . . . . . . . . . . . . . . . . 84

Protocol 2: Auto-trawl Standardization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Protocol 3: Operations Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Protocol 4: Trawl Construction and Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Appendix 3 - Southwest Fisheries Science Center Standard Operating Protocols . . . . 103

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Protocol 1: Length Measurement of Trawl Warps . . . . . . . . . . . . . . . . . . . . . . 106

Protocol 2: Use of Auto-trawl Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Protocol 3: Survey Operations Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Protocol 4: Trawl Construction and Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Appendix 4 - Northeast Fisheries Science Center Standard Operating Protocols . . . . . 123

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Protocol 1: Length Measurement of Trawl Warps . . . . . . . . . . . . . . . . . . . . . . 127

Protocol 2: Use of Autotrawl Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Protocol 3: Survey Operations Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Protocol 4: Trawl Construction and Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

Protocol 5: Changes to Regional Trawl Survey Protocols . . . . . . . . . . . . . . . . 163

NOAA Fisheries Trawl Survey Protocols
1

INTRODUCTION

The National Trawl Survey Standardization Workshop was convened 13-15 November 2002

with the directive, based on the 16 September 2002 V.ADM. Conrad Lautenbacher memo, to

“review current protocols and directives regarding trawl survey operation, determine what

changes are needed and publish a new protocol”. The objective of this effort was “to ensure that

all aspects of preparation for trawl surveys and trawl survey procedures are consistent and in

keeping with the highest quality standards to provide for survey data accuracy and consistency

from one survey to the next”. For greater focus in the workshop, the definition of “trawl

surveys” was narrowed to exclude surveys using towed sampling devices with rigid-frames, such

as clam or scallop dredges, surveys not producing measures of catch per unit of effort as a

product, such as the trawling associated with fishery-acoustic surveys and surveys not conducted

with bottom trawls on groundfish. The focus was further narrowed to exclude catch sampling to

allow the workshop sufficient time to adequately address issues influencing the trawling process

itself.

Since the principal products of trawl surveys are fishery-independent indices of stock abundance

used in stock assessment models, the essential feature of maintaining “consistency from one

survey to the next” is that survey catchability (i.e., the relationship between the true population

abundance and the survey index) must remain stationary and therefore lack any time trend. For

surveys that geographically encompass the target stock, stationarity in survey catchability can

often be achieved by ensuring constancy in the sampling efficiency of the trawl, which, in turn,

can be achieved by ensuring constancy in the construction and repair of the trawl and the

procedures used in its operation. The protocols proposed in this report are therefore focused on

these issues. 

NOAA Fisheries conducts groundfish trawl surveys with a wide variety of characteristics. Not

only do the target species, and therefore the appropriate sampling methods, differ among surveys,

but the characteristics of the survey vessels differ and include chartered fishing vessels as well as

NOAA research vessels. Because of this variety, NOAA Fisheries protocols for standardization

of groundfish trawl surveys are specified in general terms to establish the purpose of the protocol

and delineate a strategy for its use. The implementation of the protocols for each trawl survey in

each region is then provided in appendices. An overarching theme through this document is that

the intent of standardization is not to eliminate variability in methodology among Science

Centers, but to ensure that the methodology that is used by each Science Center is consistent over

time.

Introduction

3

NOAA FISHERIES TRAWL SURVEY PROTOCOLS

Protocol 1: Length Measurement of Trawl Warps

Problem Statement

For trawls having two warps (i.e., towing cables), consistency in the measurement of warp length

is important for maintaining consistency in trawl performance in two distinct ways. First, the

length of the warp relative to the water depth (i.e., scope ratio) influences door spread and other

aspects of trawl geometry. Second, the length of the warp on one side of the vessel relative to

that on the other side influences the symmetry of the trawl and, depending on the degree of net

skew, potentially influences trawl efficiency by affecting footrope contact with the bottom,

headrope height, or fish herding. Since trawl performance is relatively insensitive to small

variations in scope ratio, all measurement methods currently used on NOAA or chartered

vessels are considered sufficiently accurate for scope ratio determination. In contrast, trawl

performance may be quite sensitive to differences in lengths of the warps relative to each other

and additional measures to ensure that the difference is maintained within a specified tolerance is

considered important. This is especially true for surveys in which trawling is conducted with a

fixed length of warp throughout the tow (i.e., locked winches). For surveys using autotrawl

systems, however, the warp length is dynamically increased or decreased on each side of the

vessel during a tow in response to differences in tension and precise measurement of relative

warp length is relatively unimportant. 

Currently during NOAA trawl surveys, warp length is determined either statically by

periodically measuring and marking the warps at fixed increments or dynamically by attaching

some real-time measuring device to the warps. All of the currently used methods of measurement

have inherent problems that can lead to inaccurate measurement. For example, differential warp

length can result from inaccurate measurement before a survey begins, from differential warp

stretch and contraction of marked warps during a survey or from inaccuracy and slippage of

metering devices. As a consequence, the proposed protocol uses the comparison of redundant

measuring systems to detect differences in warp length beyond a tolerance limit.

Procedures

For two warp trawling systems, two independently-calibrated measuring methods or devices

shall be used on each warp, one of which will measure the warp in real time.

If the difference between the two measured distances, summed over both warps, becomes greater

than 4% (or another value specified by each program and justified by independent research) of

the door-to-door cable distance (i.e., sum of bridle lengths and the footrope), operations must be

suspended until a cause is found and resolved.

When chartering vessels for surveys, programs will clearly specify and verify use of the same

wire type and size consistently among vessels and years.

Protocols
4

Specification of the warp measurement system used on each survey will be included in an

Operations Plan provided by the Science Center to the officers and crew of the survey vessel.

Sub-protocols for Specific Warp Measurement Technologies

Protocol 1a: Physical Warp Markings

Physical marking of trawl warps generally involves spooling the wires off the drums and onto a

flat surface to measure the wire relative to standard lengths. The NOAA standard for such

measurements will be that both port and starboard wires will be measured and marked side-byside to ensure that the relative warp measurements between wires are exact. The spacing of such

marks, details of marking method (fiber marks interwoven in wire rope strands or painting of

marks), and degree of tension on the wires will be specific to the application. These marks will

be checked and recalibrated at least annually and rechecked after a survey or whenever

unreconcilable discrepancies between warp marks and the redundant measurement system

persist.

Under circumstances where remarking of warps side-by-side may be impossible, trawl warps

may be measured and marked at sea using the following procedure. Calibrated in-line wire

meters can be used to measure and mark length intervals of one warp at a time when deployed

under tension (i.e., loaded with doors and trawl during a setting-retrieval exercise). Position of

all marks should be confirmed by repeating the measurements. The wire meters will be

calibrated at least annually using a known length of wire.

Protocol 1b: In-line Wire Meters

In-line wire meters measure wire lengths directly using running line tensiometers or

instrumented blocks over which the warp travels as it is payed out or retrieved. Such systems

deflect the running wire by a known amount to facilitate measuring under tension and may be

subject to deviations from true measurements due to wire slippage. These devices should be

calibrated using known lengths of wire at least annually, using manufacturer recommended

procedures, with moving parts (bushings, sheaves, etc.) inspected and replaced, as required.

Since some in-line wire meters are relatively small and portable, they may be provided to the

vessels by the Science Centers provided they are appropriately calibrated.

Protocol 1c: Block Wire Counters

Block wire counters measure the length of wire passing over a trawl block or another wheel of

known circumference which is equipped with a proximity counter to enumerate the number of

revolutions of the sheave. Length of the wire is thus calculated by multiplying the number of

block revolutions by the circumference of the sheave. These devices may be subject to

deviations from true measurements due to wire slippage. Block counters should be calibrated at

least annually with a known length of wire after assuring the proper functioning of the proximity

counter and measuring sheave.

NOAA Fisheries Trawl Survey Protocols
5

Protocol 1d: Geometric Wire Counters

Geometric wire counters (used as stand-alone wire measuring method or as a component of

autotrawl systems) utilize the number of winch turns, diameter and width of the winch drum,

diameter of wire and other parameters to compute the absolute amount of wire off each winch. 

These systems may lose calibration if the wire diameter decreases due to stretch or if the wires

do not wrap properly on the winches. The counter can be recalibrated by using a known length

of wire wrapped on the winches. These calibrations should be performed at least annually, or

more frequently if there are changes in wire diameter or the performance of wire wrapping on

the winches.

Discussion

The proposed protocol requires that the two independent warp measurements be reconciled when

the differences in the warp lengths exceeds 4% of the cable distance (curved distance) from one

door to the other aft of the doors (e.g., if the cable distance is 50 m, a warp difference greater

than 2 m would be considered critical). The 4% standard is documented in the Northeast

Fisheries Science Center Reference Document 02-15 - Report of the Workshop on Trawl Warp

Effects on Fishing Gear Performance posted on the web October 25, 2002. This is a general

guideline, and specific research on the effects of various wire offsets on trawl catch performance

may document different critical warp offset distances, depending on the gear and target species

for individual trawl survey programs.

Protocol 2: Use of Autotrawl Systems

Problem Statement

Autotrawls can be used in a static mode to spool out warp after a hang-up as a means of reducing

trawl damage or in a dynamic mode to maintain equal tension on both warps. Autotrawl systems

are quite common on large trawlers and are standard in most European trawl surveys. When used

in a dynamic mode, autotrawls help preserve proper trawl function by adjusting the lengths of

the two warps independently to correct for asymmetry of the trawl caused by a sloping bottom or

oblique water flow and obviates the need for precise measurement of warp length. Although this

leads to better standardization in trawl performance, such benefits are only realized when the

autotrawl system is in good working condition and properly calibrated. 

Protocols
6

Procedures

NOAA vessels or chartered fishing vessels supporting trawl surveys using dynamic autotrawl

systems must have the system tested and certified by a qualified technician at least annually, or

more frequently, as required. Items inspected may include, but are not limited to, correct

operation of pumps, motors and other moving components, and verification of parameters in

controller software. 

Protocol 3: Survey Operational Procedures

Problem Statement

Standardization of station selection, gear deployment, operation, and retrieval procedures are

critical for maintaining consistency in survey catchability over time. Factors that can affect gear

performance and catchability of marine organisms include selection of tow location; speed

during setting, towing, and retrieval of gear; determination of scope ratio; estimation and

standardization of tow distance; tow direction; and maximum sea state. Written unambiguous

protocols specifying these and other issues that may affect survey consistency provide a

mechanism for communication between scientific staff and the officers and crew of the research

vessel which maintains continuity in procedures as personnel and vessels change over time. 

Procedures

Each Science Center will provide a written Operations Plan to their staff and the crew of the

survey vessels that provides clear and unambiguous definitions of all procedures required to

properly conduct trawl sampling. The Operations Plan will be discussed by the Chief Scientist

and the vessel crew at the start of each survey and again when crew changes occur. The

Operations Plan may include, but is not limited to, the following issues:

a. Scope ratio

b. Speed of a tow

c. Duration or distance of a tow

d. Direction of tow 

e. Location of sampling sites, and procedures to use if stations are not suitable for towing.

f. Criteria for determining the success of a tow and procedures to use if a tow was

unsuccessful.

g. Vessel and winch operation during trawl deployment and retrieval.

h. Methodology for warp measurement and verification.

i. Trawl construction plans, at-sea repair instructions and repair verification checklist.

j. Defining responsibility (i.e., survey scientists or vessel crew) for decisions regarding

various aspects of the operations.

NOAA Fisheries Trawl Survey Protocols
7

Discussion

Although nearly all NOAA Fisheries trawl surveys provide some form of an operations plan to

their staff and the officers and crew of the survey vessels, some aspects of the operation that

potentially influence survey catchability may be omitted or specified in insufficient detail to

eliminate individual interpretation. By increasing the level of detail, and formalizing the

communication of procedures, the intent is to make operations consistent among members of

scientific staff and vessel crew and consistent over time.

Protocol 4: Trawl Construction and Repair

Problem Statement

Standardization of trawl construction and repair is unquestionably the most critical element for

survey standardization because, on NOAA Fisheries trawl surveys, trawls are not simply devices

to capture fish but are scientific instruments used to sample fish populations. Our sampling

trawls must conform to higher levels of tolerance in their construction and repair than

commercial fishing gear. The difference in the objectives of commercial fishing and scientific

sampling, and its concomitant effects on trawl design and repair, are rarely appreciated and often

have contributed to misunderstanding between NOAA Fisheries and the commercial fishing

industry. This misunderstanding can directly impact trawl survey standardization in two distinct

ways. First, Science Centers lacking the capability to build their own survey trawls must instead

rely on the services of trawl manufacturers whose primary customers are commercial fishermen.

As a consequence, survey trawls may be constructed with the level of tolerance needed for

commercial fishing rather than with the more rigorous level required for scientific sampling.

Second, all members of the crew of NOAA or charter trawlers that make at-sea repairs to survey

trawls have gained their expertise for doing so from their past experience as commercial trawl

fishermen. The repair techniques used by commercial fishers, however, are typically those

needed to return the gear to service as soon as possible rather than those needed to return it to

service in the same condition as before damage. Because NOAA survey trawls are true scientific

sampling instruments, the protocols considered in this sections are designed so that survey trawls

are constructed and repaired with a level of detail needed to ensure, within specified tolerances,

that the identical trawl is used at every sampling site on every cruise.

Procedures

Construction plans for each survey trawl design will be maintained by each Science Center and

included in an Operations Plan. The plans must include engineering drawings of the net, doors

and rigging with a level of detail at least as specific as that in the ICES recommended standard

(ICES C.M. 1989/B:44 Report of the Study Group on Net Drawing). In addition, each plan must

contain a description of all materials used, and the qualities of these materials considered

important for proper trawl function.

Protocols
8

A checklist will be developed for each trawl design specifying the dimensions, and their

tolerances, or other design features considered important for proper trawl function. The check

list will be used to verify that each newly constructed or repaired trawl is within operational

tolerances before use.

Verification that trawls are within operational tolerances will be conducted by members of the

scientific staff of each Science Center who are trained in trawl construction and repair

verification.

Methodology for at-sea trawl repairs will be specified in an Operations Plan and communicated

by the Chief Scientist to the crew of the vessel at the start of each cruise. A trawl repair

checklist will be included in the Operations Plan and used by a member of the scientific staff to

verify that repaired trawls are within operational tolerances.

A national training course in trawl construction and repair verification for both survey scientists

and crews of NOAA vessels will be conducted at regular intervals.

Discussion

The intent of this protocol is to ensure that, through more exacting specification and verification,

the trawls used in a survey will perform identically regardless of the circumstances under which

the trawl was constructed and repaired.

Protocol 5: Changes to Regional Trawl Survey Protocols

Changes to trawl survey operational protocols will be at the discretion of the appropriate Science

Director who may approve such changes directly or specify a peer review process to further

evaluate the justification and impacts of the proposed changes.

NOAA Fisheries Trawl Survey Protocols
9

RECOMMENDATIONS FOR ADDITIONAL WORK 

TO IMPLEMENT PROTOCOLS

Wire Rope Specifications and Measurement Standards

Given the requirements for accuracy and repeatability of wire rope performance and

measurement, an engineering study to determine standards and specifications for wire ropes to

be used in various trawling applications should be conducted. Additionally, a review of 

available wire rope measurement technologies and their accuracy, precision and re-calibration

for trawling applications is deemed a high priority.

Survey Standardization Working Group (SSWG)

The Trawl Survey Standardization Workshop has identified an ongoing need to coordinate the

development of national and regional standards and protocols, and to share information to

improve the precision and accuracy of such surveys. Accordingly, the formation of an ongoing

NOAA Fisheries Survey Standardization Working Group is recommended. In addition,

information and technology exchange among Science Centers could be facilitated with National

Marine Resource Survey Workshops, similar to those conducted periodically for stock

assessments.

Training in Trawl Construction and Repair Verification

To improve quality control in the construction and repair of survey trawls, survey scientists have

been assigned (Protocol 4) responsibility for verification that trawl dimensions and other

important operational qualities remain within specified tolerances. To do this, survey scientists

need additional training to obtain sufficient knowledge about trawl geometry to allow them to

verify important dimensions and properties of a trawl against a checklist of standards. It is also

recommended that the crews of NOAA vessels participating in at-sea trawl repair also take a

more in-depth training course in trawl construction so that the more exacting methods needed for

the repair of NOAA sampling trawls are clearly understood. A national training program must be

implemented to achieve this goal.

Recommendations

11

WORKSHOP PARTICIPANTS

Line Offices and Addresses: Name: Email:

Alaska Fisheries Science Center Erika Acuna Erika.Acuna@noaa.gov

7600 Sand Point Way NE Dave King David.L.King@noaa.gov

Seattle, WA 98115-0070 Bob Lauth Bob.Lauth@noaa.gov

Michael Martin Michael.Martin@noaa.gov

Dan Nichol Dan.Nichol@noaa.gov

David Somerton David.Somerton@noaa.gov

Gary Stauffer Gary.Stauffer@noaa.gov

Paul Von Szalay Paul.Von.Szalay@noaa.gov

Ken Weinberg Ken.Weinberg@noaa.gov

Mark Wilkins Mark.Wilkins@noaa.gov

Northeast Fisheries Science Center John Boreman John.Boreman@noaa.gov

 Woods Hole Laboratory Russell Brown Russell.Brown@noaa.gov

166 Water Street Charles Byrne Charles.Byrne@noaa.gov

Woods Hole, MA 02543-1026 Henry Milliken Henry.Milliken@noaa.gov

Steve Murawski Steve.Murawski@noaa.gov

NOAA Fisheries Headquarters John Herring John.Herring@noaa.gov

1315 East West Highway, SSMC3

Silver Spring, MD 20910

Workshop Partcipants
12

Southeast Fisheries Science Center Terry Henwood Terry.Henwood@noaa.gov

Mississippi Laboratories Gilmore Pellegrin Gilmore.Pellegrin@noaa.gov

 P.O. Drawer 1207 Charles Taylor Charles.W.Taylor@noaa.gov

Pascagoula,MS 39568-1207 Perry Thompson Perry.A.Thompson@noaa.gov

John Watson John.Watson@noaa.gov

Northwest Fisheries Science Center Elizabeth Clarke Elizabeth.Clarke@noaa.gov

2725 Montlake Boulevard East Teresa Turk Teresa.Turk@noaa.gov

 Seattle, WA 98112 Vanessa Tuttle Vanessa.Tuttle@noaa.gov

Newport Research Station Bldg 955 Rick Brown Rick.Brown@noaa.gov

2032 S. Oregon State Univ. Dr. Jean Rogers Jean.Rogers@noaa.gov

Newport , OR 97365

Office of Marine and Aviation Operations: Tim Clancy Tim.Clancy@noaa.gov

Marine Operations Center, Pacific John Clary John.C.Clary@noaa.gov

1801 Fairview Ave E Mike Francisco Mike.Francisco@noaa.gov

Seattle, WA 98102-3722 John Mcadam John.M.Mcadam@noaa.gov

Frank Wood Frank.Wood@noaa.gov

Northeast Marine Support Facility Michael Abbott Michael.S.Abbott@noaa.gov

166 Water Street Ken Rondeau Kenneth.Rondeau@noaa.gov

Woods Hole, MA 02543

NOAA Fisheries Trawl Survey Protocols
13

Southwest Fisheries Science Center Dave Griffith Dave.Griffith@noaa.gov

La Jolla Laboratory Chris Jones Chris.D.Jones@noaa.gov

8604 La Jolla Shores Drive Wayne Perryman Wayne.Perryman@noaa.gov

La Jolla, CA 92037-1508

Santa Cruz Laboratory Keith Sakuma Keith.Sakuma@noaa.gov

110 Shaffer Road

Santa Cruz, CA 95060

Honolulu Laboratory Michael Seki Michael.Seki@noaa.gov

2570 Dole Street 

 Honolulu Hawaii, 96822-2396 

ICES Experts:

Department of Fish and Oceans, MPO

St. Johns, Newfoundland, Canada Barry McCallum McCallumB@DFO-MPO.gc.ca

Fisheries Research Service Marine Lab

Aberdeen, Scotland Derek Galbraith R.D.Galbraith@marlab.ac.uk

Institute of Marine Research

Bergen, Norway

John

Willy Valdemarsen John.valdemarsen@imr.no

Gear Fabricators:

Applied Fish Gear Technology

8775 Fletcher Bay Rd. Gary Loverich Gloverich@oceanspar.com

 Pacific Fishermen Inc.

5351 24th Ave. NW

Seattle WA 98107

Doug Dixon DougD@Pacificfishermen.com

Workshop Partcipants

15

REGIONAL PROTOCOLS

Because of the diversity among NOAA trawl surveys, the trawl standardization protocols were,

in most cases, specified in general terms to allow each Science Center flexibility in its approach

to standardization. In this section, the specific methodology used by each NOAA survey is

detailed in either a complete Field Operations Plan or additions to existing Plans to bring them in

conformity with the requirements of the protocols.

Appendix 1 Alaska Fisheries Science Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Eastern Bering Sea Shelf Survey

Gulf of Alaska Survey

Aleutian Islands Survey

Eastern Bering Sea Upper Continental Slope Survey

Appendix 2 Northwest Fisheries Science Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

West Coast Survey

Appendix 3 Southwest Fisheries Science Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Antarctic Bottom Trawl Survey

Appendix 4 Northeast Fisheries Science Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Spring, Autumn and Other Bottom Trawl Surveys

Regional Protocols Introduction

17

Appendix 1

Alaska Fisheries Science Center

Standard Operating Protocols

Eastern Bering Sea Shelf Bottom Trawl Survey

Gulf of Alaska Bottom Trawl Survey

Aleutian Islands Bottom Trawl Survey

Eastern Bering Sea Upper Continental Slope Bottom Trawl Survey

Alaska Fisheries Science Center

19

Introduction

The Alaska Fisheries Science Center (AFSC) conducts four bottom trawl surveys, the Eastern

Bering Sea Shelf Survey, which occurs annually, and the Gulf of Alaska, Aleutian Islands, and

Eastern Bering Sea Upper Continental Slope Surveys, which are conducted biennially. Since

there are many similarities in the characteristics of these surveys, rather than presenting the

complete operations manual for each survey as evidence for their compliance with the new

NOAA trawl survey standardization protocols, we have instead presented, for each protocol and

survey, either excerpts of existing material from the current operations manuals or the new

material to be inserted into the revisions of the manuals.

Protocol 1: Warp Measurement Standardization

NOAA trawl survey standardization protocols (Protocol 1) require that two independentlycalibrated measuring methods or devices shall be used on each trawl warp, one of which will

measure the warp in real time. For AFSC bottom trawl surveys, the two measurement methods

will be: 1) warps measured and marked at sea using in-line Olympic trawl wire meters and 2)

warps measured in real time using geometric wire meters associated with the auto-trawl system.

Calibration of Warp Measurement Devices

Calibration of the Olympic Model 750-N in-line wire meter will occur during annual

maintenance and again at-sea. Annually, prior to the surveys, each meter will be returned to the

manufacturer (Olympic Instruments Inc.16901 Westside Highway S. W., Vashon, WA 98070)

where broken or worn parts (wheels, springs, counters, etc.) will be replaced and the unit cleaned

and lubricated. Each unit will be tested to determine whether it is performing within factory

specifications and calibrated to a known length of cable of similar properties to the warps used

on the surveys. 

At sea, each in-line meter must first be inspected to ensure it has not been damaged during

transport, then cleaned and again calibrated against a known length of warp (at least 50 m)

measured using the tape measures provided to each field party. The calibration can be done as

follows: 1) set the trawl with the doors just underwater at a speed of 2 knots, 2) mark the warp

with a piece of tape near the trawl sheave, 3) measure from this mark forward, in increments,

until a distance of at least 50 m of warp has been measured, then again mark with tape, 4) attach

the meter to the warp in an accessible location and secure fore and aft with rope, 5) measure the

marked distance with the in-line meter three times and 6) calculate a calibration coefficient (i.e.,

known length / measured length ) from the average of the three measurements.

Warp Measurement with the In-line Meter

Using the same in-line meter calibrated as above, measure each warp separately as follows: 1)

set the trawl, keeping the doors just below the sea surface and maintaining a speed of 2 knots, 2)

attach the meter to the warp as described above and set the counter to zero, 3) let out warp until

Alaska Fisheries Science Center
20

the counter indicates the corrected distance (i.e., measured distance multiplied by the calibration

coefficient) to the first mark, 4) mark the wire with paint at the reference position determined by

the skipper (e.g., forward of the blocks) and dry with a heat gun if necessary, 5) repeat 3 and 4,

until the last mark is applied using 25 fathom (45.73 m) intervals. After all marks are applied,

haul the trawl back until the doors are again just below the sea surface, zero the counter and

verify that the marks are in the correct positions. If the difference between the first and second

measurement of any mark exceeds 1 m, the entire marking procedure must be repeated.

Calibration of the Geometric Counters

During the warp marking process, record the warp length measured by the geometric counter for

each mark when the mark is at the reference position. Develop a table in which these reference

lengths and the marked lengths are recorded for each warp. These reference lengths will be used

during trawling operations to determine if stretching or shrinkage of the warps has occurred.

Warp Mark Verification During Survey Operations

During normal survey operations, the length of warp used on each tow will be verified by

performing a test based on the left and right warp lengths measured by the geometric wire meters

relative to the tabled values of the reference lengths. The procedure used will be as follows: 1)

set the trawl with the warp mark in the standard position relative to the block or other reference

point, 2) compare the length determined by the geometric meter for that tow with the tabled

value and enter the signed difference on the Haul Form for each warp, 3) if the difference of the

signed differences from both warps exceeds the critical value (see below), then retrieve and reset

the trawl (for example, with the 200 m marks set at the blocks, the port tabular value was 202

and now reads 203. The signed difference is +1. The starboard tabular value was 197 and now

reads 195, a signed difference of -2. The difference of the signed differences (+1 and -2) is 3.

This is within the critical value listed below and is acceptable), 4) if, after resetting, an

unacceptable difference persists then remark the warps. If a warp is damaged or repaired in any

manner, it shall be recalibrated.

Determination of Critical Value

According to Protocol 1, the maximum allowable offset between trawl wires is 4% of the

distance from door to door as measured around bridles and footrope. For the trawls used by the

AFSC, this critical value is determined as follows:

Poly Nor’eastern trawl: 

Door legs = 50'/side, bridles = 180'/side, footrope=120'

critical length = (50 + 50 + 180 + 180 + 120) * 0.04 

= 23.2 ft = 7.1 m

83-112 Eastern trawl:

Door legs = 50'/side, bridles = 180'/side, setback= 2'/side, footrope=112'

critical length= (50 + 50 + 180 + 180 + 2 + 2 +112) * 0.04

 = 23.0 ft = 7.0 m

NOAA Fisheries Trawl Survey Protocols
21

Proper Care and Stowage of In-line Meters

 During use, avoid any rough treatment of wire counters (for example do not leave them laying

out on deck, or allow them to slide around, or drop them between decks) and thoroughly clean

after each use with undiluted Simple Green detergent with particular attention to remove warp

grease buildup on roller. Allow the meter to dry completely before placing in case (dry in engine

room) and store in dry area.

Protocol 2: Auto-trawl Standardization

Three of the four AFSC bottom trawl surveys, Aleutian Islands, Gulf of Alaska, and Eastern

Bering Sea Upper Continental Slope, utilize auto-trawl systems in a dynamic mode and therefore

require annual servicing of the auto-trawl system by the charter vessels. The fourth bottom trawl

survey, the Eastern Bering Sea Shelf, maintains locked winches during trawling operations and

therefore does not require annual servicing of the auto-trawl system. However, the geometric

wire counters of the system are also used on the Eastern Bering Sea Shelf as an independent

measure of the warps after calibration with the measured marks. When required, a description of

the servicing of the auto-trawl system will be included in the vessel charter specifications. The

auto-trawl servicing requirements will read as follows: 

Prior to every trawl survey, NOAA and chartered fishing vessels must provide testing and

certification of their autotrawl systems by a qualified autotrawl mechanic no more than 30 days

prior to the start of the charter. Items inspected should include but are not limited to: 1) trawl

winch motors, including tests for internal leaks, 2) trawl winch drums to ensure that both drums

have equal widths and windings, 3) equalizing valve and all relief valves, 4) controller system to

ensure proper function and that all operational parameters (e.g., wire diameter, drum dimensions)

are correctly specified. In addition, sea trials are to be performed to verify proper winch function

(level wire winding), and proper dynamic operation (equal tension is maintained).

Additional information will be added to each operations manual describing the standard use of

an auto-trawl system. For each of the three surveys using auto-trawl systems the information will

read as follows:

 The auto-trawl wire tensioning system is designed to reduce net damage during hang-ups and

help square the net when making turns, on uneven slopes, and in currents. To ensure consistency

between vessels and over time, the Field Party Chief (FPC) will instruct the vessel crew to adjust

the equalization valve to allow the winches to respond to rapid increases in tension when the

trawl snags the bottom. However, the pressure differential needed to initiate winch adjustment

should not be so low that the winches are frequently adjusting warp length. All vessels will use

the same warp length difference as a parameter to initiate the offset alarm.

Alaska Fisheries Science Center
22

Protocol 3: Operations Procedures

Eastern Bering Sea Shelf (EBS) Bottom Trawl Survey

A. Scope

The following scope table will be used to determine the amount of warp to be set given the depth

of the survey station location. The FPC will discuss this table with the skipper and ensure that

this guideline is adhered to. It is understood that some events, including current velocity and

weather, may create a need to deviate from the specified value of scope. Should a deviation

occur, skippers must document and provide justification on the Haul Form.

Depth Range (fm) Wire Out (fm)

1 to 21 75

22 to 29 100

30 to 38 125

39 to 47 150

48 to 57 175

58 to 67 200

68 to 78 225

79 to 90 250

91 to 102 275

103 to 114 300

115 to 128 325

B. Speed of tow

The skipper is responsible for maintaining a constant towing speed of 3 knots from the time of

brake-set to haul back. Speed variations from 2.8 to 3.2 knots are acceptable, but the target is 3

knots and should be adhered to as closely as possible. Monitoring of tow speed will be

accomplished in real time using the global positioning system (GPS) unit supplied by the

scientific party. Should this NOAA provided GPS fail, the skipper should use the vessel

instrumentation that he/she believes most closely matches that of the supplied unit. In such

cases, the skipper/FPC will document in the Haul Form the instrumentation used to monitor tow

speed.

C. Duration and distance of tow and use of trawl mensuration / performance monitoring

instrumentation

The performance and geometry of trawls used during AFSC survey tows will be measured using

several sensors. Net height and width will be measured in real time using Scanmar or Netmind

sensors mounted on the center of the headrope and on the upper bridle just forward of the

NOAA Fisheries Trawl Survey Protocols
23

wingtips. Depth and temperature data will be measured using a self-contained bathythermograph

mounted near the center of the headrope. Bottom contact information will be measured with a

self-contained Bottom Contact Sensor (BCS) mounted on the center of the footrope. Detailed

descriptions of the rigging for each of these sensors is provided in the AFSC Net Mensuration

Manual, which is carried aboard all survey vessels. Annual training is mandatory for all staff

operating net mensuration and monitoring instruments and interpreting the data collected with

them.

Target duration of all tows will be 30 minutes towing time, which equates to approximately 1.5

nmi or 2.8 km at the standard towing speed of 3 knots. The 30 minute tow time is a proxy for a

target distance fished of 1.5 nmi at a speed of 3 knots, which is used in the swept area calculation

of catch per unit of effort (CPUE). The tow time will begin when the brakes are set (on the

relatively shallow Bering Sea Shelf it has been found that brake set and trawl touch down are

usually within a minute of each other). Haulback will occur after 30 minutes. Tows may be

shortened due to upcoming obstructions, inability to follow a depth contour, hangups, gear

problems, or extremely large catches which affect the efficiency of the trawl.

After the haul is completed, data from each of the sensors will be synchronized with the GPS

data and displayed simultaneously using custom designed software (ScanPlot). Using this

software, the operator will determine the precise moments that the footrope initially contacts

(On-Bottom) and leaves bottom (Off-Bottom) and calculate the duration, distance fished, and

average net spread and height during each tow. The trace of the BCS data is the most useful tool

for determining the On- and Off-Bottom times. The transition between when the net is on or off

bottom is usually clearly signaled by an abrupt change in readings from around 40 degrees to

around 60 degrees (vice versa when leaving bottom). Distance fished is determined from the

GPS vessel track between the On- and Off-Bottom positions. All tows will be made between 0.5

hr after sunrise and 0.5 hr before sunset. Sunrise and sunset times at a given latitude-longitude

are available on the AFSC GPS units.

D. Direction of tows

Tows will be made in the direction of the next tow. Due to the survey design, most tows will be

made in either a north or south direction, with the exception of corner stations. Tow direction

may be different from above if the skipper determines that safety is a concern, or if the net

performance in terms of trawl configuration is severely compromised (e.g., doors falling over

due to tow in direction of a strong current). The skipper must notify the FPC and document the

reason in the Haul Form for any deviation of the standard towing direction.

E. Location of sampling sites and procedures to use if stations are not suitable for towing

Tow locations are predetermined stations at the centers of a 20 × 20 nmi grid, except where

additional corner stations are allocated to obtain more precise estimates of king crab abundance

near the Pribilof Islands and St. Matthew Island, and stations where known obstructions prevent

using that location. All station locations are listed in Appendices of the Survey Operations

Manual. Two vessels are used in the survey. The survey shall begin at the easternmost stations

of Bristol Bay and the two vessels shall work alternate north-south columns toward the shelf

edge in the west. It is understood that occasional alterations may occur at the extremities of a

Alaska Fisheries Science Center
24

column to save time, but effort should be made to maintain the alternate column sampling. The

skipper shall begin the tow at a position before the station location, such that the middle of each

approximately 1.5 nmi tow shall cross near the center point of that station location.

For stations that cannot be completed at the listed station due to untrawlable bottom, an alternate

location shall be chosen which is no further than 1 nmi away from this center point (e.g., within

the same grid square). A list of stations for which poor tow performances have occurred in past

surveys is provided in a separate document (good-tow / bad-tow log). This document also

provides a list of alternate locations for these poor performance stations. These alternate station

locations were successfully completed within those grid squares during past EBS surveys.

F. Criteria for determining the success of a tow and procedures to use if a tow was

unsuccessful

A successful tow is defined as a tow in which the trawl was maintained on the bottom in the

standard fishing configuration as determined by net mensuration, bathythermograph, and bottom

contact instrumentation. The FPC will assure himself that the trawl was in adequate fishing

configuration, and preponderantly on bottom for the duration of the tow. As instructed above, 30

minute tows are the standard and should be completed as such unless otherwise instructed by the

FPC. Tows as short as 10 minutes are acceptable under conditions described in Item C or below.

Tows with any loss of fish or invertebrates due to significant tears in the net or with improper

fishing configuration are considered unsuccessful. Tows for which obstructions in the net (e.g.,

derelict crab pots) that could have potentially affected the CPUE are also considered

unsuccessful.

In some cases, if a hang-up or gear obstruction has occurred at a time that is fairly obvious, such

as a shudder or stopping of the vessel, and haulback is immediately started, the trawl should be

examined. If any damage is minimal and restricted to forward parts of the trawl, then the tow

may be considered successful. This assumes that at least 10 minutes of on bottom time was

achieved. If a significant tear-up or obstruction occurs, or it cannot be determined when the tear

or obstruction happened, then the tow must be considered unsuccessful.

Stations considered unsuccessful tows will be re-towed unless factors beyond the control of the

survey party make it impossible to complete the station within the grid square (e.g., extreme

current or ice coverage). The FPC will make the final decision as to whether the tow was

successful or not and whether it will be re-towed.

G. Vessel and winch operation during deployment and retrieval

To ensure comparability between vessels and years, vessel operators will be asked to follow

standard procedures when setting, towing, and retrieving the trawl gear. These procedures will

be established before the beginning of the first leg by the captain and the FPC and must be

maintained throughout the survey. The goals for each part of the standard tow are as follows:

NOAA Fisheries Trawl Survey Protocols
25

Setting

Primary Goal

• To ensure that the trawl is in fishing configuration (height and width) when it

makes bottom contact.

• To ensure that the procedure is easily repeatable.

Secondary Goals

• To ensure that the trawl reaches bottom quickly to minimize the midwater catch.

Towing

Goal

• To maintain the trawl in fishing configuration (height and width) at a continuous

towing speed of 3 knots.

Haulback

Primary Goals

• To maintain the trawl in fishing configuration until it leaves the bottom. 

• To ensure that the net leaves bottom quickly to avoid changes in fishing

configuration due to decreased scope and changes in net speed over ground (this

will usually require an increase in RPM).

• To ensure that the procedure is easily repeatable.

Implementation

Vessel speed, engine RPM, wire payout rate, etc., required to achieve these goals may require

some experimentation at the beginning of the first leg of the survey on each vessel. The captain

and the FPC should work out a standard procedure for setting, towing, and hauling back the

gear. The procedures decided upon should facilitate consistently achieving the above stated

goals and will be documented in writing on the Standard Trawling Procedures Form provided

and adhered to thereafter. Since the power settings (RPM and/or propeller pitch) to achieve

particular vessel speeds will change with the wind, sea state, and currents, approximate power

settings used to achieve these speeds in good weather conditions (little wind, no current) should

be recorded. If different procedures are developed for various depths, these should be recorded

as well. Any procedural modifications during the survey must be mutually agreed upon between

the FPC and the captain and must be carefully justified and documented in writing. It is

particularly important to maintain the procedures should the vessel captain change during the

survey. 

H. Defining responsibility (e.g., survey scientist or vessel crew) for decisions regarding

various aspects of the operation

All aspects of the survey operation will overseen by the FPC. Final decisions regarding station

locations and station scheduling are the responsibility of the FPC. Vessel operation, trawl gear

deployment and retrieval, and all matters related to vessel safety will be the responsibility of the

vessel Captain.

Alaska Fisheries Science Center
26

It is the responsibility of both the FPC and the captain of the vessel to keep lines of

communication open between survey vessels, not only for safety purposes, but to ensure that all

operations are proceeding in the manner outlined here.

I. Staff training

The scientific staff participating in AFSC trawl surveys will undergo periodic mandatory

training which includes classes addressing use of net mensuration instrumentation and

interpretation of the mensuration data, fish and invertebrate identification, survival skills, remote

duty first aid, oxygen therapy, and principles of trawl net maintenance. In addition, the FPC

leading each cruise leg will be trained to carry out the objectives and sampling instructions for

the specific survey leg he/she is assigned to. Training of FPCs includes learning about the

design, logistics, and sampling requirements of the survey; staff management; and evaluating

survey fishing gear repairs. The FPC is responsible for working directly with the captain of the

vessel to coordinate overall and daily work plans and coordinating with the FPCs of partner

vessels to efficiently and successfully achieve the sampling objectives of the survey.

The AFSC surveys are conducted with chartered vessels, captains, and crew. As such, we have

limited influence over the training requirements of the captains and crew. Our staff will work

closely with vessel personnel before and during the charter periods to communicate with and

educate them regarding matters important to the standard and proper sampling procedures

required during groundfish bottom trawl surveys. AFSC Net Loft staff will review prescribed

maintenance and repair objectives and standards with vessel personnel and FPCs will interact

constantly with captains regarding survey objectives and standardized fishing protocols.

NOAA Fisheries Trawl Survey Protocols
27

EBS Upper Continental Slope (EBSUCS) Bottom Trawl Survey

A. Scope

The EBSUCS survey utilizes the following scope ratio table that was empirically established to

determine the amount of warp used at each trawling depth when the warps are constructed of 1

inch, die-formed, steel-core wire. When other types or sizes of warps are used, a new table

should be re-established. Use warp marks to determine the amount of warp out during trawling

operations. To prevent net collapse or door crossing, the warp should be let out evenly in the

“free-wheel mode” while maintaining the vessel speed at least 1 knot above the payout rate. 

Gradually decrease vessel speed and payout rate as the desired amount of wire is approached.

Bottom Depth Scope

Minimum (m) Maximum (m) Meters Fathoms

146 176 550 301

177 206 600 328

207 237 650 355

238 267 700 383

269 298 750 410

299 328 800 437

330 358 850 465

360 389 900 492

390 420 950 519

421 450 1000 547

451 481 1050 574

482 511 1100 601

512 542 1150 628

543 572 1200 656

573 603 1250 683

604 633 1300 710

634 664 1350 738

665 694 1400 765

695 725 1450 792

726 755 1500 820

756 786 1550 847

787 816 1600 874

817 847 1650 901

848 877 1700 930

878 908 1750 957

909 938 1800 984

939 969 1850 1012

970 999 1900 1039

1000 1030 1950 1066

1031 1060 2000 1094

1061 1091 2050 1121

1091 1121 2100 1148

B. Speed of tow

The EBSUCS survey targets an average towing speed over ground of 2.5 knots with an

acceptable range of momentary towing speed between 2.2 knots and 2.8 knots when the net is in

Alaska Fisheries Science Center
28

contact with the bottom and in fishing configuration. It is important to keep the vessel speed as

constant as possible and near 2.5 knots when the net is fishing on bottom. After brake-set, vessel

speed can be used to regulate sink time of the trawl, however vessel speed should be as close to

2.5 knots as possible when the net reaches the bottom. Monitor vessel speed frequently during a

tow using the NOAA supplied GPS unit.

C. Duration and distance of tow and use of trawl mensuration / performance monitoring

instrumentation

The performance and geometry of the trawl are measured using several sensors. Net height and

width is measured in real time using SCANMAR sensors mounted on the center of the headrope

and on the upper bridle just forward of the wingtips. Depth and temperature data is measured

using a self-contained bathythermograph mounted near the center of the headrope. Bottom

contact information will be measured with a self-contained Bottom Contact Sensor (BCS)

mounted at the center of the footrope. Detailed descriptions of the rigging for each of these

sensors is provided in the AFSC Net Mensuration Manual, which is carried aboard all survey

vessels. Annual training is mandatory for all staff operating net mensuration and monitoring

instruments and interpreting the data collected with them.

Target tow duration is 30 minutes, which equates to approximately 1.3 nmi or 2.4 km at the

standard towing speed of 2.5 knots. The start of the 30 minute towing period is determined from

the net height data and is defined as when the height decreases to 8 m. Winches are engaged

and haulback begins 30 minutes later. Tows may be shortened due to obstructions, inability to

follow a depth contour, hangups, gear problems, or extremely large catches which affect the

efficiency of the trawl.

After a haul is completed, data from each of the sensors will be synchronized with the GPS data

and displayed simultaneously using custom designed software (ScanPlot). Using this software,

the operator will determine the precise moments that the footrope initially contacts (On-Bottom)

and leaves bottom (Off-Bottom) and calculate the duration, distance fished, and average net

spread and height during each tow. The trace of the BCS data is the most useful tool for

determining the On- and Off-Bottom times. The transition between when the net is on or off

bottom is usually clearly signaled by an abrupt change in readings from around 40 degrees to

around 60 degrees (vice versa when leaving bottom). Distance fished is determined from the

vessel track between the On- and Off-Bottom positions.

D. Direction of tow

On the EBSUCS survey, the towing direction is dictated by bottom topography, current

direction, wind speed and direction, and wave height and direction. Bottom topography often

precludes all but a single towing direction to complete a tow successfully because of the need to

follow a depth contour. In strong current, the tow is directed up-stream to prevent net distortion.

In strong winds, the trawl is directed up-wind to allow the skipper better control of vessel

direction and towing speed. In summary, tow direction is not a random variable, but it is not

always predictable because of variation in wind and current. 

NOAA Fisheries Trawl Survey Protocols
29

E. Location of suitable sampling sites

The EBSUCS survey uses random sampling within strata defined by depth and sub-area. To

minimize lost time in transit, stations should be completed in the order of proximity, proceeding

from one station to the next closest station. Prior to trawling, each station should be surveyed,

using a depth sounder, to determine if it is in the correct depth stratum and trawlable.

Unfortunately the best available bathymetry data is poor and the actual station location and

depth must be changed from the redetermined stations. A successful sampling area with a good

potential for success is characterized by relatively low relief substrate with at least 1.5 nmi of

trawlable bottom within the depth stratum boundaries. If trawlable ground is not found at the

predetermined site, a search should be conducted within the same sub-area and depth stratum to

locate another site as close to the original site as possible. A site is designated as untrawlable if

the skipper and/or FPC determine that the bottom topography precludes a successful tow due to

potential net damage, insufficient distance, widely changing depth range, and obstruction in the

tow path. Trawlable ground decisions are governed by the skipper and FPC’s experience with

the net and its ability to perform given the bottom topography. 

F. Successful tow criteria

The success of a tow should be assessed considering events during the trawl operation as well as

examination of data after the tow is completed. Attention to the net mensuration monitor may

indicate a tear-up or obstruction causing the net to deviate from normal dimensions. Under some

conditions it may be impossible to maintain proper speed during the tow. After the tow,

examination of the net for evidence of damage and examination of the trawl mensuration data,

bottom contact data and depth data are used to assess trawl performance. The following are

minimal criteria which must be met to consider a haul satisfactory: 

1. The BCS tilt angle should indicate proper footrope bottom contact (variable footrope contact

indicates poor performance). 

2. Net mensuration data should indicate the net dimensions are within those expected for the

towing depth. 

3. Trawl time should be > 15 minutes and < 35 minutes. 

If the tow is deemed unsuccessful then a second attempt is made at the same location, or another

location is found in the same depth and sub-area, to replace the unsuccessful tow.

At the end of the survey, mensuration data is reviewed by another party and any differences in

opinion are discussed. The FPC has the final determination.

G. Vessel and winch operations

During trawl deployment, vessel speed should be maintained at least 1 knot faster than the net

pay out rate (up to brake-set). Deploy the wire to the prescribed length using the painted marks

on the wires. Set the brakes at the determined warp length and adjust the vessel speed to 2.5

knots as soon as possible. Use vessel speed to regulate settling rate of the trawl. Vessel speed

should be as close to 2.5 knots as possible when the net is on the bottom. Speeds between 1 and

2 knots can be used to increase sink rate and speeds up to 3.5 knots can be used to decrease the

sink rate. The auto-trawl system should be ON during the tow to avoid net damage if there

should be a hang-up or a large catch. The skipper should haul back the trawl and end the tow by

Alaska Fisheries Science Center
30

“popping” the net off the bottom as quickly as possible. This is accomplished in most cases by

increasing engine RPM when starting the winches. Use net mensuration data to verify that the

skipper is quickly lifting the trawl net off bottom. 

H. Defining responsibility for decisions

The FPC is responsible for every aspect of the survey from trawling operations to catch

processing, and data entry. These responsibilities are often shared with members of the

scientific party and vessel crew depending on the abilities of the people available, time and

ability of the FPC to perform all tasks successfully. The catch processing, sample collections and

data collection are handled entirely by members of the scientific crew on board. The EBSUCS

survey utilizes a “deck boss” who is responsible for the catch processing and data entry and a

FPC who is responsible for the net mensuration monitoring and trawling operations. The FPC

determines when and where to trawl and the skipper and crew are responsible for actually

carrying out this goal. The FPC defers many trawl decisions to the skipper who is often much

more experienced with the vessel and fishing operations. The FPC provides the final decision on

when to retire or repair a net but only after deliberating with the skipper and crew experienced in

net repair and reaching a consensus.

I. Staff training

The scientific staff participating in AFSC trawl surveys will undergo periodic mandatory

training which includes classes addressing use of net mensuration instrumentation and

interpretation of the mensuration data, fish and invertebrate identification, survival skills, remote

duty first aid, oxygen therapy, and principles of trawl net maintenance. In addition, the FPC

leading each cruise leg will be trained to carry out the objectives and sampling instructions for

the specific survey leg he/she is assigned to. Training of FPCs includes learning about the

design, logistics, and sampling requirements of the survey; staff management; and evaluating

survey fishing gear repairs. The FPC is responsible for working directly with the captain of the

vessel to coordinate overall and daily work plans and coordinating with the FPCs of partner

vessels to efficiently and successfully achieve the sampling objectives of the survey.

The AFSC surveys are conducted with chartered vessels, captains, and crew. As such, we have

limited influence over the training requirements of the captains and crew. Our staff will work

closely with vessel personnel before and during the charter periods to communicate with and

educate them regarding matters important to the standard and proper sampling procedures

required during groundfish bottom trawl surveys. AFSC Net Loft staff will review prescribed

maintenance and repair objectives and standards with vessel personnel and FPCs will interact

constantly with captains regarding survey objectives and standardized fishing protocols.

NOAA Fisheries Trawl Survey Protocols
31

Gulf of Alaska (GOA) Bottom Trawl Survey

A. Scope

The length of trawl warp to be deployed during a tow of any given depth is specified in the

following standard scope and depth table. In general, tows should not involve great depth

changes (i.e., more than 20 m), but if the depth changes over the tow, the wire out should be

adjusted to the new depth and the amount of wire change and time noted on the Haul Form. In

cases where the depth falls in between wire amounts in the scope table, the captain should err on

the side of too much wire out rather than too little.

Bottom Depth Range

(m) (fm)

Wire Out

(fm)

Bottom Depth Range

(m) (fm)

Wire Out

(fm)

10 - 11 5 - 6 75 469 - 491 257 - 268 600

12 - 34 7 - 19 100 492 - 520 269 - 284 625

35 - 57 19 - 31 125 521 - 547 285 - 299 650

58 - 80 32 - 43 150 548 - 574 300 - 313 675

81 - 102 44 - 55 175 575 - 601 314 - 328 700

103 - 125 56 - 68 200 602 - 627 329 - 342 725

126 - 148 69 - 80 225 628 - 654 343 - 357 750

149 - 171 81 - 93 250 655 - 681 358 - 372 775

172 - 194 94 - 106 275 682 - 708 373 - 387 800

195 - 217 107 - 118 300 709 - 734 388 - 401 825

218 - 240 119 - 131 325 735 - 761 402 - 416 850

241 - 262 132 - 143 350 762 - 788 417 - 430 875

263 - 285 144 - 155 375 789 - 815 431 - 445 900

286 - 308 156 - 168 400 816 - 841 446 - 459 925

309 - 331 169 - 181 425 842 - 868 460 - 474 950

332 - 354 182 - 193 450 869 - 895 475 - 489 975

355 - 377 194 - 206 475 896 - 922 490 - 504 1000

378 - 400 207 - 219 500 923 - 948 505 - 518 1025

401 - 422 220 - 230 525 949 - 975 519 - 533 1050

423 - 445 231 - 243 550 976 - 1002 534 - 547 1075

446 - 468 244 - 256 575 1003 - 1028 548 - 562 1100

B. Speed of tow

Bottom trawl hauls will be made at a constant speed of 3 knots (nmi/hr) over ground. The

captain of the vessel is responsible for monitoring and maintaining the speed during the entire

tow. Speed at any point during the tow can be verified using the continuous stream of GPS data,

which is logged to a computer file. There is strong evidence that the center of the footrope

begins to lose contact with the bottom at speeds over 3 knots, so speeds exceeding 3 knots

should especially be avoided. 

Alaska Fisheries Science Center
32

C. Duration and distance of tow and use of trawl mensuration/performance monitoring

instrumentation 

The performance and geometry of trawls used during AFSC survey tows will be monitored using

several sensors. Net height and width will be monitored in real time using Scanmar or Netmind

sensors mounted on the center of the headrope (height sensor) and just forward of the upper

wingtips (width sensors). Depth and temperature data will be collected using a self-contained

bathythermograph mounted near the center of the headrope. Bottom contact information will be

logged with a self-contained Bottom Contact Sensor (BCS) mounted on the center of the

footrope. Detailed descriptions of the rigging for each of these sensors is provided in the AFSC

Net Mensuration Manual, which is carried aboard all survey vessels. Annual training is

mandatory for all staff operating net mensuration and monitoring instruments and interpreting

the data collected with them.

Target duration of all tows will be 15 minutes towing time, which equates to approximately 0.75

nmi or 1.4 km at the standard towing speed of 3 knots. This duration ensures an adequate

sample of the biota and usually results in a catch that is a reasonably manageable size to sort and

process. The start of the 15 minute towing period will be determined from the near-real-time

readout of the net height instrumentation, which enables the operator to determine when the net

approaches bottom and settles into its fishing configuration. The time that the footrope touches

down can usually be detected by watching the headrope height measurements decrease rapidly

from over 10 m to under 8 m as the net approaches bottom. The start of the tow should be

defined as when the height decreases to 8 m. Winches are engaged 15 minutes later to haul

back the net. Tows may be shortened due to upcoming obstructions, inability to follow a depth

contour, hangups, gear problems, or extremely large catches which affect the efficiency of the

trawl.

After the haul is completed, data from each of the sensors will be synchronized with the GPS

data and displayed simultaneously using custom designed software (ScanPlot). Using this

software, the operator will determine the precise moments that the footrope initially contacts

(On-Bottom) and leaves bottom (Off-Bottom) and calculate the duration, distance fished, and

average net spread and height during each tow. The trace of the BCS data is the most useful tool

for determining the On- and Off-Bottom times. The transition between when the net is on or off

bottom is usually clearly signaled by an abrupt change in readings from around 40 degrees to

around 60 degrees (vice versa when leaving bottom). Distance fished is determined from the

GPS vessel track between the On- and Off-Bottom positions.

D. Direction of tow 

Tow direction is currently determined only by the directive to follow depth contours and by any

conditions which might influence the decision of the captain and/or FPC, such as bottom

obstructions, peculiarities of the substrate, wind, current, or sea state.

E. Location of sampling sites and procedures to use if sites are not suitable for towing

Stations to be sampled during the survey will be selected during the design process. The entire

survey area is covered by an overlay of 25 km2

 grid cells based on lines of latitude and longitude

(fishable area of a grid cell may be less than 25 km2 due to land masses, stratum boundaries, or

untrawlable areas). The exact location of a station is actually unspecified but must fall within a

NOAA Fisheries Trawl Survey Protocols
33

chosen grid cell. Stations are allocated among strata using groundfish catch data from previous

GOA bottom trawl surveys and Neyman allocation to minimize variance. Each stratum is

required to have at least two samples. 

Stations for each stratum are randomly selected without replacement from the set of full or

partial grid cells falling within that stratum, excluding partial grid cells smaller than 5 km2

 and

grid cells that had been deemed untrawlable in previous surveys. The stations in each stratum

are then assigned among the vessels. Paper and electronic charts depicting station locations and

successful tows made during previous surveys are used to guide sampling. 

Within each assigned grid cell, the captain and FPC collaborate to find enough trawlable bottom

to complete a standard 15-minute tow made at the standard speed of 3.0 knots (approximately

0.75 nmi or 1.4 km). Each tow should be surveyed before trawling operations begin in order to

minimize time lost to gear damage and bad performance tows. However, because the goal is to

maximize the coverage of the GOA with the survey trawl, some risk of gear damage is

acceptable. While it is not necessary to begin the tow within the grid cell, at least half the tow

(and preferably the entire tow) should be within the cell. A reasonable effort should be made to

search the entire cell for trawlable bottom, but the search time should generally not exceed two

hours.

If no trawlable bottom is found within an assigned grid cell, that cell should be designated as

untrawlable in the station log, including any pertinent notes. An alternate grid cell should then

be sampled. Alternate sites should be selected from unallocated grid cells in the correct stratum

as close as possible to the abandoned grid cell. Historical successful tows shown on the paper

and electronic charts should be used to locate nearby areas of potentially trawlable bottom

within the correct stratum. If trawlable bottom is encountered while in transit to an alternate

station, a haul should be conducted in that area provided it is in an unallocated grid cell and in

the correct stratum. It is essential that the vessels communicate clearly whenever conducting

hauls in alternate grid cells to avoid sampling the same grid cell twice.

F. Criteria for determining the success of a tow and procedures to use if tow was

unsuccessful

The criteria that need to be met for a totally satisfactory tow are:

• 15 minutes towing time

• constant towing speed of 3 knots

• length of wire out as specified by the scope table

• net mensuration instruments indicate gear operating within normal limits

(historical normal ranges: width = 12.9-17.5 m, height = 5.2-9.4 m )

• constant gear contact with the sea bottom

• no hang ups, gear damage, or gear conflicts (e.g., crab pots or longlines)

• all survey tows made during daylight hours (start and end times shall fall between

30 minutes after sunrise and 30 minutes before sunset, as determined by actual

observation, Tides & Currents software, or other position-related means).

Acceptable performance includes tows with the following conditions: durations of between 10

and 20 minutes, occasional minor separations between bottom and the footrope, small tears

Alaska Fisheries Science Center
34

unlikely to significantly affect catch rates, gear conflicts unlikely to have affected the fishing

efficiency of the trawl, etc. The net mensuration operator will use data collected with

monitoring instrumentation to evaluate the performance of each trawl haul performed. Data

streams from each of the net-mounted monitoring sensors will be synchronized and displayed

simultaneously using ScanPlot software. Using this information, the operator will evaluate the

quality of each tow considering whether the fishing dimensions fell within normal limits,

whether the footrope maintained contact with the bottom, and the apparent consequences of

encountering snags or obstructions. Based on this evaluation, each tow is judged to be either

satisfactory or unsatisfactory. If it is judged to be unsatisfactory, it will be repeated until either a

satisfactory tow is accomplished or the station is abandoned. Following completion of the

survey, one person will review the mensuration and performance information for each haul. If

the reviewer has a difference of opinion with the original operator about the success of the tow,

they will discuss the issues and develop a consensus evaluation. 

G. Vessel and winch operation during deployment and retrieval

To ensure comparability between vessels and years, vessel operators will be asked to follow

standard procedures when setting, towing, and retrieving the trawl gear. These procedures will

be established at the beginning of the first leg by the captain and the FPC and must be

maintained throughout the survey and for all subsequent surveys. The goals for each part of the

standard tow are as follows:

Setting

Primary Goal

• To ensure that the trawl is in fishing configuration (height and width) when it

makes bottom contact.

• To ensure that the procedure is easily repeatable.

Secondary Goals

• To ensure that the trawl reaches bottom quickly to minimize the midwater catch.

Towing

Goal

 • To maintain the trawl in fishing configuration (height and width) at a continuous

towing speed of 3 knots.

Haulback

Goals

• To maintain the trawl in fishing configuration until it leaves the bottom. 

• To ensure that the net leaves bottom quickly to avoid changes in fishing

configuration due to decreased scope and changes in net speed over ground (this

will usually require an increase in RPM).

• To ensure that the procedure is easily repeatable.

Implementation

Vessel speed, engine RPM, wire payout rate, etc., required to achieve these goals may require

some experimentation at the beginning of the first leg of the survey on each vessel. The captain

NOAA Fisheries Trawl Survey Protocols
35

and the FPC should work out a standard procedure for setting, towing, and hauling back the

gear. The procedures decided upon should facilitate consistently achieving the above stated

goals and will be documented in writing on the Standard Trawling Procedures Form and adhered

to for the remainder of the survey and for all subsequent surveys. Since the power settings

(RPM and/or propeller pitch) to achieve particular vessel speeds will change with the wind, sea

state, and currents, approximate power settings used to achieve these speeds in good weather

conditions (little wind, no current) should be recorded. If different procedures are developed for

various depths, these should be recorded as well. Any procedural modifications during the

survey must be mutually agreed upon between the FPC and the captain and must be carefully

justified and documented in writing. 

H. Defining responsibility for decisions regarding aspects of the operations

Vessels progress from west to east during the survey. Station selections for each day of work are

made by the FPCs aboard all vessels working together through daily consultations. Daily plans

are made considering the advice of vessel captains regarding weather, safety, and logistics.

I. Staff training

The scientific staff participating in AFSC trawl surveys will undergo periodic mandatory

training which includes classes addressing use of net mensuration instrumentation and

interpretation of the mensuration data, fish and invertebrate identification, survival skills, remote

duty first aid, oxygen therapy, and principles of trawl net maintenance. In addition, the FPC

leading each cruise leg will be trained to carry out the objectives and sampling instructions for

the specific survey leg he/she is assigned to. Training of FPCs includes learning about the

design, logistics, and sampling requirements of the survey; staff management; and evaluating

survey fishing gear repairs. The FPC is responsible for working directly with the captain of the

vessel to coordinate overall and daily work plans and coordinating with the FPCs of partner

vessels to efficiently and successfully achieve the sampling objectives of the survey.

The AFSC surveys are conducted with chartered vessels, captains, and crew. As such, we have

limited influence over the training requirements of the captains and crew. Our staff will work

closely with vessel personnel before and during the charter periods to communicate with and

educate them regarding matters important to the standard and proper sampling procedures

required during groundfish bottom trawl surveys. AFSC Net Loft staff will review prescribed

maintenance and repair objectives and standards with vessel personnel and FPCs will interact

constantly with captains regarding survey objectives and standardized fishing protocols.

Alaska Fisheries Science Center
36

Aleutian Islands (AI) Bottom Trawl Survey

A. Scope

The length of trawl warp to be deployed during a tow of any given depth is specified in a

standard scope and depth table. In general, tows should not involve great depth changes (i.e.,

more than 20 m), but if the depth changes over the tow, the wire out should be adjusted to the

new depth and the amount of wire change and time noted on the Haul Form. In cases where the

depth falls in between wire amounts in the scope table, the captain should err on the side of too

much wire out rather than too little. 

Bottom Depth Range

(m) (fm)

Wire Out

(fm)

Bottom Depth Range

(m) (fm)

Wire Out

(fm)

10 - 11 5 - 6 75 469 - 491 257 - 268 600

12 - 34 7 - 19 100 492 - 520 269 - 284 625

35 - 57 19 - 31 125 521 - 547 285 - 299 650

58 - 80 32 - 43 150 548 - 574 300 - 313 675

81 - 102 44 - 55 175 575 - 601 314 - 328 700

103 - 125 56 - 68 200 602 - 627 329 - 342 725

126 - 148 69 - 80 225 628 - 654 343 - 357 750

149 - 171 81 - 93 250 655 - 681 358 - 372 775

172 - 194 94 - 106 275 682 - 708 373 - 387 800

195 - 217 107 - 118 300 709 - 734 388 - 401 825

218 - 240 119 - 131 325 735 - 761 402 - 416 850

241 - 262 132 - 143 350 762 - 788 417 - 430 875

263 - 285 144 - 155 375 789 - 815 431 - 445 900

286 - 308 156 - 168 400 816 - 841 446 - 459 925

309 - 331 169 - 181 425 842 - 868 460 - 474 950

332 - 354 182 - 193 450 869 - 895 475 - 489 975

355 - 377 194 - 206 475 896 - 922 490 - 504 1000

378 - 400 207 - 219 500 923 - 948 505 - 518 1025

401 - 422 220 - 230 525 949 - 975 519 - 533 1050

423 - 445 231 - 243 550 976 - 1002 534 - 547 1075

446 - 468 244 - 256 575 1003 - 1028 548 - 562 1100

B. Speed of tow

Bottom trawl hauls will be made at a constant speed of 3 knots (nmi/hr) over ground. The

captain of the vessel is responsible for monitoring and maintaining the speed during the entire

tow. Speed at any point during the tow can be verified using the continuous stream of GPS data,

which is logged to a computer file. There is strong evidence that the center of the footrope

NOAA Fisheries Trawl Survey Protocols
37

begins to lose contact with the bottom at speeds over 3 knots, so speeds exceeding 3 knots

should especially be avoided. 

C. Duration and distance of tow and use of trawl mensuration/performance monitoring

instrumentation 

The performance and geometry of trawls used during AFSC survey tows will be monitored using

several sensors. Net height and width will be monitored in real time using Scanmar or Netmind

sensors mounted on the center of the headrope (height sensor) and just forward of the upper

wingtips (width sensors). Depth and temperature data will be collected using a self-contained

bathythermograph mounted near the center of the headrope. Bottom contact information will be

logged with a self-contained Bottom Contact Sensor (BCS) mounted on the center of the

footrope. Detailed descriptions of the rigging for each of these sensors is provided in the

AFSC’s Net Mensuration Manual, which is carried aboard all survey vessels. Annual training is

mandatory for all staff operating net mensuration and monitoring instruments and interpreting

the data collected with them.

Target duration of all tows will be 15 minutes towing time, which equates to approximately 0.75

nmi or 1.4 km at the standard towing speed of 3 knots. This duration ensures an adequate

sample of the biota and usually results in a catch that is a reasonably manageable size to sort and

process. The start of the 15 minute towing period will be determined from the near-real-time

readout of the net height instrumentation, which enables the operator to determine when the net

approaches bottom and settles into its fishing configuration. The time that the footrope touches

down can usually be detected by watching the headrope height measurements decrease rapidly

from over 10 m to under 8 m as the net approaches bottom. The start of the tow should be

defined as when the height decreases to 8 m. Winches are engaged 15 minutes later to haul

back the net. Tows may be shortened due to upcoming obstructions, inability to follow a depth

contour, hangups, gear problems, or extremely large catches which affect the efficiency of the

trawl.

After the haul is completed, data from each of the sensors will be synchronized with the GPS

data and displayed simultaneously using custom designed software (ScanPlot). Using this

software, the operator will determine the precise moments that the footrope initially contacts

(On-Bottom) and leaves bottom (Off-Bottom) and calculate the duration, distance fished, and

average net spread and height during each tow. The trace of the BCS data is the most useful tool

for determining the On- and Off-Bottom times. The transition between when the net is on or off

bottom is usually clearly signaled by an abrupt change in readings from around 40 degrees to

around 60 degrees (vice versa when leaving bottom). Distance fished is determined from the

GPS vessel track between the On- and Off-Bottom positions.

D. Direction of tow

Tow direction is currently determined only by the directive to follow depth contours and by any

conditions which might influence the decision of the captain and/or FPC , such as bottom

obstructions, peculiarities of the substrate, wind, current, or sea state.

Alaska Fisheries Science Center
38

E. Location of sampling sites and procedures to use if site not suitable

Stations to be sampled during the survey will be selected during the design process. Stations are

allocated among strata using groundfish data from previous Aleutian bottom trawl surveys and

Neyman allocation to minimize the variance. Each stratum is required to have at least two

samples. 

The station locations are randomly selected without replacement from a collection of stations

successfully sampled during the 1991 survey or thereafter. This collection covers virtually the

entire survey area. The stations are assigned randomly between the two survey vessels. Each

year several additional, previously unsampled stations must be added in various strata to satisfy

the sample allocation scheme. Generally these additional tows come from strata that have

proven to be difficult to sample in the past. Paper and electronic charts depicting station

locations and successful tows made during previous surveys are used to guide sampling. 

Each tow should be surveyed before trawling operations begin in order to minimize time lost to

gear damage and bad performance tows. However, because the goal is to maximize the coverage

of the Aleutian region with the survey trawl, some risk of gear damage is acceptable. It is not

necessary to begin the tow at the exact location listed for the station. A reasonable effort should

be made to search and locate a trawlable station within a 5-nmi radius of the listed station, but

the search should generally not exceed two hours.

In most cases it will be unnecessary to locate alternate stations, since most stations have been

sampled successfully before. Tows from previous surveys made by foreign vessels were usually

conducted with larger trawls rigged with tire gear designed for very rough bottom conditions,

but stations fished by U.S. vessels were sampled with our standard survey gear. Therefore,

should the need arise to find an alternate station location, use the following rules:

1) When bottom conditions preclude sampling at an assigned station, choose an alternate

station from the list of stations previously sampled by a U.S.-flagged vessel. 

2) If no previously sampled (by U.S.-flagged vessel) station fulfills the requirements for

an alternate haul, then stations sampled by foreign vessels should be used to narrow the

search for areas with trawlable bottom. 

3) To facilitate future surveys, strata being searched for new stations should be searched

intensively, recording the search trackline with the electronic navigation system in a

distinct color to distinguish it from other tracklines. A record of the trawlability of each

assigned station, with other comments pertinent to the suitability of a given location,

should be maintained in the station log. The beginning and end of the search trackline

should be recorded, as well as whether or not the entire area was searched.

It is essential that the vessels communicate clearly whenever conducting hauls at alternate

stations avoid sampling the same station twice.

NOAA Fisheries Trawl Survey Protocols
39

F. Criteria for determining the success of a tow and procedures to use if tow was

unsuccessful

The criteria that need to be met for a totally satisfactory tow are:

• 15 minutes towing time

• constant towing speed of 3 knots

• length of wire out as specified by the scope table

• net mensuration instruments indicate gear operating within normal limits

(historical normal ranges: width = 12.9-17.5 m, height = 5.2-9.4 m)

• constant gear contact with the sea bottom

• no hang ups, gear damage, or gear conflicts (e.g., crab pots or longlines)

• all survey tows made during daylight hours (start and end times shall fall between

30 minutes after sunrise and 30 minutes before sunset, as determined by actual

observation, Tides & Currents software, or other position-related means).

Acceptable performance includes tows with the following conditions: durations of between 10

and 20 minutes, occasional minor separations between bottom and the footrope, small tears

unlikely to significantly affect catch rates, gear conflicts unlikely to have affected the fishing

efficiency of the trawl, etc. The net mensuration operator will use data collected with

monitoring instrumentation to evaluate the performance of each trawl haul performed. Data

from each of the sensors will be synchronized and displayed simultaneously using ScanPlot

software. Using this information, the operator will evaluate the quality of each tow considering

whether the fishing dimensions fell within normal limits, whether the footrope maintained

contact with the bottom, and the apparent consequences of encountering snags or obstructions. 

Based on this evaluation, each tow is judged to be either satisfactory or unsatisfactory. If it is

judged to be unsatisfactory, it will be repeated until either a satisfactory tow is accomplished or

the station is abandoned. Following completion of the survey, one person will review the

mensuration and performance information for each haul. If the reviewer has a difference of

opinion with the original operator about the success of the tow, they will discuss the issues and

develop a consensus evaluation. 

G. Vessel and winch operation during trawl deployment and retrieval.

To ensure comparability between vessels and years, captains will be asked to follow standard

procedures when setting, towing, and retrieving the gear. These procedures will be established

at the beginning of the first leg by the captain and the FPC and must be maintained throughout

the survey and for all subsequent surveys. A standard tow should follow these guidelines:

Setting the trawl

• The trawl is in fishing configuration with respect to vertical opening and spread

when it makes bottom contact and is moving across the bottom at 3 knots.

• The trawl reaches bottom quickly to minimize the midwater catch.

• The proper trawl warp length is used (from the scope table).

• To ensure that the procedure is easily repeatable.

Towing the trawl

• Maintain the trawl in fishing configuration relative to vertical opening and

spread.

Alaska Fisheries Science Center
40

• Maintain a continuous towing speed of 3 knots.

Haulback

• Trawl maintains fishing configuration until it leaves the bottom.

• Trawl leaves bottom quickly to avoid changes in fishing configuration due to

decreased scope and changes in net speed over ground. This will usually require

an increase in RPM.

• To ensure that the procedure is easily repeatable.

Implementation

Vessel speed, engine RPM, wire payout rate, etc., required to achieve these goals may require

some experimentation at the beginning of the first leg of the survey on each vessel. Given that

different power settings (RPM and/or propeller pitch) will be needed in different depths, current,

wind, and sea conditions, the captain and the FPC should develop a set of standard procedures

for setting, towing, and hauling the gear by performing test tows, keeping in mind that those

procedures should be easily repeatable. The procedures decided upon should facilitate

consistently achieving the above stated goals and will be documented in writing on the Standard

Trawling Procedures Form and adhered to for the remainder of the survey and for all subsequent

surveys. If different procedures are developed for various depths, these should be recorded as

well. Any procedural modifications during the survey must be mutually agreed upon between

the FPC and the captain and must be carefully justified and documented in writing. 

H. Defining responsibility (i.e., survey scientists or vessel crew) for decisions regarding

various aspects of the operations.

Vessels will generally progress from east to west during the survey. Station selections for each

day of work are made by the FPCs aboard all vessels working together through daily

consultations. Daily plans are made considering the advice of vessel captains regarding weather,

safety, and logistics.

I. Staff training

The scientific staff who participate in AFSC trawl surveys will undergo periodic mandatory

training which includes classes addressing use of net mensuration instrumentation and

interpretation of the mensuration data, fish and invertebrate identification, survival skills, remote

duty first aid, oxygen therapy, and principles of trawl net maintenance. In addition, the FPC

leading each cruise leg will be trained to carry out the objectives and sampling instructions for

the specific survey leg he/she is assigned to. Training of FPCs includes learning about the

design, logistics, and sampling requirements of the survey; staff management; and evaluating

survey fishing gear repairs. The FPC is responsible for working directly with the captain of the

vessel to coordinate overall and daily work plans and coordinating with the FPCs of partner

vessels to efficiently and successfully achieve the sampling objectives of the survey.

The AFSC surveys are conducted with chartered vessels, captains, and crew. As such, we have

limited influence over the training requirements of the captains and crew. Our staff will work

closely with vessel personnel before and during the charter periods to communicate with and

educate them regarding matters important to the standard and proper sampling procedures

required during groundfish bottom trawl surveys. AFSC Net Loft staff will review prescribed

NOAA Fisheries Trawl Survey Protocols
41

maintenance and repair objectives and standards with vessel personnel and FPCs will interact

constantly with captains regarding survey objectives and standardized fishing protocols.

Alaska Fisheries Science Center
42

Protocol 4: Trawl Construction and Repair

Descriptions of Trawls and Their Rigging

The four bottom trawl surveys conducted regularly by the AFSC utilize three trawls, all of which

are constructed at the AFSC Net Loft. The 83-112 Eastern trawl is used for the Eastern Bering

Sea shelf survey. The Poly Nor’Eastern trawl is used for the Gulf of Alaska, and Aleutian

Islands surveys where it is configured with bobbin ground gear and a two-point attachment of

the otter doors to the bridles. The Poly Nor’Eastern trawl is also used for the Eastern Bering Sea

upper continental slope survey where is rigged with 8" mudsweep groundgear and a four-point

attachment of the otter doors. Information concerning trawl construction and repair is included

in the operations manual for each survey. This information includes:

• Description of the construction of the trawl components

• Description of the materials used in the trawl construction

• Net plan 

• Rigging plan

• Ground gear plan

• Checklist for verifying trawl dimensions and specifications.

• Trawl Repair Form

The AFSC Net Loft staff will inspect and measure each trawl prior to loading it onto the vessel

to ensure that it conforms to the specifications set forth on the survey trawl checklist. In

addition, each trawl will have an identification number, stamped on a metal tag, that will be

included on all haul forms and trawl repair forms. Whenever the trawl requires repair during

survey operations, such repairs will be done following the standards set forth in the following

section and documented on the trawl repair form. Components potentially affected by at-sea

repairs will be remeasured to confirm that the trawl is meeting specifications.

Gear Repairs Aboard Vessels

At the start of every survey, vessels will be provided with an inventory of supplies used to repair

trawl gear during the survey. Materials include web, hardware, floats, breastlines, twine, pre-cut

bottom panels (only for the Poly Nor’Eastern trawl), etc. These supplies should provide each

vessel with the resources needed to make typical repairs. If a survey vessel has experienced

frequent net damage, the FPC should transmit a list of trawl repair supplies to the AFSC Net

Loft sufficiently far in advance of the next scheduled port of call to allow time to ship the

supplies. To ensure quick access to spare nets, the FPC should locate, at the start of each cruise

leg, where spare nets are stored and, if access to the nets could be difficult in less than ideal

conditions, store at least one spare net on deck.

Net, doors, and bridles should be examined routinely during every haul back, checking for any

damage and noting any repairs that are needed. When large rocks are dumped from the net, 

codend liners should be checked for damage. The FPC, in consultation with the vessel crew,

NOAA Fisheries Trawl Survey Protocols
43

will determine whether it is more expedient to repair a damaged trawl or to replace the trawl

with a spare.

Survey trawls are research sampling tools and the success of our surveys depends on maintaining

our survey gear to AFSC standards. The FPC should stress this to fishers responsible for making

trawl repairs to ensure that trawls will be replaced if they cannot be repaired to AFSC survey

standards. Fishers must follow the trawl repair protocols provided to them at the pre-cruise

meeting with personnel from the AFSC Net Loft. In particular, they must replace torn or

abraded web with patches or new panels, rather than hand sewing new meshes. Straight tears,

however, can be sewn as long as there is no need to build meshes to close the hole. Lacing of

holes or tears is not allowed in the body, wings or codend of the trawl. Special attention should

be given to repairs involving the inside of the bottom wings (where the bar cut and chaffing

strips are sewn to the body). Poor repairs in this area may affect the way the footrope tends

bottom. Repairs that should not be attempted aboard vessels include broken headropes,

footropes, riblines or rehanging long sections of riblines (repairs that involve more that 25

benzels, approx. 40'). Given the limited deck space aboard our survey vessels, these repairs are

difficult to do correctly to ensure the finished product meets our standards. 

The FPC is responsible for overseeing net repairs and deciding if a net should be retired. When

a net is damaged, repaired, or retired, the Net Repair Form should be completed, noting the net

ID number and all damage and repairs made. When retired, the net should be picked and

cleaned before it is bundled and stowed.

Alaska Fisheries Science Center
44

Eastern Bering Sea Shelf Bottom Trawl Survey

Gear Description for 83-112 Eastern Trawl

Netting: Body and wing 4" stretched measure (including length of one knot) 60 T

nylon, three-strand twist, preshrunk and dyed green.

Intermediate and codend - 31⁄2" stretched measure 96 T nylon, threestrand, twist, preshrunk and dyed green.

Codend liner - 11⁄4" stretched measure 18 T nylon, three-strand twist,

preshrunk and dyed green.

Headrope: 83' 9" of 1⁄2" (6×19) galvanized fiber core wire rope wrapped with d"

polypropylene rope. 

Both eyes have 1⁄2" gusseted thimbles. 

The headrope doesn’t include the length of either eye. 

Length is measured from the top of the nicro sleeve to the top of nicro at

the other end. 

Top wings are hung over 36'.

Footrope: 111' 9" plus thimbled eyes of e", (6×19) galvanized, fiber core wire rope,

wrapped with 1⁄2" polypropylene rope. 

Loops of 5/16" galvanized, proof coil chain, (approx. 170') are tied to

wrapped footrope by passing two fathoms of double 21 T nylon twine

through every tenth link starting at the top of the nicro forming the eye

splice. 

Chain links are secured to footrope every 8" throughout length of wing

forming 76 chain hangings over 50' each wing. 

Busom has 16 chain hangings equally spaced over 11' 9". 

There are four bars (2 meshes) per hanging in wings and 4 meshes per

hanging in busom, hung with 96 T nylon round braid hanging twine. 

After the net is hung, split pieces of heavy rubber hose are served around

footrope, passing the hose twice between each chain hanging for the

length of the footrope.

Breastlines: 1⁄2" (6×19) galvanized wire rope wrapped with d" polypropylene rope. 

Top and bottom breastlines are 8', measured from the top of the nicro

press forming one eye through the bearing point of the other eye.

Riblines: 3⁄4" Samson 2 and 1® Duralon braided trawl rope. 

Riblines are hung at 97% of stretched measure of the gored seam. 

All measurements are made with 400 lbs of tension on rope. 

Gored seams are attached to riblines using white, untreated 60 T braided

nylon hanging twine used to tie a benzel every 16".

NOAA Fisheries Trawl Survey Protocols
45

Flotation: Seventeen 8" aluminum side lug floats along each wing and seven 8"

floats in center. 

Total of 41 floats along headrope spaced 241⁄4" apart. 

Buoyancy of 6.3 lbs each (258 lbs total).

Side seams: Side seams are laced in top and bottom individually gathering 3 meshes 

(4 knots) using white, double 21 T perma-grip® (or like kind) nylon

three-strand twine. 

Top and bottom panels are then laced together using green, double 21 T

perma-grip® (or like kind) nylon three-strand twine.

Codend: 31⁄2" stretched measure (including one knot) nylon, dyed green, 96 T nylon

three-strand mesh. 

Codend is a “double wall” construction. 

Four panels of 96 T web cut 64 meshes long by 120 meshes deep. 

Two meshes on each side are laced together, leaving 60 “open meshes”

per panel. 

Gored seams are laced together using 60 T round braid hanging twine and

hung to riblines of 3⁄4" Samson 2in1® Duralon braided trawl rope. 

Riblines in codend are hung at 90% of stretched measurement of gored

seams. 

Riblines are measured under 400 lbs of tension. 

Codend is closed at aft end using 24-21⁄2" x 5/16" galvanized steel rings. 

A 1⁄4" Duralon braided rope is passed through 5 selvage meshes and a ring

is attached to the rope using a cow hitch every 12" leaving five open

meshes between each ring. 

The bag is then closed using a e" - 3⁄4" hauling clip. 

A liner of 11⁄4" three strand twine nylon, 360 meshes long by 200 meshes

deep is hung on the inside of the bag 78 meshes up from terminal end.

Alaska Fisheries Science Center
46

Eastern Bering Sea Shelf Bottom Trawl Survey

Materials List for 83-112 Eastern Trawl

Specifications of wire, chain, and rope include rated breaking strength (BS), specific gravity

(SG), and density.

WEB: Mesh sizes listed are given in “stretched measure”, a standard method of

measuring mesh size that includes the length of one knot. 

Body and wings ~ 4" # 60T three strand nylon - dyed green.

Intermediate ~ 31⁄2" # 96T three strand nylon, dyed green, single wall

construction.

Codend ~ 31⁄2" # 96T three strand nylon, dyed green, double wall

construction.

Liner ~ 11⁄4" # 18T three strand nylon - dyed green.

 Chaffing gear ~ 6", 6-mm polyethylene knotted web.

WIRE ROPE: 1⁄2" 6×19 galvanized fiber core (BS 9,700 kg, 0.62 kg/m), eyes are formed

using galvanized reinforced thimbles.

CHAIN: 5/16" galvanized proof coil (BS 4,750 kg, 1.21 kg/m).

FLOATS: 8" side lug trawl floats, depth rated to a minimum 400 fm, 258 lbs of total

buoyancy.

RIBLINES: 3⁄4" Samson DuralonTM 2-in-1® stable braid, white, light bonding (BS

8,800 kg, SG 1.83, 0.27 kg/m).

TWINE: Sewing panels together: # 60T three strand nylon.

Lacing seams: double, white # 21T three strand nylon.

Joining seams together: double, green # 21T three strand nylon.

Hanging on framing lines: white, # 96T round braid hanging twine.

 Fly mesh at end of bag- # 182T round braid hanging twine

ROPE: Float lines - 1/4" polypropylene (BS 570 kg, SG 0.95).

Pucker ring lines- Samson 1/4" DuralonTM 2-in-1®(BS 1,270 kg, SG

1.38). 

Restrictor rope- 1 1/8" Poly PlusTM three strand (BS 10,740 kg, SG 0.91).

Splitting strap- 3/4" SpectraTM braided rope with eye each end (BS 21,773

kg, SG 0.98).

Splitting ring lines- 1⁄2" Samson DuralonTM 2-in-1® stable braid (BS 4,477

kg, SG 1.38).

Hole through trawl float line- 1⁄2" hollow braid Poly-PlusTM (BS 2,721 kg,

SG 0.91).

NOAA Fisheries Trawl Survey Protocols
47

FOOTROPE: e" 6×19 galvanized, fiber core wire rope with reinforced thimbled eyes.

1⁄2" three strand polypropylene rope served around wire rope.

5/16" galvanized proof coil chain.

Split heavy rubber hose served between chain hangings.

 Footrope setback/extension, 1⁄2" long link alloy chain connected to

footrope with a e" hammer lock. Total length including connecting

hardware - 24".

 Splitting rings - 51⁄2" × 3⁄4".

 Pucker rings at end of codend- 21⁄2" × 1⁄4".

Alaska Fisheries Science Center
48

Eastern Bering Sea Shelf Bottom Trawl Survey

Framing Lines for 83-112 Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
49

Eastern Bering Sea Shelf Bottom Trawl Survey

Net Plan for 83-112 Eastern Trawl

(“Cut Plan” = Total Mesh Counts)

Alaska Fisheries Science Center
50

Eastern Bering Sea Shelf Bottom Trawl Survey

Net Reel/Bridle Rigging Plan for 83-112 Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
51

Eastern Bering Sea Shelf Bottom Trawl Survey

Trawl Door Rigging Plan Detail for 83-112 Eastern Trawl

Sole Manufacturer NET Systems, Inc., Bainbridge Island, WA

Alaska Fisheries Science Center
52

Eastern Bering Sea Shelf Bottom Trawl Survey

Trawl Door Rigging Plan for 83-112 Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
53

Eastern Bering Sea Shelf Bottom Trawl Survey

Footrope Construction Plan for 83-112 Eastern Trawl

Alaska Fisheries Science Center
54

Survey Trawl Check List

Eastern Bering Sea Shelf Bottom Trawl Survey

83-112 Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
55

Eastern Bering Sea Shelf Bottom Trawl Survey

Net Repair Form for 83-112 Eastern Trawl - Top Panel

Alaska Fisheries Science Center
56

Eastern Bering Sea Shelf Bottom Trawl Survey

Net Repair Form for 83-112 Eastern Trawl - Bottom Panel

NOAA Fisheries Trawl Survey Protocols
57

Eastern Bering Sea Slope Survey

Gear Description for Poly Nor’Eastern Trawl

Netting: Polyethylene, 5" stretch measure - 4 mm top and sides, 5 mm bottom and

intermediate.

Headrope: 89' 1" of 1⁄2" (6×19) galvanized wire rope wrapped with d" polypropylene

rope. 

Both eyes have 1⁄2" gusseted thimble; 89' 1" doesn’t include the length of

either eye. 

Headrope length is measure from the top of the nicro sleeve to the top of

the nicro at other end. 

Top wing is hung over 16.31" per taper combination. 

Headrope setback - 18" of 1⁄2" long link galvanized alloy chain and

connecting hardware.

Bolsh line: 81' 7" plus thimbled eyes of d" (6×19) galvanized wire rope, wrapped

with d" polypropylene rope.

Fishing Line: 81' of 1⁄2" long link galvanized alloy chain. 

Safe working load of 11,300 lbs.

Breastlines: 1⁄2" (6×19) galvanized wire rope wrapped with d" polypropylene rope. 

Top corner 19' 6", bottom corner 8' 8", bottom side panel 30' 6". 

All lengths are measured from the top of nicro sleeve at wing tip and

including thimbled eye at ribline.

Riblines: 3⁄4" Samson 2in1® Duralon braided trawl rope. 

Riblines are hung at 98% of stretch measure of gored seam. 

All measurements are made with 400 lbs of tension on rope. 

Gored seams are attached to the ribline using white untreated 60 T braided

nylon hanging twine used to tie a benzel every 16".

Groundgear: 8" rubber discs strung on 1⁄2" galvanized, long link marine deck lashing

chain, grade 70, 79' 6" bearing to bearing (eye to eye). “Flying wing”

outboard sections, 4" rubber discs strung on 3⁄4" (6×19) fiber core wire

rope.

See groundgear diagram for more detailed description.

Alaska Fisheries Science Center
58

Side Seams: Side seams are laced in each panel individually. 

Seams are made by gathering 3 meshes (4 knots) and lacing them together

using white, double 21 thread perma-grip® (or like kind) nylon, threestrand twine. 

Individual panels are laced together using green, double 21 thread permagrip® nylon, three-strand twine. 

Panels which are secured to framing lines have selvage edge created by

gathering 3 meshes as described above. 

These selvage edges are hung tight to framing lines using 60 T braided

nylon hanging twine.

Flotation: Ninety 8" side lug deep-water trawl floats (5.4 lbs of buoyancy each) hung

evenly to headrope starting 1' from wing tip, leaving 3' open in the center

of the headrope. 

Total buoyancy - 486 lbs.

Splitting Gear: 3⁄4" Spectra® rope spliced 21' with eyes in each end. 

The rope is passed through four galvanized rings secured to each ribline

18 meshes from the bottom. A second identical splitting strap is located

38 meshes from the bottom.

Codend: 31⁄2" stretched measure (including 1 knot) polyethelene 4 mm double bar

mesh. 

Four panels cut 30 meshes long by 100 meshes deep. 

Two meshes in a gored seam each side, leaving 26 open meshes per panel. 

Gored seams are laced together using double 21 T nylon twine. 

Riblines in codend are 3⁄4" 2in1® Duralon braided trawl rope, hung at 90%

of the stretch measure of the gored seams. 

Codend is closed at terminal end using 25 21⁄2" X 1⁄4" galvanized steel

rings. 

A 1⁄4" Duralon rope is passed through the selvage mesh and a ring is

attached to the rope using a cow hitch every 12", with five open meshes

between each ring. 

The bag is then closed using a e"-3⁄4" hauling clip.

NOAA Fisheries Trawl Survey Protocols
59

Eastern Bering Sea Slope Survey

Materials List for Poly Nor’Eastern Trawl

Specifications of wire, chain, and rope include rated breaking strength (BS), specific gravity

(SG), and density.

WEB: All web in the trawl should be depth stretched and heat set in the

manufacturing process. Mesh sizes listed in the plan are given in

“stretched measure”, a standard method of measuring mesh size that

includes the length of one knot.

Top, body and wings, side panels ~ 5", 4-mm polyethylene knotted web.

 Bottom, body and wings, intermediate ~ 5", 5mm polyethylene knotted

web. All polyethylene web in net panels is orange.

Liner ~ 1.25", # 18T three strand nylon knotted web - dyed green.

Chaffing gear ~ 6", 6mm double bar mesh, polyethylene knotted web -

orange.

 Chaffing strip, bottom~ 5", 5mm double bar mesh, polyethylene knotted

web - orange.

WIRE ROPE: 1⁄2" 6×19 galvanized fiber core (BS 9,700 kg, 0.62 kg/m), eyes are formed

using galvanized reinforced thimbles.

CHAIN: 1⁄2" (16 mm) galvanized, long link marine deck lashing chain, grade 70 

(BS 20,500 kg, 3.42 kg/m).

FLOATS: Ninety 8" side lug deep-water trawl floats (5.4 lbs buoyancy each) depth

rated to a minimum of 2,000 m.

RIBLINES: 3⁄4" Samson DuralonTM 2-in-1® stable braid, white, light bonding (BS

8,800 kg, SG 1.83, 0.27 kg/m).

TWINE: Sewing panels together: 5-mm polyethylene twine, any color other than

orange.

Lacing seams: # 21T white, three strand nylon. 

Joining top and side seams together: # 21T green three strand nylon.

Joining bottom and intermediate seams: 60T white braided hanging twine.

ROPE: Float lines - 1/4" polypropylene (BS 570 kg, SG 0.95).

Pucker ring lines- Samson 1/4" DuralonTM 2-in-1®(BS 1,270 kg, SG 1.38) 

Restrictor rope- 1 1/8" Poly PlusTM three strand (BS 10,740 kg, SG 0.91).

Splitting strap- 3/4" SpectraTM braided rope with eye each end (BS 21,773

kg, SG 0.98).

Rope to serve cables- 3/8" polypropylene three strand.

Chaffing gear- Poly hula skirt material.

Alaska Fisheries Science Center
60

FOOTROPE: 1⁄2" galvanized, long link marine deck lashing chain, grade 70, 79' 6".

8" rubber disc with a 21⁄2” center hole.

 Steel plate chain washers- 5" x d" - 21⁄2” center hole.

 Chain toggles- 5.5 lbs. each, chain droppers are 61⁄2” long, spaced 18" 

on center along length of footrope. Toggles are attached to fishing line

with 5/16" import trawl shackles. Four hole triangle delta plate, d" steel.

NOAA Fisheries Trawl Survey Protocols
61

Eastern Bering Sea Slope Bottom Trawl Survey

Framing Lines for Poly Nor’Eastern Trawl

Alaska Fisheries Science Center
62

Eastern Bering Sea Slope Bottom Trawl Survey

Net Plan for Poly Nor’Eastern Trawl

(“Cut Plan” = Total Mesh Counts)

Twine Sizes: top and sides 4 mm 

bottom and intermediate 5 mm 

NOAA Fisheries Trawl Survey Protocols
63

Eastern Bering Sea Slope Bottom Trawl Survey

Trawl Door Rigging Plan Detail for Poly Nor’Eastern Trawl

Sole Manufacturer NET Systems, Inc., Bainbridge Island, WA

Alaska Fisheries Science Center
64

Eastern Bering Sea Slope Bottom Trawl Survey

Trawl Door Rigging Plan for Poly Nor’Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
65

Eastern Bering Sea Slope Bottom Trawl Survey

Groundgear Construction Plan for Poly Nor’Eastern Trawl

Alaska Fisheries Science Center
66

Survey Trawl Check List

Eastern Bering Sea Slope Bottom Trawl Survey

Poly Nor’Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
67

Eastern Bering Sea Slope Bottom Trawl Survey

Net Repair Form for Poly Nor’Eastern Trawl - Top Panel

Alaska Fisheries Science Center
68

Eastern Bering Sea Slope Bottom Trawl Survey

Net Repair Form for Poly Nor’Eastern Trawl - Bottom and Side Panels

NOAA Fisheries Trawl Survey Protocols
69

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Gear Description for Poly Nor’Eastern Trawl

Netting: Polyethylene, 5" stretch measure - 4 mm top and sides, 5 mm bottom and

intermediate.

Headrope: 89' 1" of 1⁄2" (6×19) galvanized wire rope wrapped with d" polypropylene

rope. 

Both eyes have 1⁄2" gusseted thimble; 89' 1" doesn’t include the length of

either eye. 

Headrope length is measure from the top of the nicro sleeve to the top of

the nicro at other end. 

Top wing is hung over 16.31" per taper combination. 

Headrope setback - 18" of 1⁄2" long link galvanized alloy chain and

connecting hardware.

Bolsh line: 81' 7" plus thimbled eyes of d" (6×19) galvanized wire rope, wrapped

with d" polypropylene rope.

Fishing Line: 81' of 1⁄2" long link galvanized alloy chain. 

Safe working load of 11,300 lbs.

Breastlines: 1⁄2" (6×19) galvanized wire rope wrapped with d" polypropylene rope. 

Top corner 19' 6", bottom corner 8' 8", bottom side panel 30' 6". 

All lengths are measured from the top of nicro sleeve at wing tip and

including thimbled eye at ribline.

Riblines: 3⁄4" Samson 2in1® Duralon braided trawl rope. 

Riblines are hung at 98% of stretch measure of gored seam. 

All measurements are made with 400 lbs of tension on rope. 

Gored seams are attached to the ribline using white untreated 60 T braided

nylon hanging twine used to tie a benzel every 16".

Roller Gear: 79' 6" bearing to bearing (eye to eye). 3⁄4" (6×19) galvanized wire rope

with 14" bobbins (Footrope) and 4" discs. 

See attached diagram for more detailed description.

Alaska Fisheries Science Center
70

Side Seams: Side seams are laced in each panel individually. 

Seams are made by gathering 3 meshes (4 knots) and lacing them together

using white, double 21 thread perma-grip® (or like kind) nylon, threestrand twine. 

Individual panels are laced together using green, double 21 thread permagrip® nylon, three-strand twine. 

Panels which are secured to framing lines have selvage edge created by

gathering 3 meshes as described above. 

These selvage edges are hung tight to framing lines using 60 T braided

nylon hanging twine.

Flotation: Twenty 12" Cycolac® side lug trawl floats (23 lbs of buoyancy each)

hung evenly to headrope starting 1' from wing tip, and four 8" side lug

trawl floats (5.4 lbs buoyancy each) hung two each on both sides of

center, leaving 3' open in the center of the headrope. 

Total buoyancy - 486 lbs.

Splitting Gear: 3⁄4" Spectra® rope spliced 21' with eyes in each end. 

The rope is passed through four galvanized rings secured to each ribline

18 meshes from the bottom. A second identical splitting strap is located

38 meshes from the bottom.

Codend: 31⁄2" stretched measure (including 1 knot) polyethelene 4 mm Double Bar

mesh. 

Four panels cut 30 meshes long by 100 meshes deep. 

Two meshes in a gored seam each side, leaving 26 open meshes per panel. 

Gored seams are laced together using double 21 T nylon twine. 

Riblines in codend are 3⁄4" 2in1® Duralon braided trawl rope, hung at 90%

of the stretch measure of the gored seams. 

Codend is closed at terminal end using 25 21⁄2" X 1⁄4" galvanized steel

rings. 

A 1⁄4" Duralon rope is passed through the selvage mesh and a ring is

attached to the rope using a cow hitch every 12", with five open meshes

between each ring. 

The bag is then closed using a e"-3⁄4" hauling clip.

NOAA Fisheries Trawl Survey Protocols
71

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Materials List for Poly Nor’Eastern Trawl

Specifications of wire, chain, and rope include rated breaking strength (BS), specific gravity

(SG), and density.

WEB: All web in the trawl should be depth stretched and heat set in the

manufacturing process. Mesh sizes listed in the plan are given in

“stretched measure”, a standard method of measuring mesh size that

includes the length of one knot.

Top, body and wings, side panels ~ 5", 4-mm polyethylene knotted web -

orange.

 Bottom, body and wings, intermediate ~ 5", 5mm polyethylene knotted

web - orange.

Liner ~ 11⁄4", # 18T three strand nylon knotted web - dyed green.

Chaffing gear ~ 6", 6mm double bar mesh, polyethylene knotted web -

orange.

 Chaffing strip, bottom~ 5", 5mm double bar mesh, polyethylene knotted

web - orange.

WIRE ROPE: 1⁄2" 6×19 galvanized fiber core (BS 9,700 kg, 0.62 kg/m), eyes are formed

using galvanized reinforced thimbles.

CHAIN: 1⁄2" (16 mm) galvanized, long link marine deck lashing chain, grade 70

(BS 20,500 kg, 3.42 kg/m).

e" (16 mm) galvanized, long link marine deck lashing chain, grade 70

(BS 28,670 kg, 5.06 kg/m).

FLOATS: Twenty 12" side lug trawl floats (23 lbs. buoyancy each) depth rated to a

minimum of 450 fm. Four 8" side lug trawl floats (5.4 lbs buoyancy

each).

RIBLINES: 3⁄4" Samson DuralonTM 2-in-1® stable braid, white, light bonding (BS

8,800 kg, SG 1.83, 0.27 kg/m).

TWINE: Sewing panels together: 5-mm polyethylene twine, any color other than

orange.

Lacing seams: # 21T white, three strand nylon. 

Joining top and side seams together: # 21T green three strand nylon.

Joining bottom and intermediate seams: 60T white braided hanging twine.

Alaska Fisheries Science Center
72

ROPE: Float lines - 1/4" polypropylene (BS 570 kg, SG 0.95).

Pucker ring lines- Samson 1/4" DuralonTM 2-in-1®(BS 1,270 kg, SG 1.38)

Restrictor rope- 1 1/8" Poly PlusTM three strand (BS 10,740 kg, SG 0.91).

Splitting strap- 3/4" SpectraTM braided rope with eye each end (BS 21,773

kg, SG 0.98).

Rope to serve cables- 3/8" polypropylene three strand.

Chaffing gear- Poly hula skirt material.

FOOTROPE: (GOA, Aleutian Islands, MACE)

3⁄4" 6×19 galvanized, fiber core wire rope 79' 6", (BS 21,600 kg, 1.41

kg/m) .

4" rubber disc with a 1" hole- wing extensions, center section between

bobbins

8" rubber disc with a 21⁄4" hole - wing extensions.

e" Long link marine deck lashing chain, grade 70.

Laminated rubber “cone style” wing bobbins with a 21⁄2" steel reinforced

hole.

Chain droppers 10" in length. Five links of d" chain and one ring

21⁄2"×1⁄4"

3⁄4" barrel clamps

Steel plate wire rope washers- 5" ×d"- 1" center hole.

11⁄4" ID - 13⁄4" OD heavy hose over bare 3⁄4" wire.

 Four hole triangle delta plate, d" steel.

NOAA Fisheries Trawl Survey Protocols
73

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Framing Lines for Poly Nor’Eastern Trawl

Alaska Fisheries Science Center
74

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Net Plan for Poly Nor’Eastern Trawl

(“Cut Plan” = Total Mesh Counts)

Twine Sizes: top and sides 4 mm 

bottom and intermediate 5 mm 

NOAA Fisheries Trawl Survey Protocols
75

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Trawl Door Rigging Plan Detail for Poly Nor’Eastern Trawl

Sole Manufacturer NET Systems, Inc., Bainbridge Island, WA

Alaska Fisheries Science Center
76

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Trawl Door Rigging Plan for Poly Nor’Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
77

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys 

Bobbin Roller Gear Construction Plan for Poly Nor’Eastern Trawl

Alaska Fisheries Science Center
78

Survey Trawl Check List

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Poly Nor’Eastern Trawl

NOAA Fisheries Trawl Survey Protocols
79

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Net Repair Form for Poly Nor’Eastern Trawl - Bottom and Side Panels

Alaska Fisheries Science Center
80

Gulf of Alaska and Aleutian Islands Bottom Trawl Surveys

Net Repair Form for Poly Nor’Eastern Trawl - Top Panel

NOAA Fisheries Trawl Survey Protocols
81

Appendix 2

Northwest Fisheries Science Center

Standard Operating Protocols

West Coast Bottom Trawl Survey

Northwest Fisheries Science Center

83

Introduction

Scientists from the Northwest Fisheries Science Center (NWFSC) Fisheries Resources Analysis

and Monitoring (FRAM) Division conduct annual bottom trawl surveys of the groundfish

resources of the West Coast upper continental slope (WCUCS). These surveys comprise a series

of standard tows at stations that extend from Cape Flattery, Washington (47/ 20') to the US -

Mexican border (32/ 40') and encompass depths that range from 30 to 700 fathoms (fm). The

resulting catch data are used to assess the status and trends of the various groundfish populations

through application to population models that also incorporate data from the fishery and

life-history studies. The surveys collect data on a variety of WCUCS fishes and invertebrates,

but are principally focused on assessing the sablefish (Anoplopoma fimbria), the shortspine

thornyhead (Sebastolobus alascanus), the longspine thornyhead (Sebastolobus altivelis), and the

Dover sole (Microstomus pacificus), commonly referred to as the Dover-Thornyhead-Sablefish

species complex (DTS), and the rockfishes (genus Sebastes). 

The goal is to develop long-term indices of relative abundance for these species and to

characterize their distribution. Moreover, specimens and other recorded data from the survey

will be used to improve our understanding biological conditions, trends in population dynamics,

and to identify community relationships. Specific objectives of these surveys include:

1. Quantify the distribution and relative abundance of commercially valuable groundfish

species, with an emphasis on the fish of the DTS complex, as well as rockfish species of

the genus Sebastes.

2. Obtain biological data from individual fish including length, weight, sex, and maturity

stage for species of interest.

3. Gather ageing structures from Dover sole, sablefish, longspine thornyhead, and

shortspine thornyhead.

4. Collect accurate net mensuration data on the trawls used in this survey.

5. Collect associated oceanographic data (i.e., water temperature, salinity).

6. Collect ancillary biological data and specimens for other projects.

Since 1998, The NWFSC has used chartered, commercial fishing vessels to conduct these

surveys. The following operation protocols are designed to document our established survey

standards, act as a reference to ensure data quality and consistency, and to show adherence to the

NOAA Fisheries Trawl Survey Protocols.

Northwest Fisheries Science Center
84

Protocol 1: Warp Measurement Standardization

The NWFSC will provide each chartered survey vessel 2 spools of 1200 fm of 5/8" steel-core

wire rope. Each warp should be attached to the winch on each vessel in the same fashion during

vessel mobilization. At the completion of the survey, the wire cable will be taken off the vessel

and retained by NMFS.

NOAA trawl survey standardization protocols (Protocol 1) require that two independentlycalibrated measuring methods or devices shall be used on each trawl warp, one of which will

measure the warp in real time. For NWFSC bottom trawl surveys, trawl warps will be measured

by at least two of three procedures. (1) In all cases, trawl warps will be measured and marked

side by side by a private vendor with FRAM supervision – the measurements and markings will

be made prior to each cruise, and at the completion of the contract. The markings will be made

in twenty-five fm increments. Also (2), an electronic trawl warp measurement system (e.g., 3

Point Systems Inc. via Sensors Northwest) will provide a real time digital display of amount

(distance) of wire deployed for each tow, or (3) in-line trawl wire meters (e.g., Sensors

Northwest or Olympic Instruments, Inc.) to provide a mechanical method of length

determination for trawl warp deployment.

Length Measurement of Trawl Warps

We will measure and mark warps side-by-side prior to each deployment. This marking

procedure, to be conducted by Englund Marine in Newport, Oregon or other appropriate vendor.

Trawl block or mechanical warp counters will be used for real-time measurement of trawl warps

during each haul and retrieval event. NMFS scientists will monitor the real time information and

measurement data will be stored either directly within SCS or recorded on data sheets and

entered electronically at a later date. If at any time during a haul an observed difference between

the two warps exceeds 20.7 ft. (based on 4% of the distance from trawl doors), all operations

must cease and a determination made as to the cause of the discrepancy. This discrepancy must

be remedied before survey operations can proceed.

During normal operations, some stretching of the warp will likely occur due to hanging the doors

or footrope on the seafloor bottom. If more than 6 inches distance from the marked warp to the

block counter occurs, the warp interval will be remarked with a different paint color. The

real-time trawl warp counter will be re-calibrated whenever remarking of warps has occurred.

Special attention should be paid to the monitoring system when door and footrope hangs occur

to observe if stretching of the warp has taken place and remarking is necessary.

Calibration of Warp Measurement Devices

Calibration of the 3 Point Solution, Inc. electronic system and the Sensors Northwest in-line

mechanical odometer trawl warp measurement system will be carried out by: (1) visual

inspection to ensure that damage has not occurred during installation, (2) regular maintenance

performed according to the manufacturer, and (3) making paired measures against a known

NOAA Fisheries Trawl Survey Protocols
85

length section of warp as determined with a tape measure or equivalent (at least 50m) during

each survey. If this procedure shows inaccuracy, a payout scaling correction will need to be

made by the following calculation: 3.14159 × (root diameter of the sheave + line diameter)] /

(number of targets). The units for sheave diameter and line diameter in the above formula must

be the same as the units for displaying payout on the display. For example, if the display units

are feet, then the number for the line diameter in the formula must also be in feet. The payout

scaling can be modified easily on the sensor unit at sea. 

Calibration of the Olympic Model 750-N and the Systems Northwest in-line wire meters will

occur during annual maintenance and again at-sea. Annually, prior to the surveys, each meter

will be returned to the manufacturer (Olympic Instruments Inc.16901 Westside Highway S. W.,

Vashon, WA 98070; Sensors Northwest, 23632 Highway 99, F-505, Edmonds, WA 98026)

where broken or worn parts (wheels, springs, counters, etc.) will be replaced and the unit cleaned

and lubricated. Each unit will be tested to determine whether it is performing within factory

specifications and calibrated to a known length of cable of similar properties to the warps used

on the surveys. At sea, each in-line meter must first be inspected to ensure it has not been

damaged during transport, then cleaned and again calibrated against a known length of warp (at

least 50 m) measured using the tape measures provided to each field party. The calibration can

be done as follows: 1) set the trawl with the doors just underwater at a speed of 2 knots, 2) mark

the warp with a piece of tape near the trawl sheave, 3) measure from this mark forward, in

increments, until a distance of at least 50 m of warp has been measured, then again mark with

tape, 4) attach the meter to the warp in an accessible location and secure fore and aft with rope,

5) measure the marked distance with the in-line meter three times and 6) calculate a calibration

coefficient (i.e., known length / measured length ) from the average of the three measurements.

Determination of Critical Value

According to Protocol 1, the maximum allowable offset between trawl wires is 4% of the

distance from door to door as measured around bridles and footrope. For the trawl used by the

NWFSC, this critical value is determined as follows:

Two door legs of twenty-five ft (2 × 25') + four ninety-ftsweeps (two on each side) (4 × 90'),

+Footrope, including extensions 104' [(2 × 20'6")+(4 × 12')+(1 × 15')], + (4.67') for connection

hardware which includes: 12 - 5/8" hammerlocks at 3.0" per hammerlock (3') + two delta plates

at 4.0" per delta plate (8.0"or .67') + two butterfly plates at 6.0" per plate (1.0'). 

50+360+104+4.67=518.67' (ft) × 0.04 = 20.75 ft or 6.3 m.

Proper Care and Stowage of In-line Meters

 During use, avoid any rough treatment of wire counters (for example do not leave them laying

out on deck, or allow them to slide around, or drop them between decks) and thoroughly clean

after each use with undiluted Simple Green detergent with particular attention to remove warp

grease buildup on roller. Allow the meter to dry completely before placing in case (dry in engine

room) and store in a dry area.

Northwest Fisheries Science Center
86

Protocol 2: Auto-trawl Standardization

Auto-trawl systems are not used by vessels chartered by the NWFSC.

Protocol 3: Operations Procedures

A. Scope

To date, we have relied on the individual vessel operator’s experience and judgment for

choosing an initial scope ratio. In practice, scope ratio varies non-linearly with depth, from

about 3:1 at 100 fm to 2.5:1 at 300 fm, 2:1 at 400-500 fm, and as low as 1.7:1 on out to 700 fm. 

We will continue to depend on these values until such time as a formal study of net performance

and scope ratio over various depths is completed. Because the appropriate scope depends on

other immediate factors (e.g., weather; the force and direction of any bottom currents), the final

scope fished at any particular event will be based on the observed trawl geometry and bottom

tending performance on each and every tow.

B. Speed of tow

Bottom trawl hauls will be made at a constant speed of 2.2 knots (nmi/hr) over ground. The

Captain of the vessel is responsible for monitoring and maintaining the speed during the entire

tow. Speed at any point during the tow can be verified using the continuous stream of GPS data,

which is logged to a computer file. Speed variations of ± 0.5 knot are acceptable, but the target is

2.2 knots and should be adhered to as closely as possible. Monitoring and recording of tow

speed will be accomplished in real time using the GPS unit supplied by the scientific party. 

Should this government provided GPS fail, the Captain should use the vessel instrumentation

that he/she believes most closely matches that of the government unit. In such cases, the

Captain/FPC will document in the instrumentation used to monitor tow speed.

C. Duration and distance of tow calculations and use of trawl mensuration / performance

monitoring instrumentation

The performance and geometry of trawls used during NWFSC survey tows will be measured

using several sensors. The Simrad Integrated Trawl Instrumentation (ITI) System, Bottom

Contact Sensor (BCS), and a secondary temperature/depth recorder will be deployed on every

haul. ITI data is logged continuously on a computer. The BCS and secondary temperature/depth

data will be downloaded after every tow.

The ITI system consists of four sensors that are clearly marked with respect to their orientation

(i.e., Up, Towards Vessel, Port, and Starboard). There is the Trawl Eye, which measures

headrope height and footrope clearance; a temperature/depth recorder (TDR); and a pair of wing

units (one master & one slave), which measures the wing spread. Together, all ITI data is

automatically logged. The FPC will monitor the ITI display throughout each haul, and will

periodically record the values on the Haul Data Form. Prior to the first haul, the Trawl Eye and

TDR are mounted in mesh bags at the center of the head rope. These units can be left attached to

the net between tows. The wing units are clearly marked Port and Starboard and are attached to

the wing of the net. Always use a clip-on safety line attached to the vessel when attaching or

NOAA Fisheries Trawl Survey Protocols
87

removing the sensors. The units are quite rugged and can stand the abuse of shooting and

heaving the gear, but excessive and continuous rough treatment can affect their operation. The

FPC is responsible for these operations, or delegating this responsibility to another person. All

sensors must be recharged at the end of each day’s fishing operations with the supplied battery

chargers.

Two BCSs will be attached to drop chains on either side of center-point of the footrope. The

FPC will provide the proper link for attachment. Each BCS will be designated port or starboard

and the downloaded shuttles must be kept separate. Each BCS has an “up” and “down”

orientation and should be attached so that it is oriented correctly, such that the BCS is horizontal

as it is dragged across the seafloor and perpendicular when the net is off the seafloor. Directions

for programming and downloading the BCS units are provided in a separate manual.

A Vemco TDR, secured in a section of pipe, will be attached to the center of the head rope using

a snap shackle. This unit may be left on the net between tows and will be downloaded and

backed up to a disk at the conclusion of each day’s fishing operations. Instructions for

downloading and maintenance of the unit are provided in the unit’s operations manual.

Each vessel will be equipped with at least one backup PC, Fish Meter head and board, scale,

battery pack, and flat screen monitor. There is one complete backup set for the ITI system and

one ITI box for both vessels. If for whatever reason a backup system is unavailable, it will be

necessary to use the BCS system for tow duration data during the sampling period. When this

occurs it is critical that the FPC keep detailed records on the Haul Data Form of the exact times

of the trawl events (i.e., Doors Fully Out, Gear On Bottom, Begin Tow, Start Haulback, Doors

On Surface). It is essential that the clocks in the BCS, computer, and the FPC’s time reference

are precisely synchronized at all times in order to make later interpretation of BCS data possible.

The time display on the GPS is the most accurate time reference on the vessel. 

Target duration of all tows will be 15 minutes towing time. This duration ensures an adequate

sample of the biota and usually results in a catch that is a reasonably manageable size to sort and

process. The start of the 15 minute towing period will be determined from the near-real-time

readout of the net height instrumentation, which enables the operator to determine when the net

approaches bottom and settles into its fishing configuration. The time that the footrope touches

down can usually be detected by watching the headrope height measurements decrease rapidly

from over 10 m to under 8 m as the net approaches bottom. The start of the tow should be

defined as when the height decreases to 8 m. Winches are engaged 15 minutes later to haul

back the net. Tows may be shortened due to upcoming obstructions, inability to follow a depth

contour, hangups, gear problems, or extremely large catches which affect the efficiency of the

trawl.

After the haul is completed, data from each of the sensors will be synchronized with time stamps

and displayed using an in-house, custom designed software package. Using this software, an

initial computation of time of on bottom and off bottom is available in the field. Later, using the

same software an operator will determine the precise points in time that the footrope initially

contacts and leaves bottom and calculate the duration, distance fished, and average net spread

Northwest Fisheries Science Center
88

and height during each tow. The trace of the BCS data is the most useful tool for determining

the on and off bottom times. The transition between when the net is on or off bottom is usually

clearly signaled by an abrupt change in readings from around 0-20 degrees to around 60-80

degrees (vice versa when leaving bottom).

The data recorded from the sensor systems (BCS, ITI, and global positioning systems (GPS))

provide the principal data for effort related estimations. All sensor streams are reviewed to

address spurious readings known to be related to the recordings from the electronics. In

particular, because the computer system receiving the ITI sensor signals often record readings at

a rate exceeding that at which new readings are delivered, some sensor readings are recorded

multiple times. This "persistence" of a single sensor reading through several recordings is

evident in the data streams as varying length strings of constant value.

Persistent strings that greatly distort the overall signal pattern are removed using a variety of

techniques. They include objective statistical trimming methods and more subjective manual

removal of data points. In particular, persistent strings that originated before and extended into

the time intervals bounding subsamples used for estimation were routinely removed manually

prior to analysis. But for the most part, the phenomena under observation vary little during the

on-bottom time period of interest, so that the overall pattern of sensor readings was not

substantially distorted by moderate periods of data repetition. Therefore, it is assumed that

treating the members of a persistent string as independent samples within the sample set would

not substantially affect the mean estimate. However, it would result in unacceptable

underestimation of the standard error of the mean and, accordingly, standard error estimates are

not reported for mean estimates.

Because none of the ITI sensor readings should ever be zero during the tow duration, such are

considered missing values and are filtered out prior to all depth, net dimension, and

temperature estimations. Large spikes in the depth, net dimension, and temperature signals are

assumed to be the result of electronic noise and are filtered out prior to processing. Such data

points are even more questionable when several isolated occurrences seem to be identical in

value, as is apparent for various gear depth data sets. In contrast, sensor data streams also

indicate that there can be large swings in the net during a tow, sloping and bumpy substrates, and

trawl execution problems that manifest themselves in highly variable data sets. Extreme points

that appeared to be part of some contiguous variation in magnitude, or some particularly variable

stretch of readings are not excluded prior to analysis.

The sensor reading sample sets used to estimate depths and net width and height are limited to

the center 80% of the tow duration to ensure only on-bottom readings are included. In the vast

majority of tows, this boundary does not appreciably reduce the number of observations, but

does effectively exclude small timing offsets between the BCS and ITI sensor systems and any

instantaneous noise introduced by net touchdown and liftoff. 

Tow duration is measured as the simple difference between the times marking touchdown and

lift-off of the trawl net. Wherever possible, these times are determined from bottom contact

sensor traces of tow progression from net deployment to retrieval. Gaps left by unrecorded or

NOAA Fisheries Trawl Survey Protocols
89

otherwise suspect bottom contact sensor information are filled using either patterns in ITI sensor

readings or field party chief observations of net touchdown and lift-off times.

Mean estimates of net width and height are calculated from trawl sensor readings of wingspread

and headrope height from bottom, respectively. Electronically recorded sensor readings provide

the preferred basis for estimation; hand recorded sensor readings are substituted where necessary

and reasonable. When neither data set provides acceptable information, estimates are calculated

by prediction from separate linear regressions over the width and height estimates of the other

survey tows. Each dimension was regressed against tow depth, with vessel identification

incorporated as an indicator variable. Net height predictions are made using robust linear

regression. Although the interaction between vessel identification and depth proved to be

significant by ANOVA, it neither added appreciably to the proportion of explained variation nor

produced coefficients that were significantly different from zero. All estimates are tagged with

qualifying information indicating estimation method.

To estimate distance fished, the period of time a net is dragged over the seafloor is split into two

distinct phases. The first phase, defined as normal towing, starts when the net begins fishing as

it reaches the seafloor and ends when net haulback is initiated. The length of the first phase is

controlled by the FPC and, unless problems occur, is maintained for 15 minutes. The second

phase follows the first and represents the time required for the net to lift off the seafloor in

response to the haulback operation. Labeled "liftoff lag", the length of this phase varies by

vessel and depth. 

Smoothing of the trackline yields a reasonable estimate of the location of the net and an estimate

of towing distance for the normal towing phase. However, typically the vessel is not moving

forward during the liftoff lag phase, and consequently the survey's GPS sends erroneous bearing

information to the ITI. The ITI, in turn, calculates an invalid geographical position of the trawl

net. Hence, the distance and direction the net moves during the liftoff lag phase needs to be

extrapolated. 

The extrapolation technique begins by fixing the trawl's bearing at the average bearing from the

last 5 minutes of normal towing. This is combined with the range information (the distance

between the vessel and the net) and the geographic location of the vessel, to obtain the

extrapolated location and distance covered by the net during the liftoff lag phase. This

extrapolated trackline is connected to the end of the normal towing trackline, and the combined

trackline is then smoothed with a two-dimensional Simple Exponential Smoother. Visual

examination is used to determine the correct amount of smoothness that is needed for each haul. 

A default value for the smoothing parameter has been found to work in a majority of cases,

including, but not limited to, those tows that were done in a relative straight line with good

signal from the ITI system. The percent of tows for which the default smoothing parameter

works varies by vessel, but all vessels have extreme cases for which the default value is not

used.

Northwest Fisheries Science Center
90

The trigonometric method, developed for the 1998 survey analysis, is used when the there is

insufficient information for the above procedure. Within the database, all estimates were tagged

with qualifying information indicating which estimation method was employed.

Gear depth and bottom depth are estimated from electronically recorded trawl sensor readings of

headrope depth and headrope distance from bottom. Gear depth is taken as the headrope depth

sensor reading and bottom depth is taken as the sum of headrope depth and headrope distance

from bottom. Hand recorded data sets are substituted when necessary and reasonable. For cases

where data of sufficient quality are available, mean estimates are calculated for each, using a

subsample limited to the center 80% of the tow duration to ensure only on-bottom readings are

included. In a few cases where no acceptable data exist within the center 80% of the tow

duration in either the electronically or hand recorded sets of gear depth readings, estimation is

made from observations just outside of it, but within what could reasonably be assumed to be the

observed limits of net touchdown and lift-off. For some tows, few to no coincident records of

headrope depth and headrope distance from bottom exist. In these cases, if gear depth and net

height are estimable for a tow, bottom depth is estimated as the sum of these two endpoints,

regardless of how the separate estimates had been derived. In cases where no reasonable

observation of gear depth is recorded, but depth from the vessel navigational equipment is,

bottom depth is estimated from these vessel records. All estimates are tagged with qualifying

information to indicate estimation method.

D. Direction of tows

Due to the survey design, tows can be made any direct that allows the entire tow duration to

occur with the pre-selected grid. Tows will be made in the direction determined to be best to

accommodate a variety of local conditions: bottom obstructions, peculiarities of the substrate,

wind, current, or sea state, and direction to next tow.

E. Location of sampling sites and procedures to use if stations are not suitable for towing

Stations to be sampled during the survey will be selected during the design process. The entire

survey area is covered by an overlay of 2 nmi (latitude) × 1.5 nmi (longitude) grid cells. The

exact location of a tow is actually unspecified but must fall within a chosen grid cell. 

Stations for each stratum are randomly selected without replacement from the set of full or

partial grid cells falling within that stratum. The stations in each stratum are then assigned

among the vessels. Paper and electronic charts depicting station locations and successful tows

made during previous surveys are used to guide sampling. 

Within each assigned grid cell, the captain and FPC collaborate to find enough trawlable bottom

to complete a standard 15 minute tow made at the standard speed of 2.2 knots (approximately

0.55 nmi or 1.02 km). Each tow should be surveyed before trawling operations begin in order to

minimize time lost to gear damage and bad performance tows. However, because the goal is to

maximize the coverage of the area with the survey trawl, some risk of gear damage is acceptable. 

While it is not necessary to begin the tow within the grid cell, the majority of the tow (and

preferably the entire tow) should be within the cell. A reasonable effort should be made to

NOAA Fisheries Trawl Survey Protocols
91

search the entire cell for trawlable bottom, but the search time should generally not exceed 2

hours.

If no trawlable bottom is found within an assigned grid cell, that cell should be designated as

untrawlable in the station log, including any pertinent notes. An alternate grid cell should then

be sampled. Alternate sites will be selected from the list of secondary grid cells within in the

correct stratum.

F. Criteria for determining the success of a tow and procedures to use if a tow was

unsuccessful

A successful tow is defined as a tow in which the trawl was maintained on the bottom in the

standard fishing configuration as determined by net mensuration and bottom contact

instrumentation. The FPC will ensure that the trawl was in adequate fishing configuration, and

preponderantly on bottom for the duration of the tow. As instructed above, 15 minute tows are

the standard and should be completed as such unless otherwise instructed by the FPC. Tows are

acceptable under conditions described below.

• If the net is off bottom less than 2 minutes during a tow (regardless of depth) then

it is a good haul and work up the catch according to the operations manual.

• If the net is off bottom more than 2 minutes, but less than 5 minutes, work up the

catch by only sorting, counting and weighing all species. No lengths, otoliths or

any other special projects are to be collected from this haul. 

• All net geometry readings within tolerance limits (opening 4.2-6.8 m, wingspread

12-16 m)

• Tow speed within tolerance limits (2.2 ± 0.5 knots)

Tows with any loss of fish or invertebrates due to significant tears in the net or with improper

fishing configuration are considered unsuccessful. Tows for which obstructions in the net (e.g.,

fishing gear and other debris) that could have potentially affected the CPUE are also considered

unsuccessful.

In some cases, if a hang-up or gear obstruction has occurred at a time that is fairly obvious, such

as a shudder or stopping of the vessel, and haulback is immediately started, the trawl should be

examined. If any damage is minimal and restricted to forward parts of the trawl, then the tow

may be considered successful. This assumes that at least 12 minutes of on bottom time was

achieved. If a significant tear-up or obstruction occurs, or it cannot be determined when the tear

or obstruction happened, then the tow must be considered unsuccessful.

Stations considered unsuccessful will be re-towed unless factors beyond the control of the

survey party make it impossible to complete the station within the grid square (e.g., extreme

current). The FPC will make the final decision as to whether the tow was successful or not and

whether it will be re-towed.

Northwest Fisheries Science Center
92

G. Vessel and winch operation during deployment and retrieval

To ensure comparability between vessels and years, vessel operators will be asked to follow

standard procedures when setting, towing, and retrieving the trawl gear. These procedures will

be established at the beginning of the first leg by the captain and the FPC and must be

maintained throughout the survey and for all subsequent surveys. The goals for each part of the

standard tow are as follows:

Setting

Primary Goal

• To ensure that the trawl is in fishing configuration (height and width) when it

makes bottom contact.

• To ensure that the procedure is easily repeatable.

Secondary Goals

• To ensure that the trawl reaches bottom quickly to minimize the midwater catch.

Towing

Goal

• To maintain the trawl in fishing configuration (height and width) at a continuous

towing speed of 3 knots.

Haulback

Goals

• To maintain the trawl in fishing configuration until it leaves the bottom. 

• To ensure that the net leaves bottom quickly to avoid changes in fishing

configuration due to decreased scope and changes in net speed over ground.

• To ensure that the procedure is easily repeatable.

Implementation

Vessel speed, engine RPM, wire payout rate, etc., required to achieve these goals may require

some experimentation at the beginning of the first leg of the survey on each vessel. The captain

and the FPC should work out a standard procedure for setting, towing, and hauling back the

gear. The procedures decided upon should facilitate consistently achieving the above stated

goals and will be documented in writing on the Standard Trawling Procedures Form and adhered

to for the remainder of the survey and for all subsequent surveys. Since the power settings

(RPM and/or propeller pitch) to achieve particular vessel speeds will change with the wind, sea

state, and currents, approximate power settings used to achieve these speeds in good weather

conditions (little wind, no current) should be recorded. If different procedures are developed for

various depths, these should be recorded as well. Any procedural modifications during the

survey must be mutually agreed upon between the FPC and the captain and must be carefully

justified and documented in writing. 

NOAA Fisheries Trawl Survey Protocols
93

H. Defining responsibility (e.g., survey scientist or vessel crew) for decisions regarding

various aspects of the operation

All aspects of the survey operation will overseen by the FPC. Final decisions regarding station

locations and station scheduling are the responsibility of the FPC. Vessel operation, trawl gear

deployment and retrieval, and all matters related to vessel safety will be the responsibility of the

vessel captain.

It is the responsibility of both the FPC and the captain of the vessel to keep lines of

communication open between survey vessels, not only for safety purposes, but to ensure that all

operations are proceeding in the manner outlined herein.

I. Staff training

The scientific staff participating in NWFSC trawl surveys will undergo periodic mandatory

training which includes classes addressing use of net mensuration instrumentation and

interpretation of the mensuration data, fish and invertebrate identification, survival skills, remote

duty first aid, oxygen therapy, and principles of trawl net maintenance. In addition, the FPC

leading each cruise leg will be trained to carry out the objectives and sampling instructions for

the specific survey leg he/she is assigned to. Training of FPCs includes learning about the

design, logistics, and sampling requirements of the survey; staff management; and evaluating

survey fishing gear repairs. The FPC is responsible for working directly with the captain of the

vessel to coordinate overall and daily work plans and coordinating with the FPCs of partner

vessels to efficiently and successfully achieve the sampling objectives of the survey.

The NWFSC surveys are conducted with chartered vessels, captains, and crew. As such, we

have limited influence over the training requirements of the captains and crew. Our staff will

work closely with vessel personnel before and during the charter periods to communicate with

and educate them regarding matters important to the standard and proper sampling procedures

required during groundfish bottom trawl surveys. Consultation with AFSC Net Loft staff will be

used to review prescribed maintenance and repair objectives and standards with vessel personnel

and FPCs will interact constantly with captains regarding survey objectives and standardized

fishing protocols.

Northwest Fisheries Science Center
94

Protocol 4: Trawl Construction and Repair

Descriptions of Trawls and Their Rigging

The NWFSC Slope Survey net is a 4-panel ‘Aberdeen’ trawl. This design trawl is used by West

Coast chartered commercial trawlers, which range from 400 to 600 horsepower. The net is

spread by 5' × 7' steel ‘Vee’ doors. The Aberdeen trawls are routinely used throughout the region

where FRAM conducts its assessment and research activities (i.e., the waters off the West Coast

of the continental United States, from nearshore environments out to depths of 700 fm) and are

fished on all types of bottom types found in these areas. The FPC and captain must understand

that our trawl is a research sampling tool and the success of our surveys rides on consistent

deployment and maintenance of our nets. When a trawl is damaged, it is necessary to determine

whether the trawl can be repaired to its original state. If there is any question of its suitability,

the trawl net should be decommissioned and the back-up trawl rigged for service. If the damage

can be repaired, all repairs must be documented on the net repair forms provided by the FPC.

The FPC should work with either the Captain or the lead fisherman to fill out the form and

document what was replaced or repaired and how this was accomplished.

 Information concerning trawl construction and repair is included in the operations manual for

each survey. This information includes:

• Description of the construction of the trawl components

• Description of the materials used in the trawl construction

• Net plan 

• Rigging plan

• Ground gear plan

• Checklist for verifying trawl dimensions and specifications

• Trawl Repair Form

The FRAM staff will inspect and measure each trawl prior to loading it onto the vessel to ensure

that it conforms to the specifications set forth on the survey trawl checklist. In addition, each

trawl will have an identification number, stamped on a metal tag, that will be included on all

haul forms and trawl repair forms. Whenever the trawl requires repair during survey operations,

such repairs will be done following the standards set forth in the following section and

documented on the trawl repair form. Components potentially affected by at-sea repairs will be

measured again to confirm that the trawl is meeting specifications.

Gear Repairs Aboard Vessels

At the start of every survey, vessels will be provided with an inventory of supplies used to repair

trawl gear during the survey. These supplies should provide each vessel with the resources

needed to make typical repairs. If a survey vessel has experienced frequent net damage, the FPC

should transmit a list of trawl repair supplies far in advance of the next scheduled port of call to

allow time to ship the supplies.

NOAA Fisheries Trawl Survey Protocols
95

Net, doors, and bridles should be examined routinely during every haul back, checking for any

damage and noting any repairs that are needed. When large rocks are dumped from the net, 

codend liners should be checked for damage. The FPC, in consultation with the vessel crew,

will determine whether it is more expedient to repair a damaged trawl or to replace the trawl

with a spare.

Survey trawls are research sampling tools and the success of our surveys depends on maintaining

our survey gear to NWFSC standards. The FPC should stress this to fishers responsible for

making trawl repairs to ensure that trawls will be replaced if they cannot be repaired to NWFSC

survey standards. Fishers must follow the trawl repair protocols provided to them at the precruise meeting with personnel from the FRAM Division. In particular, they must replace torn or

abraded web with patches or new panels, rather than hand sewing new meshes. Straight tears,

however, can be sewn as long as there is no need to build meshes to close the hole. Lacing of

holes or tears is not allowed in the body, wings or codend of the trawl. Special attention should

be given to repairs involving the inside of the bottom wings (where the bar cut and chaffing

strips are sewn to the body). Poor repairs in this area may affect the way the footrope tends

bottom. Repairs that should not be attempted aboard vessels include broken headropes,

footropes, riblines or rehanging long sections of riblines (repairs that involve more that 25

benzels, approx. 40'). Given the limited deck space aboard our survey vessels, these repairs are

difficult to do correctly to ensure the finished product meets our standards. 

The FPC is responsible for overseeing net repairs and deciding if a net should be retired. When

a net is damaged, repaired, or retired, the Net Repair Form should be completed, noting the net

ID number and all damage and repairs made. When retired, the net should be picked and

cleaned before it is bundled and stowed.

Northwest Fisheries Science Center

97

West Coast Slope Survey

Scientific Operations Plan

Aberdeen Trawl Schematics

Northwest Fisheries Science Center

99

Northwest Fisheries Science Center
100

Aberdeen Trawl Rigging Diagram

NOAA Fisheries Trawl Survey Protocols
101

5' X 7' Vee-Door Rigging

Northwest Fisheries Science Center
102

Float Placement on Aberdeen Trawl

NOAA Fisheries Trawl Survey Protocols
103

Appendix 3

Southwest Fisheries Science Center

Standard Operating Protocols

Antarctic Bottom Trawl Survey

Southwest Fisheries Science Center

105

Introduction

The U.S. Antarctic Marine Living Resources (AMLR) Program is a program mandated by the

Antarctic Marine Living Resources Act of 1984, assigned to the Antarctic Ecosystem Research

Group at the Southwest Fisheries Science Center. The AMLR Program provides a basis for U.S.

policy on the management and conservation of Antarctic living resources and supports this

nation's participation with international efforts to protect the Antarctic and its marine life under

both the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR)

and its Scientific Committee.

The U.S. AMLR Programconcentrates research activity in CCAMLR Statistical Area 48,

primarily in the Southern Scotia Arc Region of the Southern Ocean near the Antarctic Peninsula. 

Research cruises and land based operations are primarily directed at gathering biological

information to prevent overexploitation of fish and krill, as well as assess seal, penguin, and

pelagic seabird populations for their protection. In order to achieve these goals, several

components of the Antarctic food web and ecosystem are sampled. These include collection of

physical and chemical oceanographic information, primary and secondary productivity, and

acoustic and net sampling of marine predators (finfish) and their prey. 

To collect information on finfish and the role of finfish in the Antarctic ecosystem, the U.S.

AMLR Program conducts periodic (non-annual) bottom trawl surveys which examine standing

stocks, community structure, reproduction, feeding guilds, and other ecosystem related aspects

of demersal and benthic marine organisms, as well as habitat characteristics of seabeds. These

bottom trawl surveys are based on a random, depth stratified sampling design, and target shelf

areas between 50 and 500 m. Sampling sites are situated in areas that are very poorly charted (to

uncharted) regions of the Southern Ocean. The survey targets as many species as possible

(about 45 species). In most cases, these species exhibit a patchy spatial distribution; the

mechanisms that influence these distributions is the subject of ongoing research.

Since 1996, the U.S. AMLR Program has chartered a 104 meter, 5626 ton ice-class vessel, the

R/V Yuzhmorgeologiya, to conduct the research cruises and resupply the land bases. The AMLR

Program initiated the bottom trawl survey component during the 1996/1997 Austral summer,

when seven hauls were conducted. During the 1997/1998 Austral summer, the first large-scale

bottom trawl survey was initiated in CCAMLR Statistical Subarea 48.1 (the South Shetland

Islands). These surveys have continued on a periodic basis in other CCAMLR Statistical

Subareas within the Southern Ocean.

This document presents information on aspects of the bottom trawl survey component of the

AMLR Program, and should be considered as one of the Southwest Fishery Science Center’s

Regional Protocols within the framework of the NOAA Trawl Survey Standardization Protocol.

Southwest Fisheries Science Center
106

Protocol 1: Length Measurement of Trawl Warps

The two trawl winches (STV-160) are installed at the port and starboard in 5 m from the stern,

with a reel capacity of 32,000 m on each winch. The winches can run together or separately. 

We currently do not use an auto-trawling system.

The trawl warps are comprised of 25 mm diameter, 6 × 19 class, right and regular lay, fiber core

wire rope (weight - 2.28 kg/m; breaking strength - 31 tons). Cables are continuously checked

for damage, rust, and broken wires (no more than 15% on length equal to 8 diameters).

Line speed and line amount data are collected during deployment and retrieval by means of a

Russian made magnetic block wire counter (SDT-SI2). The calculation of warp is realized by

noncontact magnetic sensors installed on the block (sheave) and block frame. The conversion is

based on the number of constant magnets, the circumference of the block groove, the number of

revolutions, and the conversion efficiency parameter for each block. These wire counters are

calibrated prior to each survey by passing a measured wire through the block. Parts are

periodically inspected and replaced if needed during the course of the cruise.

As specified in Protocol 1 of the report of the National Trawl Survey Standardization Workshop,

a pair of mechanical in-line wire counters (Olympic Model 750-N Trawl Cable Meter) will be

installed and used to verify the readings of the primary wire counter. The primary wire counter

will operate in real time and daily calibration checks between wires and between in-line and

block wire counters will be undertaken. The mechanical in-line wire meters will undergo

maintenance and calibration by the manufacturer between each survey to ensure accuracy of the

instruments.

The port and starboard trawl warp lengths will be compared on a daily basis. If the average

difference between trawl warps exceeds 4% of the groundgear distance measured from door to

door, trawling operations will cease and the wire counters examined to determine whether

discrepancies are due to mechanical or electronic failure. Should it be determined that wire

counters are functioning properly and warp lengths continue to demonstrate a discrepancy,

trawling operations will cease until the problem is resolved. In addition to the monitoring of

warp length, the net configuration and trawl mouth geometry/symmetry will be monitored with a

headrope mounted net sonar.

Protocol 2: Use of Auto-trawl Systems

An auto-trawl system is not used on the Antarctic Bottom Trawl Survey.

NOAA Fisheries Trawl Survey Protocols
107

Protocol 3: Survey Operations Procedures

The AMLR finfish bottom trawl survey is conducted in remote regions of the Southern Ocean

where sea state and weather can be severe, where bathymetric data has only been collected

sporadically, and bottom conditions are extremely variable and largely unknown. In addition,

icebergs, growlers, and sea ice can present considerable challenges while conducting the survey. 

The survey design and sampling strategy is based on random depth stratified survey design, with

stations positioned to account for wide geographic contrast across all accessible shelf areas. 

However, initial coordinates for fishing stations within a depth strata determined prior to the

survey must be often be revised depending on sea, wind, bottom, and ice conditions. All final

decisions regarding sampling operations during the survey are made by the chief scientist in

consultation with the fishing master and ship captain. The following factors are significant in

determining that tows are consistent within and between surveys. 

1. Determination of Seabed Suitability for Bottom Trawling 

The chief scientist will provide the officers and crew with a list of proposed starting and ending

coordinates for a station. Due to sea state and other factors, there may need to be adjustments in

these coordinates. Prior to the haul, an initial acoustic reconnaissance transect will be taken. 

The echogram shall be examined by the chief scientist and the trawl master to determine if the

seafloor is within the targeted depth strata, and that there are no seafloor features which subject

the trawl to a high risk of damage (e.g., pinnacles, steep ledges, large rock formations). After

agreement from the chief scientist and trawl master that bottom conditions are suitable for

trawling, the station will be taken. 

2. Setting the Trawl

The procedure the vessel follows while setting, towing, and retrieving the trawl are highly

dependent on weather conditions. In calms seas, the vessel should follow as close as possible

the acoustic reconnaissance line. When wind is less favorable, the trawl should be set into wind,

then the vessel turned while the trawl is being deployed to follow the acoustic reconnaissance

course. Trawling operations will be suspended if the weather and seas expose substantial risk to

the gear, fishing crew, or scientific party. The decision to suspend operations until weather

calms is made by the chief scientist in consultation with the trawl master and ship’s captain. 

Scope ratio data will be collected and used during future surveys to ensure that the same scope

ration is maintained over time. Should a new net be required during the course of the survey, the

gear will first be deployed and washed out pelagically. The net will then be deployed on the

bottom for 30 minutes at least one time prior to a valid haul.

3. Speed of Vessel During Gear Deployment and Trawling Operations

The vessel speed while setting the net should be between 2.7 and 2.8 knots. While bottom

trawling, vessel speed should slow to 2.3-2.4 knots. Upon net retrieval, the vessel should slow

to 2.0-2.1 knots. All measurements are speed over ground measured with GPS.

Southwest Fisheries Science Center
108

4. Timing and Duration of Tow 

All hauls are conducted during daylight hours, between nautical sunrise and nautical sunset. The

target time for a successful tow is 30 minutes. Any haul less than 20 minutes is considered

invalid, and discarded. Trawling starts as soon as the footrope is determined by the trawl master

and chief scientist to make contact with the bottom. An Ocean Systems Netsweep 325 Trawl

Sonar (325 Khz. Transducer) mounted to the headrope is used to monitor the mouth of the trawl

as it is deployed, as well as when it makes contact with the bottom. The net sonar is also used to

measure the trawl mouth dimensions in real time as it is deployed and while sampling. Once

contact with the bottom is made, position, time, ship speed, bearing, headrope depth, bottom

depth, and trawl mouth width (i.e., the widest point below the headrope-mounted net sonar

transducer) and height (i.e., vertical distance between the headrope transducer and the seabed)

are recorded. Recordings were made every 5 minutes thereafter, for a total of seven

observations for each haul. The distance of seabed sampled is determined by the latitude

longitude coordinates taken with GPS from the start to the end of bottom trawling. 

5. Determination of Successful Haul

While the trawl is being retrieved and spooled onto the net reel, a visual inspection of the netting

and gear is conducted by the trawl master to determine any damage was sustained during the

haul (see Protocol 4, section on Quality Assurance Procedures for further details). A visual

inspection of the ‘shine’ pattern on the trawl doors is also performed by the trawl master as an

added assessment of proper gear deployment. If the above conditions regarding duration and

deployment are met, and the net has not sustained a tear >15 cm in any dimension, the chief

scientist will consult with the trawl master to determine if the haul is successful. If the haul was

deemed problematic for any of the above reasons, the station will be dropped, repairs to the trawl

will be made if necessary, and an alternate station near the coordinates of the discarded station

and within the same depth strata will be taken. 

6. Supplementary Data Collected at Each Station

Supplementary data collected for each haul includes ship course, air temperature, wind direction

and speed, weather, cloud conditions, sea state, light and ice conditions. In addition, a CTD cast

is taken at each strata/geographic shelf region during the course of the survey. The Station and

Tow information sheet (Bridge Log) details information collected during each haul. This

information is also entered into the AMLR bottom trawl survey database.

NOAA Fisheries Trawl Survey Protocols
109

Station and Tow Information (Bridge Log)

CATCH RECORD PAGE NO.

VESSEL NAME: CRUISE:

DATE TIME ZONE UTC OTHER

STATION NO. HAUL NO.

CCAMLR AREA/SUBAREA STRATUM

START NET ON BOTTOM LATITUDE °

LONGITUDE °

END NET OFF BOTTOM LATITUDE °

LONGITUDE °

BOTTOM DEPTH FROM M

TO M

FISHING DEPTH START M END M

MEAN FISHING DEPTH M

OPENING: HORIZONTAL M VERTICAL M

TIME START NET ON BOTTOM H

END NET OFF BOTTOM H

DURATION OF HAUL MIN

COURSE °

TRAWLING SPEED KN TRAWLING DISTANCE NM

TEMP. FISHING DEPTH FROM °C TO °C

TEMP. BOTTOM °C TEMP. SURFACE °C

SALINITY FISHING DEPTH FROM PSU TO PSU

SALINITY BOTTOM PSU SALINITY SURFACE PSU 

AIR TEMP. °C

WIND DIRECTION ° WIND SPEED KN

WAVE HEIGHT M

ICE CONDITIONS *)

WEATHER *) LIGHT *)

Southwest Fisheries Science Center
110

Codes for Ice Conditions, Weather and Light

Ice Conditions: Weather: Light:

0 : no ice 0 : clear sky, no clouds 1 : daylight

1 : ice present, but indeterminate 1 : partly clouded 2 : dawn/dusk

2 : < 10 icebergs 2 : overcast 3 : dark

3 : > 10 icebergs 3 : snowstorm

4 : < 6/10 sea-ice cover 1 nm from ship 4 : fog or dense mist

5 : > 6/10 sea-ice cover 1nm from ship 5 : drizzle

6 : < 6/10 sea-ice close to ship 6 : rain

7 : > 6/10 sea-ice close to ship 7 : snow, sleet

8 : heavy pack-ice 8 : rain squalls

9 : no observation 9 : no observation

Additional Comments:

Net Mensuration

Time Net Height Net Width Tow Speed Headrope Comment

:

:

:

:

:

:

:

Average

NOAA Fisheries Trawl Survey Protocols
111

Protocol 4: Trawl Construction and Repair

Specifications

The AMLR bottom trawl survey uses a NET Systems Hard Bottom Snapper Trawl rigged with

tiregear ground tackle with a headrope length of 92.0 ft and a footrope length of 127.6 ft. The

technical designs of the trawl are provided here in both engineering schematics and detailed part

descriptions. 

Drawings 

The following are engineering drawings (obtained by the manufacturer NET Systems,

Bainbridge Is., WA) of the gear used during all AMLR bottom trawl surveys.

Drawing Sheet

Rigging Profile A

Net Plan B

Ground Gear C

Intermediate D

Codend E

Rigging Hardware Detail F

Door Design G

Southwest Fisheries Science Center
112

NOAA Fisheries Trawl Survey Protocols
113

Southwest Fisheries Science Center
114

NOAA Fisheries Trawl Survey Protocols
115

Southwest Fisheries Science Center
116

NOAA Fisheries Trawl Survey Protocols
117

Southwest Fisheries Science Center
118

NOAA Fisheries Trawl Survey Protocols
119

Trawl Specifications and Parts List

The following list provides the details for the materials, design, and components required for the

trawl that the AMLR Program uses during bottom trawl surveys, and serves as a checklist for

verifying that newly constructed or repaired trawls are within operational tolerances.

Components list

The AMLR bottom trawl survey uses factory made NET System Hard Bottom Snapper Trawls –

(# 92/122/5”). Refer to drawings A through F. All web in the trawl should be depth stretched

and heat set in the manufacturing process. Mesh sizes listed in the plan are given in “stretched

measure”, a standard method of measuring mesh size that includes the length of one knot.

Net Mesh Component Mesh Size Twine Size & Type

Top Wing Heavy 5” D6.0 mm polyethylene knotted - orange

Top Wing 5” 5.0 mm polyethylene knotted - orange

Top Overhang 5” 5.0 mm polyethylene knotted - orange

Top Belly 5” 5.0 mm polyethylene knotted - orange

Bottom Wing Heavy 5” D6.0 mm polyethylene knotted - orange

Bottom Wing 5” 5.0 mm polyethylene knotted - orange

Bottom Belly 5” 5.0 mm polyethylene knotted - orange

Bottom Belly Boson 5” D6.0 mm polyethylene knotted - orange

Tear Seam 5” #333 Nylon twine

Side Wing 5” 5.0 mm polyethylene knotted - orange

Side Overhang 5” 5.0 mm polyethylene knotted - orange

Side Belly 5” 5.0 mm polyethylene knotted - orange

Bottom Heavy Edge 5” D6.0 mm polyethylene knotted - orange

Tapered Intermediate 5” D4.0 mm polyethylene knotted - orange

Straight Intermediate 4” D4.0 mm polyethylene knotted - orange

Codend 4” D4.0 mm polyethylene knotted - orange

Codend Liner 1.5” #21 Nylon three strand nylon web, green

Other Net Components Specifications

Headrope 5/8” 6×19 PC (92’)

Breast Lines 5/8” 6×19 PC (2 × 9’, 2 × 30’, 4 × 20.5’)

Bolsh Line 1 1⁄4” Ultraline, 3 pieces

Fishing Line 1⁄2” Long Link B-7 Chain

Riblines 1” RP-12 Ultra Blue

Floats 22 Ube Eared, 12" side lug trawl floats, depth rated to

minimum of 450 fm; 23 lbs buoyancy each.

Floats Four 8” side lug trawl floats (headrope bosom) 5.5 lbs

buoyancy each.

Southwest Fisheries Science Center
120

Trawl Rigging Components Number Specifications 

Bare Sweeps 2 3⁄4” × 90’ 8×19 Wire Rope

Mud Sweeps 2 3⁄4” × 90’ IWRC w/3’ Rubber Disks

Lower Bridles 4 3⁄4” × 180’ IWRC w/3’ Rubber Disks

Center Bridles 4 5/8” × 180’ 8×19 Wire Rope

Upper Bridles 4 5/8” × 180’ 8×19 Wire Rope

Idlers 2 3⁄4” × 60’ 8×19 Wire Rope

Center Setbacks 2 1⁄2” × 9” Long Link Chain

Connectors 36 3⁄4” Hammerlocks

Connectors 8 5/8” Hammerlocks

Rigging Plates 4 3⁄4” 4-Hole Delta Plate

Links 4 1” G-hooks

Links 4 1” Flat Link

Footrope & Tiregear – NET Systems # XFTR1739804 - Refer to drawing C. 

Rockhopper Line - Fiber core wire rope 3/4" 6×19 galvanized 

Tiregear Bosom 24”

18” & 14” Cone bobbins for wings and extensions 

1⁄2” decklashing chain 

Reg. Toggles, 1⁄2”×4” dropper chains 

14”& 5” rubber disks 

5/8” butterfly plates 

Codend – NET Systems # XCOD1739804 - Refer to drawing E

Characteristics: 112ma × 50md 

4”-D5.0 w/ 11⁄2” #21 Liner w/ 11⁄4” Ultraline Lift Strap 

1” RP12 Ultra Blue Riblines 3⁄4”×15’ Steeline Container Lines 

3”×2” Galv. Pucker rings w/ 5/8” Puckerline & 3⁄4” codend release attached 

Six 8” CH floats attached to each top ribline 6mm Double Bar Mesh 

Polyethylene knotted web chaffing strip 

Bottom - 5" 5mm Double Bar Mesh, polyethylene knotted w/ 100# of hula attached to bottom

and 1⁄2 way up sides of chafing.

Trawl Doors – NET Systems Vented-V 5.5 m2 Refer to drawing G.

Air wgt - 2250 lbs (1023- kg), 2,025 lbs (920 kg) water weight. 

Quality Assurance Procedures

At the start of every survey, the vessel will be provided with an inventory of supplies that may

be needed to make any repairs to the trawl gear during the survey. The fishing crew will ensure

that the trawl is in excellent condition prior to the start of the cruise by measuring all

components listed on the trawl diagram to determine if they are within operational tolerances. 

NOAA Fisheries Trawl Survey Protocols
121

Materials supplied to the fishing crew includes net plans, web, hardware, floats, breastlines,

twine, pre-cut bottom panels, floats etc. At the beginning of each survey, the cruise leader will

verify that all spare nets and parts are on the vessel. At least one spare net will be stored on

deck. This is essential if the crew potentially has a problem getting to stored replacement nets in

less than ideal conditions.

When the trawling gear is spooled onto the net reel prior to the survey, there will be a detailed

inspection by the trawl master and fishing crew of every component of the trawl to ensure that

the gear is within operational tolerance. Net, doors, and bridles should be examined routinely

during every haul back, checking for any damage and noting/performing any repairs needed.

When large rocks are dumped from the codend, liners should be thoroughly checked for damage

and any repairs will be noted/performed. The cruise leader will decide in consultation with the

trawl master if the net requires changing or repairing given other time constraints imposed by

survey objectives. Trawls will be individually identified with an affixed tag that will be entered

into a history log describing damage sustained, repairs done, and number of hauls it was used.

Damage to netting (holes & breaches etc.) will be repaired prior to deployment of the next haul. 

Repairs that should not be attempted aboard vessels include broken headropes, footropes,

riblines or rehanging long sections of riblines (repairs that involve more that 25 benzels, approx.

40' ). Given the limited deck space, these repairs are difficult to do correctly to ensure the

finished product meets sufficient standards. No lacing of holes or tears should be allowed in the

body, wings or codend of the trawl. Special attention will be given to repairs involving the

inside of the bottom wings (where the bar cut and chaffing strips are sewn to the body). 

The cruise leader will emphasize the requirement with the trawl master and fishing crew that the

gear must be maintained at the highest standards. If the fishing crew is unable to repair a net to

sufficient standards, the net should be retired and a new one put on the reel. The fishing crew is

encouraged to replace torn or abraded areas on the net with patches or new panels, rather than

hand sewing new meshes. Straight tears, like those often seen in bottom bellies can be sewn as

long as there is no need to build meshes to close the hole.

Southwest Fisheries Science Center
122

Trawl Repair Checklist

The trawl master and fishing crew in collaboration with the cruise leader will address all aspects

of the trawl checklist prior to the cruise, and as repairs are required to the trawl during the course

of the survey.

COMPONENT SPECIFICATION PORT STARBOARD

Upper Bridle 5/8” × 180’

Upper Bridle Setback 1/2 “ LL Chain × 18”

Middle Bridle 5/8” × 180’

Middle Bridle Setback 1/2 “ LL Chain × 9”

Lower Bridle 3⁄4” × 180’

Flying Wing* 3⁄4” wire × 19”6” w/ disks

Lazyline (Transfer) 3⁄4” wire × 60”

Door Leg Extension 3⁄4” wire × 40”

Trawl Doors 6’8” × 10 Vented V-Door

 1 1/8” trawl shackle

Upper Lower Upper Lower

Doorlegs 5/8” LL Chain × 10’

Condition Fully Repaired?

Top Wing Web No tears, holes, breaches

Top Overhang Web “

Top Belly Web “

Bottom Wing Web “

Bottom Belly Web “

Side Wing Web “

Side Overhang Web “

Side Belly Web “

Tapered Intermediate “

Straight Intermediate “

Codend “

Codend Liner “

Splitting Strap “

* Measure from bearing point on wire to fishing line attachment point on delta plate

NOAA Fisheries Trawl Survey Protocols
123

Appendix 4

Northeast Fisheries Science Center

Standard Operating Protocols for

Spring, Autumn and Other Bottom Trawl Surveys

Northeast Fisheries Science Center

125

Abbreviations 

The abbreviations used in Appendix 4 (NEFSC Protocols) and associated attachments are 

defined below: 

A&G Age and Growth – an investigation in the Fishery Biology Branch of the Northeast Fisheries Science 

Center responsible for ageing material collected during bottom trawl surveys 

CO Commanding Officer 

CS Chief Scientist – designated person in charge of supervising all onboard scientific operations 

CTD Conductivity-Temperature-Depth – an instrument used to measure conductivity, temperature and depth 

DGPS Differential Global Positioning System 

ESB Ecosystem Surveys Branch 

ET Electronics Technician 

ETA Estimated Time of Arrival 

fm fathom 

FRV Fishery Research Vessel 

FSCS Fishery Scientific Computing System – a system of hardware, software and peripheral equipment 

utilized to measure and log data from sampled marine organisms 

GPS Global Positioning System 

ITI Integrated Trawl Instrumentation 

m Meter(s) 

NEFSC Northeast Fisheries Science Center 

nmi Nautical Mile 

NMAO NOAA Marina and Aviation Operations (a division of NOAA) 

OOD Officer of the Deck 

OPS Operations 

OT Overtime 

QA Quality Assurance 

RPM Revolutions per Minute 

SCS Scientific Computer System – a system of hardware, software and peripheral sensors utilized to 

measure and log ship and environmental characteristics during operations 

SHG Station-Haul-Gear – a standardized system for evaluating tow quality through specific coding of the 

station type, haul quality, and gear condition 

SOP Standard Operations Procedures 

WC Watch Chief – designated person in charge of supervising operations during a designated watch 

Northeast Fisheries Science Center

127

 

Introduction 

The Northeast Fisheries Science Center (NEFSC) currently conducts four bottom trawl surveys: 

an autumn bottom trawl survey conducted annually since 1963, a spring bottom trawl survey 

conducted annually since 1968, a winter bottom trawl survey conducted annually since 1991, and 

a Northern Shrimp survey (outlined under a separate set of protocols). The spring and autumn 

bottom trawl surveys provide synoptic coverage of continental shelf waters from Cape Hatteras, 

North Carolina, to the Scotian shelf in Canadian waters. The winter bottom trawl survey 

provides opportunistic coverage of the continental shelf from Cape Hatteras to along the 

southern flank of Georges Bank. Surveys are generally conducted aboard the FRV 

ALBATROSS IV and DELAWARE II. 

The goal of each of these surveys is to provide long-term relative indices of abundance and 

biomass for finfish and key marine invertebrate species and to document their distribution. 

Core objectives of these surveys include: 

1. Determine the distribution, relative abundance and biodiversity of fish and 

invertebrate species 

2. Collect biological samples for studies of age and growth relationships, fecundity, 

maturity, and feeding ecology 

3. Collect hydrographic and meteorological data 

4. Collect data and samples for cooperative researchers and programs 

5. Collect continuous hydroacoustic data along the cruise trackline 

6. Perform evaluations of survey gear performance. 

The spring and autumn surveys are conducted using a Yankee 36 Roller trawl while the 

winter survey is conducted using a NEFSC winter flat trawl. There are slight rigging 

differences when these trawls are utilized on the two primary research vessels and these 

differences are described within the Appendix. Other than these gear related differences, 

survey protocols included in this Appendix are generally applicable across all three bottom 

trawl surveys currently being conducted by the NEFSC. 

Protocol 1: Length Measurement of Trawl Warps 

1.1 Wire 

Responsibility for procurement, installation, and maintenance of trawl warps currently 

resides with the NOAA Marine and Aviation Operations (NMAO), the division of 

NOAA currently responsible for the operation of fishery research vessels utilized to 

conduct NEFSC trawl surveys. The ALBATROSS IV currently utilizes 7/8” 6×19 Seale 

die-form strand, right hand lay, fiber core wire rope for trawling operations. The 

DELAWARE II currently utilizes 1” right hand lay, fiber core wire rope for trawling 

operations. The diameter and weight per unit length of wire rope utilized in trawling 

operations has an effect on catchability of marine organisms sampled by the survey. 

Northeast Fisheries Science Center
128

Differences in wire rope diameter and weight per unit length between the two FRVs 

currently utilized to conduct bottom trawl surveys are accounted for in catchability 

coefficients developed through previous experimental work. 

The lay direction of the wire rope is not known to have a direct effect on fishing gear 

performance, but use of the same lay wire in the both the port and starboard 

winches/blocks may result in differential stretching of wire rope over time. The NEFSC 

and NMAO are considering use of right hand laid wire in the starboard winch/block and 

left hand lay wire in the port winch/block in the future. This change can be expected to 

reduce the incidence of differential stretch between the starboard and port wires over 

time, but is not expected to have any effect on gear performance or catchability when 

wires are maintained within calibration standards. 

Wire calibration methodology (wire marks and redundant shipboard wire measurement 

systems) shall be checked and recalibrated upon initial installation, at least biannually, 

and whenever shipboard wire measurement systems indicate that wire measurements fall 

outside of established standards. The established standard for NEFSC bottom trawl 

surveys is that starboard and port wire calibration systems should deviate by no more 

than either 4% of the door to door distance measured along the bridles and head rope of 

the net or a maximum deviation of 2.0 m. Calibration should be conducted more 

frequently if significant differences in warp length are detected, as might be expected 

following the initial installation of wire or onboard metering systems. Frequency of warp 

measurements may be reduced when an understanding of the variability in measurements 

is achieved and NEFSC and NMAO personnel determine that differences in 

measurements are primarily due to measurement error, temperature or other factors. 

When marks are employed as a measurement or calibration tool on wire rope utilized to 

deploy bottom trawl gear, it is critical that marks on the starboard and port wires are 

paired and even with each other to ensure that equal lengths of wire are deployed at any 

depth or warp deployment. The following procedures should be employed during 

measurement or remarking operations: 

• Wires may be measured from existing eye splices (as wire is unwound from the 

vessel’s winches) or from a fixed existing mark in each wire (i.e., 1200-m mark, as 

wire is wound back onto the vessel’s winches). 

• If wire is measured or remarked as wire is wound back onto the vessel’s winches, 

remaining wire at the terminal end should be cut at even distance intervals on both 

wires. 

• During marking, measurement, or remarking operations, the starboard and port wires 

should be laid next to each other and measured, marked, or remarked simultaneously. 

Slight and equal tension on the wires is necessary to ensure that wires are straight 

when measured or compared. 

• Measurement of wire should employ a measurement device not prone to 

measurement error, such as pre-marked length of thin diameter wire. 

• During measurement or remarking operations, if differences between existing and 

true marks are detected, wire shall be remarked at correct distance intervals 

NOAA Fisheries Trawl Survey Protocols
129

• During measurement or remarking operations, a representative of the NEFSC or a 

designee shall record differences between existing marks and newly measured 

distance intervals. 

The NEFSC and NMAO continue to investigate the properties of wire rope utilized on 

NEFSC bottom trawl surveys and methodology available to calibrate distance of wire 

rope deployed during trawling operations. As new information is obtained, methods used 

to calibrate wire rope will be updated in future revisions of these protocols. 

Protocol 2: Use of Autotrawl Systems 

 Autotrawl systems are not currently used during the NEFSC bottom trawl surveys. 

Northeast Fisheries Science Center
130

Protocol 3: Survey Operations 

3.1 Station Selection 

The NEFSC spring, autumn and winter bottom trawl surveys employ a stratified, random 

sampling design that has remained constant through each survey time series. Survey 

strata are based on fixed depth ranges and regions of bathymetry along the continental 

shelf of the survey area (Attachment G). Strata coverage and the target number of 

stations to be sampled within each stratum are determined prior to conducting each 

survey. The target number of stations currently utilized for the spring, autumn, and 

winter surveys is shown in Attachment F. 

 

3.1.1 Subdivision of strata -- All strata are subdivided into blocks 5 minutes of 

latitude by 10 minutes of longitude. These large blocks are further subdivided 

into 10 small blocks measuring 2.5 minutes of latitude by 2.0 minutes of 

longitude. The large blocks are defined as being the largest area that can be 

characterized by one tow. 

Exceptions occur with very long, narrow strata, and strata with irregular borders. 

In these cases, the strata are subdivided directly into 2.5 × 2.0 minute blocks. 

These smaller blocks are then grouped into larger blocks so that the numbers of 

small ones are evenly distributed throughout the large ones. At least two large 

blocks are formed within each stratum. Each large block is composed of, as 

nearly as possible, 10 small ones. No large blocks are formed if there are an 

insufficient number of small blocks. 

3.1.2 Random station selection and plotting -- Stations selected within each 

stratum are determined using a Perl program called sta_selector. This program 

was written to generate a random selection of stations within each stratum. Each 

small block within a stratum is numbered sequentially. The number of small 

blocks contained within the stratum in which the numbers are being selected 

determines the range of random numbers. A random number selected then 

corresponds with a numbered small block. The center point of the selected small 

block will be the starting location of the tow. The numbering of tows is directly 

related to the order of random number selection (tow no. 1 is selected first and so 

on). A stratum number and the tow number within that stratum then identify 

stations. Once a small block is selected, all members of the corresponding large 

block are excluded from the selection population until there is at least one station 

selected in every large block within the stratum. 

The sta_selector program creates several output files: a station data file 

(station_location.xls), nav.txt file, and a station.dat file. The Chief Scientist uses 

the station data file in Excel, in conjunction with charts, to create the cruise track 

by visually determining the most efficient or shortest distance between two 

stations. The nav.txt file is imported into a navigation software package 

(Navtrek), which is used by the bridge officers to set up the routes once the Chief 

Scientist has provided the sequential list of stations to occupy. An Arc-Info 

NOAA Fisheries Trawl Survey Protocols
131

program employs the station.dat file to create 8" × 11" charts and the large 

bathymetric charts that have the station locations plotted. 

Arc-info programs are employed to create strata lines and stations on digital 

rasterized copies of NOAA nautical charts (Attachment G). Rasterized renditions 

of the NOAA charts currently used are “Bay of Fundy to Cape Cod" (No. 13260); 

"Georges Bank and Nantucket Shoals" (No. 13200); "Approaches to New York, 

Nantucket Shoals to Five Fathom Bank" (No. 12300); "Cape May to Cape 

Hatteras" (No. 12200); and, "Cape Hatteras to Charleston" (No. 11520). The 

bridge officers continue to navigate by using the official NOAA charts. 

Geographic positions, loran lines-of-position, and charts are saved internally at 

the NEFSC the completion of a cruise and made available to stakeholders. 

3.2 Pre-Cruise Procedures 

3.2.1 FSCS setup -- Currently responsibility for the maintenance of the Fisheries 

Scientific Computing System hardware and servers resides with the NOAA 

Marine and Aviation Operations (NMAO). Responsibility for setup and 

maintenance of peripheral equipment to the system (electronic balances, 

electronic measuring boards, bar code readers, calipers and printers is an 

Ecosystem Surveys Branch function. Details concerning FSCS hardware and 

software can be found in the NEFSC FSCS manual, maintained as a separate 

document. 

3.2.2 Survey supplies -- One week before a cruise is scheduled to depart staff of 

the Ecosystem Surveys Branch (ESB) are responsible for gathering and packing 

supplies using the supply list specific to the type of cruise (groundfish, scallop, 

shrimp, etc). These lists are located in shared_files\pre_cruise_docs\supply_lists 

and should be updated if additional supplies are needed for a cruise. ESB staff can 

reference the inventorymaster.xls and gear shed inventory.ppt documents under 

the same directory to attain a list of locations for supplies. ESB staff will arrange 

for pick-up or delivery of larger gear items stored at the warehouse and will load 

supplies onto the vessel one full business day before the scheduled departure. 

ESB staff will inventory supplies on board and restock as necessary between legs. 

The Chief Scientist should inform the ESB staff of any supplies needed for the 

next leg. 

Mensuration system: Prior to sailing 

• Charge sensors (the sensors should be recharged every week or when they 

cease to provide readings) 

• Attach ropes to sensors for attachment to the net 

• Test sensors to make sure they are operational 

• Confirm with Electronics Technician (ET) that the event logger is working on 

the Scientific Computing System (SCS). 

• Request that the ET setup the ITI system to record the sensors that you request 

be logged. This request needs to be submitted prior to sailing. 

Northeast Fisheries Science Center
132

Directions for Data Logging: 

The following three steps must be followed to monitor and automatically log 

Simrad ITI trawl mensuration data aboard the ALBATROSS IV and 

DELAWARE II. 

On the FRV ALBATROSS IV and DELAWARE II, the Simrad ITI trawl 

mensuration system must be used to monitor trawl performance parameters. The 

data must be automatically logged with the SCS (Scientific Computer System) 

through use of the Event Logger. The event logger can be built with the help of 

the Electronics Technician or an existing event logger may already be available 

for use. On the ALBATROSS IV the event: iti.tpl should be used to log data on a 

per station basis. This event must be run from the "Event Logger OLD" 

application and is usually initiated just before the trawl doors are deployed: 

• On any SCS terminal select Acquisition from the main menu 

• Select Event Logger OLD 

• Select Start Event Manager (OLD) 

• Highlight Iti. tpl from the list of events 

• Select Initialize Event OR double click on Iti. tpl 

• Click on Start Event 

• Click on Station and add the correct station number 

• Click on Notes and add if any 

• Exit the event (usually when the doors reach the surface) by clicking the Stop 

button 

Outputting Data from Simrad ITI:

Four steps must be followed in order to send valid data from the Simrad ITI unit 

to the SCS system. From the main menu of the Simrad ITI unit located in the 

computer room of both ships: 

• Select ACTIVE SENSORS 

• Select each individual unit placed on the net, e.g. SPREAD2 

• Select 1:1 

• Make sure that all other units are set to OFF1

• Return to the main menu 

• Select RATE 

• Select MAX 

• Return to the main menu 

• Select SERIAL OUT 

• Select DUMP 

• Select DUMP again 

• Select CONTINUOUS 

• Return to the first DUMP menu 

 1

 If a unit which is not deployed on the net is turned on, the ITI will keep searching for the unit, preventing other 

measurements from being taken 

NOAA Fisheries Trawl Survey Protocols
133

• Select a minimum of all codes representing the sensors placed on the net2, e.g. 

IITDS 

• Select ON 

• Repeat this process until all desired data codes are turned on 

• Return to the main menu 

• Select SIMULATE: 

• Select OFF 

• Return to the main menu 

• Exit the main menu 

A data string starting with the characters $PSIM followed by 16 comma delimited 

fields will now be sent to the SCS for logging. Under the settings listed above, 

data will be logged at the maximum rate of once every 30 seconds (that is, one 

complete data string with full sensor data). Depending on which codes were 

turned on in the SERIAL OUT > DUMP menu, either all or only some of the 

fields will contain data. If a code is not turned on, then its comma-delimited field 

will be blank. It is important to note when checking the files that the actual trawl 

performance data follows the $PSIM character. SCS event logger programs may 

add data to the start of each line of records, giving the appearance that data is 

being logged properly - you must check to see that there is data immediately 

following the $PSIM character. The three data files may be examined on the SCS 

server of the vessel under the following directory3

: 

(SCS server name) \DataLog\EventData\ (ITI event name) 

Additionally, the raw Simrad ITI output may be viewed as files saved under (SCS 

server name) \DataLog\ITI-$PSIM timestamp. RAW4

Sensor Deployment and Monitoring: 

See survey ITI documentation for sensor placement on net. Fine-tuning of sensor 

placement may be necessary, and can be accomplished by trial and error (see 

below). 

Important caveats in sensor attachment: 

• Attachment must be made in a manner to prevent sensors from flipping 

• Attachment points made to webbing should be checked to ensure that some 

slack exists - a tightened net will otherwise pull against the sensor 

attachments, deform the net or tear the webbing 

• Attachments should never be made to webbing alone 

• Attachments should be connected to the most solid net piece possible (i.e. a 

section of combination wire headrope is preferable to a rope float line) 

 2

 You must have access to the SIMRAD ITI manual in order to determine which codes represent the sensors you 

have on the net. If you do not have this manual, then select all of the codes 

3

 The exact name of the server can be obtained from the ET 4

 The nomenclature for the filenames may change from vessel to vessel, ask the ET what the raw ITI sensor 

stream is called on that vessel - the directory structure will remain the same 

Northeast Fisheries Science Center
134

• Attachments should be inspected after each tow - often forces on the net 

loosen shackles or undo clips 

• Refer to the Simrad ITI manual for correct left-right orientation of spread 

sensors 

To monitor the sensors during a tow: 

• Select MODE in the main Simrad ITI menu 

• Select TEST 

• Remove the menu from the screen by using left pushes on the joystick that 

controls menu movement 

• Observe the COMMENT and DATA fields 

Common Display Messages: 

START – SHOT: means the transducer on the vessel is initiating a search for the 

sensor on the net 

SEARCHING: means the transducer is searching for a signal from the net 

sensor5

TIMEOUT _#: means problems with signal reception, and may suggest the 

need for a change in sensor placement 

• The data field will display degrees in three planes when the transducer is still 

looking for a signal from the sensors 

• Sensor data will be displayed when a good signal is being received from the 

sensor 

• The headrope unit will display two numbers - the first is supposed to be 

distance to footrope, and second distance to bottom - for our trawls the first is 

distance to bottom 

• The wingspread (and doorspread) sensors will display a value of 320 m when 

the receiver and transponder unit on the starboard and port wings can not 

properly send a signal to each other 

• The SR column stands for slant range and represents the diagonal distance of 

the sensor from the vessel transducer - this value should reflect the 

approximate wire out, but is often way off when bottom trawling 

• See the Simrad ITI manual for more information on error messages 

• The STATUS mode under MODE in the main menu is also helpful and gives 

additional info on sensor performance (but not on a per query basis) 

• If routine sensor values are not obtained, or if obviously incorrect values are 

obtained, the sensor placement will need to be adjusted. This is accomplished 

by trial and error. It is important to anticipate how the sensors will be riding 

on the net, and to try to ensure an unobstructed path from the transmitting 

ends of the sensor (or "transducer window") to the ship. See the ITI manual 

for more information. 

 5

 As indicated earlier, a sensor that is turned on but not present, or turned on but no signal can be received from, 

will cause the ITI to search repeatedly and miss receiving data from other sensors 

NOAA Fisheries Trawl Survey Protocols
135

Inclinometer: 

• Inclinometers are used periodically to evaluate bottom contact of the trawl 

gear. 

Prior to deployment: 

• The inclinometer must be initialized. To initialize, the optic base station 

should be attached to the cable that is attached to the COM port of the 

computer. Open the Boxcar program and hold the base station with the tidbit 

coupler attached to the inclinometer with the pin inserted in the hole at the 

window. In Boxcar, select “logger” and “launch”. The software will attempt to 

communicate with the inclinometer. Once open, you can modify the 

description and tow interval-recording time. 

Troubleshooting connection problems: 

• Check the cable from the computer to the base station and make sure all are 

properly connected. 

• Make sure you are positioning the tidbit properly on the inclinometer and that 

the magnet is touching the metal. 

• Make sure that the communications port is correct. Usually COM 1 is used but 

sometimes COM 2 needs to be selected. 

Downloading data to shuttle: 

• To read the inclinometer file you need to utilize the optic shuttle and tidbit 

coupler with magnet. 

• Position the optic shuttle over the circular window of the inclinometer with 

the pin from the tidbit coupler inserted in the hole. 

• Press the button on the optic shuttle to download data. The middle light on the 

shuttle should start blinking (XFER). 

• Continue to hold the shuttle until the green “OK” light flashes. This can take 

over a couple of minutes. 

• If the “fail” light flashes, you were not holding the shuttle properly or the 

magnet moved away from the housing. Repeat previous steps. 

Downloading data to the computer: 

• Bring the shuttle inside to the computer to download. 

• Marry the shuttle to the base station using the “coupler” device. 

• Open Boxcar Pro and select “logger” from the menu bar. 

• Select “optic shuttle readout”. 

• Press the button on the optic shuttle and the file should download to the 

program. 

• The software will choose the filename and location. Change the filename to 

correspond to the file naming convention that you are using (usually the 

station number) and select the file folder that you would like it saved under. It 

is suggested that the file is saved in alfscsserver (or DELAWARE equivalent) 

Northeast Fisheries Science Center
136

\cruisecode\fscs\loggeddata\sampling location1\station_XXX before running 

data manager because the inclinometer files will be grouped with the rest of 

the data for that station. To open the file, select “file” and “open” and go to 

the folder that you saved. This folder usually will open automatically. Click 

on the file and view. You can select part of the graph with the mouse to zoom 

to that section. 

3.3 Delineation of Responsibilities

The OOD (Officer on Deck) is the Captain’s designated representative on the 

bridge whose principal responsibility is the safe navigation of the vessel. This 

implicitly means that the ship, its people, its machinery, and other vessels shall 

not be put in peril. Safety always takes precedence over the ship’s mission. 

The CO/OPS officer/OOD shall: 

• Conduct mission operations that are consistent with the safe navigation of the 

vessel. 

• Work closely with the Chief Scientist to determine the most efficient track 

line. 

The Watch Chief is the Chief Scientist’s designated representative whose 

principal responsibility is the completeness and quality of data and samples being 

collected. 

Only the Chief Scientist may: 

• Change planned track-lines 

• Change mission priorities (e.g., request change of course or speed to meet 

other objectives) 

• Cancel stations 

Only the Watch Chief or Chief Scientist may: 

• Direct the work of the scientific party 

• Relocate stations more than 1 mile 

The Chief Scientist and/or Watch Chief may not: 

• Direct or interfere with the work of the ship’s crew 

Both the CO and the Chief Scientist have the authority to stop operations due to 

inclement weather; the CO because of potential danger to the ship or its people, 

the Chief Scientist because of compromised data quality. Neither person will 

override a decision to cancel operations made by the other. 

NOAA Fisheries Trawl Survey Protocols
137

3.4 Chief Scientist Duties 

Pre Cruise Activities (One month before): 

• Work with Cruise Staff Coordinator regarding staffing experience 

• Identify Watch Chief (WC), Fisheries Scientific Computing System (FSCS), 

Bongo, Conductivity Temperature and Depth (CTD) staff and arrange for 

CTD training. 

Pre Cruise Activities (One week before):

• Contact cruise staff to see if there are any questions & determine arrival time 

• Verify that the Canadian Permits have been delivered to the ship 

• Distribute Sampling Booklet to Watch Chief for review/discussion 

• Send scientific roster to OPS officer and CO 

Pre Cruise Activities (Workday before sailing):

• Assign/post watches/rooms and distribute watch schedule to timekeepers and 

Branch Chief 

• Notify the ship’s Operations Officer of cruise staff arriving early and notify 

the Chief Steward of any special dietary needs 

• Attend post-cruise meeting from previous survey leg 

• Notify cruise staff of maturity /fish identification workshop and requirement 

to be on board 1 hr before departure 

• Final roster sent to Vessel Coordinator 

• Discuss any FSCS related problems troubleshooting with previous Chief 

Scientist/Watch Chief/FSCS Specialist 

• Make sure min/max Age and Growth (A&G) envelope numbers are on the 

vessel 

 Day of sailing: 

• Attend maturity /fish identification workshop 

• Meet with Captain and Branch Chief regarding location of first station 

• Organize pre-cruise Fisheries Scientific Computing System (FSCS) training 

• Discuss status/completion of special sample requests with previous Chief 

Scientist/Watch Chief 

• Show volunteers where to park their vehicles, how to attain a parking permit 

and ensure that all car keys are left in Port Captain=s office 

• Make sure the Navigation Officer has a digital / electronic copy of the station 

locations 

• Determine if all &/or additional supplies have been loaded 

• Make sure that all charts are on board & know status of station sequence xls 

file 

• Obtain Chief Scientist sea-pack binder from Ecosystem Surveys Branch 

(ESB) 

• Send volunteers to obtain foul weather gear in cutting room 

• Chief Scientist should attain a list of gear going aboard from the Gear 

Specialist. 

Northeast Fisheries Science Center
138

Prior to sailing:

• Send scientist muster to bridge officer 30 minutes before sailing 

Pre first tow activities (FSCS Related Tasks):

• Modify default values in SCS Event log metadata 

• Ensure that RealTime plots have been set up/standardized 

• Ensure that all computers (including bridge) are synchronized to network time 

server 

• Review parent sensor displays 

• Enter cruise init data for FSCS if first leg of the survey 

• Modify deployed equipment table 

• Modify species protocol table as needed 

• Modify Scientists.csv file 

• Ensure that all electronic devices are powered on and calibrated (e.g. scales & 

electronic fishboards) 

• Assist Watch Chief/FSCS manager to solve FSCS problems 

Pre first tow activities (Non-FSCS Related Tasks):

• Hold ship and scientific pre-cruise meeting with all staff (introductions and 

identification of the Watch Chiefs, announce ETA to first station, general 

cruise direction, area of operations, review special sample booklet) 

• Call scientist muster to bridge during fire & boat drill 

• Hold pre-first tow meeting with Watch Chiefs & emphasize sampling 

priorities (Age and Growth, Food Habits, NOAA Fisheries requests, outside 

requests) 

• Select station sequence for bridge officers & assign random depth ranges to 

the stations in the outermost strata (100-125, 126-150, 151-175, 176-200 fms) 

• Post station sequence on freezer wall, in CTD room, and give copy to Bridge 

• Arrange timing and station number of practice tow with Captain or OPS 

Officer 

• Provide the setting and hauling log to the Chief Boatswain (Attachment H) 

• Help to train scientific staff during practice sessions and general sampling 

operations 

• Work on deck in absence of Bongo/CTD person 

• Assist Watch Chief/FSCS manager to solve FSCS problems 

• Help with fish/maturity/food habits identification 

Daily activities during the cruise: 

• Communicate with Woods Hole via email and cc the Master / Commanding 

Officer 

• Update station sequence as needed 

• Record extra over time for FSCS person and Watch Chiefs (if applicable) 

• Document FSCS software/hardware problems in C:\FSCS\cruise_notes 

• Look at RealTime displays of key sensors 

NOAA Fisheries Trawl Survey Protocols
139

• Review FSCS data using forms/reports. Sql queries will generate a variety of 

reports that will allow the Chief Scientist to examine station and biological 

data for a collective group of stations. Patterns of missing or questionable 

data can be quickly identified and corrected using the QA forms. It is strongly 

encouraged that time is taken while at sea to generate and review these forms. 

See FSCS Operating Manual for sql commands and examples. 

What data should the Chief Scientist fix/leave alone?:

• Fix:

o SHGs/missing comments (e.g. add reason for SHG not equal to 111, 

gear # changes)

 Missing data (find and enter)

 Special samples that were not entered

• Leave alone:

o Species code changes (record info on log)

• Document:

o All subsample and mixes (record details on log)

o Any sampling problems

o FSCS software operations problems (describe error messages and what 

you did to correct the problem). Make comments in 

C:\FSCS\cruise_notes\ 

End of Cruise Leg: 

• Contact technicians in ESB branch regarding new office and gear supplies 

needed for the next leg 

• Discuss with Watch Chief which ship areas will be cleaned by which watch & 

how to power down FSCS hardware 

• Organize off loading/distribution of frozen (complete inventory form posted 

outside of lab freezer) and preserved samples/supplies 

• Remind staff/volunteers to return cleaned foul weather gear to the wet lab. 

• Consult with Watch Chiefs and fill out a Volunteer evaluation form 

(Attachment H) for each volunteer and contractor. 

Post Cruise: 

• Participate in post cruise meeting 

• Provide date/time return to timekeeper 

• Return all charts, reports, trawl logs, CTD logs, Chief Boatswain logs to the 

Ecosystem Surveys Branch 

• Complete cruise evaluation form and return to the Branch Chief of the 

Ecosystem Surveys Branch 

• Provide copies of tort claim info to Branch Chief of the Ecosystem Surveys 

Branch 

Northeast Fisheries Science Center
140

3.5 Watch Chief Responsibilities: 

Pre cruise activities (one week before): 

• Request sampling booklet from Chief Scientist and review 

Day of sailing:

• Attend Maturity /fish identification Workshop 

• Check with Chief Scientist regarding supplies to put on ship 

• Help to train new staff/volunteers with FSCS 

• Discuss FSCS related problems and troubleshooting methods with the 

previous Chief Scientist/Watch Chief/FSCS Specialist 

Once underway, meet with watch members & emphasize: 

• Typical operation of a station; 10 minute warning to CTD/bongo, trawl, sort, 

weigh, cut, special sample workup, cleanup area & buckets/baskets, resupply, 

and warnings to stay clear of deck operations when winch is functioning 

• Importance of asking for/verifying the station number at each station. 

• Importance of collecting quality data (species identification guides, work 

methodically, ask questions, beware of scale tare). 

• How to measure: fish are measured to the end of central caudal ray, shark 

total length, lobster and crab carapace length, ray wing span, skate total 

length, squid/octopus mantle length. 

• Do not discard any species over the side without checking with Watch Chief. 

• Do not discard anything over the side while the net is in the water. 

• Everyone will help with cleanup and freezer runs (important to put samples in 

correct boxes). 

• Importance of updating tallies on special requests. 

• Describe differences between similar appearing species (e.g. red/white hake, 

little/big skates) and to use fish identification books. 

• Review of maturity stages and prey identification. 

• Use gloves to handle fish. 

• Demonstrate proper way to handle equipment (e.g. how to set tare, how to 

read calipers). 

• Cutting teams must wait for instructions from Watch Chief before proceeding 

to open their sampling location. 

• Remind everyone to read the FSCS error messages carefully & to take all 

override messages seriously. 

• Cutters must wait for the recorders to get to the length screen before 

measuring fish...cutters & recorders must still communicate biohazards with 

electronic boards (don=t put torpedo rays on boards, keep lobster claws away 

from wires). 

• Notify Watch Chief if fish measuring board is not responding quickly (buffer 

may need clearing). 

• Notify Watch Chief if species are incorrectly identified at the sampling 

location. 

NOAA Fisheries Trawl Survey Protocols
141

• Care of scales, fishboards, magnets, calipers, monitors, barcode readers and 

label printers. 

• Supervise organization/storage of chemicals & supplies, make & label freezer 

special sample boxes, set up plastic sampling boxes with knives, Food Habit’s 

chimes, herring tags, misc. plastic bags, visual aids. 

• Post/review status of special sample requests in wet lab.

Pre-First Tow Activities: 

• Train/review with watch members FSCS standard processing procedures 

• Monitor computer screen temperatures & adjust brightness 

• Calibrate, clear buffer, verify correct mode for fish boards 

• Calibrate scales 

• Calibrate monitor screens 

• Change printer ribbons and labels as needed 

• Designate unique sounds for each sampling location 

• Demonstrate the correct distance and angle the Age envelope should be 

oriented from the barcode scanner in order for the coded number to be 

registered. Records the species name on the first envelope of the first fish 

sampled of a given species and keeps all envelopes for that species together 

with a rubber band. 

During Tow: 

• Monitor RealTime plots & report bad sensor readings to ET/Chief Scientist 

After a Tow: 

• In the Computer Room: Check to see if EK500 is still running (ask ET for 

Instructions) 

• Stop at the freezer to check the posted station, strata-tow numbers and record 

on log (if station has to be repeated, adjust tow and station sequence number) 

• Look for special sampling, bongo, depth, or special sample comments on the 

list 

On deck: 

• Reset the Controller on FSCS SERVER1 

• Make sure all sampling locations are offline 

• Verify trawl event is stopped and exited after the tow is complete 

• Initiate and oversee FSCS operations (Refer to FSCS manual for FSCS 

operations). 

• Oversee and direct species identification & sorting 

• Look at door edges to see shine on shoes 

• Document all subsamples and mixes (record details on log) 

• Inspect damage to the gear. Assess the severity of the damage to ascertain 

what SHG value to input 

• If there is a question about if the tow needs to be repeated, contact Chief 

Scientist 

Northeast Fisheries Science Center
142

• Contact bridge if difficult to work/stand in rough weather 

• Determine if species will be part of mix or subsample 

• Enter catch species into FSCS 

• Begin entering species that were recorded on trawl log 

• Make sure that all baskets and buckets are re-sorted before weighing 

• Verify correct tare is on the large scale 

• Verify that the correct species is called out during weighing by looking in 

each bucket/basket as it is being weighed. 

• Weigh the buckets and baskets B it=s very helpful to have an experienced 

watch member record the weights on the trawl log as they are automatically 

entered from the scale. 

• Manually enter the weights, using small scale, for species too light for the 

large scale (check tare) 

• If fixed gear is caught, document gear description and net/trap tag numbers. 

Subsampling guidelines: 

• As Watch Chief, maintain control of all subsampling 

• No one is permitted to initiate a subsample or to initiate measurement of 

subsampled fish without approval of the Watch Chief

• Try to select all subsampling from the Species and Weights screen during the 

initial weighing of species

• You can reload at any workstation without problems

• Do not attempt a mix within a mix, sort instead

• If subsampling must be used at the fish sampling level:

o Wait until all other fish are measured

o Reload if necessary before any fish to be subsampled are measured

o Use Remaining Weight 

• If a species has already been started, and you must subsample immediately: 

o Stop measuring the species

o Exit and save from the Lengths screen

o Set aside the portion of fish that were NOT measured

o Finish sampling on all other species

o Reload if necessary

o Perform remaining weight sub (use the Sub Sampling button on the 

main Fish Sampling screen and enter the weight of the fish that were 

set aside) 

Option for large tows or time crunch: 

• If you have a large amount of fish at a station, you can direct a sampling 

location to start working on a species before you have finished weighing all 

species. Only allow them to start after you have totally finished weighing the 

selected species, have chosen the desired subsampling method if any, have 

entered the weights, counts, or volume to be used if subsampling, and have 

clicked on the Save Data button on SL1. 

NOAA Fisheries Trawl Survey Protocols
143

• It is imperative that the Watch Chief communicates with the recorders at SL2 

and SL3 about when to reload. The recorders should reload as soon as they 

have finished the species they are sampling after being told by the Watch 

Chief. 

 

Data Quality Review: 

• Load data 

• Perform QA using forms 

• Document FSCS software and hardware problems in C:\FSCS\cruise_notes\ 

• Going through the QA process after the tow workup has been completed (and 

as time allows) is designed to: 

• Find missing and/or erroneous station and biological data while at sea 

• Identify special samples that may have not been entered at an individual 

sampling location. If special samples are not being recorded correctly, this 

could mean a procedural problem that should be addressed early with the 

sampling team 

• Alert the Watch Chief if certain teams are repeatedly overriding important 

error messages that may need further explanation as to their significance and 

ramification. 

• At this time, it is requested that the Watch Chief continue to: 

• Double check expansion factors 

• View overrides to identify potential sampling errors 

• Examine the species processed at a sampling location more carefully if there 

are any problems encountered at a sampling location during the tow 

• Compare species between watches 

• View special sample data for proper “value” data 

 What the Watch Chief should fix/leave alone? 

• Fix: 

o SHGs/missing comments (e.g. add reason for SHG not = to 111, gear # 

changes) 

o Special samples that were not entered 

o Leave alone: 

o Species code changes (record info on trawl log and in Cruise Notes 

file) 

• Document: 

o All subsamples and mixes (record details on trawl log) 

o Unusual mix-ups 

o FSCS software operations problems (describe error and solution). 

Make comments in c:\FSCS\cruise_note\ 

Watch Change: 

• Speak with other Watch Chief on status of station sequence, station workup, 

special sample request completion 

• Calibrate scales 

Northeast Fisheries Science Center
144

During Cruise: 

• Speak with Chief Scientist regarding any personnel problems 

• Clear electronic fishboard buffers daily 

End of Cruise: 

• Remind Scientists to clean staterooms and heads 

• Speak with Chief Scientist regarding area cleanup responsibilities 

• Help with offloading special samples 

• Fill out freezer log in cutting room as samples are being stored 

3.6 FSCS Manager Responsibilities: 

Day of Sailing: 

• Use HyperTerminal to test hardware connections (set up icon shortcuts) 

• Make sure PC Anywhere/Terminal Services is on all computers 

• Ensure FSCS.cfg file reflects the FSCS directories and environment being 

used 

• Check with shore-side FSCS manager to see if previous cruise data has been 

deleted 

• Ensure that the data drives on both the FSCS server and the local sampling 

workstation are not full 

Assist Chief Scientist with FSCS-related review of files/directories: 

• During cruise: 

• Modify/generate reports (refer to FSCS manual) 

• Help to train scientific staff in FSCS use 

• Help Watch Chief or Chief Scientist to solve & document software and 

hardware problems in C:\FSCS\cruise_notes 

• Transmit data if necessary 

• Help Chief Scientist with any EventBuilder tasks 

• Help with error checking 

• Ensure Dimension 4 software is running 

3.7 Bridge Officer Responsibilities: 

3.7.1 Preparation and Setting Procedures -- Throughout the entire operation 

described below, the OOD (Officer on Deck) MUST exercise prudent seamanship 

and safe navigation, as well as maintaining all logs and performing bridge collateral 

duties. 

NOAA Fisheries Trawl Survey Protocols
145

 Procedures When Approaching a Station: 

• Make a PA system announcement, “10-minutes to station, 10-minutes to CTD 

(or) BONGO”. 

• Notify engine room by sound powered phone, “10-minutes to CTD (or) 

BONGO.” After a long transit (> 2 hours), provide the engine room with a 

half hour notification in order to allow the trawl winch diesel and hydraulics 

to warm up. 

• Plan the trawl run in accordance with the Fishing operations guidelines. It is 

preferable to start the trawl at the marked location and tow in a direction 

toward the next station. Review the paper chart for obstructions and the 

electronic chart for stratum boundaries when planning the trawl run. If a trawl 

cannot start at the marked location, it may be moved and/or the direction 

changed providing some portion of the trawl run passes within 1 nmi of the 

marked station. If the station must be moved more than 1 nmi, the Bridge 

Officer must consult with the Watch Chief or Chief Scientist 

• Set up for and conduct the CTD or BONGO in accordance with their 

respective Standard Operating Procedures (SOP) . 

• After the CTD or BONGO is completed, activate the Trawl Event window on 

the Scientific Computing System (SCS) computer and enter the Header and 

Weather information. Ensure the TRAWLTENSION window is active on the 

SCS computer. 

• Set speed to maintain 2 to 3 knots through the water in preparation for 

streaming the net. 

As applicable: 

• Hoist Trawling Day Shapes (two cones with apexes together) and log . 

• Energize Trawling Lights (Green over White, extinguish forward masthead 

light) and log. 

• Sound Trawling Fog Signals (one prolonged and two short blasts) and log. 

• Ensure the trawl timer is set for 30-minutes. 

• Set the proper DGPS, LORAN, and SCS displays (ensure differential mode is 

active) . 

• Ensure the Simrad EQ-50 is adjusted to accurately track the bottom. 

CTD and or bongo deployment without trawling: 

If a CTD and/or Bongo are performed but no trawl is set, the bridge officers must 

start the Trawl Event Logger and enter the station number and meta data prior to 

the CTD cast, then select Start Event followed by Start Trawl, let this run for 10 

seconds and select Stop Trawl followed by Stop Event. A note that a CTD and/or 

Bongo was set and “trawl was not set" must be added to the ST-comments in the 

Meta Data window of the opened Trawl Event Logger for that station. After the 

Trawl Event Logger is closed, station initialize must be run and a note must be 

placed in the comments section indicating that the "trawl was not set”. The trawls 

SHG code should be given a value of 551. If the station is revisited later in the 

cruise, the Chief Scientist will assign a new stratum and tow number. 

Northeast Fisheries Science Center
146

Wire monitoring: 

On the ALBATROSS IV and DELAWARE II marks and a wire metering system 

on each wire (warp) will measure the wire. If the difference between the two 

measured distances becomes greater than 4% of the door-to-door cable length or 

exceeds 2.0 meters, operations shall be suspended until a cause is found and 

resolved. 

Marks are placed at fixed distances along the warp to allow for consistent 

deployment of known lengths of wire in fifty-meter (ALBATROSS IV) or 25-

meter (DELAWARE II) increments along the warp. As the trawl is being set, the 

marks must be counted on the trawl wire. When the proper length has been 

deployed, a member of the deck crew must visually inspect the marks to insure 

that the final marks on both port and starboard cables come to rest parallel to one 

another. During this time, the readings from the wire metering system must be 

inspected and any discrepancies between the metering system and the marks must 

be noted on the setting and hauling log (Attachment H). 

If the difference between the marks and the metering system are greater than the 

above tolerances, the following must occur: 

• The net must be hauled back, wire measuring system reset and the gear reset 

to determine if the problem was a result of slippage of the wire metering 

system. 

If this does not resolve the problem then the following procedures must be 

followed to ascertain where the problem originates: 

• The marks and metering system should be visually compared as the net is 

retrieved and notes taken that can be used to indicate where the discrepancies 

appear. 

• A separately marked cable should be used to verify the marks on the wire. 

When the wire marks are different that the pre measured cable, the wires 

should be remarked at sea or otherwise accounted for so that we can be certain 

that the above tolerances are not exceeded. 

Streaming and setting/shooting: 

• Prior to streaming the net, make sure it is safe to do so. 

• Check for traffic and fixed gear, observe bottom on the sounder, be familiar 

with the chart of the area, and avoid obstacles. 

• Check traffic conditions and look for fixed gear. If all is clear, notify the 

winch operator to “stream the net.” 

• Avoid turning the vessel during this phase of the deployment. 

• When the net has been streamed and the doors are at the trawl blocks, it is safe 

to maneuver the ship as necessary. Be sure to keep the winch operator 

informed of intended changes in speed or course. 

• A speed of 6 knots will be maintained during setting to ensure adequate door 

spread. 

• After the ship has steadied up on course and speed, note the depth from the 

NOAA Fisheries Trawl Survey Protocols
147

Simrad EQ-50. Using this depth, select the proper “wire-out” length from the 

Trawl Warp Scope table (Attachment E). 

• The port and starboard marks will be aligned at either the winch or the blocks. 

The amount of wire set will never be less than that indicated in the scope 

table. Therefore, when the amount of wire has reached its predetermined 

length as dictated by the scope table, additional wire will be let out until the 

marks are aligned at either the blocks or the winch. This will ensure that the 

marks are evenly set. 

• Notify the winch operator of the “wire-out” length. The winch operator will 

then begin “setting/shooting the net.” Avoid turning the ship during this 

phase of deployment also. If the depth changes significantly while shooting 

the net, you may give the winch operator a (timely) revised wire-out length. 

• When the winch operator has paid out all but the last 50-meters of wire for the 

tow, he will instruct you to slow down. Reduce the speed to 3.8 knots. 

 Observations to ensure proper net deployment: 

• As the trawl passes over the stern roller and down the ramp, attention should 

be directed to those areas where shackles, links, cable splices and roller gear 

meet the trawl webbing. 

• Net meshes may becomes tangled, pinched, caught, snagged or otherwise 

snagged. Problem spots or areas appear as an unusual gathering of webbing 

or as a strain where the meshes of the webbing are tightly stretched from the 

point of origin, which usually leads forward toward the vessel. Left 

uncorrected, tears or rips in the webbing can result, or if not cleared, can 

prevent the trawl from attaining proper bottom configuration. To correct this 

situation haul-in the trawl before the door hook-up has been made and free the 

webbing. If a bad cable splice is the problem, wrap with electrical tape or 

cover appropriately with layers of mending twine. 

• As the net is streaming and before the doors are deployed, a deck fisherman 

should inspect the floats to ensure that the net has been deployed correctly. 

 Configuration: 

• Once the trawl wings have cleared the stern ramp and trail the vessel at towing 

length (under tension), but before the trawl door hook-up is made, be certain 

that a proper surface trawl configuration has been attained. 

• Proper configuration is evidenced when the headrope floats all appear at the 

surface and not confined by webbing. 

• Proper configuration will resemble a horseshoe. 

• At this point, an inspection of the towing legs can be easily accomplished. 

Both port and starboard pairs (bottom and top) should nearly reflect the same 

wedge profile; the apex of the wedge appears at the leg attachment to the main 

towing cable, with top and bottom legs leading back to their respective 

attachments to the trawl wings. 

• If it appears that due to twisting of the top and bottom legs the overall 

effective length of the legs will have been reduced in excess of two feet, the 

trawl should be hauled to such a point that the twists can be removed. Left 

Northeast Fisheries Science Center
148

unattended, there remains the possibility that headrope overhang and/or 

headrope height could seriously be affected. 

 Setting the doors: 

• Once the doors are lowered into the water by the winchman, note how the 

doors plane-off. 

• If there appears to be instability or if the doors do not move evenly outboard, 

this may indicate that other than matched pairs of doors were used, or that 

towing brackets are worn or have become otherwise loose. If left uncorrected, 

instability of the doors while on the bottom could result in the doors riding on 

their side, or not providing the desired (or expected) trawl wingspread. 

 Depth: 

• Winch operator should check station depth with officer on bridge. 

• Depth multiplied by desired scope should approximately agree with the 

amount of cable accounted for on the scope chart (Attachment E). 

• Some reasonable variation will occur since each shot of wire out is 50 meters 

(ALBATROSS IV) or 25 meters (DELAWARE II) in length with the final 

position of the markers being used to reflect the best approximation of the 

desired scope (i.e., markers may be over the deck, on the blocks, over the 

ramp, or at the water, depending on the judgment of the winch operator 

relative to attaining desired scope). 

 Wire-out and scope ratio: 

• The wire-out length for a tow is based on the depth as read from the EQ-50. 

The wire-out scope table on the bridge (Attachment E) has been precalculated for the proper scope for each depth. 

• The port and starboard marks will be aligned at either the winch or the blocks. 

The amount of wire set will never be less than that indicated in the scope 

table. Therefore, when the amount of wire has reached its predetermined 

length as indicated by the scope table, additional wire will be let out until the 

marks are aligned at either the blocks or the winch. This will ensure that the 

marks are evenly set. 

Simplified trawling rules:

• Stay within stratum boundaries 

• Tow shall start at the marked location and be towed in a direction towards the 

next station 

• Tows shall be 30 minutes long 

• Speed is 3.8 knots 

• Don't move tow more than 1-mile from station without permission of the CS 

or WC 

• Never tow in less than 30-feet/9-meters/5-fathoms of water 

• Never tow in greater than 1200-feet/366-meters/200 fathoms 

• Never change wire length after the trawl hits the bottom 

NOAA Fisheries Trawl Survey Protocols
149

There are eight fundamental rules that an OOD shall attempt to comply with when 

conducting a trawl survey as noted above. As with all rules, there are always 

special circumstances or allowable exceptions. These guidelines attempt to 

discuss the reasoning and thought processes the OOD must apply to the decision 

making process (tactics) when planning for, setting up for, and conducting a 

survey trawl. 

One point that must be remembered is that the survey is based on “relative 

abundance”, not the number of fish caught. For statistical purposes, this is the 

reason why constant speed is more important than distance covered. OODs 

should avoid tactics aimed at catching the maximum amount of fish as this 

introduces a bias to the data set. 

3.7.2 Directions for using the SCS TrawlEvent Application on a NEFSC 

Bottom Trawl Survey -- 

 Overview (trawl event):

The officer on the bridge will start the Trawl Event application from the Event 

Logger in the Scientific Computer System (SCS) program prior to deploying the 

gear. Prior to deploying the net, the Start Event button will be pressed which 

will trigger the logging of meta-data and sensor stream data to specific output 

files. When the net is set and starts fishing, the officer will push the Start Trawl

button to mark the data of the event. When the tow is complete, pushing the Stop 

Trawl button will mark the data of the event ending. Once the doors reach the 

surface of the water, the Stop Event button will be pushed to stop the logging of 

data to the output files. Once the Stop Event button has been pushed, the data for 

that tow will be available for the scientists on deck via the FSCS Station Initialize 

program. 

 Important Facts (trawl event): 

Scientists will be unable to access the full data for a given station until the Trawl 

Event application has been stopped for the current trawl. Standard procedure for 

scientists will be to access the data for a given station by running the Station 

Initialize program at that point when the net is hauled aboard. (It is now possible 

to retrieve station data in the Station Initialize program for multiple stations with 

FSCS version 1.5 (instituted in February 2003). 

 Step-by-Step Instructions for Officer on Deck (trawl event): 

At the first survey station, ensure that the Chief Scientist has updated the 

appropriate default values for the following fields: ST-CruiseCode, STVesselName, SequentialCruiseNumber, and ST-DesignatedSpeed. These values 

remain the same for the entire cruise, and are entered by the Chief Scientist using 

the Event Builder on SCS at the beginning of the cruise. 

Northeast Fisheries Science Center
150

The bridge officer must be logged in as administrator: 

• Double click on SCS Menu if the menu bar is not currently displayed. 

• Pull down the Acquisition menu. 

• Highlight Event Logger NEW and click once.

• Select TrawlEvent.tpl by double clicking on filename.

• Select Meta Data radio button of the Components block in the upper left 

corner of the screen.

• Select the Cruise tab by clicking once. 

• Populate the following fields:

• ST-StationNumber

• ST-StratumType

• ST-Stratum

• ST-Tow

• ST-Pitch (when determined)

• ST-RPM (when determined)

• ST-Comments (you may need to return to this field at the end of the event to 

add comments regarding the tow).

• ST-DesignatedWireout

• Click on the Weather tab and populate the following fields:

• ST-CloudCover

• ST-WeatherCode

• ST-WaveHeight

• ST-SwellDirection

• ST-SwellHeight 

• Select radio button, Buttons, located in the Components block. 

• Push the Start Event button just prior to deployment of the doors (prior to 

doors entering the water, i.e. doors at surface). 

• Push the Start Trawl button when the winch operator announces that all wire 

is paid out, and the brakes are set. 

• If during the trawl, bad bottom is encountered or the gear hangs up enough to 

stop the tow, the Hang button should be pressed. 

• If during the trawl, the doors should become crossed, the Doors Crossed

button should be pressed. 

• The Stop Trawl button should be pressed at the same moment that haulback 

begins. 

• All comments should be entered in Bridge Comments field before the doors 

hit the surface. 

• The Stop Event button should be pressed just after the doors hit the surface 

(all data entry must be complete before this point). 

NOAA Fisheries Trawl Survey Protocols
151

TIME SEQUENCE FOR TRAWLEVENT.TPL 

EVENT BUTTONS 

WHEN TO 

PRESS YOUR TIMING COMMENTS 

Start Event Prior to 

deploying doors 

MODERATE This can be pressed 

earlier if necessary 

Start Trawl Winch operator 

reports that all 

wire is paid out 

and brakes set 

(Tow timing 

begins) 

CRITICAL This button MUST be 

hit the same time as 

the brakes are set 

Hang* Net hangs on the 

bottom 

MODERATE Try to press this 

button as soon as 

possible after a hang 

is determined 

Doors Crossed* Winch operator 

reports crossed 

doors 

MODERATE Try to hit this button 

as soon as door cross 

is determined 

Stop Trawl Haulback begins CRITICAL This button must be 

hit the moment 

haulback begins 

Stop Event Doors hit the 

surface 

IMPORTANT Scientists can not 

access data until event 

is stopped 

Exit Catch is on deck 

and being sorted 

MODERATE Less problems likely 

if event is exited 

* Pressing the Hang or Doors Crossed buttons only marks the data when the button is 

pressed. This action does not stop data collection. 

3.7.3 Trawling --The winch operator will advise when the requested wire-out 

length has been paid out (plus an adjustment for “length at the water”) and the 

winch brakes have been set. DO NOT adjust wire-out after the brakes have been 

set. At that time do the following in rapid succession: 

• Start the timer 

• Press “save” on the DGPS 

• Mouse-click “start” in the Trawl Event window button 

• If a helmsman is present, they should assist you with initially fine tuning and 

maintaining the ships towing speed using DGPS while you are making the 

following log entries. 

• Log the time, station #, position, and depth of the start of the tow in the SCS 

Trawl Event. 

• Enter data in the SCS acquisition menu 

Northeast Fisheries Science Center
152

During the tow, be alert for traffic and fixed gear, monitor and adjust the towing 

speed as necessary, watch for significant bottom topography variations, and 

complete all logs and perform bridge collateral duties. A constant over ground 

speed of 3.8 knots should be maintained during trawling and reasonable and 

practical efforts shall be made to maintain the desired towing speed. Vessel 

safety concerns always supercede scientific protocols. If a safety concern arises, 

the tow can be aborted. 

Notify the winch operator at 5 minutes and 1 minute to the end of the tow. Note 

any special conditions or events encountered during the tow in the SCS Trawl 

Event bridge comment field. 

Stratum boundaries:

• A “complete tow” begins with streaming the net over the stern and ends when 

the nets codend has been landed on deck. A “complete tow” track line should 

never cross a stratum boundary. 

• An “official tow” starts when the trawl winch brakes are locked after paying 

out the designated trawl warp length, and ends when the trawl winch brakes 

are released and the trawl warps are engaged. 

• An “official tow” track line shall never cross a stratum boundary. 

• It takes approximately 3 nmi to conduct a “complete tow” with slightly less or 

more distance required for shallow or deep tows: 

• 0.5 nmi to stream and set the trawl 

• 2 nmi to conduct the “official” 30-minute standard survey trawl 

• 0.5 nmi to retrieve the trawl 

Keeping a “complete tow” within the stratum boundaries requires planning when 

stations boundaries: 

• Ensure there are 3 nmi available for towing 

• Allow for the effects of set and drift of the vessel 

• Avoid all obstructions such as land, vessels, wrecks, buoys, outfall pipes, fish 

haven and trap areas, fixed gear, cables, other charted obstructions, bad bottom 

topography, or stratum boundaries. 

• The stratum boundaries are supposed to represent specific depth ranges, 0-5 

fms, 5-10 fms, 10-15 fms, etc. These stratum boundaries were established 

many years ago, thus may not currently reflect the actual depths, most notably 

in the shallowest and deepest strata due to limitations in knowledge regarding 

bathymetry when the strata were created. It is critical that tows are made both 

within established stratum boundaries and at depths consistent with the depth 

range for the stratum. The only allowable exception to the “stay within the 

stratum boundaries” rule is when the Chief Scientist or Watch Chief requests a 

specific depth for a tow (generally only done for deep tows along canyon 

walls). This request should be noted on the station sequence list. 

NOAA Fisheries Trawl Survey Protocols
153

Start of tow:

• It takes approximately 0.5 nmi to stream and set the trawl. When preplanning 

the track line, the OOD may wish to veer off their course while transiting 

toward the next station in order to arrive 0.5 nmi from the station and going 

the correct speed and pointed in the correct direction. This set up will allow 

the doors to be set, and the “official tow” started, near the plotted station 

location. 

• Bongo plankton casts, CTD casts, and/or water casts are usually performed 

before a tow. Generally, these should be conducted within the same stratum 

and at a similar depth as required for the tow. During the preplanning of a 

tow, the OOD should make allowances for the distance and ship direction 

these events require. 

• Alternately, if the “official tow” cannot start at the plotted location, it is 

acceptable for some point on the 2 nmi “official tow” track line to pass over 

the plotted station location. Note that this permits towing toward the station 

as well as towing away from the station. 

• Obstructions or traffic may make starting at, or towing over the plotted station 

location impossible. Protocol allows the OOD to relocate the tow track line 

within 1 nmi without permission providing the “official tow” is in the same 

stratum, is at approximately the same depth, and passes within 1 nmi of the 

original station. 

• If, for any reason, any portion of an “official tow” cannot pass within 1 nmi of 

the original station, the chief scientist should be consulted. The OOD should 

explain why the original station location is unacceptable and offer alternative 

locations. 

Tow Direction: Tow direction must be towards the next station unless one of the 

following occurs: 

• When towing towards the next station would put you out of the stratum and 

into another. 

• When following a depth curve, generally offshore. 

• Bad bottom, wreck, cables or obstructions. 

• Fixed gear in the tow path and a clear tow exists in another direction. 

• Traffic in the area. 

• Moderate to heavy seas. 

Tow duration: 

• Standard survey trawls are 30 minutes in duration. 

• It is the NEFSC policy that a tow should not be shortened if there is a 50% 

chance or better of successfully completing a full 30-minute tow. 

• Time starts when the trawl winch brakes are locked. Time stops when the 

trawl winch brakes are released for haul-back. 

• Intentional or planned reductions in tow duration shall be avoided and only 

done after consultation with the chief scientists and/or watch chief. If 

unexpected obstacles are encountered, tows should be aborted. 

Northeast Fisheries Science Center
154

Shortened or lengthened tow: 

• If for any reason a tow has to be shortened or lengthened to ANY time other 

than 30 minutes, the scientists require that the Trawl Event still be completely 

filled out (even totally invalid tows for estimating abundance or biomass can 

be used for biological studies). 

• If a tow has to be shortened or lengthened, note that the tow was a nonstandard tow in the bridge comments field. If a re-tow is required, another 

Trawl Event with the next sequential Station number shall be generated (i.e., a 

new sequential number every time the net goes in the water). Contact the 

Chief Scientist for the new tow number because you cannot assign the next 

sequential number for that tow. 

Tow speed: 

• When streaming the net over the stern, the ships speed through the water 

should be between 2 knots and 3 knots, adjusted for weather conditions and 

current. This is necessary to provide sufficient tension to pull the net over the 

roller without so much tension to hinder or endanger the deck force while 

connecting the doors. 

• When initially placing the doors into the water and while shooting the net, the 

ship’s speed should be at least 6 knots through the water in order to ensure 

proper door spread, prevent the likelihood of crossing the doors, and to 

provide sufficient tension to pull the net and wire off the trawl winch drums. 

• During the initial phase of recovery, the ship’s speed should be maintained at 

the 3.8-knot trawling speed settings or slightly reduced. 

• Once the doors have cleared the water, the ship’s speed should be reduced 3.0 

knots to minimize tension while bringing the net aboard. Again, the OOD 

must correct for the speed and direction of the current. 

• The “official NEFSC standardized trawling speed” is a constant 3.8 knots over 

the bottom (not through the water) as measured and monitored by DGPS. 

Speed of the vessel during haulback varies between the ALBATROSS IV and 

DELAWARE II. It is important that each vessel continue to use their individual 

haulback protocols as the differences between the two vessels are accounted for in 

conversion coefficients that have been derived for the catch data. The historical 

reason that the speed at haulback varies between the two vessels is due to the 

different configurations of the hydraulics on each vessel. 

ALBATROSS IV 

During haulback, the vessel must not reduce trawling speed until the doors clear 

the water. After the doors have reached the surface, the vessel shall reduce speed 

to the minimum speed that will allow the vessel to maintain steerage. 

DELAWARE II

During haulback, the vessel must reduce trawling speed as soon at the winches are 

engaged. The vessel must reduce RPMs to 110 or approximately 1 knot over the 

ground. After the doors have reached the surface, the vessel shall keep speed to 

NOAA Fisheries Trawl Survey Protocols
155

the minimum that will allow the vessel to maintain steerage. 

During the initial minutes of the “official tow,” adjust speed settings to achieve 

the desired speed. Settings, which worked at the previous station or under similar 

weather conditions, are also very helpful. The ship will nearly always be 

traveling too fast when the doors are initially set on the bottom, but once the 

winch brakes have been set, the drag of the doors and net will slow the ship 

rapidly. DGPS speed is the standard and vessel speed should be determined using 

DGPS. 

 

Tow distance should not be used as a primary indicator of over the ground speed, 

distance versus time can provide a convenient double check. The NEFSC’s survey 

standardizes speed which will result in a standard distance covered. The 

designated 3.8-knot speed equates to 1.9 nmi traveled during a 30 minute tow. 

Based on this speed, the approximate distance covered at various points in the tow 

are as follows: 

 

@ 10 minutes into tow 0.63 nmi 

 @ 15 minutes into tow 0.95 nmi 

 @ 20 minutes into tow 1.27 nmi 

 @ 30 minutes 1.90 nmi 

Distance traveled should only be used as a secondary check of primary speed 

indicators. Speed should never be adjusted during a tow to achieve a target 

distance. 

Maneuvering during a tow: 

Maneuvering (turning) during any portion of a tow greatly increases the 

likelihood of crossing the doors, or having them fall over and not recover leading 

to a net malfunction. The wire angle from the trawl blocks and low trawl warp 

tensions are not reliable indicators of a malfunctioning net. Although 

maneuvering the ship during any portion of a tow is discouraged, there are three 

times when it is relatively safe to do so: 

• The most common reason for maneuvering during the deployment or recovery 

phase of a tow is to reduce the ideal 3 nmi straight run generally required for a 

30-minute tow, usually to avoid an obstruction such as fixed gear. 

• The only time it is safe to turn the ship during the deployment and recovery 

phases of a tow is when the trawl warps are connected to the doors and the 

doors are at the trawl blocks hanging over the stern. 

• In some instances, it may be permissible to turn the ship during deployment or 

recovery so long as the doors are NOT connected to the net or trawl warps. 

In all cases, ask the lead fisherman if it is okay to turn. Never turn while shooting 

the net. 

Northeast Fisheries Science Center
156

Maneuvering while the net is on the bottom should be avoided, but can generally 

be safely accomplished in small, widely spaced increments, e.g., three 5-degree 

course changes over 5 minutes. Course changes greater than 15 degrees are not 

recommended. The most common reasons to maneuver while the net is on the 

bottom are to: 

• Clear an obstruction or traffic. 

• To maintain a constant depth when following a contour line. 

• To stay within designated stratum boundaries 

Hung net or crossed doors: 

• Never back down. 

• In the event of a hung net or crossed doors, slow the ship to bare steerage 

speed (no less than 10% to 20% pitch) and follow the winch operator’s 

instructions. Ensure that the ship does not ride over the trawl warps. 

• Hit the “HANG” button on the trawl event 

• Have one of the fishermen at the transom to warn the winch operator and 

bridge if the trawl warps start to tend forward. If there is any chance of the 

net or the warps going under the ship, de-clutch the propeller. 

• DO NOT try to turn to a reciprocal course. Be prepared to set Not under 

Command lights or shapes. 

• The idea behind breaking a hung net free is to have the trawl winch pull the 

ship backwards until the stern of the ship is directly over the obstruction and 

the net can be pulled vertically off the obstruction. 

• The idea behind uncrossing crossed doors is to minimize the tension in the 

trawl warps so the doors may be flipped over each other to undo the tangle. 

• Be sure to annotate the Deck Log, and the SCS Trawl Event log of all events 

(sometimes a hang breaks free and you continue the tow). If the hang is the 

end of the tow, fill out the above as if it were the end of a normal tow, but 

noting the special events. 

 

 Depth changes: 

• Radical depth changes during a tow affect the mouth opening of the trawl 

because the scope of wire out to depth becomes inconsistent. In the worst 

cases, the trawl may even lift off the bottom and not fish at all. 

• If the charted contour lines indicate a steep depth gradient, the OOD must tow 

along a contour of (relatively) constant depth. This is particularly true near 

the canyons at the edge of the continental shelf. If depth changes cannot be 

avoided, it is best to tow from deeper to shallower depths because too much 

scope (too much wire out) is preferable to too little. 

• Never adjust the wire-out scope during a tow to correct for changing depth 

although scope changes can be made while shooting the net. 

Current: 

Tow direction relative to prevailing current has historically been treated as a 

random variable. Conscious efforts to tow into the current or avoid cross currents 

will impart an undesirable bias to the data, which is to be avoided. The only 

NOAA Fisheries Trawl Survey Protocols
157

exceptions are avoiding a cross current severe enough to collapse the doors or 

avoiding a stern current that leaves the ship without steerage. Cross-current 

readings approaching 2 knots should be a concern to the OOD; (especially on 

hard bottoms) because the doors do not hold their set well in these conditions and 

will tend to fall over or cross. 

 Sea state: 

Survey tow direction (or the ability to tow at all) may be determined by sea state. 

If the conditions are as severe as to pose a safety issue or data quality issue 

operations may be affected. Safety related decisions might be made by either the 

vessel Command or the Chief Scientist. The Chief Scientist will make data 

quality decisions. 

 Wind: 

Wind direction is generally not a factor for trawling operations. Sustained high 

winds with a long fetch often cause the waves and swells to come from the same 

direction. In this case, the direction of tow may have to be based on the seas. In 

open waters, canceling of operations is considered when sustained winds of 35 

knots are observed because this speed usually corresponds to sea states that are 

excessive for safe work on deck and proper gear performance. 

 Bottom Topography:

Bathymetry may become a factor in tow site location. If the alteration will result 

in a more than 1.0 nmi relocation of the station from the original station location 

the Watch Chief or Chief Scientist must be consulted. Areas of “bad bottom” 

may be determined to be untowable. This determination will be because of 

scouting the area, using all available navigation and scientific resources, and 

consultation between the Chief Scientist, the Officer of the Deck or Commanding 

Officer, and the Lead Fisherman. Barring safety issues, the Chief Scientist will 

make the final decision. 

 

 Traffic: 

Tow direction and tow site may be altered by marine traffic. With regard to 

traffic as it affects the survey operations, the OOD will notify the Chief Scientist 

or Watch Chief if there is going to be a delay of more than 15 minutes due to 

other vessels in the area or if the alteration will result in a more than a 1.0 nmi 

relocation of the station. The OOD is primarily responsible for the safe 

navigation of the ship. Delays of this nature should be rare as tow direction may 

be changed to avoid any close quarters situations. 

 Fixed Gear: 

Fixed gear may become a factor in tow site location. If the alteration will result in 

more than 1.0 nmi relocation, the Chief Scientist must be consulted. Areas of 

fixed gear may be determined to be untowable. This determination will be made 

after scouting the area, using all available navigation and scientific resources, and 

consultation between the Chief Scientist, the Officer of the Deck or Commanding 

Northeast Fisheries Science Center
158

Officer, and the Lead Fisherman. Barring safety issues, the Chief Scientist will 

make the final decision. The mere presence of fixed gear in an area is not a 

sufficient condition to abandon attempts to complete a tow. Often, through 

scouting and/or communication with local fishery operators results in 

identification of a towable area, even when fixed gear is present. Efforts to locate 

towable area should be made for a period of up to one hour. 

 Trawl recovery (Haulback):

From the stern, observe the trawl trailing out behind the vessel and note any holes, 

tears or other gear damage requiring immediate attention. 

 Fixed gear retrieved from trawl: 

When lobster traps or fishing gear is captured in the trawl, the following 

procedures shall take place: 

• Chief Scientist or Watch Chief records on the trawl log and in the FSCS 

comments: 

o Trap or buoy number(s) 

o Contents (count and measure lobsters –these data are not included in 

the trawl catch) 

o Location 

o Presence or absence of buoys 

o Condition of the gear (i.e. ghost gear, new traps) 

 Hauling back: 

Haulback procedures will be adhered to in order to minimize gear damage. The 

Watch Chief should observe this operation. As the codend becomes stationary in 

the water, just before being hauled aboard, note any loss of catch. If fish are 

escaping, there is a good chance that there may be some damage to the liner 

and/or codend. Once the catch has been placed in the checker, it may be 

necessary to cut several meshes in the belly section to remove larger entwined 

fish. If this becomes necessary, these holes should be immediately repaired and if 

necessary, inspected by a qualified Watch Chief. 

 Float Check: 

Once the trawl is completely positioned on deck, the deck crew should inspect 

headrope floats for damage and physically position. If needed, they should be 

repositioned or replaced. 

 Proper repair:

When net damage requires more than 20% repair of any trawl mesh section or 

significant damage to any other trawl component, consultation will occur between 

the Lead Fisherman or Boatswain and the scientific Watch Chief. The decision as 

to whether repair or replace the damaged section or repair or replace the entire net 

will then be made. Authority for the final decision rests with the Chief 

Boatswain. 

NOAA Fisheries Trawl Survey Protocols
159

Once it has been determined that 20%, of any mesh section has been damaged or 

significant damage has been observed on other trawl components, the trawl repair 

Checklist will be used to assess the completed repairs or newly installed trawl. 

Proper repair requires that the gear be returned to its specified configuration 

(Attachment A and B). 

 Tie liner: 

Before the codend is closed, the Watch Chief should inspect and ensure that the 

codend liner is properly closed to prevent escapement of any portion of the next 

catch. 

When to repeat a tow: 

Occasionally it is necessary to repeat a trawl haul because of malfunction or 

damage to the trawl. In cases of severe malfunction (crossed doors) or severe 

damage (whole sections torn out such as a wing or belly), the tow will not be 

counted as a standard haul and must be repeat although, it may be sampled for 

biological data which is independent of abundance and biomass information. For 

recording purposes, the tow is recorded as a valid station, but the coding for 

Station-Haul-Gear (SHG) value shall be greater than 1-3-6, indicating a non-valid 

catch for assessment purposes. Descriptions of the types of damage that 

constitute an SHG value of greater than 1-3-6 are given in the coding details 

(Attachment H). 

In some cases, it may be difficult to determine how to properly code a haul that 

has encountered problems. The following guidelines should be used: 

• It is essential to indicate a minimum of 2 for haul value, which flags data 

auditors that something abnormal occurred during the tow. 

• If in doubt, about SHG coding consult with the Chief Scientist 

• Ensure that the catch is worked up at least to the point of weights and lengths 

• An accurate and complete account of what occurred to the gear must be given 

in the Station Initialize Watch Chief comments field; the lead fisherman or 

boatswain must be interviewed to determine details on gear condition. 

• When gear significant gear damage occurs, the Chief Scientist should be 

informed, and the decision to re-tow must be made based on the severity of 

the damage.

• A plot of the starboard and port line tensions should be printed out and saved 

for the auditors, to help determine at what point the gear encountered 

problems.

• Note: The plot of tension may help to code a tow when on deck, for example, 

a severely damaged net with cod-end intact, and trawl tension plot showing 

heavy bottom contact at 29 minutes into the tow may be a good tow. The 

important point to remember is to provide enough information to allow 

independent evaluation (by those on land) of every station where an 

abnormality occurred.

Northeast Fisheries Science Center
160

The decision to repeat a tow is made by the Chief Scientist and is based on a 

coded SHG value greater than 1-3-6. The following factors may override this 

decision: 

• The probability of the same or greater damage to the net occurring; in this 

case, the station location should be moved 

• The current progress of the cruise as a whole (when time remaining in the 

cruise threatens the completion of the entire survey area) 

• The status of shipboard gear inventory (i.e., how many undamaged nets are 

left?) 

The following factors must be weighed with every decision to override a retow: 

• The overall progress of the cruise (does time in the context of the entire 

survey permit extended effort on any one station?) 

• The phase of the cruise (a subset of above) (e.g., risking the last undamaged 

net on the last day of leg III may not be a serious risk for the cruise at all, as 

the ship will return to port and can replenish the supply of nets without much 

loss of operational time) 

• The number of stations completed in the stratum in question (higher priority 

would be placed on a station that represents the sole tow in the stratum, lower 

priority would be placed on a station that would represent the 8th successful 

tow in the stratum) 

• The current relative importance of the stratum in question (is it a critical 

stratum for certain assessment species?) 

• The geographic coverage within stratum that the tow represents 

3.8 Post Trawling Activities 

Gear condition report: 

After conferring with the Chief Boatswain, the Chief Scientist or their designee 

must contact the NOAA Fisheries warehouse 2 days before return to Woods Hole 

to inform them of gear needs for the next leg. This communication should be by 

email and a copy of this information should be sent to Survey’s Gear Specialist. 

The Boatswain will ensure that all gear being returned to Woods Hole is tagged 

and that a record of its condition is supplied to both Survey’s Gear Specialist and 

the Gear Warehouse. The form for this information is provided in Attachment D. 

Post cruise meeting: 

The Scientific Vessel Coordinator will hold a post cruise meeting the day the 

vessel arrives in port. Attendees shall include the Captain, Port Captain, Chief 

Scientist, oncoming Chief Scientist, and the Ecosystems Survey Branch Chief. 

Others may be directed to attend. The Port Captain will take the minutes. 

The goal of the meeting is to discuss the overall success of the cruise and any 

problems, which may have arisen. The number of stations completed taking into 

NOAA Fisheries Trawl Survey Protocols
161

account weather conflicts, gear conflicts, and ship performance determines the 

success of the cruise. Also discussed at the meeting are electrical or sensor issues 

and any equipment that needs repair. A plan is discussed for the upcoming leg, 

as to the general cruise track and any coordination with other research vessels. 

Return / notification of fixed gear: 

• Traps or gear returned to shore will be brought to the gear shed in Pocasset. 

• The Chief Scientist is responsible for passing the intercepted gear information 

to the person designated by the ESB Branch Chief. 

• Assigned person will contact the fishermen and: 

 Explain the circumstances resulting in the interception of gear 

 Apologize for gear interception 

 Arrange for the return of undamaged gear if owner desires 

 Inform owner of right to file Tort claim 

• If a Tort claim is filed: 

 The claim goes to the Branch Chief for signature and then to 

Washington, DC for approval. 

 The fishermen must supply an itemized cost breakdown of losses and 

signature. 

 The Branch Chief will review the information for fairness: (i.e. fair 

market value and probability of NOAA Fisheries involvement in the 

loss). 

 Copy of letter and cover letter is sent to Purchasing Department

 Protocol 4: Trawl Construction and Repair 

4.1 Trawl Nets 

The NEFSC spring and autumn bottom trawl surveys utilize a Yankee 36 trawl with 

16” rollers on the sweep while the NEFSC Winter bottom trawl survey employs a 

similar net with a 4” cookie sweep. 

Construction plans for each survey trawl design are included in Attachments A and B. 

The plans include engineering drawings of the net, doors and rigging with a level of 

detail at least as specific as that in the ICES recommended standard (ICES C.M. 

1989/B:44 Report of the Study Group on Net Drawing). In addition, each plan 

contains a description of all materials used, and the qualities of these materials 

considered important for proper trawl function. 

 

A checklist is included in Attachment C, which was developed for each trawl design 

specifying the dimensions, and their tolerances, or other design features considered 

important for proper trawl function. The checklist is used to verify that each newly 

constructed or repaired trawl is within operational tolerances before use. Members of 

the scientific staff of each Science Center, who are trained in trawl construction and 

repair verification, will verify that trawls are within operational tolerances. 

Northeast Fisheries Science Center
162

Methodology for at-sea trawl repairs will be specified in an Operations Plan and 

communicated by the Chief Scientist to the crew of the vessel at the start of each 

cruise. A trawl repair checklist will be included in the Operations Plan and used by a 

member of the scientific staff to verify that repaired trawls are within operational 

tolerances.

4.2 Trawl Doors 

Trawl doors are critical to the performance of bottom trawl gear. Doors function to 

spread the trawl net and have a direct effect on net wingspread, head rope height, 

bottom tending, and mud cloud. The spring, autumn, and winter NEFSC bottom 

trawl surveys utilize 450-kg, Portuguese polyvalent (Euronete) doors (reference 

number 126) in the trawling systems (Attachment A and B). Doors shall be 

purchased in pairs and immediately numbered in a permanent manner to allow 

tracking during use and maintenance. 

Trawl doors shall be maintained in a fashion to ensure proper paired functioning. 

Door pairs shall be certified by NEFSC personnel prior to deployment on fishery 

research vessels. Door pairs must have shoes that are in good condition, be free of 

dents and other significant changes in shape, and have brackets secured in a manner 

to eliminate shifting. 

Door spread resulting from deployment of specific sets of doors will be measured 

using trawl mensuration equipment upon initial deployment and at intervals of a 

minimum of every 50 tows. When door spread is determined in successive tows to 

fall outside of target ranges, the corresponding door pair shall be removed from the 

trawling system until proper performance can be verified. 

Backstrap chains shall be paired, measured for length and maintained within 

tolerances outlined in Attachments A and B. Backstraps will be attached to the doors 

in the hole closest to the back end of the door. Pairs of backstrap chains shall remain 

associated with a specific door pair during transport to and from fishery research 

vessels, and during deployment during trawling operations. If backstrap chains are 

removed from doors during trawl operations due to damage or determination that 

measured lengths are no longer within specified tolerances, removed backstrap chains 

shall be tagged with information including the door pair number, the date of removal, 

and reason for removal from the door pair. Removed backstrap chains shall be 

returned to NEFSC gear personnel for inspection. 

4.3 Gear Certification / Inspection 

Prior to being placed on the vessel, the trawl gear and equipment will be certified by 

two individuals. The attached checklist (Attachment C) will be used to evaluate the 

trawl gear. The trawl gear is described in detail in Attachment A (Groundfish net) and 

Attachment B (Flat net). A condition report form (Attachment D) will be forwarded 

to the Chief Boatswain. When the gear is returned, the Chief Boatswain is requested 

NOAA Fisheries Trawl Survey Protocols
163

to fill out this gear condition report form, return it with the gear, and supply a copy to 

the Branch Chief of the Ecosystems Surveys Branch. 

Protocol 5: Changes to Regional Trawl Survey Protocols 

Changes to trawl survey operational protocols will be at the discretion of the 

NEFSC’s Science Director who may approve such changes directly or specify a peer 

review process to further evaluate the justification and impacts of the proposed 

changes. 

Northeast Fisheries Science Center

165

ATTACHMENT A 

Specifications for Construction of NEFSC 

Standard #36 Bottom Survey Trawl 

(60 - 80) 

Updated 4/22/03

Body of the Net

Dimensions of the sections are shown on the attached net plan and cutting diagram. Webbing 

for wings, square, and bellies is 5" stretched mesh measured knot center to knot center (or 4 

3⁄4” inside measurement). It is single selvedge, stretched, and stabilized. The webbing is 

woven with white #96/108 (3 mm) (R5263tex), 16-carrier virgin braided nylon twine. 

Webbing in the codend is 4 1/2" stretched mesh, center-to-center, single selvedge, stretched, 

and stabilized. Twine for the codend webbing is white #182 (R11764tex), 16-carrier virgin 

braided nylon. 

Net sections are joined together by sewing a half mesh row of double twine of a contrasting 

color for easy identification of sections (usually red shot cord). 

The top and bottom sections of the net are joined together at their sides by a gore or laceage. 

Gathering six knots from each of the top and bottom sections makes the gore. These are 

seized every foot and wrapped in between the seizings using single #120 (R8333tex) threadbraided nylon twine. 

Dog-ear meshes are sewn onto top and bottom wings with single #182 thread-braided nylon 

twine. 

Gore Lines

Gore lines are 3/4" diameter PolyDacron ropes that run from the after end of the codend to the 

top of the wing end where the rope is tied into the head rope eye splice. The gore line is 

slightly shorter than the laceage and is seized to the laceage at intervals of 18 inches. 

Footrope

The footrope is constructed from 120' (20 fathom) total length of 3/4" diameter polydacron 

(polyplus) rope. This length is used to construct the 100’ (16.67 fathom) footrope including 

eye splices, and the seven-foot up-and down lines. The remainder of the rope at each end is 

tied into the wing end eye of the head rope, with the excess seized back down the door end 

line. Lower wings are hung in 45’ (71⁄2 fathom) lengths while the lower belly is hung in a 10’ 

(1.67 fathom) length. 

Northeast Fisheries Science Center
166

Belly Lines

Belly lines are two strengthening lines on the bottom belly made of 5/8" Poly Dacron. They 

are seized to the footrope at the corner and run out and back to the gore line on the bar of the 

belly webbing. They are seized to the webbing and to the gore line. 

Headrope

The headrope is made of 7/8" diameter nylon or polypropylene and steel combination rope 

with a fiber core. It consists of three 20' (31/3 fathom) sections. Each section has eyes 

spliced at each end without thimbles and sections are joined by 1/2" hammerlock links. The 

square is hung in 12’ (2 fathom) and the wings are hung in 24’ (4 fathom) lengths. 

Hanging

The dogs on the wings are hung to the headrope and the footrope with hanging meshes of 

single #120 braided nylon twine. The belly and the square selvedge meshes are evenly hung 

on the bosom sections of the footrope and the headrope with single #120 braided nylon twine. 

The hanging lengths for the wings and bosom on the headrope and footrope are shown on the 

attached plan. Each dog is seized to the headrope with bar-tight seizings. 

Up-and Down

Door end meshes of the bottom wing are evenly hung on the seven-foot up-and-down line that 

runs from the footrope to the headrope. The end meshes of the top wing are gathered together 

and seized into the headrope eye splice with single #120. 

Floats

There are 36 eight-inch spherical aluminum floats. The floats have a 5/8" polypropylene line 

threaded through their double beckets. This poly line is then seized to the headrope. Float 

arrangement: 20 floats evenly spaced on the center 20' (31/3 fathom) section of headrope, and 

8 floats evenly spaced on each 20' (31/3 fathom) side section. The first float is 18 inches from 

the wing end. Float line is seized to backside of the headrope, so floats lie above the webbing 

and behind the headrope. 

Fishing line (Not the footrope and not a fishing line) 

10/28/02 - The terminology for this piece is being changed from “traveler” to “fishing line”. 

This was previously called a “fishing line” but was changed to “traveler” to differentiate it 

from the footrope. No change in the configuration of the net has resulted from the change in 

the terminology of this piece. 

The Fishing line is made up of five lengths of 5/8" diameter combination rope with eyes 

spliced in each end without thimbles and joined with 1/2" hammerlocks. These lengths, from 

wing end to wing end are 23’(3.83 fathom), 91⁄2' (1.58 fathom), 16'(2.67 fathom), 91⁄2'(1.58 

fathom), and 23'(3.83 fathom). Measurements are total overall length, including eye splices. 

Combination rope is a combination of nylon or polypropylene strands and steel wire with a 

fiber core. 

NOAA Fisheries Trawl Survey Protocols
167

Sweep

The sweep is made up of five sections of 3/4" diameter 6 x l9 fiber core, galvanized wire rope. 

The sections have eyes without thimbles. The sections are joined with 5/8" hammerlocks. 

The lengths of the sections from wing end to wing end are 221⁄2'(33/4 fathom), 91⁄2'(1.58 

fathom), 16'(2.67 fathom), 91⁄2'(1.58 fathom), and 221⁄2'(33/4 fathom). Dimensions are total 

lengths including splices. The wing end sections 221⁄2 feet each, have 4" diameter rubber tire 

stampings cookies) on their entire length with 7 link roller chains (toggles) every 2'. The 

roller chains consist of a 3" I.D. ring of 3/8" steel rod at each end linked together by 7 links of 

5/16" chain. The distance between the end rings is 8". The footrope is passed through the 

ring at one end of the roller chain. The fishing line is passed through the ring at the other end 

of the roller chain, except for the roller chains located at joins of the fishing line or the 

footrope; then the ring is inserted in the split link or the shackle used to join the two sections. 

The two 91⁄2' (1.58 fathom) long sections and the center 16' (2.67 fathom) section have 16" 

diameter by 5" wide "Fenner" or equivalent solid, hard rubber (no spokes) rollers on them. 

Two rubber spacers, each 7” in length by 5” in diameter, separate these rollers. They have a 

21⁄4" hole through the center. Between each pair of spacers a roller chain is strung on the 

sweep. The rollers and spacers are arranged on the sweep sections so there is a single spacer 

at each end of the center 16’ (2.67 fathom) sections. On each of the 91⁄2’ (1.58 fathom) 

sections there are two spacers at the outer, wing, end and no spacers at the inner end that is 

adjacent to the center section. Each outer section has five rollers and ten spacers on it and the 

center section has 9 rollers with 18 spacers. There is a 41⁄2" diameter steel washer at each end 

of each of the 5 sections of the sweep. 

There are 42 droppers used in the sweep. Eleven droppers are placed every two feet in each 

wingend starting 2 feet forward of a dropper that is placed between the 22 1⁄2’ wing section 

and the 9 1⁄2’ roller section (see sweep diagram). There are droppers placed between the two 

spacers that separate the rollers except for the forward most spacers. Thus, each wing section 

has 11 droppers, each 9 1⁄2’ roller section has five droppers, including the dropper between the 

wing section and the roller section, and there are 10 droppers in the 16’ center section, 

including the droppers between the center section and the 9 1⁄2’ roller sections. 

Seizings

Prior to 2001, the footrope was seized to the fishing line and not to the rings that are attached 

to the droppers. This change was made to eliminate the problem of the seizings slipping and 

bunching of the footrope. 

The footrope is seized to rings that are used to attach the droppers to the sweep. The fishing 

line passes through the 3 1⁄2” circular rings that the footrope is seized. 

Liners

The after part of the upper belly is lined with 1⁄2" mesh liner material, as is the entire codend. 

Both liners are made of 1⁄2" mesh #147 knotless white nylon webbing. The belly liner is 30’ (5 

fathoms) across the leading edge, 21’ (31⁄2 fathoms) down each side, and 18’ (3 fathoms) 

across the after edge. The codend liner is 30’ (5 fathoms) around by 24’ (4 fathoms) long. 

These measurements are made with the meshes open but without stretching the webbing 

Northeast Fisheries Science Center
168

tightly. The belly liner is reinforced along the leading edge and down each side by gathering 

and seizing a 1/2' diameter roll of liner material. This roll of material is then seized to 54-

thread strengthener that is knotted with an overhand knot every 8" along its length. The top 

belly liner is attached to the inside of the top belly 35 meshes up from the after end of the 

belly. It is also seized down the sides off the belly, 1 mesh in from the gore. The after end of 

the belly liner is not seized. 

The codend liner is also reinforced along the forward edge by gathering and seizing a 1/2" roll 

of the material and then seizing onto a knotted 96/108 strengthener to it. This same technique 

is used down the gore of the liner where the two edges are joined, and down a false gore 

opposite the join. The after end is not reinforced. The codend liner is attached inside the 

codend to every mesh around the codend. This is done one and one-half mesh back from the 

codend - belly join. 

Codend

The mesh in the codend is 4 1⁄2" stretched mesh, center-to-center, single selvedge, stretched, 

and stabilized. Twine for the codend webbing is white #182 (R11764tex), 16-carrier virgin 

braided nylon. Rings are hung to the codend with codend twine at a ratio of one ring for each 

3 meshes. Rings are 2" diameter galvanized steel made from 5/16" rod stock. The codend 

measures 50 meshes deep by 80 meshes in circumference or 35 meshes between the gores. 

The remainders are taken up in the gore. Chaffing mat is constructed from 41⁄2” nylon and is 

30Wx35D. 

Legs & Ground cables

The upper legs are constructed from five fathoms of 5/8 in. wire. The lower legs are 

constructed from five fathoms of 1⁄2 in. chain. The backstraps are 9’6” of 1⁄2” Trawlex and are 

attached in the last aft hole closest to the aft end of the door. 

Doors

The doors are Portuguese Polyvalent 450 kg (see door specifications). 

NOAA Fisheries Trawl Survey Protocols
169

Northeast Fisheries Science Center
170

A 17’ idler extends 

from the junction of the 

backstraps to the door 

NOAA Fisheries Trawl Survey Protocols
171

The DELAWARE 

II uses an 

additional 11 foot 

extension between 

the backstraps and 

the legs to allow 

the crew to hook 

up the gear. 

Calibrations have 

been performed 

between the 

ALBATROSS IV

and the 

DELAWARE II

and a conversion 

factor is applied to 

data collected from 

the DELAWARE

to account for 

differences in 

catchability 

between the two 

vessels.

A 33’ idler extends 

between the extension / 

legs and the door 

Northeast Fisheries Science Center
172

NOAA Fisheries Trawl Survey Protocols
173

Northeast Fisheries Science Center

175

ATTACHMENT B 

Specifications for Construction of NEFSC 

Winter Survey Flat Net Trawl 

(60-80) 

Body of the net

The dimensions of the net sections are given in the accompanying net plans. The webbing for 

the upper and lower wings, square, and bellies is made of 4 mm dark green polyethylene 16 

carrier braided twine. The webbing is depth stretched, heat stabilized and single selvedge. The 

mesh size is 5.5 in. knot center to knot center. 

The net sections are joined together by sewing a half mesh row of double 3 mm Euro-flex twine 

green and white in color for easy identification of sections. 

The top and bottom sections of the net are joined together at their sides by a gore or laceage that 

gathers four meshes from each of the top and bottom sections. These are seized every 18 inches 

and wrapped in between the seizings using single # 120 nylon twine. 

Dog-ear meshes are woven onto the top and bottom wings with single 8 mm nylon twine. 

Gore lines

Gore lines are 3/4 in. diameter polyplus Dacron ropes that are tied to the eye of the headrope and 

extend to the end of the belly, where another eye splice is made. The codend has a separate 3/4 

in. gore line, which extends to two meshes from the aft end and is tied into the eye splice from 

the main gore line with a fisherman’s bend. The gore lines are made slightly shorter than the 

laceage and are seized to it at intervals of approximately 18 inches with single #120 nylon. 

Footrope

A 120-foot piece of 3/4 in. polyplus Dacron rope is used to construct the hanging line. The 

hanging line is marked in the middle at 60'. On either side of the middle mark, five-foot marks 

are made to hang the corners where the first dog-ear for each wing will be attached. Therefore, a 

total of 10' is used to attach the lower belly. From each corner, mark 42' towards the door end. 

The last dog is attached onto the mark of the lower wing. After the 42' mark on each side, a five 

inch eye is made by pinching the rope and tying it off with #120 nylon twine. The next section 

of rope immediately after the eye is measured and marked at seven feet and used for the up-anddown line, which is tied into the headrope eye by a clove hitch and is seven feet in length from 

eye to eye, not including the eyes.. The extra line is seized to the up and down line and used for 

future repairs. The hanging line is seized to the lower wings and belly using yorkings with a 

hitch. 

Belly Lines

The belly lines are two strengthening lines on the bottom belly made out of 5/8 in. polyplus 

Dacron rope. They are seized to the hanging line at the corner and run out and back to the gore 

line on the bar of the belly webbing, where they are seized to the webbing and to the gore line. 

Northeast Fisheries Science Center
176

Headrope

The headrope is made of 7/8 in. diameter combination manila/wire rope. It consists of three 20' 

sections. All sections have eyes swedged at each end without thimbles. The sections are joined 

by 1/2 in. marine grade hammerlocks. 

Hanging

Dog-ear meshes on the upper and lower wings are hung to both the headrope and footrope with 

seizings of single #120 braided nylon twine. The square and lower belly selvedge meshes are 

evenly hung on the headrope and footrope with single #120 braided nylon twine. Hanging 

lengths for the headrope and footrope are shown on the attached plan. 

Floats

Attached to the headrope are 13 eight-inch diameter spherical gray aluminum floats with double 

beckets. The floats are arranged with five evenly spaced in the bosom or center section of the 

net (the square), and four each evenly spaced on the wings, starting at 1.5' from the door end eye. 

Each float is attached with a 5/8 in. polyplus Dacron rope that is threaded through the beckets, 

and then seized to the backside of the headrope with #120 braided nylon twine. 

Fishing line (Combination wire) 

The Fishing line is made up of three lengths of 7/8 in. diameter combination manila/wire rope 

with swedged eyes. The wing sections are 32', and the center section is 16’; lengths include the 

swedged eyes. They are joined with 1/2 in. hammerlocks. The Fishing line is seized to the 

hanging line at evenly spaced intervals with double #54 braided nylon twine. The seizings are 

centered between the dog chains that connect the sweep at 1.5' intervals (approximately 12 

links). The excess hanging line is evenly spread out in equal sized bights. 

Sweep

The sweep consists of three lengths of chain with loosely spaced cookies. The center section of 

the sweep consists of 16' of 5/8 in (75 links) Trawlex chain with 6.5 in. rubber cookies with 

approximately 2 3/8 in. center holes. The wing sections are made from 1/2 in. Trawlex chain and 

are each 32' (183 links) in length, with 4.5 in. rubber cookies that have a center hole of 

approximately 2 1/8 in. The sections are joined with 5/8 in. hammerlocks. The rubber cookies 

are made from stamped rubber truck tires. The stamping process results in the cookies having 

varying diameters of 1⁄2 in.. The sweep is connected to the Fishing line by droppers, which 

consist of a 5/16 in. shackle, one 5/16 in. chain link, and one 5/16 in. steel ring of three-inch 

inner diameter. The shackle is connected to the sweep, and the Fishing line is threaded through 

the rings. The droppers are spaced 18 in. apart (10 links) on the sweep starting one link back 

from the end of the sweep. There are a total of 47 droppers in the construction of the sweep. 

1⁄2 in. chain extends nine feet down each wing starting eight links back from the end of the 

sweep. There are eight links between attachments and there are five attachments in the span. The 

mouth of the trawl has 23' of 1⁄2 in. tickler chain hung evenly on each side of the center of the 

sweep, with approximately 15 links between shackles for each bite. 

NOAA Fisheries Trawl Survey Protocols
177

Liners

The top belly is lined starting 30 meshes up from the bottom and sewn down the sides to the 

codend. The dimensions of the liner pieces are 30' (5 fathom) [top] x 21' (3.5 fathoms) deep x 

18' (3 fathoms) [bottom]. The liner material is #147 knotless white nylon webbing, with a mesh 

size of 1/2 in. 

The top belly liner is reinforced along the leading edge and down each side by gathering and 

seizing a 1/2 in. diameter roll. This roll is then seized to #18 braided nylon twine, used as a 

strengthener. The #18 strengthener is knotted with an overhand knot every eight-inch. The 

strengthened liner is then seized into the belly one mesh in from the gore. The remaining belly 

liner, at the start of the codend, is then left unseized and overlaps the codend liner. 

The codend is lined with #147 knotless white nylon webbing, with a mesh size of 1/2 in. and is 

15’ (2.5 fathoms) across by 24’ (4 fathoms deep). 

The codend liner is reinforced along the forward edge by gathering and seizing a 1/2 in. roll. #18 

braided nylon twine, with overhand knots every eight inch, is seized to the roll of liner material. 

This same technique is used to make a gore with the two edges of the liner. A false gore is then 

made opposite this by seizing another piece of the knotted #18 thread to the liner. The codend 

liner is attached by seizing to the codend starting at one and one half meshes from the top. The 

liner is seized at each codend mesh around the interior circumference of the codend, and then 

hangs down from this point 

Codend 

The webbing in the codend is double mesh, 5.5 inches measured between the center of the knots; 

depth stretched, and heat stabilized. The twine used to construct the webbing is made from 16-

carrier dark green polyethylene braided twine, with a diameter of 5 mm. 

The codend measures 36 meshes deep by 25 meshes across. There are five meshes gathered on 

each side in each gore. The codend is constructed from one panel of 60 meshes wide by 36 

meshes deep. 

Rings are hung at the end of the codend at a ratio of one ring for every three meshes. The rings 

are made from 5/16 in. galvanized steel, two inches ID. 

Legs & Ground cables

The upper legs are constructed from five fathoms of 5/8 in. wire. The lower legs are constructed 

from five fathoms of 1⁄2 in. chain. The ground cables are constructed from 30 fathoms of 7/8 in. 

wire. The backstraps are 9’6” of 1⁄2” Trawlex and are attached in the last aft hole closest to the aft 

end of the door. 

Doors

The doors are Portuguese Polyvalent 450 kg (see door specifications). 

Northeast Fisheries Science Center
178

NOAA Fisheries Trawl Survey Protocols
179

Northeast Fisheries Science Center
180

NOAA/NMFS Flat Net Specifications: 

Net material 

Size 5.5 in. 

Material 4 mm 16 carrier braided Poly 

Color Dark Green 

Headrope 

Length (including eyes) 61’ (three 20’ sections + 6 in. past the eye) 

Material (i.e. nylon, poly) Combination manila/wire rope 

Size (diameter) 7/8 in. 

Other Joined with paten links 

Footrope 

Length (including eyes) 80’ - See spec on page 174 

Material (i.e. nylon) Poly Dacron 

Size (diameter) 5/8 inch 

Other See spec on page 174 

Ground Gear 

Top leg - 

Size of wire 5/8 in. wire 

Length of wire 30 feet 

Other 

Bottom leg - 

Size of wire / chain 1/2 in. Trawlex chain 

Length of wire / chain 30 feet 

Other 

Ground cables – 

Size of wire 7/8 in. wire 

Length of wire / chain 30 fathom 

Other 

Gore Lines / belly strengthener 

Material 5/8 poly-plus Dacron rope 

Flotation 

Number of floats 13 

Size of floats 8 in. 

Buoyancy of floats Aluminum (Uncertain of buoyancy) 

Placement of floats Placement shown on page 175 

 

NOAA Fisheries Trawl Survey Protocols
181

Sweep Design 

Size of chain Middle = 5/8 in. Trawlex 

Outers = 1⁄2 in. Trawlex 

Length of wire Middle = 16 feet 

Outers = 32 feet 

Number of droppers or attachments Number shown on page 174 

Placement of droppers or attachment Placement shown on page 174 

Cookies 

Number Variable 

Size Middle = 6.5 in. 

Outers = 4.5 in. 

Chain Sweep 

Link size 1⁄2 in. standard chain 

Number of links 

Wing sections 82 

Center section 174 

Attachments See figure on page 174 

Codend 

Material 5 mm Double mesh green poly 5.5 in. 

Number of meshes deep 36 

Number of meshes in circumference 60 = 25 top + 25 bottom and 5 in each gore 

Liner Starts one and a half meshes back from the 

attachment to bellies. Made from #147 knotless 

white nylon webbing, with a mesh size of 1/2 in. 

Lower Belly 

Number of meshes deep 80.5 

Tapers See drawing on page 176 

 

 

Northeast Fisheries Science Center
182

SWEEP CONFIGURATION

(Drawing not to scale) 

CHAIN SWEEP CONFIGURATION

(Drawings not to scale) 

Footrope Sweep

 |----------------- 32 ‘ ------------|--------------16 ‘ ------------|------------ 32’ ----------------|

 |-------------- 4.5” cookies -----|-----------6.5” cookies-----|----------4.5” cookies --------|

|------ 9’ -------| |------ 9’ ------| |----------------------- 23’ -------------------------| 

Chain is attached as follows: 

Wing – the first attachment is 8 links (L) back from the end of the sweep. The next attachments 

are 9 L, 8 L, 8 L, 8 L. 

Center – the first attachment is 15 L, then 14 L, all others are 15 L. There are a total of 15 

attachments 

Droppers are attached as follows: 

The first dropper is attached 4 links back from the door end of the sweep. Thereafter, 

there is 10 links between droppers. There are 47 attachments. 

DROPPER CONFIGURATION

NOAA Fisheries Trawl Survey Protocols
183

HEADROPE CONFIGURATION

(Drawing not to scale) 

Eyes and hammer link Eyes and hammer link 

Total length of headrope = 61’2” 

Floats 

Northeast Fisheries Science Center
184

NET CONFIGURATION: 

(Drawing not to scale) 

Tapers: 

Lower Wing = 1M, 10B, 1M, 10B, 1M, 10B, 1M, 9B. 

Upper Wing = 3M, 1B 

Square = 1M, 4B 

Belly = 1M, 4B, 1M, 3B, 1M, 3B, 

D 

59 1⁄2 

30 1⁄2 

80 1⁄2 

90 dog ears 

59 dog ears 

10 

45 

60 

30 

140 140 

180 

40 40 

D

90 1⁄2 

NOAA Fisheries Trawl Survey Protocols
185

Northeast Fisheries Science Center

187

ATTACHMENT C 

Yankee 36 Checklist Roller Net Date _____/_____/_____ 

 

Net number:

Gear shed Inspectors: 

Woods Hole Inspector(s): 

OK Problems/Comments FIXED

Up and Down line: Check for wear and 

make sure hangings are not bunched up. 

Also, check seizing at fishing line. The 

length including the eye should be 7 feet (6 

1⁄2’ without the eye). 

 

Wings: Check dog-ear meshes to ensure 

they are hung evenly allowing for no 

"pockets" of twine. This allows the wings 

and floats to rise properly. 

 

Headrope: Check for wear or brittle 

strands of wire. Also, check eye splices for 

flattened strands where the wire's core is 

exposed or wire is broken. 

 

Float line: Check to ensure the line is 

secured and snug to the headrope and the 

floats do not have excessive play. 

 

Floats: Count floats to make sure all 36 

are evenly spaced (20 located in the center 

and 8 on each wing). Check floats for 

cracks and flooding. 

Droppers: From wing end to wing end 

there are 42 dropper chains located in the 

sweep section. Make sure the small chain 

is not stretched, distorted, and that the rings 

have not broken off or split.

Footrope: Check to ensure the center mark 

of the footrope is hung in the center of the 

roller sweep. Each corner mark is hung 5 

feet from the center back towards the door 

end.

 

Northeast Fisheries Science Center
188

Net number: OK Problems/Comments FIXED

Footrope Seizings: Check seizings for 

wear and to ensure the rings are evenly 

spaced and the seizings are tight. They 

should not slip. 

 

Fishing line (combo) Check for wear at 

eye splices and where it passes through 

dropper chain rings.

 

 

 

Sweep: Check to ensure the correct 

amount of rollers (19) and spacers (38) are 

in use. Also, check for wear on rollers. 

After a hang, check rollers and metal 

sleeves for damage. Check the length of 

the wing end sections, these should 

measure 22 1⁄2’.

 

 

Square: Check to ensure the center of the 

square is hung in the center of the 

headrope. Count the meshes across from 

one wing corner to the other wing corner. 

There should be 60 meshes across (30 to 

the middle). 

 

Upper Belly: Check upper belly liner to 

ensure it is attached properly. It should 

start 35 meshes up from the end of the top 

belly where it joins the cod end. It is then 

sewn down each side one mesh in from the 

gore. 

 

Bottom Belly: Check for wear in the 

bosom section of bottom belly close to the 

roller sweep. Also, check for bunching of 

twine in the bosom area after a hang. 

 

Liners: Check liner for holes. Check to 

ensure that liner is of proper length. It 

should hang a minimum of three feet out of 

the bottom of the bag when it is empty. 

 

Mesh sizes: Periodically check the mesh 

size of the Standard #36 Bottom Trawl 

(body is 5-inch mesh and cod end is 4 1/2 

inch). Look for deformity, slipped knots, 

and meshes made oversize or undersize 

during repair work. 

 

NOAA Fisheries Trawl Survey Protocols
189

Net number: OK Problems/Comments FIXED

Gore Lines: Gore lines should be checked 

for wear and ensure there are no excess 

pockets of twine. 

 

Cod end: Check for appropriate amount of 

rings (minimum of 26, maximum of 30). 

Check length and width of codend. Codend 

should measure 50 meshes deep by 35 

meshes across not including meshes in the 

gore.

 

 

Doors: Check to make sure the shoes have 

an edge and are not rounded. Check the 

stops on the brackets to make sure they are 

present and there is no vertical movement 

of the brackets . 

 

Backstraps: Check to make sure 

backstraps are attached to the last hole on 

the door, are nine feet six inches long and 

that three swivels are present, two at the 

attachment to the door and one between the 

legs (or extension on the DE II) and the 

backstraps. Check the condition of the 

chain to ensure that it has not worn to a 

point where it is likely to break.

Legs: Check to make sure all legs measure 

30 feet and are constructed from 5/8 inch 

wire. This task is usually performed on the 

vessel.

Extension (DE II only): Check to make 

sure both extensions measure 11 feet. 

After a Hang: If it is possible to determine what part of the net was caught, check the surrounding area for torn mesh, 

broken lines and combination wires, or knots that may have slipped. Otherwise, check the gear for signs of damage and pay 

close attention to the sweep, wings, and lower belly. 

Other Remarks 

 

 

Northeast Fisheries Science Center

191

ATTACHMENT D 

Northeast Fisheries Science Center
192

ATTACHMENT E 

NEFSC 36 YANKEE NET WIRE OUT TO DEPTH SCOPE 

AMOUNT OF WIRE MEASURED FROM THE TRAWL DOORS TO THE SURFACE 

 

DEPTH WIRE OUT DEPTH WIRE OUT DEPTH WIRE OUT DEPTH WIRE OUT DEPTH WIRE OUT DEPTH WIRE OUT

M M M M M M M M M M M M 

<18 75 77 231 137 411 197 493 257 643 317 793 

18 72 78 234 138 414 198 495 258 645 318 795 

19 76 79 237 139 417 199 498 259 648 319 798 

20 80 80 240 140 420 200 500 260 650 320 800 

21 84 81 243 141 423 201 503 261 653 321 803 

22 88 82 246 142 426 202 505 262 655 322 805 

23 92 83 249 143 429 203 508 263 658 323 808 

24 96 84 252 144 432 204 510 264 660 324 810 

25 100 85 255 145 435 205 513 265 663 325 813 

26 104 86 258 146 438 206 515 266 665 326 815 

27 108 87 261 147 441 207 518 267 668 327 818 

28 84 88 264 148 444 208 520 268 670 328 820 

29 87 89 267 149 447 209 523 269 673 329 823 

30 90 90 270 150 450 210 525 270 675 330 825 

31 93 91 273 151 453 211 528 271 678 331 828 

32 96 92 276 152 456 212 530 272 680 332 830 

33 99 93 279 153 459 213 533 273 683 333 833 

34 102 94 282 154 462 214 535 274 685 334 835 

35 105 95 285 155 465 215 538 275 688 335 838 

36 108 96 288 156 468 216 540 276 690 336 840 

37 111 97 291 157 471 217 543 277 693 337 843 

38 114 98 294 158 474 218 545 278 695 338 845 

39 117 99 297 159 477 219 548 279 698 339 848 

40 120 100 300 160 480 220 550 280 700 340 850 

41 123 101 303 161 483 221 553 281 703 341 853 

42 126 102 306 162 486 222 555 282 705 342 855 

43 129 103 309 163 489 223 558 283 708 343 858 

44 132 104 312 164 492 224 560 284 710 344 860 

45 135 105 315 165 495 225 563 285 713 345 863 

46 138 106 318 166 498 226 565 286 715 346 865 

47 141 107 321 167 501 227 568 287 718 347 868 

48 144 108 324 168 504 228 570 288 720 348 870 

49 147 109 327 169 507 229 573 289 723 349 873 

50 150 110 330 170 510 230 575 290 725 350 875 

51 153 111 333 171 513 231 578 291 728 351 878 

52 156 112 336 172 516 232 580 292 730 352 880 

53 159 113 339 173 519 233 583 293 733 353 883 

54 162 114 342 174 522 234 585 294 735 354 885 

55 165 115 345 175 525 235 588 295 738 355 888 

56 168 116 348 176 528 236 590 296 740 356 890 

57 171 117 351 177 531 237 593 297 743 357 893 

58 174 118 354 178 534 238 595 298 745 358 895 

59 177 119 357 179 537 239 598 299 748 359 898 

60 180 120 360 180 540 240 600 300 750 360 900 

61 183 121 363 181 543 241 603 301 753 361 903 

62 186 122 366 182 546 242 605 302 755 362 905 

63 189 123 369 183 549 243 608 303 758 363 908 

64 192 124 372 184 460 244 610 304 760 364 910 

65 195 125 375 185 463 245 613 305 763 365 913 

66 198 126 378 186 465 246 615 306 765 366 915 

67 201 127 381 187 468 247 618 307 768 

68 204 128 384 188 470 248 620 308 770 M SCOPE 

69 207 129 387 189 473 249 623 309 773 <18 75M 

70 210 130 390 190 475 250 625 310 775 

71 213 131 393 191 478 251 628 311 778 18-27 4:1 

72 216 132 396 192 480 252 630 312 780 

73 219 133 399 193 483 253 633 313 783 28-183 3:1 

74 222 134 402 194 485 254 635 314 785 

75 225 135 405 195 488 255 638 315 788 >184 2.5:1 

76 228 136 408 196 490 256 640 316 790 Version 3.2 . 

 

NOAA Fisheries Trawl Survey Protocols
193

ATTACHMENT F 

Example of station allocation to strata: 

 # Stations # Stations

Stratum Spring survey Fall survey Winter survey Stratum Spring survey Fall survey Winter survey 

1010 7 7 8 3060 1 1 0 

1020 7 7 8 3070 2 2 0 

1030 2 2 4 3080 2 2 0 

1040 1 1 2 3090 1 1 0 

1050 5 5 7 3100 2 2 0 

1060 8 8 12 3110 2 2 0 

1070 2 2 4 3120 1 1 0 

1080 1 1 2 3130 2 2 0 

1090 5 5 7 3140 2 2 0 

1100 8 8 12 3150 1 1 0 

1110 2 2 4 3160 2 2 0 

1120 1 1 2 3170 2 2 0 

1130 9 9 9 3180 1 1 0 

1140 3 3 4 3190 2 2 0 

1150 1 1 2 3200 2 2 0 

1160 10 10 10 3210 1 1 0 

1170 3 3 3 3220 2 2 0 

1180 1 1 2 3230 2 2 0 

1190 9 9 9 3240 2 2 0 

1200 6 6 6 3250 2 2 0 

1210 4 4 4 3260 2 2 0 

1220 4 4 4 3270 1 1 0 

1230 5 5 5 3280 2 2 0 

1240 6 6 9 3290 2 2 0 

1250 4 4 0 3300 1 1 0 

1260 5 5 0 3310 2 2 0 

1270 4 4 0 3320 2 2 0 

1280 7 7 0 3330 1 1 0 

1290 8 8 0 3340 2 2 0 

1300 3 3 0 3350 2 2 0 

1330 4 4 0 3360 2 2 0 

1340 6 6 0 3370 2 2 0 

1351 2 2 0 3380 2 2 0 

1360 8 8 0 3390 1 1 0 

1370 5 5 0 3400 2 2 0 

1380 5 5 0 3410 2 2 0 

1390 5 5 0 3420 1 1 0 

1400 3 3 0 3430 2 2 0 

1610 3 3 7 3440 2 2 0 

1620 2 2 3 3450 2 2 0 

1630 2 2 4 3460 2 2 0 

1640 1 1 2 3550 5 5 0 

1650 7 7 12 3560 1 1 0 

1660 3 3 4 3580 1 1 0 

1670 2 2 4 3590 1 1 0 

1680 1 1 2 3600 2 2 0 

1690 6 6 9 3610 2 2 0 

1700 4 4 5 3630 1 1 0 

1710 2 2 4 3640 1 1 0 

1720 1 1 2 3650 1 1 0 

1730 5 5 5 3660 2 2 0 

1740 4 4 5 7510 2 2 0 

1750 2 2 4 7520 2 2 0 

1760 1 1 2 8500 4 4 0 

3020 2 2 0 8510 2 2 0 

3030 1 1 0 8520 2 2 0 

3040 2 2 0 

3050 2 2 0 Sum all 332 332 213 

Northeast Fisheries Science Center
194

ATTACHMENT G 

NOAA Fisheries Trawl Survey Protocols
195

Northeast Fisheries Science Center
196

NOAA Fisheries Trawl Survey Protocols
197

Northeast Fisheries Science Center
198

NOAA Fisheries Trawl Survey Protocols
199

Northeast Fisheries Science Center
200

NOAA Fisheries Trawl Survey Protocols
201

Northeast Fisheries Science Center
202

NOAA Fisheries Trawl Survey Protocols
203

ATTACHMENT H 

Northeast Fisheries Science Center
204

ATTACHMENT I 

VOLUNTEER APPRAISAL 

Volunteer / Contractor Name: _______________________________________ 

Cruise: ________________ Leg #: ____________ Start date of cruise: ________ / ________ / _______ 

Chief Scientist or Watch Chief: _________________________________________ 

I would would NOT (check one) recommend the above volunteer for future cruises. 

Comments (please elaborate, especially if you would NOT recommend the volunteer): 

When complete, please update Contractors.xls file in shared 

files\cruise_staffing\contractors.xls 

NOAA Fisheries Trawl Survey Protocols
205

ATTACHMENT J 

STATION VALUE - STATION TYPE CODE: 

1=Survey haul (random-stratified) 

2=Non-random haul 

3=Special random add-on station haul 

4=Comparison haul 

5=No trawl haul (e.g., bongo, CTD or XBT) 

6=Site-specific 

7=Systematic grid 

8=Depletion site 

9=Systematic parallel transects 

0=Systematic zig zag transects 

HAUL VALUE - CODE FOR RELATIVE SUCCESS OF HAUL: 

1=Good tow. No gear or tow duration problem. 

2=Representative, but some problem encountered due to gear or tow duration. 

3=Problem tow. May or may not be representative due to gear or tow duration. 

4=Not representative, due to gear or tow duration. 

5=No bottom trawl (e.g., bongo, CTD or XBT ONLY). 

GEAR CONDITION - CODE FOR GEAR CONDITION: (ALL GEAR PROBLEMS MUST BE NOTED ON 

TRAWL LOG OR IN FSCS WC COMMENTS SECTION) 

 

1=No damage or insignificant damage. 

2=Wing twisted or tears in upper or lower wings not exceeding 10 ft; tear in square not exceeding 5 ft; tears not 

exceeding 3 ft in upper belly, or 6 ft in lower belly; cod-end or liner with tears not exceeding 2 ft; parted idler; 

liner hanging out of cod-end; 1-2 floats missing, bottom falls out for a few minutes. 

3=Hung up with no to minor damage or due to sand waves. 

4=Parted legs, sweep or head-rope; cod-end liner untied; wire out slippage; floats, rope or buoys hung up on 

door, loss of a few cookies. 

5=Tear-up exceeding limits for code 2, but not a total failure. 

6=Significant obstruction in trawl, such as fixed gear, large rocks, mud, coral, tires, old anchors, timbers etc. 

Problem with third wire; unmatched doors; strong current throughout tow. 

7=Crossed doors. Net was not on bottom or did not perform due to currents or other factors. 

8=Open gear. 

9=Hung up with major damage; total tear-up, rim-rack; loss of all gear; loss of trawl; loss of one or both doors. 

(Note: This is version of the SHG coding details does not contain all coding criteria) 

Northeast Fisheries Science Center