U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

NOAA Technical Memorandum NMFS-F/SPO-66

October 2004

Evaluating Bycatch

A National Approach to Standardized

Bycatch Monitoring Programs

Evaluating Bycatch

A National Approach to Standardized

Bycatch Monitoring Programs
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-F/SPO-66

October 2004

Evaluating Bycatch:

A National Approach to Standardized

Bycatch Monitoring Programs

iii

Acknowledgments

The methodological approach for determining bycatch was developed through a series of

meetings and conference calls by a team of the National Marine Fisheries Service (NMFS) over

a 9-month period beginning in early 2003. This was followed by internal and external reviews

and responses that resulted in this final report. The team was made up of fisheries managers and

scientists from NMFS Regional Offices, Science Centers and headquarters:

Joseph E. Powers, Chair Southeast Fisheries Science Center, Miami, Florida

Lee Benaka Office of Sustainable Fisheries, Silver Spring, Maryland

Victoria R. Cornish Office of Science and Technology, Silver Spring, Maryland

Jonathan Cusick Northwest Fisheries Science Center, Seattle, Washington

Tanya Dobrzynski Office of Protected Resources, Silver Spring, Maryland

Michael Fogarty Northeast Fisheries Science Center, Woods Hole,

Massachusetts

Svein Fougner Southwest Regional Office, Long Beach, California

James M. Nance Southeast Fisheries Science Center, Galveston, Texas

Joseph M. Terry Alaska Fisheries Science Center, Seattle, Washington

Colleagues throughout NMFS provided voluminous data, information, comments and

suggestions throughout the development of this report. We thank them for their efforts in

ensuring that all perspectives were heard and for providing insight into frequently contentious

aspects of bycatch in their regions. 

Cover photo credits: background photos by Conor Nolan, MRAG Americas (under contract to

the NMFS Observer Program), and Tom Wilson, NMFS Observer; small photos were taken by

Brett Jagger, NMFS Groundfish Observer. 

 

To be cited as:

NMFS (National Marine Fisheries Service). 2004. Evaluating bycatch: a national approach to

standardized bycatch monitoring programs. U.S. Dep. Commer., NOAA Tech. Memo. NMFSF/SPO-66, 108 p. On-line version, http://spo.nmfs.noaa.gov/tm 

For additional copies, contact:

NMFS Office of Sustainable Fisheries 

1315 East-West Highway, 13th Floor 

Silver Spring, MD 20910 

v

Executive Summary

On March 6, 2003, the National Marine Fisheries Service (NMFS) issued a National

Bycatch Strategy to address issues related to the management of bycatch within the Nation’s

fisheries. One component of that strategy was the establishment of a National Working Group

on Bycatch (NWGB) to develop a national approach to standardized bycatch reporting

methodologies and monitoring programs. This work is to be the basis for regional teams (also

established in the National Bycatch Strategy) to make fishery-specific recommendations.

The NWGB reviewed regional issues related to fisheries and bycatch and discussed

advantages and disadvantages of various methods for estimating bycatch, including: (1) fisheryindependent surveys; (2) self-reporting through logbooks, trip reports, dealer reports, port

sampling, and recreational surveys; (3) at-sea observation, including observers, digital video

cameras, digital observers, and alternative platform and remote monitoring; and (4) stranding

networks. All of the methods may contribute to useful bycatch estimation programs, but at-sea

observation (observers or electronic monitoring) provides the best mechanism to obtain reliable

and accurate bycatch estimates for many fisheries. Often, observer programs also will be the

most cost-effective of these alternatives.

At-sea sampling designs should be formulated to achieve precision goals for the least

amount of observation effort, while also striving to increase accuracy. This is done through

random sample selection, by developing appropriate sampling strata and sampling allocation

procedures and by implementing appropriate tests for bias. These designs and tests are needed

for each fishery. Sampling programs will be driven by the precision and accuracy required by

managers to address management needs: for estimating management quantities such as allowable

catches through a stock assessment, for evaluating bycatch relative to a management standard

such as allowable take and for developing mitigation mechanisms. The recommended precision

goals for estimates of bycatch are defined in terms of the coefficient of variation (CV) of each

estimate. The recommended goals are as follows:

Protected Species

For marine mammals and other protected species, including seabirds and sea

turtles, the recommended precision goal is a 20-30% CV for estimates of bycatch

for each species/stock taken by a fishery.

Fishery Resources

For fishery resources, excluding protected species, caught as bycatch in a fishery,

the recommended precision goal is a 20-30% CV for estimates of total discards

(aggregated over all species) for the fishery; or if total catch cannot be divided

into discards and retained catch then the goal is a 20-30% CV for estimates of

total catch.
vi

These CV goals are the levels of precision that NMFS will strive to achieve. However, it

is important to recognize that:

• The goals may in some instances exceed minimum statutory requirements.

• There are intermediate steps in increasing precision that may not immediately

achieve the goals but that represent progress nonetheless.

• There are circumstances in which higher levels of precision may be desired,

particularly when management is needed on fine spatial or temporal scales.

• There are circumstances under which meeting these precision goals would not be

an efficient use of public resources.

• Funding and logistical constraints, safety considerations and additional objectives

for observer programs may prevent the attainment of these goals.

• When a numeric limit is set for a bycatch species, the uncertainty associated with

setting that limit and the methods used for addressing that uncertainty are two of

the factors that determine the appropriate CV for the bycatch estimate for that

species.

• If CVs of 20-30% for individual fishery species can be obtained and are needed

for management, then this precision should be encouraged.

• In some instances decreasing bias (including that caused by the observer effect)

will be more important than increasing precision.

• The absolute precision (in numbers of animals) may be more appropriate than the

percent precision for some protected species (see Appendix 4 for technical

comments on this issue).

• If bycatch is being monitored principally in order to manage a fishery within

bycatch limits, an alternative to the above CV goals is to set the bycatch limits

based on a management regime that incorporates uncertainty (see Section 5.4).

• Flexibility is needed when setting CV targets for specific fisheries and bycatch

species.

• A decision to accept lower precision should be based on analyses and

understanding of the implications of that decision.
vii

Eighty-four fisheries were evaluated for bycatch monitoring and classified into one of

five categories (None, Baseline, Pilot, Developing, or Mature). Additionally all of these fisheries

were rated as to their vulnerability (High, Moderate or Low) to bycatch of three types of

resources: (1) fishery resources (excluding protected species); (2) marine mammals; and (3) other

protected species, that is, ESA-listed species (excluding marine mammals), other sea turtles and

other seabirds. Of the 84 fisheries, 5% have a Mature observer program, 20% were Developing

(25% were either Mature or Developing), 10% have a Pilot program, 29% have a Baseline

program and 37% do not have a program (None). (Note that the percentages sum to 101 due to

rounding.) Thirty-one percent of these 84 fisheries are rated High for bycatch vulnerability of

one or more of the three resource types (thus, 69% are rated Moderate or Low for all three types

of resources); 6% of these fisheries are both rated High for bycatch vulnerability of one or more

of the three resource types and recommended for establishment of Baseline or Pilot observer

programs. A strategy for bycatch monitoring was developed based upon the vulnerability of a

fishery, the adequacy of current monitoring programs and sampling cost estimates.

ix

Table of Contents

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

1. Introduction ............................................................1

2. Statutory Requirements and International Agreements . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Magnuson-Stevens Fishery Conservation and Management Act . . . . . . . . . . . . . 3

2.2 Endangered Species Act . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.3 Marine Mammal Protection Act . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4 FAO Code of Conduct for Responsible Fisheries .........................6

3. Regional Characteristics of Bycatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.1 Southwest Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.2 Southeast Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Northwest Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4 Alaska Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.4.1 Groundfish Fisheries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.4.2 Pacific Halibut Fisheries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.4.3 MMPA Category II Salmon Fisheries . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.5 Northeast Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.6 Pacific Islands Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4. Alternative Methods for Monitoring Bycatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1 Fishery-Independent Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1.1 Costs of Estimating Bycatch from Fishery-Independent Surveys . . . . . . 26

4.1.2 Safety Aboard Fishery-Independent Surveys . . . . . . . . . . . . . . . . . . . . . . 27

4.1.3 Summary of Fishery-Independent Surveys . . . . . . . . . . . . . . . . . . . . . . . 27

4.2 Fishery-Dependent Self-Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2.1 Logbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2.1.1 Accuracy of Logbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2.1.2 Costs Associated with Logbook Programs . . . . . . . . . . . . . . . . . 32

4.2.1.3 Safety and Logistics of Logbooks . . . . . . . . . . . . . . . . . . . . . . . . 32

4.2.1.4 Logbook Program Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
x

4.2.2 Port Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.2.3 Recreational Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.3 At-Sea Observations of Fishing Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3.1 At-Sea Observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3.1.1 Estimating Bycatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3.1.2 Precision of Bycatch Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.3.1.3 Accuracy and Bias of Bycatch Estimates . . . . . . . . . . . . . . . . . . . 37

4.3.1.4 Cost and Logistics in Observer Programs . . . . . . . . . . . . . . . . . . 39

4.3.1.5 Safety in Observer Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4.3.1.6 Observer Programs Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4.3.2 Digital Video Cameras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

4.3.3 Digital Observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.3.4 Alternate Platforms and Remote Monitoring . . . . . . . . . . . . . . . . . . . . . . 43

4.4 Stranding Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5. Estimation of Bycatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

5.1 Definition of Bycatch and Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

5.2 Estimation from At-Sea Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5.2.1 Sample Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

5.2.2 Sampling Strata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.2.3 Sample Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.2.4 Estimators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5.2.5 Sample Size Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

5.2.6 Accuracy and Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

5.3 Precision of Bycatch Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

5.3.1 Management Uses of Bycatch Estimates . . . . . . . . . . . . . . . . . . . . . . . . . 55

5.3.1.1 Assessment Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.3.1.2 Monitoring Relative to Management Standards . . . . . . . . . . . . . 56

5.3.1.3 Developing Mitigation Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.3.2 Precision of Bycatch Estimates from Fisheries . . . . . . . . . . . . . . . . . . . . 57

5.4 Precision Goals for Estimating Bycatch from a Fishery . . . . . . . . . . . . . . . . . . . 58

5.5 Other Factors That May Affect Observer Coverage Levels . . . . . . . . . . . . . . . . . 60

6. Status of At-Sea Observation Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.1 A Survey of Observation Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.2 Enhancement of Observer Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
xi

6.2.1 Criteria for Enhancing Observer Programs . . . . . . . . . . . . . . . . . . . . . . . 64

6.2.2 Enhanced Sample Sizes and Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

7. Vulnerability of Fisheries to Adverse Impacts of Bycatch . . . . . . . . . . . . . . . . . . . . . . . 79

7.1 Vulnerability Criteria for Fishery Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

7.2 Vulnerability Criteria for Marine Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

7.3 Vulnerability Criteria for Other Protected Species, Including Seabirds . . . . . . . 81

7.4 Bycatch Vulnerability of Fisheries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

8. Strategies to Address Bycatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

8.1 The Nature and Source of the Bycatch Problem . . . . . . . . . . . . . . . . . . . . . . . . . 85

8.2 Information Needed to Implement an Effective and Efficient Solution to the

Bycatch Problem for the Fishery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

8.3 Expected Net Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

8.4 Setting National Priorities for Improving Bycatch Monitoring . . . . . . . . . . . . . . 87

9. Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Appendix 1. 

Definition of Bycatch Terms 

(from NMFS 1998a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Appendix 2. 

A Characterization of the Relationship Between the Precision of the Assessment

Components and the Precision of Management Quantities . . . . . . . . . . . . . . . . . . . . . . . 95

Appendix 3. 

Precision of a Bycatch Estimate of an Aggregate of Species and the Precision of

Estimates of Individual Species within the Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Appendix 4. 

Comments on Precision Requirements for Rare-event Species . . . . . . . . . . . . . . . . . . . . 99

Appendix 5.

NMFS Objectives, Protocol, and Recommended Precision Goals 

for Standardized Bycatch Reporting Methodologies . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
xii

Appendix 6.

Acronyms Used in this Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
1

Unobserved mortality is mortality of living marine resources due to a direct encounter with

fishing gear that does not result in the capture of that species by a fisherman. This includes

mortality due to lost or discarded fishing gear, as well as fish and other species that escape from

fishing gear before it is retrieved but die due to the stress or injury resulting from the encounter.

2

 NMFS (1998a) notes: After careful review of the various definitions of bycatch and associated

terms, NMFS considered the definitions contained in the Magnuson-Stevens Act as the basis for

development of an inclusive definition of bycatch. The Magnuson-Stevens Act defines bycatch

as “fish which are harvested in a fishery, but which are not sold or kept for personal use . . . ” To

fully meet the agency’s responsibilities, as defined principally by the Magnuson-Stevens Act, the

Marine Mammal Protection Act, and the Endangered Species Act, NMFS expanded this

definition. Specifically, living marine resources other than “fish” as defined in the MagnusonStevens Act (i.e., marine mammals and seabirds) were included to consider all species taken or

encountered in marine fisheries and “retained catch of non-target species was included.”

1

1. Introduction

Bycatch for the purposes of this report is defined as the discarded catch of any living

marine resource plus unobserved mortality1

 due to a direct encounter with fishing gear. This

definition is based on the bycatch definition that appears in the 1998 National Marine Fisheries

Service (NMFS) report Managing the Nation’s Bycatch (NMFS 1998a)2 but it does not include

retained incidental catch as a component of bycatch. However, NMFS is aware that for some

species, such as protected species, the primary management concern is the level of incidental

catch, not the disposition of that catch. To meet its stewardship responsibilities, NMFS is

committed both to account for target catch, retained incidental catch and bycatch and to decrease

each of these three sources of fishing morality as appropriate to prevent overfishing, to rebuild

overfished stocks and in general to provide the greatest net benefits to the Nation over time from

the fisheries.

Bycatch occurs if a fishing method is not perfectly selective. A fishing method is

perfectly selective if it results in the catch and retention only of the desired size, sex, quality, and

quantity of the desired species without other fishing-related mortality (See Appendix 1 for related

definitions from NMFS 1998a). Very few fishing methods are perfectly selective and typically

the discard survival rate is less than 100 %; therefore, bycatch is a source of fishing mortality in

most fisheries.

The Magnuson-Stevens Fishery Conservation and Management Act (MSA), the

Endangered Species Act (ESA), the Marine Mammal Protection Act (MMPA), and international

agreements identify the stewardship responsibilities of NMFS (NOAA Fisheries) to lead and

coordinate the Nation’s collaborative effort to monitor and reduce the bycatch of living marine

resources. As part of its efforts to meet these responsibilities, NMFS reported on the scope and

complexity of bycatch in the United States and approaches to addressing bycatch problems

(NMFS 1998a). In early 2003, NMFS developed a National Bycatch Strategy to monitor and

mitigate bycatch within the Nation’s fisheries. Within that strategy, a National Working Group

on Bycatch (NWGB) was appointed to formulate procedures for monitoring bycatch, in particular

to provide information that could be used to develop standardized bycatch reporting
2

methodologies. This report presents the results of the efforts of the NWGB and should guide the

NMFS efforts to further develop bycatch monitoring and mitigation programs.

The report includes the following: (1) a review of the statutory requirements and

international agreements to monitor and reduce bycatch; (2) updated discussions of the regional

perspectives on bycatch problems; (3) an evaluation of the options that are available to monitor

bycatch; (4) an evaluation of statistical design and precision criteria for monitoring bycatch; (5) a

fishery-by-fishery examination of current monitoring capabilities; and (6) suggested priorities for

addressing bycatch problems. 
3

2. Statutory Requirements and International Agreements 

NMFS has a variety of bycatch monitoring and reduction responsibilities. They are

identified in its governing statutes and in international agreements. The former (e.g., the MSA,

ESA, and MMPA) include bycatch responsibilities that were constructed to respond to bycatch

concerns for different species in different ways. Throughout this report, bycatch monitoring and

reduction activities and responsibilities should be viewed within the context of relevant statutory

requirements and standards for fish, marine mammals, and other protected species, including

seabirds and sea turtles. Links to these laws, as well as a variety of additional bycatch-related

resources, are available at the NMFS bycatch website: http://nmfs.noaa.gov/bycatch.htm

2.1 Magnuson-Stevens Fishery Conservation and Management Act

The 1996 amendments to what is now titled the Magnuson-Stevens Fishery Conservation

and Management Act (MSA) defined the term “bycatch” and required that it be minimized to the

extent practicable. Bycatch, as defined by the MSA (16 U.S.C. § 1802 (2)), “means fish which

are harvested in a fishery, but which are not sold or kept for personal use, and includes economic

discards and regulatory discards. Such a term does not include fish released alive under a

recreational catch and release fishery management program.” The term “fish” is defined in the

MSA to mean “finfish, mollusks, crustaceans, and all other forms of marine animal and plant life

other than marine mammals and seabirds.” Therefore, the bycatch reduction and monitoring

requirements in the MSA apply to a broad range of living marine species, including finfish and

shellfish, as well as sea turtles and deep-water corals, but they do not apply to marine mammals

and birds. Economic discards are “fish which are the target of a fishery, but which are not

retained because of an undesirable size, sex, or quality, or other economic reason.” “The term

‘regulatory discards’ means fish harvested in a fishery which fishermen are required by

regulation to discard whenever caught, or are required by regulation to retain but not sell.”

National Standard 9 of the MSA requires that “conservation and management measures

shall, to the extent practicable, (A) minimize bycatch and (B) to the extent bycatch cannot be

avoided, minimize the mortality of such bycatch” (16 U.S.C. § 1851(9)). Sec. 303 of the MSA

expands on this requirement somewhat, stating that fishery management plans are required to

“establish a standardized reporting methodology to assess the amount and type of bycatch

occurring in the fishery, and include conservation and management measures that, to the extent

practicable and in the following priority (A) minimize bycatch; and (B) minimize the mortality of

bycatch which cannot be avoided” (16 U.S.C. § 1853(11)).

NMFS regulations at 50 CFR 600.350(d)(3) provide the following guidance on factors

that should be considered in determining the practicability of a particular management action to

minimize bycatch or the mortality of bycatch. They state, “A determination of whether a

conservation or management measure minimizes bycatch or bycatch mortality to the extent

practicable, consistent with other national standards and maximization of net benefits to the

Nation, should consider the following factors: (A) Population effects for bycatch species; (B)

Ecological effects due to changes in the bycatch of that species (effects on other species in the

ecosystem); (C) Changes in the bycatch of other species of fish and the resulting population and

ecosystem effects; (D) Effects on marine mammals and birds; (E) Changes in fishing, processing,

disposal, and marketing costs; (F) Changes in fishing practices and behavior of fishermen; (G)
4

Changes in research, administration, and enforcement costs and management effectiveness; (H)

Changes in the economic, social, or cultural value of fishing activities and non-consumptive uses

of fishery resources; (I) Changes in the distribution of benefits and costs; and (J) Social effects.” 

Although the MSA excludes fish released alive under a recreational catch and release

fishery management program, from its definition of bycatch, Section 303(a)(12) of the MSA,

states that any fishery management plan shall “assess the type and amount of fish caught and

released alive during recreational fishing under catch and release fishery management programs

and the mortality of such fish, and include conservation and management measures that, to the

extent practicable, minimize mortality and ensure survival of such fish.” Therefore, for purposes

of this report, bycatch will be defined more broadly over both commercial and recreational

fisheries. However, the distinction between commercial and recreational bycatch will be

addressed when developing mechanisms and strategies for monitoring bycatch. 

2.2 Endangered Species Act

The ESA requires the federal government to protect and conserve species and populations

that are endangered, or threatened with extinction, and to conserve the ecosystems on which

these species depend. Some of these threatened and endangered species, including certain

species of sea turtles, Pacific salmon, seabirds and marine mammals, are captured as bycatch in

the Nation’s fisheries. Under the ESA’s protection process, after a species is identified as

threatened or endangered, a recovery plan that outlines actions to improve the species’ status is

prepared and implemented. Recovery plans for marine species generally include a prescription

for reducing incidental capture of protected species in commercial fishing operations. In some

cases, fisheries can be restricted or terminated because they impose mortality rates on protected

species that impede the recovery of the listed population. Other provisions of the ESA ensure

that sources of mortality for protected species are identified and minimized or mitigated.

The bycatch reduction requirements of the ESA follow from Section 9(a)(1)(B) and

9(a)(1)(C) of the ESA, which prohibit the take of endangered species within the United States or

the territorial sea of the United States, and on the high seas, respectively. “Take” is defined by

the ESA as “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or attempt

to engage in any such conduct” (16 U.S.C. 1536(18)). ESA Sections 4, 6, 7 and 10 provide

mechanisms for the limited take of ESA-listed species. Of particular relevance for fisheries

bycatch is Section 7, which provides that “Each Federal agency shall ... insure that any action

authorized, funded, or carried out by such agency ... is not likely to jeopardize the continued

existence of any endangered species or threatened species or result in the destruction or adverse

modification of habitat of such species ...” (16 U.S.C. §1536(a)(2)).

Both NMFS and the U.S. Fish and Wildlife Service develop Biological Opinions

pursuant to a formal consultation under Section 7 of the ESA to assess the impact of proposed

activities on species under their respective jurisdictions. If the resulting Biological Opinion finds

that the proposed activity is likely to result in jeopardy to the species or adverse modification of

its habitat, the Biological Opinion will outline Reasonable and Prudent Alternatives (RPAs) that

must be taken to ensure that the species is not jeopardized. If the Biological Opinion finds that

the proposed activity is likely to result in bycatch of an endangered species, then an Incidental

Take Statement is issued that specifies the impact of any incidental taking, as well as RPAs, and
3

 The term "potential biological removal level" means the maximum number of animals, not

including natural mortalities, that may be removed from a marine mammal stock while allowing

that stock to reach or maintain its optimum sustainable population. The potential biological

removal level is the product of the following factors: (A) The minimum population estimate of

the stock; (B) One-half the maximum theoretical or estimated net productivity rate of the stock at

a small population size; and (C) A recovery factor of between 0.1 and 1.0. (16 U.S.C. 1362(20)).

5

terms and conditions to implement the measures, necessary to minimize such impacts. 

Commercial fisheries that result in bycatch of listed sea turtles, for example, would be required to

implement the relevant RPAs as applicable to protect sea turtles from fishing gear.

2.3 Marine Mammal Protection Act

The MMPA seeks to maintain marine mammal stocks at optimum sustainable population

levels, principally by regulating the human induced mortality and serious injury of marine

mammals. This includes fishing-related mortality and serious injury.

Although the MMPA prohibits the “take” of marine mammals, it provides exceptions for

incidental mortality and serious injury in the process of commercial fishing activities as well as a

limited number of other activities. “Take” is defined in the MMPA as, “to harass, hunt, capture,

or kill, or attempt to harass, hunt, capture, or kill any marine mammal” (16 U.S.C. § 1362 (13)). 

In 1994, Congress amended the MMPA to include Section 118, which established a regime to

regulate the take of marine mammals incidental to commercial fishing so that it does not occur at

a level that jeopardizes a marine mammal stock’s ability to reach its “optimum sustainable

population”, defined as “the number of animals which will result in the maximum productivity of

the population or the species, keeping in mind the carrying capacity of the habitat and the health

of the ecosystem of which they form a constituent element” (16 U.S.C. § 1362(9)). 

Section 118 of the MMPA requires that NMFS classify each U.S. fishery according to

whether there is a frequent (Category I), occasional (Category II), or remote (Category III)

likelihood of incidental mortality and serious injury of marine mammals. It also requires the

establishment of take reduction teams to develop take reduction plans (TRPs) for those fisheries

with the greatest impact on marine mammal stocks (Category I and Category II).

The MMPA establishes both a short-term (6-month) and a long-term (5-year) goal for

marine mammal bycatch reduction. TRPs are required to reduce, within 6 months of

implementation, the incidental mortality or serious injury of marine mammals incidentally taken

in the course of commercial fishing operations to levels less than a stock’s potential biological

removal3

 (PBR) level. Within five years of implementation, TRPs are required to reduce the

mortality or serious injury of marine mammals incidentally taken in the course of commercial

fishing operations to insignificant levels approaching a zero mortality and serious injury rate,

taking into account the economics of the fishery, the availability of existing technology, and

existing state or regional fishery management plans (16 U.S.C. § 1387(f)). 
6

Participants in Category I or II fisheries are required to register with NMFS, take on board

an observer if requested by NMFS to do so, and comply with all applicable TRP regulations. All

fishermen, including those participating in Category III fisheries, are required to report the

incidental mortality and serious injury of marine mammals should it occur.

2.4 FAO Code of Conduct for Responsible Fisheries

More than 170 Members of the Food and Agriculture Organization of the United Nations

(FAO) adopted the Code of Conduct for Responsible Fisheries in 1995. The Code is voluntary

and aimed at everyone working in and involved with fisheries and aquaculture, irrespective of

whether they are located in inland areas or in the oceans. The Code of Conduct, which consists

of a collection of principles, goals, and elements for action, took more than two years to develop. 

Among other things, the Code of Conduct maintains that fishing methods and gear should be

selective and designed to minimize waste and promote high survival rates for escaping fish. 

Gear should also minimize the catch of fish species that are not wanted (non-target or bycatch

fish) or that are endangered. Fishing gear and fishing methods that are not selective or that cause

high levels of waste should be phased out, according to the Code of Conduct. NMFS has been

very active in promoting the implementation of the FAO’s International Plan of Action (IPOA)

for Reducing Incidental Catch of Seabirds in Longline Fisheries and the FAO IPOA for the

Conservation and Management of Sharks, both of which have grown out of the Code of Conduct. 

More information on the IPOAs can be found at the following website:

http://www.nmfs.noaa.gov/sfa/international/index.htm
7

3. Regional Characteristics of Bycatch

3.1 Southwest Region

Fisheries of particular importance to the Southwest Region include coastal pelagic species

fisheries, the drift gillnet fishery for swordfish, and the fisheries for highly migratory species,

including the U.S. purse seine fleet that operates in the eastern Pacific Ocean.

The coastal pelagic species (CPS) fishery targets northern anchovy, jack mackerel, Pacific

sardine, and Pacific mackerel. CPS vessels fish with encircling nets, targeting a specific school,

and the most common incidental catch in the CPS fishery are other CPS species. A few

measures have been proposed to minimize bycatch (e.g., the use of grates to cover openings of

holds through which fish are pumped). In California, limited amounts of information are

available from at-sea observations; the bulk of bycatch data is derived from port sampling. 

When the sardine fishery was initiated off Washington and Oregon, the states implemented

observer programs specifically to assess bycatch. The precision and accuracy of these data have

not been assessed; however, the reported levels of bycatch support the view that bycatch of

vulnerable species is not significant. For example, the bycatch of salmon observed in the

Washington and Oregon sardine fishery in 2002 amounted to 1,800 fish. The landed catch of

chinook and coho salmon in the 2002 ocean salmon fisheries exceeded 400,000 fish off

Washington and Oregon. Based on sampling of landed catch in these areas, a small (but

unknown) percentage of the salmon taken in the CPS fishery are likely from ESA-listed

Evolutionary Significant Units. No specific measures are deemed necessary at this time to

reduce or mitigate these takes.

The California/Oregon Drift Gillnet (DGN) fishery targets swordfish and thresher shark. 

It had been classified as a Category I fishery under the MMPA as a result of interactions with

marine mammals, some of which are listed under the ESA, but was reclassified as Category II in

2003 due to successful bycatch reduction efforts. Since 1980, with the exception of a few years,

the California Department of Fish and Game and NMFS have conducted an observer program to

collect data on the bycatch of protected species. The DGN fishery was the subject of the Pacific

Offshore Cetacean Take Reduction Plan, implemented in 1997 to address incidental takes of

beaked whales, pilot whales, pygmy sperm whales, sperm whales, and humpback whales in the

DGN fishery. The Take Reduction Plan, which required the use of pingers, 36 feet net extenders,

and mandatory skipper education workshops, reduced marine mammal entanglements by an

order of magnitude in its first two years of implementation.

In 2000, NMFS conducted an internal ESA Section 7 consultation on the DGN fishery

and evaluated the incidental take of listed sea turtles and marine mammals by the DGN fishery. 

The opinion found the incidental take was likely to jeopardize the continued existence of certain

populations and specified a reasonable and prudent alternative under which the fishery could

operate. NMFS authorized the take of nine leatherback turtles in three years, and similarly low

numbers of loggerhead turtles, and implemented fishery time-area closures under ESA

regulations to ensure these levels were not exceeded. NMFS determined that the DGN fishery,

operating under the Take Reduction Plan, will have a negligible effect on listed marine mammals

in 2000. 
8

As with most pelagic gillnet fisheries, the catch of non-target species in the DGN fishery

is high (non-target catch includes common mola, blue shark, skipjack and mackerel). Eighty

percent of the molas are released alive and the majority of the tuna is landed.

The U.S. policy regarding the bycatch of marine mammals was in large part defined by

the purse seine fishery for tuna in the Eastern Tropical Pacific Ocean (ETP). In the 1960s, the

practice of setting nets around dolphins to harvest tuna swimming below was developed in the

ETP. From 1970 to 1980, the purse seine fishery expanded, dominated by the U.S. fleet. Annual

dolphin mortality exceeded 350,000 animals. In 1972, Congress ratified the MMPA, primarily

due to the public reaction to the high levels of dolphin mortality associated with the ETP tuna

fishery. During the 1980s, a progressive relocation of the U.S. fleet to the central western Pacific

occurred as a result of conflicts in the tuna fishery between the United States and Latin America

nations, the 1982/83 El Niño event, and limits imposed through the MMPA on the incidental kill

of dolphins in the ETP. In 1980, the U.S. fleet consisted of 126 seiners, 25 bait boats and 4 jig

boats with a combined carrying capacity of 118,000 metric tons (t). By 1994, only 4 U.S. flag

seiners were active in the ETP with a combined carrying capacity of less than 6,000 t. 

Mexico and Ecuador are now the dominant participants in the fishery. A small number of

large U.S. purse seine vessels (greater than 400 short tons carrying capacity) continue to fish the

ETP under jurisdiction of the Inter-American Tropical Tuna Commission (IATTC) and governed

by the Agreement on the International Dolphin Conservation Program. In 2001, 5 large U.S. tuna

purse seine vessels participated in the fishery out of a total of 140 vessels. The IATTC reports

annual estimates of finfish and dolphin mortality by species and stock, as well as standard errors

associated with the estimates for all vessels classes. No U.S. vessels currently set on dolphins. 

All large U.S. vessels carry observers while fishing, and the accuracy and precision of bycatch

estimates are accordingly high. While U.S. participation in the fishery has all but disappeared,

the bycatch of dolphins in the ETP tuna fishery remains a controversial issue (e.g., the recent

redefinition of the “Dolphin Safe” designation). NMFS continues its efforts, through its support

of the IATTC and international agreements, to reduce bycatch by U.S. and foreign flag vessels.

The Pacific Fishery Management Council's Fishery Management Plan for U.S. West

Coast Fisheries for Highly Migratory Species (HMS FMP) was approved in February 2004. The

HMS FMP establishes a framework for the management of fisheries for tuna, swordfish, and

selected sharks by West Coast vessels and institutes initial conservation and management

measures for drift gillnet and longline fisheries. The drift gillnet measures essentially continue

the measures in place under other authorities (i.e., MMPA, ESA) to prevent and/or mitigate

marine mammal and sea turtle takes in the fishery. These measures include gear (e.g., pingers)

and time/area fishery closures that have proven to be very effective. The longline measures are

new and prohibit shallow longline sets by West Coast vessels west of 150N W. longitude to

prevent sea turtle interactions. A companion measure under the ESA prohibits longline targeting

of swordfish east of 150N W. longitude, also to prevent sea turtle interactions. The HMS FMP

also establishes a catch-and-release program in recreational fisheries to promote prompt release

of fish in a manner that will promote survival of the fish. Further, the FMP requires that NMFS

develop observer sampling plans and take other measures to ensure accurate and statistically

reliable estimates of bycatch and protected species interactions. NMFS is initiating baseline

observer coverage of coastal purse seine and troll albacore fisheries in 2004 as part of this effort. 

Observer placements on charter vessels also will be evaluated. Finally, the Southwest Region is

working with the U.S. Fish and Wildlife Service to ensure development and distribution of
9

placards and other information describing how to deal with any incidental hookings of seabirds

(especially brown pelicans) in recreational fisheries for highly migratory species.

3.2 Southeast Region

Southeast fisheries (North Carolina to Texas and the U.S. Caribbean) generate about one

billion dollars in ex-vessel gross revenues per year (NMFS 2001). Fisheries of the Southeast

reflect the very diverse fauna of the region, with relatively few large fisheries and many small

fisheries. The fisheries have catches from more than 200 stocks of fish and fishery resources. 

Two fisheries dominate economically. The menhaden purse seine fishery is the volume

leader in the Southeast, with annual landings approaching 2 million t. About 60% of the landings

come from the Gulf of Mexico and 40% from the Atlantic. The shrimp trawl fishery generates

the largest revenue regionally, and sometimes nationally. The Gulf of Mexico shrimp fishery

accounts for about 75% of the entire U.S. wild shrimp production. About half the commercial

value of fisheries other than shrimp and menhaden consists of shellfish fisheries (blue crabs,

oysters, and other invertebrates), generally harvested from state waters, and managed by the

states. The remainder of the commercial harvest consists of finfish from many stocks, including

reef fish (red snapper, red grouper, etc.); coastal pelagics (e.g., king and Spanish mackerel), and

oceanic pelagics (sharks, swordfish, and tunas). 

Marine recreational fishing is a very important part of the Southeast harvest. Typically,

4-6 million participants make 30-40 million trips annually. The magnitude of recreational

participation in the Southeast is much larger than in other regions of the United States. The bulk

of recreational harvest consists of small fish from the drum family (croakers and seatrouts), but

many of the prized commercial species are also prized by recreational fishermen (e.g., red

snapper and other reef species, and king and Spanish mackerel). This shared usage makes every

conservation issue an allocation issue as well. 

Partnerships with other fishery management agencies (e.g., state fishery management

agencies, interstate marine fisheries commissions, state Sea Grant College programs, and the

Gulf and South Atlantic Fishery Development Foundation) have been crucial to addressing

bycatch issues in the Southeast Region. Efforts in this region pre-date many of the regional and

national workshops held in other areas of the country. 

The Southeast formally began to address finfish bycatch in the shrimp trawl fishery in

1990 and developed a strategic research document focusing on this important issue. Previously,

gear research had focused on excluding sea turtles from trawls through the development of turtle

excluder devices (TEDs). Initially, this research effort lead to the development of several dozen

TEDs that were approved for use in the fishery. However, in recent years the number of

approved TEDS has been reduced, and only a few larger-opening TEDs are now approved for use

in the fishery. The bycatch strategic document led to implementation of a formal Regional

Research Program, coordinated by the Gulf and South Atlantic Fishery Development Foundation. 

The major components of the program were observer programs to quantify bycatch mortality, and

gear technology research and development to reduce finfish bycatch. A four-phase development

program for bycatch reduction devices (BRDs) for shrimp trawls was successfully used under the

Regional Research Program structure to develop several BRD designs that are used in the fishery. 
10

Establishing and maintaining the distinction among these four phases proved surprisingly useful,

both to the orderly progression of candidate gear through the development program, and to

communicating the nature of different types of data and research. Within this framework, actual

research and development of candidate devices have been carried out independently by NMFS,

Sea Grant, state agencies, universities, and industry, drawing on a variety of funding sources,

primarily the Saltonstall-Kennedy (S-K) and Marine Fisheries Initiative (MARFIN) grants

programs.

Bycatch characterization and reduction research has been conducted for other fisheries in

the Southeast, but not through a formal cooperative program structure as for shrimp. Longline

fisheries for tuna, swordfish, and sharks have a history of observer programs for general

characterization of the fisheries, including bycatch. 

The observer coverage of the pelagic longline fishery, which targets swordfish and tuna

species, is monitored by the NMFS Highly Migratory Species (HMS) Management Division and

the Southeast Fisheries Science Center. A mandatory observer program has been in place since

1992, at which time there were approximately 350 active vessels. There are currently between

130 and 150 vessels actively participating in the fishery, and they work out of ports that range

along the Atlantic coast from Portland, Maine to Key West, Florida, along the Gulf from Key

West to Brownsville, Texas, and from Puerto Rico to 5N N. latitude.

The program has always had a target coverage level of 5% of the U.S. fleet within 11

geographical areas of the North Atlantic Ocean (Atlantic waters north of 5N N. latitude), as was

agreed to by the United States at the International Commission for the Conservation of Atlantic

Tunas (ICCAT). Starting in 2002, the program began requiring an 8% coverage rate. Actual

coverage levels achieved from 1992-2002 have ranged from 2% to 6% depending on quarter and

year. Data collection priorities have remained the same since the inception of the program. The

primary goal of the program is to collect catch and effort data of the U.S. pelagic longline fleet

on highly migratory fish species, although information is also collected on bycatch of protected

species (marine mammals, sea turtles and seabirds). 

NMFS, in cooperation with the U.S. pelagic longline fishery, implemented a three-year

research program in the western Atlantic Ocean to develop and evaluate sea turtle mitigation

measures. Five potential mitigation techniques were evaluated during 687 research sets in 2001

and 2002. Data were collected to evaluate the effectiveness of the mitigation measures and to

investigate variables that affect sea turtle interaction rates with pelagic longline gear. A

significant reduction in loggerhead catch may be achieved by reducing daylight soak time. The

use of 18/0 circle hooks and mackerel bait was found to significantly reduce both loggerhead and

leatherback sea turtle interactions when compared with industry standard J hooks and squid bait. 

Also, circle hooks significantly reduced the rate of hook ingestion by the loggerheads, reducing

the post-hooking mortality associated with the interactions. The combination of 18/0 circle

hooks and mackerel bait was found to be the most efficient mitigation measure for both

loggerhead and leatherback turtles. Mackerel bait was found to be more efficient for swordfish

than squid bait and circle hooks were more efficient for tuna than J hooks. 

The directed shark gillnet fishery that developed off the east coast of Florida and Georgia

in the late 1980s is classified as a Category II fishery under the MMPA because of occasional

marine mammal takes. There is also a concern about interaction with protected sea turtles. 
11

Vessels operating in the fishery are typically from 12.2-19.8 m in length. The nets used (both

nylon multi-filament and monofilament) are from 275-1,800 m long and 3.2-4.1 m deep, with

stretched mesh from 12.7-29.9 cm. The most common type of net is a drift gillnet, wherein the

vessel basically sets a gillnet in a straight line off the stern. The net soaks or fishes at the surface

for a period of time, is inspected at various occasions during the soak, and then hauled onto the

vessel when the captain/crew feel the catch is adequate. It is usually a nighttime fishery and

takes place between 3 and 9 nautical miles from shore. The other type of gear utilized is strikenetting, wherein the vessel uses a gillnet to encircle a school of sharks. This is usually done

during daylight hours, using visual sighting of shark schools from the vessel and/or a spotter

plane. The gear is set around the sharks, and is hauled back onto the vessel without much soak

time. Between 5 and 11 vessels operated in this fishery from 1993-98. Currently, between four

and six are operating. An observer program for this fishery has been in place from 1993-1995

and 1998-2002. The objectives of this program are to obtain estimates of catch and bycatch and

bycatch mortality rates of protected species (sea turtles and marine mammals), juvenile sharks,

and other fish species in the Southeast Region’s U.S. coastal shark gillnet fishery. Catch and

bycatch estimates are gathered to meet the mandates of the Atlantic Large Whale Take Reduction

Plan and the Biological Opinion issued under requirements of the Fishery Management Plan for

Highly Migratory Species.

NMFS’s Southeast Region convened a Bottlenose Dolphin Take Reduction Team

(BDTRT) in 2001 to address incidental mortality and serious injury of coastal Atlantic bottlenose

dolphins in gillnet, seine, trap/pot, and stop net fisheries along the Atlantic coast. NMFS

currently is readying a BDTRT plan proposed rule for public comment. The plan includes

measures to reduce bottlenose dolphin bycatch to levels below the stock’s PBR within six

months of its implementation. 

MARFIN and S-K grants have also funded research on bycatch in the menhaden purseseine fisheries of the Gulf and Atlantic coasts. The menhaden industry has already developed

some gear innovations to release bycatch alive during harvest. 

Estimates of fish caught, but not retained, in recreational fisheries are made through the

National Marine Recreational Fisheries Statistics Survey (MRFSS) program for much of the

Southeast Region. There have been S-K awards for short-duration projects assessing recreational

bycatch in some geographic areas not covered by MRFSS. A number of MARFIN and S-K

grants have been awarded to examine mortality of hooked and released fish. Species addressed

include red snapper, red grouper, king and Spanish mackerel, and sharks. Short-duration

observer programs have been conducted in some areas in the Gulf of Mexico to examine bycatch

of the commercial hook-and-line fishery for reef fish. Short-term research has been conducted on

bycatch in trap fisheries for finfish and crustaceans, with most projects focused on developing

escape structures for unwanted or prohibited catch, and for reduction of ghost fishing by lost

traps.

Evaluations of impacts of bycatch on the fish stocks, and thus on directed fisheries, are

made through traditional stock assessments whenever estimates of bycatch are available. 

Evaluations of the effects of bycatch in the shrimp fisheries are the most advanced. 

Incorporation of bycatch information from other fisheries in stock assessments is often less

adequate due to the lack of time series estimates for bycatch.
12

3.3 Northwest Region

Fisheries of the West Coast (coastal California, Washington and Oregon) target several

species of groundfish and salmon, while anchovy, sardines, mackerel, shrimp, crab, squid, and

other shellfish and molluscs provide other important fishing opportunities. These fisheries are

harvested using a variety of gear types (e.g., trawls, seines, pots, hook and line) that produced

about 338,000 t during 2002, and had an ex-vessel value of approximately $229 million (PacFIN

2003).

Pacific hake (whiting), the largest proportion of groundfish landed on the West Coast, are

taken by large mid-water trawl and catcher/processor vessels that have replaced the foreign and

joint-venture fleets of the 1970s and 1980s. The At-Sea Hake Observer Program has provided

information on the bycatch of other groundfish species and salmon in the at-sea hake fishery

since the early 1990s. The shoreside hake fishery is sampled by programs run by each state. 

Further, a project to deploy electronic monitoring systems on the entire shoreside hake fleet for

the 2004 season was a success and the analysis of the data will be available by late 2004. Some

species of rockfish, such as yellowtail rockfish and Pacific ocean perch, are occasionally taken as

bycatch in large numbers but are accounted for by the monitoring programs. Marine mammal

bycatch in the at-sea Pacific hake midwater trawl fishery is also monitored by the At-Sea Hake

Observer Program. Since 1990, limited mortality takes have included individuals from six

marine mammal species, specifically, California sea lion, Steller sea lion, harbor seal, northern

elephant seal, Pacific white-sided dolphin, and Dall's porpoise. During the 2002 fishing season,

observers reported three marine mammal mortalities, a level that is not considered significant.

The bottom trawl fishery targets individual rockfish, flatfish, roundfish species, and

different species complexes of rockfish, as well as the deep-water complex consisting of

thornyheads, rockfish, Dover sole, and sablefish. Fish caught are brought back to shoreside

plants for processing. Vessels discard groundfish at sea for many reasons, such as to comply

with regulatory constraints and because a portion of the catch is economically undesirable. In the

past, information on bycatch has been derived from a variety of sources, primarily research

studies or other short-term programs that sampled at-sea discards on only a small portion of the

bottom trawl fleet. However, the West Coast Groundfish Observer Program (WCGOP) began

collecting at-sea data on groundfish bottom trawlers in August 2001 and aids in monitoring the

total removals by the fishery, which is an important component of any fishery analysis program. 

In the bottom trawl fishery, total landed catch is monitored by the state-run fish sales ticket

system.

The primary economic objective for groundfish management on the West Coast is to have

seafood processors provide a continuous, year-round flow of fish to fresh fish markets to produce

a variety of benefits, including continuous employment in coastal communities. However,

overcapitalization, increased effort, and either declining or stable total allowable catch have

resulted in the need to significantly slow catch rates to spread the catch of each species or species

complex for which there is a specified optimum yield (OY) over the entire year.

The Pacific Fishery Management Council has chosen trip landing limits as the vehicle to

slow the catch rates. Because almost all species managed by trip limits are harvested in a

multispecies mixture with other trip-limit species, vessels are forced to discard species once the

trip limit for that species is reached, while the vessel continues to fish for other species until
13

those trip limits are met. As trip limits become more restrictive and as more species come under

trip-limit management, regulatory discards increase. Most species are managed under two-month

cumulative trip-landing limits.

Trip limit-induced discards also can occur when fishermen continue to harvest other

species when the OY of a single species is reached and further landings of that species are

prohibited. Discretionary discards of unmarketable species or sizes were known to occur widely

in the bottom trawl fishery and were largely unmeasured until the establishment of the WCGOP.

The other major West Coast bottom trawl fishery is the shrimp trawl fishery. Bycatch

discards in the shrimp trawl fishery are known to include groundfish species, Pacific halibut,

chinook salmon, and squid. Although the amount of groundfish bycatch in the shrimp trawl

fishery is unknown because of the lack of an at-sea sampling program, its existence is

recognized. Over the past several years, S-K grant funds were used to develop and test finfish

excluder devices for the shrimp trawl fishery. This fishery is state-managed and all three West

Coast states now require fishery participants to use finfish excluder devices.

Other groundfish fisheries include bottom longline and pot (fish trap) fisheries for

sablefish, other line (vertical longline, etc.) fisheries for rockfish and bottom gill nets for

rockfish. Very little is known about the amount of discard and discard mortality in these

fisheries. Similarly, we have little information on the biological and socio-economic effects of

bycatch and discards in these fisheries. The WCGOP is currently observing commercial fixed

gear vessels to aid in assessing their biological impact.

The five species of Pacific salmon support important commercial, recreational, and tribal

fisheries in the states of Washington, Oregon, California, and Idaho. Commercial, recreational,

and tribal fishermen harvest salmon from the Pacific Ocean, Puget Sound, estuaries, and rivers

along spawning migration routes using trolling gear, seines, gill nets, and hook and line. 

Harvests have been declining as habitat degradation and overfishing have threatened specific

populations of salmon. Several species of salmon have been or are proposed for listing under the

Endangered Species Act. The federally managed ocean salmon fisheries are divided into

commercial troll and recreational fisheries. Both groups use hook-and-line gear. Inside-water

commercial fisheries, which are managed by the states and treaty tribes, use gill nets and purse

seines. Bycatch in the ocean commercial troll and recreational salmon fisheries has two major

components. The first is the catch and discard of depressed or endangered salmon species, for

which there is no total allowable catch in a mixed-stock fishery with other salmon species. The

second is the catch and discard of salmon species either coastwide or by management area, where

the quota for one species of salmon is taken before the quota for the other species.

Recreational angling is important to the West Coast fisheries; anglers reportedly spend

about $850 million each year in the West Coast fisheries. Recreational fisheries include those for

salmon, Pacific halibut and groundfish species. West Coast recreational salmon catch was over

610,000 fish in 2002 (RecFIN 2003) and total Pacific halibut sport quota is set at 224.3 t (IPHC

2003) for 2003. The bycatch and discard rates in these fisheries have not been thoroughly

assessed, but are significant for some species such as lingcod and most nearshore groundfish

species. Discard of these species is primarily due to regulatory size and bag limits. Anglers also

preferentially retain trophy fish and specific species of fish while discarding other less desirable

fish. Limited monitoring data are collected by the states in these fisheries.
14

3.4 Alaska Region

Alaska fisheries are diverse with respect to the species sought, the gear types employed

and the sizes of both harvesting and processing operations. They target Pacific halibut, Pacific

herring and several species of groundfish, Pacific salmon, crab, and other shellfish. Since 1985,

the annual ex-vessel revenue for the commercial fisheries approached or exceeded $1 billion

(Hiatt et al. 2003). The recreational and subsistence fisheries are important parts of the Alaska

fisheries for some species and regions. 

There is an FMP for each of the following five fisheries off Alaska: the Bering

Sea/Aleutian Islands area (BSAI) groundfish fishery, the Gulf of Alaska (GOA) groundfish

fishery, the BSAI king and Tanner crab fishery, the scallop fishery, and the salmon troll fishery in

the Exclusive Economic Zone (EEZ) off Southeast Alaska. In addition, the Pacific halibut

fishery off Alaska is managed under federal regulations, and NMFS is responsible for monitoring

the incidental mortality and serious injury of marine mammals in state-managed fisheries under

the MMPA. This section focuses on the bycatch of all living marine resources in the BSAI and

GOA groundfish fisheries and the halibut fishery and on the bycatch of marine mammals in the

state-managed Category II fisheries (there are no Category I fisheries in Alaska). There are two

reasons for this focus. First, the FMPs for the crab, scallop and EEZ salmon fisheries defer most

management authority, including basically all bycatch monitoring and management authority, to

the State of Alaska. Second, with respect to the state managed Category II fisheries, the

management responsibilities and authorities of NMFS are limited principally to marine

mammals. In those fisheries, monitoring and controlling the bycatch of other living marine

resources is principally a stewardship responsibility of the State of Alaska or the U.S. Fish and

Wildlife Service (USFWS).

A variety of factors contribute to the bycatch problems both in the Alaska groundfish and

halibut fisheries and the state-managed MMPA Category II fisheries and make them more

difficult to solve. These factors include: (1) the multi-species nature of the bycatch problem; (2)

limited information concerning the biological, ecological, social, and economic effects of

alternative methods for reducing bycatch; (3) substantial excess harvesting capacity; (4) with few

exceptions, the use of the race for fish to allocate quotas among competing fishing operations;

and (5) the external benefits and costs associated with bycatch.

3.4.1 Groundfish Fisheries

In the 1980s, joint-venture and domestic fisheries rapidly replaced the foreign fisheries

that had accounted for more than 90% of the Alaska groundfish catch; and then the domestic

fisheries displaced the joint-venture fisheries. In joint-venture fisheries, domestic fishing vessels

delivered groundfish catch directly to foreign processing vessels on the fishing grounds. The last

foreign and joint-venture groundfish fisheries in the EEZ off Alaska occurred in 1986 and 1990,

respectively.

Groundfish stocks (which include walleye pollock, Pacific cod, sablefish, rockfish,

flatfish, and Atka mackerel) generally are in a healthy condition. All Alaska groundfish stocks

have fluctuated in abundance over the years, but no widespread trend toward decline is evident. 

No stocks are overfished, and overfishing is not occurring. This is in part the result of efforts to
15

set conservative quotas and to prevent them from being exceeded. For example, in 2002 the total

harvest of Alaska groundfish species (2.10 million t) was only about 59% of the acceptable

biological catch (ABC) (3.58 million t) and was about 94% of the total allowable catch (2.24

million t). The BSAI and GOA groundfish OY caps established in the FMPs explain, in part,

why groundfish harvest has been substantially less than the aggregate ABCs. 

In 2002, the retained catch of 1.96 million t resulted in ex-vessel gross revenues of about

$570 million and $1.5 billion in gross revenues for seafood processors. Trawl, hook and line

(including longline and jig gear), and pot gear account for virtually all the catch in the BSAI and

GOA groundfish fisheries. The selectivity of each gear type in the multi-species groundfish

fisheries varies by gear configuration, target species, area, and time of year. In recent years, trawl

fisheries on average accounted for about 90% of the total groundfish catch; however for some

species, such as Pacific cod and sablefish, substantially more than 50% of the catch is taken with

fixed gear (principally longline gear). There are catcher vessels and catcher/processor vessels in

the trawl, longline and pot fisheries. In 2002, vessels less than 60 feet in length accounted for

about 2% of the total retained groundfish catch, larger catcher vessels took about 45% of the

total, and catcher/processors took about 53% of the total. The distribution of catch by gear and

type of fishing vessel is, in part, due to allocations in the groundfish FMPs.

The bycatch of the non-groundfish species, such as crab, salmon, halibut, and herring, and

of marine mammals, has been an important management issue that NMFS has monitored since

before the Fishery Conservation and Management Act of 1976. More recently, the discards of

groundfish, including the major and minor groundfish species, and the bycatch of seabirds

(including the endangered short-tailed albatross) have become important management issues. 

The North Pacific Fishery Management Council (NPFMC) has recommended and NMFS has

implemented a broad range of management measures that were designed at least in part to

monitor and reduce bycatch in the groundfish fishery. The management measures include a large

observer program, groundfish quotas that are set and monitored in terms of total catch, time and

area closures, gear restrictions, gear allocations, full retention requirements for pollock and

Pacific cod, prohibitions on the retention of some non-groundfish species, bycatch limits for

some non-groundfish species, reduced quotas for some groundfish species, careful release

requirements for halibut bycatch in the longline fisheries, bird bycatch avoidance regulations for

the longline fisheries, fishery closures when groundfish or non-groundfish quotas are taken,

individual fishing quotas for the fixed gear sablefish and halibut fisheries, and the American

Fisheries Act allocations and cooperatives for the BSAI pollock fishery. Although changes in

bycatch are due to a variety of factors, the following comparisons of catch and bycatch estimates

for 1996 and 2002 for the BSAI and GOA groundfish fisheries provide an indication of the

success of the bycatch reduction measures. Although total groundfish catch increased by 2.5%,

groundfish discards decreased by 50%, the discard rate for groundfish decreased to 6.8%, halibut

bycatch mortality decreased by 8%, herring bycatch decreased by 91%, salmon bycatch decreased

by 15%, and crab bycatch decreased by 52%. Although the bycatch rates in the Alaska

groundfish fishery are relatively low compared to most other major fisheries in the U.S. or

elsewhere, the absolute levels of bycatch are high due to the size of the groundfish fishery. In

2002, bycatch (i.e., discards) in the groundfish fisheries included about 142,000 t of groundfish,

6,100 t of halibut mortality, 137,000 (individual) salmon, 133 t of herring, and almost 3 million

(individual) crab (mostly snow and Tanner crab).

Data provided by the Alaska Fisheries Science Center’s (AFSC) North Pacific

Groundfish Observer Program (NPGOP) are a critical element in the conservation and
16

management of groundfish, other living marine resources, and habitat. For example, these data

are used for: (1) assessing the status of groundfish stocks; (2) setting groundfish quotas and

monitoring them for in-season management; (3) monitoring the bycatch of non-groundfish

species for in-season management; (4) assessing the effects of the groundfish fishery on other

living marine resources and their habitat; and (5) assessing methods for improving the

conservation and management of groundfish, other living marine resources and habitat. The

NPGOP also provides the industry with bycatch data it needs to make timely fishing decisions

that decrease bycatch and increase productivity. In addition, the NPGOP has resulted in

fundamental changes in the nature of the bycatch problem. First, by providing good estimates of

total groundfish catch and non-groundfish bycatch by species, it eliminated much of the concern

that total fishing mortality was being underestimated due to fish that were discarded at sea. 

Second, the NPGOP made it possible to establish, monitor and enforce the groundfish quotas in

terms of total catch as opposed to only retained catch. For the groundfish fisheries, this means

that both retained catch and discarded catch are counted against the total allowable catches

(TACs). Third, the NPGOP made it possible to implement and enforce bycatch quotas for the

non-groundfish species that by regulation had to be discarded at sea. Finally, it provided

extensive information that managers and the industry could use to assess methods to reduce

bycatch and bycatch mortality. In summary, the observer program generally provided fishery

managers with the information and tools necessary to prevent bycatch from adversely affecting

the stocks of the bycatch species. Therefore, the bycatch in the groundfish fishery is principally

not a conservation problem, but it can be an allocation problem. Although this does not make it

less controversial, it does help identify the types of information and management measures that

are required to address the bycatch problem.

In 2002, there were approximately 35,000 observer deployment days, including over

30,000 deployment days on catcher vessels, catcher/processors and motherships. The fishing and

processing operations paid more than $12 million to observer providers for those 35,000 observer

deployment days. Vessels with observers onboard accounted for about 86% of the total

groundfish catch in the BSAI and about 33% of the total in the GOA. However, for some areas

and gear types, vessels of less than 60 feet account for most or all of the catch, and there are no

observer data for those vessels. Three other concerns with respect to the quality or availability of

observer data are: (1) the lack of random placement of observers on vessels that are required to

have observers less than 100% of their fishing days; (2) the ability of the observers to provide

accurate bycatch estimates for species either for which bycatch is a very rare occurrence or for

which species identification is very difficult; and (3) the observer effect bias. An observer effect

bias exists either if fishing practices change for trips or hauls (i.e., sets) that are observed or if

crew members take actions to prevent accurate catch or bycatch estimates for observed hauls.

In addition to the management measures that have been implemented to reduce bycatch,

gear technology research and research on the behavioral responses of fish both to fishing gear

and to the stresses imposed by coming in contact with fishing gear have contributed substantially

to addressing bycatch. Species-specific differences in the response to fishing gear have been

identified and used to develop gear modifications that increase the escapement of juvenile fish

and other fish that would be discarded if they did not escape. Much of this research has been

conducted by NMFS in cooperation with the industry and universities.
17

3.4.2 Pacific Halibut Fisheries 

Commercial, recreational and subsistence fisheries exist for Pacific halibut off Alaska. 

Although the vast majority of the commercial catch is taken with longline gear, halibut is also

taken with other types of hook and line gear. The International Pacific Halibut Commission

(IPHC) has the primary responsibility for managing the halibut resource off Alaska. Under

authority of the North Pacific Halibut Act, NMFS is authorized to develop regulations that are in

addition to, but not in conflict with, regulations adopted by the IPHC. The NPFMC developed an

individual fishing quota (IFQ) program for the commercial Alaska halibut fishery in 1992. 

NMFS implemented the program in 1995. Under the IFQ program, individual fishermen were

assigned a quota share based on past participation in the fishery and other criteria developed by

the NPFMC. The annual halibut quota established by the IPHC is allocated among fishermen

based on their individual quota shares. These quota shares are transferable harvest privileges

within specified limitations. Under the IFQ program, fishermen are able to harvest their halibut

IFQ whenever and however such harvest is most economical to their fishing operation, subject to

program limitations and seasons. The higher catch limits in recent years reflect healthier stock

conditions. Commercial halibut fishery landings in 2002 were almost 28,000 t and generated exvessel gross revenues of about $130 million.

The halibut fishery does not have an observer program to monitor bycatch, and the

halibut fishery’s logbooks do not require the reporting of discards. However, logbook data are

used by the IPHC to estimate adult halibut mortality due to lost/abandoned gear in the halibut

fishery and the IPHC stock assessment surveys collect bycatch data for undersized halibut and for

other species. In addition, bycatch data are available for joint groundfish and halibut trips for

which there is a groundfish observer. The uncertainty concerning the level of bycatch of some

groundfish species, such as demersal shelf rockfish, is a concern. Seabird bycatch mortality also

is a concern. Gear and fishery operation regulations are used to reduce seabird bycatch. 

3.4.3 MMPA Category II Salmon Fisheries

Over ten Alaska salmon fisheries are classified as Category II fisheries under the MMPA. 

An observer program in the Prince William Sound, Cook Inlet, and Kodiak Island salmon drift

and set gillnet fisheries documented incidental takes of marine mammals and seabird bycatch. 

Data on incidental mortality and serious injury confirmed the Category II classification of most

of the observed fisheries, and resulted in the reclassification of two fisheries to Category III. 

NMFS is currently developing a more comprehensive observer program for the Category II

Alaska salmon fisheries with the primary focus of determining the nature and extent of marine

mammal interactions in these fisheries; seabird and other bycatch information will also be

collected. 

The MMPA sets out several goals for which observer data are used: (1) assessing whether

the potential biological removal level of a stock is exceeded, (2) categorizing each fishery in the

annual List of Fisheries, and (3) determining whether incidental mortality and serious injury of

marine mammals from a fishery has reached insignificant levels approaching a zero mortality and

serious injury rate. These goals each require an increasing level of precision and accuracy in

estimates of serious injury and mortality. Determination of appropriate observer coverage levels

to meet the needs of accuracy and precision is currently the subject of serious interest to NMFS’

National Observer Program Advisory Team, and specific coverage levels for this program still
18

need to be assessed. Currently, the Alaska marine mammal program observes state-managed

salmon fisheries on a rotational basis, with one or two fisheries observed per year for two

consecutive years each at approximately 5% coverage. With over ten Category II fisheries to

monitor for marine mammal bycatch, ten or more years may elapse before a fishery is observed

again. Trends in fishery operations and marine mammal populations can change significantly in

the intervening years, easily rendering observer data out of date. The program would ideally

observe fisheries more frequently (probably no more than five years between observing a single

fishery) and for more than two consecutive years in each rotation (probably three to four

consecutive years). The current limiting factor in the development of this program is funding. 

Due to the remoteness of many of the fisheries, the average cost of observing one fishery is over

$1 million per year, although cost savings can be realized in combining concurrent observation of

geographically proximal fisheries.

There is a federal FMP for the relatively small salmon troll fishery in the EEZ off Alaska;

however, the FMP defers management to the State of Alaska. All other salmon fisheries are

strictly state managed. The management of the Alaska salmon fisheries is based on optimum

sustainable yield and typically has resulted in healthy salmon stocks. Management of the Alaska

salmon fishery strives to protect, to the extent possible, any depressed stock, including those

originating south of Alaska.

Commercial fishing is conducted in both state and federal waters by about 5,000

relatively small fishing vessels or boats using troll, drift gill-net, set gill-net, and purse seine gear. 

All five Pacific salmon species are harvested by commercial, recreational, and subsistence

fishermen. In 2002, about 283,000 t of salmon were landed in the commercial fishery with exvessel gross revenues of about $163 million. Due principally to depressed prices, this is the

lowest level of ex-vessel revenues for the Alaska salmon fisheries in more than 20 years.

The intercepts of salmon, including ESA-listed Pacific Northwest stocks, passing through

the marine waters off the coast of Alaska on their way to more southerly spawning grounds have

been the focus of lengthy negotiations and debate among Alaskan, Canadian, and U.S. West

Coast fishermen, management agencies, and governments. The Northwest Region has the lead

for protecting the ESA-listed Pacific Northwest salmon stocks.

3.5 Northeast Region

Northeast fisheries are diverse both with respect to the species sought and the gear types

employed. Fisheries for invertebrate species including American lobster, sea scallop, and

Atlantic surfclam are currently the most valuable in the Northeast Region. Lobster landings are

mostly taken with baited traps, with about 70% of landings from the Gulf of Maine. Sea scallop

landings are derived principally from dredge fisheries (particularly on Georges Bank and in the

Middle Atlantic). Fish species such as monkfish and menhaden also generate substantial

revenues. The greatest volume of landed fish is derived from small pelagics (menhaden and

Atlantic herring). Groundfish fishing is primarily by otter trawling, which accounts for about

70% of landings. In the Gulf of Maine, otter trawl target species include gadoids and flatfishes. 

Fixed-gear fisheries using gill nets and longlines target primarily cod, pollock, white hake,

dogfish, and monkfish. On Georges Bank, gadoids, flatfish and mixed groundfish species are

generally targeted. In Southern New England, groundfish fisheries primarily target whiting,

yellowtail flounder, winter flounder, and monkfish. In the Middle Atlantic, groundfish trawling
19

targets summer flounder, scup, black sea bass, monkfish, winter flounder, tautog, and a variety of

other species.

Regulatory discards (i.e., discard of undersized or trip-quota limited stocks) are an

important issue in the Northeast region’s groundfish fisheries. Historically, managers often

selected minimum legal sizes for groundfish that resulted in the harvest of undersized fish, given

the characteristics of nets used in the fishery, often resulting in substantial discards. Regulatory

discards also occur when catches of certain stocks are limited by trip quotas. Discards of finfish

and shellfish can represent a significant proportion of the catch, and represent an important

source of fishing-related mortality. Management programs that control fishing mortality rates

have been adopted for most of the region’s fisheries. It is anticipated that with sufficient effort

reduction, combined with other management regulations, the average size of fish in the

population will increase, thus reducing the potential catch of undersized animals and regulatory

discards.

Trip limits contribute to the discard of some species (e.g., summer flounder, haddock, and

Atlantic cod). Trip limits for summer flounder are invoked when individual states approach their

allocated share of region-wide total allowable catch (TACs). Minimum size regulations, as well

as economic factors contribute to relatively high discard rates in a number of Mid-Atlantic

fisheries, especially those for scup and, to some extent, black sea bass.

Small-mesh fisheries in the Northeast have undergone a great deal of scrutiny as

managers have sought to minimize the catch of undersized groundfish, particularly in trawl

fisheries. The trawl fishery for northern (pandalid) shrimp now requires the use of finfish

excluder devices, which, when fished properly, reduce the overall proportional weight of nonshrimp catch, particularly of flatfish and gadoids.

Other small-mesh trawl fisheries of the region targeting silver and red hakes, herring,

mackerel, squids, butterfish, ocean pout, and dogfish are subject to a performance criterion of

less than or equal to 5% of the total catch comprised of regulated groundfish species (e.g., cod,

haddock, redfish, pollock, white hake and five flounder species). On Georges Bank, a smallmesh fishery is allowed for whiting, but only in prescribed time periods and locations. Some

fisheries have been curtailed altogether or geographically restricted to meet this performance

criterion. Squid fisheries in the Mid-Atlantic and southern New England potentially generate

discards of a number of commercial species.

Bycatch is an important consideration in allocation decisions among different gear sectors

in the fishery. For example, Atlantic cod are targeted primarily by three gear types—otter trawls,

gill nets, and demersal longlines. Mobile gears tend to have the highest overall discard rates. 

Gill nets using appropriate mesh are generally more selective than either trawls or hooks. Gear

sectors are in competition for small overall target TACs for cod, and regulations are likely to

change the relative proportions of the catch derived by the various gear types.

Takes of marine mammals and sea turtles are problematic in several of the region’s

fisheries. Bottom-tending gillnet fisheries targeting groundfish in the Gulf of Maine and

Southern New England entangle harbor porpoise in numbers sufficient to be of concern to the

long-term stability of the harbor porpoise resource. Gillnet fisheries in the Gulf of Maine also
20

entangle large whales, including the endangered right whale. Take reduction team activities have

been focused on these fisheries to reduce interactions. Gillnet fisheries also result in mortalities

of some seabirds, including shearwaters, gulls, and gannets. Mid-Atlantic coastal gillnet

fisheries also take harbor porpoises and bottlenose dolphins.

Although infrequent, entanglements of whales in lobster gear are of particular concern. 

Given the status of right whales, any fishing activities that generate mortalities of this species are

subject to mitigation measures. Nearshore trawl fisheries in the Mid-Atlantic have generated

some takes of sea turtles, particularly during the summer, and the use of turtle excluder devices

has been proposed. Large mesh gillnets are known to interact with sea turtles, and NMFS has

prohibited their use in certain areas and at certain times based on sea surface temperature. NMFS

also has worked with North Carolina to restrict gillnets in inshore waters. Pound nets in areas

where currents are strong also have been documented to entangle sea turtles in large mesh

leaders. Dredges used to harvest scallops also have been shown to impact sea turtles. Recent atsea observer programs have documented high interaction rates in Hudson Canyon. 

Bycatch in Northeast commercial fisheries is monitored primarily through the Fishery

Observer Program of the Northeast Fisheries Science Center (NEFSC). Several states also

conduct monitoring activities in their waters. The NEFSC program has operated since 1989. It

is anticipated that approximately 11,000 sea days will be sampled in 2004 for monitoring of

protected species and fishery discards. Discard data are also sought from fishermen in their

mandatory logbook submissions. Preliminary information from this self-reporting program was

correlated with observer estimates from identical trips. Although analyses suggest no obvious

discrepancies, this may be due to the effect of the presence of the observer. Much more analysis

of information and communication with fishermen is necessary before self-reported estimates of

discards can routinely be incorporated into stock assessments.

3.6 Pacific Islands Region

Bottomfish fisheries occur throughout the Western Pacific region. The largest is in the

Northwestern Hawaiian Islands (NWHI). Most of the bycatch in that fishery consists of three

carangids (Caranx ignobilis, Pseudocaranx dentex, and Seriola dumerili) and sharks, all of

which are discarded for economic reasons. The first two carangids and sharks have generally

low market values and do not keep well. Most shark species require special on-board processing

and storage to make their flesh marketable. The value of S.dumerili or kahala is very low

because it has been implicated in ciguatera poisoning incidents. These species account for 80%

to 90% by number of all bycatch in the fishery. It appears that no more than 25%, by number, of

the catch in the NWHI bottomfish fishery is discarded. The mortality rate of discarded fish is

highly variable among species. Although bottom-dwelling teleost fishes generally suffer high

mortality from decompression while being brought to the surface, the carangid species that make

up most of the bycatch in the NWHI bottomfish fishery are usually released alive and apparently

viable. 

Among protected species of sea turtles, marine mammals, and seabirds, only Hawaiian

monk seals and Pacific bottlenose dolphins appear to have interactions with the NWHI

bottomfish fishery, where they take fish from fishing lines. These species are rarely hooked and

no fatal interactions have been documented. Seabirds have often been observed attempting to

steal bait, but no hookings have been observed. Complete bycatch data are not yet available for
21

the bottomfish fisheries in the main Hawaiian Islands, American Samoa, Northern Mariana

Islands, or Guam, but bycatch rates in those areas appear to be substantially less than in the

purely commercial and distant-from-port NWHI bottomfish fishery. 

An additional source of bycatch in the bottomfish fisheries is unobserved mortality,

stemming from fish that escape from the hook and fish that are taken from the hook by predators. 

Research suggests that losses due to predation in the NWHI bottomfish fishery amount to

perhaps 23-27 fish lost for every 100 fish boated. 

Bycatch is assessed and reported in the bottomfish fisheries through logbook programs

and creel surveys, many of which have undergone substantial improvements since 1996, when

the MSA was amended to include bycatch requirements. A vessel observer program in the

NWHI has provided important information on bycatch and bycatch mortality, including

interactions with protected species. Fishery-independent data sources, including experimental

fishing projects in American Samoa and the Mariana Islands, have also provided bycatch-related

data.

The Hawaii-based longline fishery is the largest pelagic fishery managed by the Western

Pacific Fishery Management Council (WPFMC). The longline fishery in American Samoa has

grown rapidly in the last three years with the entry of more and larger vessels. The largest

component of the bycatch in the Hawaii-based longline fishery is sharks, particularly blue shark. 

Sharks and other finfish species are discarded for economic reasons. According to vessel

observer data, during 1994-2001, about 40%, by number, of the total catch in the Hawaii-based

longline fishery was discarded. The percentage discard rate was about 13% for tunas, 15% for

billfish, 63% for sharks, 32% for other Management Unit Species (MUS), and 97% for nonMUS. 

In the past, many sharks were finned – that is, their fins were retained while their

carcasses were returned to the sea. The finning rate peaked in 1999, when about 65% of all

captured sharks were finned. Blue sharks represented 95% of all finned sharks. Two important

regulatory changes in 2000 and 2001 substantially altered bycatch rates and bycatch mortality

rates. State and federal prohibitions on shark finning increased the percentage of blue sharks that

were discarded, decreased the blue shark absolute bycatch mortality rate (because blue sharks

have relatively high post-hooking survival rates), and slightly increased the retention rate of

whole blue sharks. The 2000 closure of the swordfish directed fishery also greatly decreased the

catch of blue sharks and thereby decreased the fishery’s overall bycatch rate. Vessel logbook

data indicate that in 2001, 96% of the approximately 47,000 sharks caught in the Hawaii-based

longline fishery were discarded.

Interactions between the Hawaii-based longline fishery and sea turtles were significant

enough that the fishery, as managed in 1999, was determined under the ESA to jeopardize the

continued existence of three sea turtle species: the loggerhead, leatherback, and green. 

Interactions between the longline fishery and false killer whales have reached levels that exceed

the PBR of false killer whales. Subsequent regulations – particularly the closure of the

swordfish-directed fishery – have resulted in substantially lower interaction rates with sea turtles. 

The Hawaii-based longline fishery interacts with several species of seabirds. Most interactions

are with the black-footed albatross and the Laysan albatross. Regulatory changes aimed at

decreasing the incidental catch of sea turtles, as well as new seabird-related measures, have led to
22

substantially lower interaction rates with the two albatross species, and probably have

substantially reduced the likelihood of interactions with a third, endangered, species, the shorttailed albatross. An April 2004 final rule eliminated a seasonal closure for longline fishing in an

area south of the Hawaiian Islands and reopened the swordfish-directed component of the

Hawaii-based longline fishery. To minimize adverse impacts on sea turtles, the swordfish

component of the Hawaii-based longline fishery is subject to restrictions on the types of hooks

and bait that may be used, annual fleet-wide limits on fishery interactions with leatherback and

loggerhead sea turtles, an annual fleet-wide limit on fishing effort, and other mitigation

measures.

Reliable estimates of bycatch and bycatch mortality rates in the small-boat troll and

handline fisheries of all the island areas are not yet available, but bycatch and bycatch mortality

rates are believed to be relatively small because few species and sizes are unwanted and because

when fish are discarded they are often in viable condition. An additional source of bycatch in the

pelagic fisheries is unobserved mortality, but no estimates of likely mortality rates are available. 

Bycatch and protected species interactions are assessed and reported in the Hawaii-based

longline fishery through a logbook program and a recently expanded vessel observer program. 

Bycatch in the American Samoa fishery is measured through creel surveys and a logbook

program, and will soon be further assessed through a vessel observer program. Bycatch in the

other pelagic fisheries is monitored through local catch reports and creel surveys.

A variety of operational and management measures are used to minimize bycatch and

bycatch mortality in the bottomfish and pelagics fisheries. In the bottomfish and troll and

handline fisheries, the gear types and fishing strategies used tend to be relatively selective for

desired species and sizes. Measures that serve to further reduce bycatch in the bottomfish fishery

include prohibitions on the use of bottom trawls, bottom gillnets, explosives, and poisons. In the

pelagic fisheries, a prohibition on the use of drift gillnets is aimed at reducing bycatch. New area

closures and gear restrictions have been very successful in minimizing the bycatch of sharks,

marlins and protected species interactions. Longline vessels are also required to employ

specified mitigation measures to avoid catching sea turtles and seabirds and increase the

likelihood of their survival after being released. As mentioned above, the swordfish component

of the Hawaii-based longline fishery is subject to restrictions on the types of hooks and bait that

may be used, annual fleet-wide limits on fishery interactions with leatherback and loggerhead sea

turtles, an annual fleet-wide limit on fishing effort, and other mitigation measures. Restrictions

on the use of bottom-set longline gear are being developed to further reduce bycatch and

protected species interactions. Bycatch reduction is also achieved through non-regulatory means,

including outreach to fishermen and engagement of fishermen in research activities and the

management process.
23

4. Alternative Methods for Monitoring Bycatch

Various methods are being used to monitor and estimate bycatch. Some of these methods

may also be useful for developing bycatch reduction measures and for monitoring the

effectiveness of such measures. The primary emphasis of this discussion will be on an

evaluation of methods for monitoring bycatch levels in both commercial and recreational

fisheries. Clearly, it is critical to have credible estimates of the type, rate, and level of bycatch

currently occurring, as well as information on the fishing practices and other factors that may

contribute to bycatch. 

Several types of monitoring programs have been developed to estimate fisheries bycatch. 

These include the use of data collected aboard fisheries research vessels and chartered vessels,

self-reporting by fishermen and/or other industry representatives, at-sea fisheries observers, video

cameras, digital scanning devices, alternate platforms or remote monitoring, and stranding

networks. The choice of which method or mix of methods to use for monitoring bycatch in a

particular fishery is based on a number of factors including:

• Quality – in general, how precise and how accurate are the data that are collected? 

• Completeness – does sampling cover the entire range of the fishery or fisheries

that interact with the species of concern?

• Credibility – how well do the data stand up to scrutiny by affected stakeholders

and other constituents? 

• Cost – what are the relative expenses associated with the sampling method, and

are there economies of scale that can be realized?

• Timeliness – how quickly are the data available to fisheries scientists, managers

and fishermen? 

• Safety – how safe is the methodology compared to other monitoring methods, and

what safeguards are in place to ensure the safety of the data collectors?

• Logistics – how easily is the monitoring program implemented and maintained?

The following discussion of alternatives for monitoring and estimating bycatch highlight the

preceding factors where relevant.

4.1 Fishery-Independent Surveys

It is possible to use fishery-independent surveys to estimate bycatch from a fishery. This
24

is done by multiplying the effort that occurs in the fishery (by relevant strata) times the rate of

bycatch that is observed in fishery-independent surveys. The suitability of this approach depends

on how closely the fishery-independent observation methods (gear, etc.) mimic those of the

fishery. In order to discuss this more fully, one should understand the usual role of fisheryindependent surveys within NMFS’ research programs.

 NMFS conducts a variety of surveys during specific seasons in both offshore and inshore

waters, using both NOAA and chartered survey platforms. Surveys are conducted according to a

schedule that varies according to the species sampled, the availability of survey platforms, and

weather conditions (see NRC 2000, p.68, for a summary of NMFS Research and Charter Vessel

Surveys). By definition, fishery-independent data are collected independently of fishing

activities, and include information on the distribution, abundance, and biology of the species

being assessed. These data are collected using standardized sampling gear (e.g., trawls, hooks, or

pots), with multiple samples taken, distributed over the range of the stock (NMFS 2001).

The usual objective of fishery-independent research surveys is to provide information to

characterize various species of concern, specifically year-to-year variation in abundance for these

species. Other secondary goals may include spatial and temporal distribution patterns, size and

age composition, fecundity measurements, and environmental monitoring. With any survey

cruise, abundance levels and life history information for as many species as possible are

gathered. In some cases, these may include species of concern for bycatch monitoring.

To determine the abundance of the various species, the measurement or index of interest

taken during the survey is catch-per-unit-of-effort (CPUE). This value can be measured in either

weight or number. The CPUE value is a product of two terms, the actual abundance of the

species (N) and the catchability coefficient (q) related by CPUE = qN. The catchability

coefficient represents the fraction of the stock removed per unit of effort. It is desirable that this

coefficient exists as a constant, but many external factors can have pronounced effects on the

catchability coefficient for a particular species. These factors include the type of gear, bottom

topography, species distribution, and species size. The goal of this kind of research survey is to

monitor the stock in a consistent manner such that the catchability coefficient is not

systematically biased. In so doing, the CPUE derived from the survey is a measure of relative

abundance of the stock.

There are five basic principles to which any research survey cruise must adhere if the

research goals are to be achieved. Each of these principles is required for the species of interest.

1. The cruise should be synoptic in that it provides a snapshot in time (temporal

component). Both fishing and natural mortality rates are an important consideration with

this factor. If synoptic stock-wide surveys are not possible, assessment models may be

used to estimate populations from partial surveys.

2. The survey should be stock-wide in area (spatial component). If only a fraction of the

stock is sampled, calculated abundance levels can be misleading in assessments.
25

3. The sampling design should be well defined in order to obtain a representative sample of

the stock; the usual approach is to use some type of random or stratified random

statistical design.

4. The survey design should produce some level of useful precision with regards to the

abundance estimate. Both the number of observations and the quantity of catch are

important for this parameter. For each sample there must be enough of each species of

interest, but not so much as to overwhelm the effort and cause complex sub-sampling

efforts. Many bycatch species of interest may be comparatively rare in the sample. 

However, in most cases, the system is forgiving with this principle, and even low

precision estimates can be, and are often, useful in assessment efforts.

5. The survey should control bias. It is important to keep all controllable factors as constant

as possible, doing the survey in the same way, with the same gear.

In any regional research effort, both fishery-independent and fishery-dependent data are

necessary to accurately assess the various fishery stocks and to address any potential bycatchrelated problems. Resource survey trips are used to sample the stock. On the other hand,

fishery-dependent trips (e.g., observers on commercial vessels) have the potential for much

higher sampling effort. An increase in effort usually produces a higher level of precision, but it

is possible that these fishery data are not representative of the stock. Basically, when both types

of data are available, fishery-dependent data are mostly used to characterize the catch, while

fishery-independent data is intended to characterize the stock.

When using fishery-independent information, consideration must be given to the

following: 

• Surveys do not always use commercial gear, and when commercial gear is used, it

is often just one of a suite of gears that are being employed. Research gear is

generally smaller and may be of a different configuration than gear generally used

by commercial vessels. 

• Surveys use a different fishing strategy than commercial fishing vessels. Whereas

commercial fishermen generally strive to maximize their economic returns, survey

cruises set gear at predetermined sampling strata, which are sampled year after

year to ensure consistency. 

• Surveys do not generally set gear for the same amount of time as commercial

vessels, and rarely have tow durations of more than half an hour. 

• Surveys are generally limited to certain seasons, whereas commercial fishing may

occur year-round. 
4

 An ogive is a curve relating the cumulative probability of an event (e.g., being retained

by a type of fishing gear) as a function of an explanatory variable (e.g., the size of the

individual).

26

• Surveys may be limited to daytime sets, whereas commercial fishing may occur

around the clock.

A resource survey program using otter trawl gear to sample shrimp resources has existed

in the northern and western offshore waters of the Gulf of Mexico since about 1972. The survey

collects CPUE data on all species collected with this gear. Data are collected using a stratified

random sampling design. Data from these fishery-independent surveys have been used with

some success to estimate bycatch levels of 13 species in the Gulf of Mexico shrimp fishery for

years in which there was no observer coverage. Directly observed commercial finfish CPUE data

from three observer programs in the 1980s (Turtle Excluder Device evaluations, turtle incidental

catch project, and shrimp bycatch project) and one in the 1990s (shrimp bycatch program)

provide good estimates of CPUE for various species during the periods of collection. 

While directed observer observations are discontinuous in space and time, resource

survey cruises provided a common thread that could link the disconnected data from the observer

projects. A Generalized Linear Modeling (GLM) approach was used to estimate what shrimp

vessel catch rates would have been in different years, areas, and seasons, had direct observations

been made throughout. While this approach has been used initially to estimate bycatch levels in

the Southeast shrimp trawl commercial fleet when no direct observations were made, it needs to

be recognized that the data would only support broad breakdowns in time and space categories. 

Estimation of the discard component of bycatch using information derived from fisheryindependent surveys has also been employed in the Northeast region for selected species (Mayo

et al. 1981, 1992). The technique essentially applies a filter derived from a selection ogive4 to

the size composition observed in research vessel surveys in concert with information derived

from the commercial fishery. This method is currently employed to develop bycatch estimates

for two stocks: witch flounder and American plaice.

In this example discard rates are also based on catch, effort, and length frequency data

collected and recorded by the NEFSC Domestic Sea Sampling Program. Sea sample discard

rates are expanded to total discards based on effort data collected and recorded in the NEFSC

interview and weighout system, and on indices as determined by NEFSC spring and autumn

bottom trawl surveys. 

The credibility of bycatch estimates based in part on fishery-independent data will tend to

be greater when the fishing operations that occur during the survey cruises and commercial

fishing are similar.

4.1.1 Costs of Estimating Bycatch from Fishery-Independent Surveys

Although collecting fishery-independent data is expensive (up to $10,000 per day vessel
27

operating costs), the primary objective of surveys is to provide information on abundance trends

for stock assessments, and not bycatch estimates. Therefore, the additional cost of estimating

bycatch from survey cruise data is relatively low, but may involve additional sampling of species

considered to be bycatch.

4.1.2 Safety Aboard Fishery-Independent Surveys

Safety concerns are an issue any time data collection programs operate at-sea. These

concerns exist aboard both NOAA vessels and chartered research vessels. NOAA vessels are

overseen by NOAA’s Office of Marine and Aviation Operations, and NOAA vessels must

comply with safety requirements and conduct periodic safety drills (see

http://www.moc.noaa.gov/all_ships/policy.htm for a discussion of shipboard policies with

respect to safety). Although NOAA vessels are considered government vessels and are therefore

exempt from regulatory oversight by the U.S. Coast Guard (USCG), NOAA requires that all of

its vessels and small boats comply with or exceed all applicable regulatory and industrial

standards. For scientists aboard non-NOAA vessels (such as chartered fishing vessels), NOAA

requires that program managers assess the seaworthiness of vessels, the experience of the vessel

operator and crew, and its capabilities for communications and emergency response. However,

the additional safety concerns associated with collecting bycatch data on surveys are probably

minimal.

4.1.3 Summary of Fishery-Independent Surveys

Fishery-independent and fishery-dependent sources of information may differ in several

key respects. Fishery-independent surveys are intended to provide unbiased estimates of

important population attributes such as abundance or size and age composition. Although it also

is important that information derived from the fishery itself is unbiased (i.e., it is representative

of the fishery in terms of catch-per-unit-effort, species composition, size composition of the

catch, and other attributes), fishery operations are not intended to provide unbiased estimates of

population attributes. It is therefore possible to have different signals from fishery-independent

sources and those derived from the fishery. For example, a research vessel survey may detect a

declining trend in overall population size while catch-per-unit-effort remains relatively stable as

fishermen target concentrations of fish.

Inferences can be made from research surveys regarding what commercial bycatch might

be. Fishery-independent surveys may be useful in estimating total bycatch for fisheries in which

observer data are discontinuous. However, fishery-independent estimates do not replace the need

for direct fishery-dependent observer data, and the models that are used to generate such

estimates are best applied to complement direct observations of fishing effort from a developed

observer program or as a beginning point for developing more mature observer programs. 

Fishery-independent estimates of bycatch will always be subject to criticism that the

characteristics of the research effort are different from those of the fishery and that those

differences are not adequately incorporated in the estimation process. 
28

4.2 Fishery-Dependent Self-Reporting

Fishery-dependent data are data collected from commercial and recreational fishing

activities, thereby providing information on removals associated with actual fishing operations. 

Self-reporting programs include fishing logbooks completed by fishermen, landings reports

completed by fishermen and/or dealers (i.e., buyers or processors), and interviews of commercial

and recreational fishermen. In some cases these programs collect bycatch data, but in most cases

they provide effort or landed catch data that can be used with bycatch rate estimates from other

sources (e.g., observer programs) to estimate bycatch. Dealer reporting is one type of selfreporting in which dealers are required to report the amounts of fish bought and sold, by vessel

and by species. Dealer reporting is required by nearly all state resource agencies, but does not

generally include reporting of at-sea discards. One exception to this is the Alaska Department of

Fish and Game’s requirement that all discards be reported; however, compliance is a concern. 

4.2.1 Logbooks

Mandatory reporting requirements for logbooks are a type of self-reporting and are

generally more detailed, and may include information on the type of gear used, date, time of day,

and position of fishing activity, weather conditions, fishing characteristics of the deployment of

the gear (e.g., tow length, number of hooks set), and catch of non-target species. Bycatch data

reported in logbooks can be useful in estimating bycatch, but only if fishermen are willing and

able to report bycatch accurately in the logbooks. Outreach and compliance programs can be of

assistance with both. However, many logbook programs do not require the reporting of bycatch,

or do not place a strong emphasis on accurate reporting of bycatch (Table 1).

The MMPA’s Marine Mammal Authorization Program has as its primary focus the selfreporting of marine mammal incidental mortality and serious injury. Under the MMPA, all

fishermen participating in a state or federal fishery that operates in U.S. waters are required to

report all injuries and mortalities of marine mammals associated with fishing operations to

NMFS within 48 hours of returning to port. This requirement was enacted by the 1994

amendments to the MMPA, and replaced a marine mammal logbook reporting requirement that

had been in place for all Category I and II fisheries since 1989 (the Marine Mammal Exemption

Program). However, the Program has not succeeded in obtaining reliable marine mammal

bycatch data. Despite fairly good outreach and the distribution of reporting forms to all state and

Federally-permitted fishermen each year, compliance with the reporting requirement is thought to

be very low (Patricia Lawson, NMFS Office of Protected Resources, pers. comm.). Compliance

with the previous Marine Mammal Exemption Program logbook requirement varied from fishery

to fishery, but overall was also very low (Credle 1993).

Fox and Starr (1996) note that for logbooks to be useful for bycatch monitoring,

cooperation from the majority of fishermen is critical.

4.2.1.1 Accuracy of Logbooks

Inaccuracies of logbooks primarily result from misreporting of species that are of little

economic interest (particularly of bycatch species) and low compliance rates with reporting
29

requirements. If fishermen perceive that accurate reporting of bycatch will result in restricted

fishing effort or access, they have an incentive to underreport. The effects of that incentive

probably vary by fishery and fisherman.

The self-reporting system used in the Northeast for both landings and discards is typical

and is presented here in some detail. Fishery statistics were collected in the Northeast under a

voluntary reporting system prior to 1994. Landings and price data were collected by NMFS port

agents and state personnel at the point of first sale through dealer reports or "weigh-out receipts”. 

This information was complemented by interviews of vessel captains by NMFS port agents at

dockside to collect detailed data on fishing effort and gear used and areas fished, and by a

monthly canvas to collect landings data at secondary ports. 

In June of 1994, voluntary reporting was replaced by a mandatory reporting system in

which dealer reports were retained, and dockside interviews were replaced by a logbook

reporting system. The dealer reports contain total landings by market category. The Vessel Trip

Report (VTR) data contain information on area fished, species kept and discarded (in pounds),

gear type (gear size, gear quantity, mesh size), and effort (number of hauls, haul duration and

crew size). These data are from logbooks from charter, party and commercial trips, as well as

logbooks that document that no fishing took place during a given month. Essential data elements

such as location fished, gear used and amount of fishing effort, previously annotated by port

agents through interviews, do not now exist in the dealer reports and must be extracted from

corresponding VTRs. Dealer reports are assumed to provide accurate totals for landings and

revenue; VTRs are the source of a subset of the dealer data.

This system is now used in all Northeast fisheries subject to federal FMPs, except the

American lobster fishery. However, many vessels that fish for lobster are permitted under one or

more of the remaining federal FMPs, and are therefore subject to mandatory reporting. The

transition to the mandatory reporting system based on logbooks has resulted in concerns about

data quality and reliability (NEFSC 1996), and the use of VTR data for discard estimation must

be carefully evaluated on a case-by-case basis. Further comparison of discard estimates derived

from the self-reporting system and other sources such as the Northeast observer program is

essential. The observer coverage rates have increased over the last two years, making further

calibration of different systems for bycatch estimation more reliable. If the self-reported data can

be verified, the broad fishery coverage possible will substantially enhance estimation of bycatch. 

In the Northeast, a comparison of observer and logbook estimates of cod discards showed

consistency in two of the three years that were examined.

The accuracy of self-reporting can be inferred from comparisons of discard information

derived from logbooks or vessel trip report system and observers (either on the same trips or

operating in similar areas). Logbook data submitted by Hawaii longline fishermen was compared

to data gathered by longline observers (Walsh 2000). The study tested the assumption that the

accuracy of logbooks in reporting species of major commercial importance (swordfish, bigeye

tuna, and yellowfin tuna) would be greater than the reporting of species of lesser importance

(spearfish and skipjack tuna), or species caught in great numbers (blue shark and mahimahi). 

The study also examined the accuracy of fish identifications on sets with protected species

interactions, and compared reported fish catches to records from the same vessels that had sold

their fish to a public fish auction (more information on the results of the accuracy of observer

reports is in the next Section on observers). Sets with observed interactions with protected

species were of particular interest, as observers were instructed to give these sets the highest 
30

Table 1. Federally managed fisheries with mandatory logbook requirements and bycatch

reporting requirements.

Region Fishery/FMP (Gear Type(s)) Species of Bycatch Required to be Reported

Southwest Coastal Pelagics – Sardine, Anchovy,

Mackerel, Squid (Purse Seine, Lampara Net,

Drum Net)1

None

Highly Migratory Species – Swordfish, Tuna,

Sharks (Purse seine, longline, troll/baitboat,

drift gillnet, and harpoon)

All discards, including protected species

Southeast Highly Migratory Species –

Swordfish/Tuna/Shark (Limited Access

Pelagic and Bottom Longline)

All discards, including protected and prohibited

species

Snapper/Grouper/Wreckfish (Bottom

Longline, Trap) All discards, including protected species

Coastal Migratory Pelagics – Mackerel,

Dolphin and Cobia (Gillnet, Handline, Troll

Line) 

All discards, including protected species

Reef Fish (Bottom Longline, Trap) All discards, including protected species

Golden Crab (Trap/Pot) All discards, including protected species

Coastal Sharks (Bottom Longline) All discards, including protected species

Headboat/Charterboat (Rod and Reel) None

Northwest West Coast Groundfish (Limited EntryTrawl)1 All Fish

At-Sea Pacific Whiting (Trawl)2 All Fish

Recreational Salmon and Groundfish

Charterboat/Party Boat All Fish

Alaska Bering Sea/Aleutian Islands Groundfish for

vessels > 60' (Trawl, Longline, Pot, Jig) All Fish

Gulf of Alaska Groundfish for vessels > 60'

(Trawl, Longline, and Pot) All Fish

Pacific Halibut (Longline) None

Northeast Groundfish Multispecies, (Trawl, Gillnet) All discards, including protected species 3

Scallop (Dredge, Trawl) All discards, including protected species 3

Monkfish (Trawl, Gillnet) All discards, including protected species 3

Summer Flounder (Trawl) All discards, including protected species 3

Scup,black sea bass (Trawl and Pot) All discards, including protected species 3

Tilefish (Bottom Longline) All discards, including protected species 3

Bluefish (Gillnet) All discards, including protected species 3

Herring (Seine and Midwater Trawl All discards, including protected species 3
31

Table 1 (Continued)

Region Fishery/FMP (Gear Type(s)) Species of Bycatch Required to be Reported

Northeast

(Continued) Spiny Dogfish (Gillnet) All discards, including protected species 3

Red Crab (Pot) All discards, including protected species 3

Squid, Mackerel, and Butterfish (Trawl) All discards, including protected species 3

Pacific

Islands

Western Pacific Pelagics – Swordfish, tuna,

shark (Longline) All discards, including protected species

Precious Corals (direct collection) None

Crustaceans (Traps) All fish

Bottomfish (hook and line, bottom longline) All fish

1

 Reporting requirements outlined in state (not federal regulations. 

2

 Voluntary reporting.

3

 Although reporting of all discards is required, only species codes for sea turtles are provided with the Vessel Trip

Report instructions. Species codes for marine mammals and seabirds are not provided.

priority, and this may have introduced a bias with observers with respect to reporting catches of

other species. The study found biases due to underreporting in logbooks, taxonomic errors by

both novice observers and fishermen, difficulties by both groups in counting abundantly caught

species, and incorrect use of logbooks (e.g., recording data in the wrong area of the logbook). 

The study also determined that the most common errors in logbooks were underreporting of

catches and “rounding” of values reported for abundantly caught species catch. From this study,

one could infer that logbooks may not be reliable for estimating bycatch of abundantly caught

species or species of lesser economic value.

Further work evaluated the usefulness of logbooks to characterize fish catches for the

unobserved segment of the longline fleet (Walsh et al. 2002), specifically blue sharks, a retained

incidental catch in this fishery. This study reiterated the tendency of logbooks to underreport

catches as compared to observer reports, but also revealed several cases of overreporting of blue

shark catches in logbooks. However, data from logbooks in conjunction with observer data

allowed the authors to model catches of blue sharks for the unobserved portion of the fleet, using

a Generalized Additive Model (GAM). The authors also noted that reporting accuracy improved

after the deployment of observers, presumably due to increased awareness among fishermen of

their reporting requirement.

The advantage of logbooks as compared to other sampling methods is that logbooks are

usually required of all fishery participants, and therefore represent a near-census of the fishery. 

There are few other sources of data for estimating fleet-wide effort by time and area. Reliable

measures of effort are critical when using observed bycatch per unit effort to estimate bycatch for

the fishery as a whole. However, if there is less than-complete-compliance with the logbook

requirement, or reporting significantly misrepresents actual fishing effort (due to, for example,

effort limitation regulations such as days-at-sea limits), extrapolated bycatch estimates may be

inaccurate.
32

4.2.1.2 Costs Associated with Logbook Programs

The costs of logbook programs to the agency which conducts the program are typically

less than the costs of observer programs, if compared on a per-sea-day basis. The costs to the

agency include producing and distributing the logbooks, data entry, database maintenance, and

analytical costs. As with fishery surveys, logbooks are generally not implemented solely to

collect information on bycatch. Therefore, the cost of collecting bycatch data via logbooks is

marginal, and may be limited to costs associated with the entry and analysis of the bycatch data.

4.2.1.3 Safety and Logistics of Logbooks

Concerns regarding safety are limited to concerns that already exist with fishing

operations, which are substantial for fishermen but basically nonexistent for those processing

logbooks. 

Logistics associated with logbook programs considered here include the timeliness of

data submission to the government, the time required for data entry, and promising advances in

the use of technology for more timely reporting of logbook data. 

Timeliness of data varies with the fishery. Requirements for submission of data may

range from a weekly basis to an annual basis. Timeliness and overall compliance with the

reporting requirement can be improved if the issuance of permits is contingent on the submittal

of logbooks (this system is only applicable where permits are required). In some cases, port

agents or other agency employees or contractors collect logbooks dockside, which also increases

timeliness and compliance. 

Data entry can be time-consuming, and can delay accessibility to the data. A rigorous

quality control program must be integrated into data entry, with at least 5-10% of logbooks

double entered and safeguards in the software to minimize transcription errors (such as the use of

dropdown pick lists, and verification of entries that fall outside preestablished ranges). 

Recent advances in technology have automated the collection and entry of self-reported

fisheries data in some fisheries, and these advances hold the promise of more timely estimates of

effort for use in catch and bycatch estimation on a real-time or in-season basis. They can also be

a source of reliable information when spatial and temporal information is conveyed automatically

for each set (e.g., systems that have built-in GPS and time/date stamp units). Electronic logbooks

can also reduce the frequency of transcription errors, but they may introduce other errors. Proper

training of fishermen in data entry is critical but can be less rigorous for well-designed programs. 

Secure data transfer systems are also critical.

4.2.1.4 Logbook Program Summary

Logbooks may provide qualitative estimates of bycatch where bycatch is required to be

reported; however, the accuracy of these data is of concern. Logbooks are more useful in

providing estimates of total effort by area and season that can then be combined with observer

data to estimate total bycatch. Safety concerns associated with logbook programs are minimal, as

compared to at-sea data collection programs. Logistics associated with processing the data
33

collected have limited its usefulness, but may be aided by recent technological advancements

designed to increase the speed at which data are transferred while also improving the quality of

data submitted.

4.2.2 Port Sampling

Port samplers are federal or state government-employed or contracted biologists trained

to collect fishery information and biological samples from fishermen and/or dealers, at or near

the time of landing. In some cases, the presence of a port sampler is required to offload fish (the

port sampler is making direct observations of what is landed); in other cases, a random sampling

strategy is employed, while taking advantage of opportunistic sampling where possible.

Port samplers collect information primarily on catch, but also on bycatch when such

information is available. Bycatch data collected by port samplers are similar to logbook data in

that there are significant concerns about the completeness and accuracy of these reports. Because

fish discards are not observed by the port sampler, information on discards is less reliable than

information on landings. Data from interviews with fishermen or dealers may not be

representative of total catch, as they depend on the ability and willingness of these individuals to

report catches accurately. Biological sampling is limited to only the landed catch. In addition,

port sampling typically results in only a small sample of total fishing effort, and port samplers are

not consistently used in all U.S. ports. An advantage over logbooks, though, is the timeliness of

these reports and their usefulness in directing further sampling towards potential problem areas. 

4.2.3 Recreational Sampling

In most coastal states, recreational fishery data have been collected under the annual

Marine Recreational Fisheries Statistics Survey (MRFSS) since 1979. The objective of this

survey is to provide estimates of recreational catch and effort over fairly large strata (by state and

two-month period). In 1997, nearly 17 million anglers made 68 million marine fishing trips to

the Atlantic, Gulf, and Pacific coasts. The estimated marine recreational finfish catch was 366

million fish, and more than 50% of the fish caught were released alive. The survival rates for the

released fish are highly variable. 

The MRFSS data are collected by two independent but complementary surveys: (1) a

telephone survey of households in coastal counties, and (2) an intercept (i.e., interview) survey of

anglers at fishing access sites. The telephone survey is used to collect reliable data on

recreational fishing effort. Information on the actual catch (and bycatch), such as species

identity, number, and both weights and lengths of fish are collected via the intercept survey. 

Estimates of landed catches are based primarily on direct observations made by trained samplers. 

Estimates of bycatch are based on self-reporting during the intercept interviews. However,

because fish discards are not observed by the interviewer, information on bycatch is less reliable

than information on landings.

In an effort to increase the quality of data on bycatch, NMFS has also initiated an at-sea

component of the intercept survey on the party/headboat fleets. This sampling is currently

focused on vessels operating in the Atlantic. NMFS also funds at-sea data collection in Pacific

states through the Pacific States Marine Fisheries Commission’s Recreational Fisheries

Information Network (also known as RecFIN). If this program is successful, it would improve
34

the accuracy of counts and species identifications of discards and provide estimates of size

distribution of discarded fish, which are currently unavailable (Dave Van Voorhees, NMFS

Office of Science and Technology, pers. comm.).

4.3 At-Sea Observations of Fishing Operations

4.3.1 At-Sea Observers

At-sea fisheries observers are biologists trained to collect information onboard fishing

vessels. Observers may be deployed for various reasons, including monitoring of protected

species interactions or total removals (including discarded species), monitoring compliance with

fishery regulations or other environmental laws, validating or adjusting self-reported data,

providing vessel-by-vessel catch, providing data to support in-season quota management, and

monitoring experimental or exempted fishing activities. See NMFS (2004) for a more detailed

discussion of observer program goals and objectives.

Regardless of the primary objective for placing observers in a fishery, at-sea observers are

generally trained to collect information on the catch and bycatch, as well as information on the

disposition (e.g., released alive vs. dead, or where hooked in the case of protected species taken

in longline fisheries) of some or all of the bycatch species. Observers routinely collect biological

samples and also may assist with fisheries research or tagging studies. Besides data on catch and

bycatch, observers may also collect information on gear used, vessel type and power, fishing

techniques, fishing effort, gear characteristics, environmental conditions, and, in certain fisheries,

economic information (e.g., crew size, crew shares and the cost of fuel, bait and ice). 

The wide range of information collected by observers is useful for analyzing life history,

determining gear selectivity and fishing efficiency over time, and studying the behavior of fish

and fishermen. Observer data can also be used in combination with information collected from

fishery-independent sources, port observations, and landings receipts to estimate the relative

abundance of target and bycatch species in some fisheries.

NMFS’ authority to place observers on certain fishing vessels comes from the MSA, the

MMPA, and the ESA, as well as other marine laws. Table 2 summarizes fisheries that recently

have had some level of mandatory or voluntary observer coverage under federally managed

observer programs.

4.3.1.1 Estimating Bycatch

The impetus for implementing an observer program is often based on bycatch of one or

more species. In most fisheries, it is neither physically nor economically feasible to monitor all

fishing effort, catch and bycatch and to do so without measurement error. The factors that

prevent this include funding limitations, observer program costs, safety considerations, and

logistical constraints. Therefore, observer programs usually sample a portion of total effort. The

reliability of the resulting bycatch estimates is then gauged by such factors as the precision and

accuracy of the estimates.
35

0

0.5

1

0 10 20 30 40 50

CV

0

1

2

3

4

5

6

CV versus Cost

CV of Bycatch Estimate

Cost of Sampling

Number of Observers (increasing ------->) 

Cost (increasing ----->)

Figure 1. Trade-offs between precision (CV) and

cost.

Bycatch mortality can be estimated using standard approaches in which the estimated

bycatch per unit effort for each stratum is multiplied by the total effort and the proportion of

bycatch that die in that stratum (Hall 1999). Fishing effort can be determined from observer data

in fisheries where observers are monitoring all fishing effort. However, for most fisheries,

fishing effort is derived from self-reporting, such as logbooks, port sampling, or landing receipts. 

Alternatively, bycatch mortality can be estimated by multiplying observer estimates of bycatch

per unit of landed catch, total landed catch and the proportion of bycatch that die by stratum.

The proportion of individuals discarded that die can be determined from observer

estimates of the proportion of bycatch in each of several viability categories and research that

links a specific discard mortality rate to each category. That research includes tagging animals

before they are released and tracking them after they are released, holding the animals in nets or

tanks, and conducting stress tests on bycatch species in a controlled environment. The post

release mortality is often referred to as “latent mortality.” For example, the mortality rates of

discarded Pacific halibut vary between 16-100% depending on gear type (Williams et al. 1989)

and method of release (Hoag 1975). The reliability of the bycatch mortality estimate must then

also take into account the reliability of the effort or landed catch estimate and the reliability of

the latent mortality estimate.

4.3.1.2 Precision of Bycatch Estimates

The measure of precision commonly used in reference to estimates of bycatch is the

coefficient of variation, or CV, which is given by the ratio of the square root of the variance of

the bycatch estimate (i.e., the standard error) to the estimate, itself. The lower the CV, the

greater the level of precision. The CV of an estimate can be decreased by increasing the number

of observations which increases sampling cost. However, as the number of observations is

increased, the CV decreases at a decreasing rate. For large samples, the CV of an estimate is

inversely proportional to the square root of the size of a sample. This means that at some point a

further increase in the number of observations cannot be justified in terms of the reduction in the

CV and the associated benefits of the more precise estimate given the increase in sampling cost. 

Therefore, managers seek to achieve a level of sampling that has an acceptable balance between

precision (CV) and cost. Figure 1 illustrates the nature of the relationships between the number

of observations and both the CV of the estimate

and sampling cost. The specific relationships

will vary by fishery and species. 

Fogarty and Gabriel (unpub. ms.)

calculated first-order estimates of relative

precision for discard rates of key species in the

Northeast groundfish fishery, based on observed

bycatch rates at a trip level, stratified by quarter. 

The relative precision is determined by scaling

the standard error of the discard estimates and

dividing by the discard level. The relative

precision of discarded catch estimates (by stock)

ranged from 0.13 for American plaice, to 1.56

for the Gulf of Maine-Georges Bank

windowpane flounder, illustrating the difficulty

in designing a sampling program that generates

precise estimates for all bycatch species. For the 
36

Table 2. Fisheries with federally managed observer programs.

Region Fisheries Authority to 

place observers 

Program

duration

Southwest California/Oregon Pelagic Drift Gillnet MMPA Cat. II, MSA 1990 to present

California Set Gillnet MMPA Cat. I Reinitiated in

2003

California Pelagic Longline MMPA Cat. II, MSA 2002 to present

Coastal Purse Seine for Tuna MSA Initiated in 2004

Troll Albacore MSA Initiated in 2004

Southeast Southeastern Shrimp Otter Trawl (including rock

shrimp and calico scallop) Voluntary 1992 to present

Southeast Directed Shark Gillnet MMPA Cat. II, MSA 1998 to present

Atlantic Pelagic Longline MMPA Cat. I, MSA 1992 to present

Southeast Directed Large Coastal Shark Bottom

Longline MSA 1994 to present

Northwest West Coast (CA/OR/WA) Groundfish Trawl and

Non-Trawl Gear MSA 2001 to present

Pacific At-Sea Whiting Trawl Voluntary 1975 to present

Alaska Bering Sea/Aleutian Islands and Gulf of Alaska

Groundfish Trawl, Longline and Pot Fisheries MSA 1973 to present

Alaska Inshore Salmon Gillnet and Purse Seine

Fisheries – (Kodiak Setnet planned for FY04) MMPA Cat. II 1999 to present

Northeast New England Groundfish Trawl and Fixed Gear

(including gillnet) Fisheries

MMPA Cat. I

(gillnet only), MSA 1990 to present

Mid-Atlantic Coastal Gillnet (includes monkfish,

dogfish, and several state fisheries) MMPA Cat. I 1994 to present

Mid-Atlantic Small Mesh Trawl (Squid, Mackerel,

Butterfish) MMPA Cat. I, MSA

2001 was first

year of dedicated

funding

Mid-Atlantic Large Mesh Trawl (summer

flounder, bluefish, monkfish, dogfish) MSA 1998 to present

Atlantic Sea Scallop Dredge - Closed Areas

Exempted Fishery MSA 1999 to present

Atlantic Sea Scallop Dredge - Open Areas MSA 1994 to present

Pacific Islands Hawaii Pelagic Longline MSA 1994 to present

flounder example, the use of combined strata substantially improved the precision of the

estimate. However, this analysis was based on non-target species that are easy to identify. The

true challenge occurs when species are not readily identifiable and when several species need to

be identified in a single haul. If the same type of study were conducted with 80 to 100 species,

the results might be quite different because of the difficulty encountered for species with patchy
37

spatial or temporal distributions. Sampling designs and precision goals are examined in Section

5.

4.3.1.3 Accuracy and Bias of Bycatch Estimates

Observer programs strive to achieve samples that are representative of both fishing effort

and catches. Representativeness of the sample is critical not only for obtaining accurate (i.e.,

unbiased) estimates of bycatch, but also for collecting information about factors that may be

important for mitigating bycatch. Bias may be introduced at several levels: when vessels are

selected for coverage, when hauls are selected for sampling, or when only a portion of the haul

can be sampled. Biases in sampling may also be introduced just by having an observer onboard

the vessel, this is referred to as the observer effect.

Vessel selection strategies vary from fishery to fishery, depending on how the fishery is

prosecuted, the nature of the observer program (voluntary vs. mandatory coverage), the

distribution of fishing vessels, and safety and accommodation concerns. In the West Coast

groundfish fishery, vessels are selected for coverage for an entire two-month cumulative trip

limit (NWFSC 2003). This selection strategy minimizes bias associated with estimation of

discards, as the tendency to discard certain species that are managed by trip limit quotas may

increase as the trip limit period draws to an end (Jon Cusick and Rick Methot, NMFS Northwest

Fisheries Science Center, pers. comm.). Voluntary programs may be designed to achieve a

representative sample, but may be subject to bias if there are refusals by selected vessels. The

fishing effort associated with vessels fishing out of one or a few major ports may be easier to

track to ensure randomization of observer coverage than with vessels fishing out of many smaller

ports. Concerns regarding safety or accommodations may limit the pool of sampled vessels and

affect NMFS’s ability to achieve a random sample. Therefore, vessel selection strategies must be

representative of actual fishing effort, in terms of time (i.e., over the entire fishing season) and

space (i.e., over the full geographic range of the fishery), as well as vessel type, gear type and

targeting strategy.

Once the vessel has been selected for coverage, either all hauls are sampled, or a portion

of the hauls are sampled. For fisheries that operate around the clock, where only a portion of the

hauls can be sampled, methodologies must be used that randomize which hauls are chosen for

sampling. The North Pacific Groundfish Observer Program uses a combination of Random

Sampling Tables and Random Break Tables to assist observers in determining which hauls

should be sampled to ensure randomness (AFSC 2003). 

In certain fisheries, such as some trawl and purse seine fisheries, observers may only be

able to sample a portion of the entire catch in a sampled haul. Sampling methodologies have

been developed in the North Pacific groundfish trawl fishery to ensure a random sample of the

catch is taken, and observers are also encouraged to maximize their sample size to minimize bias. 

However, they are also cautioned to be aware of sources of bias such as mechanical interferences

that affect how fish flow to the point where they are sampled, or deliberate interference and

intentional pre-sorting of the catch, and steps that should be taken to avoid and/or document

these biases (AFSC 2003). Sampling of the catch can also be biased in gillnet or longline

fisheries, if an observer is unable to see the net or line as it comes out of the water, due to where

the observer is physically located on the vessel or due to weather conditions that may limit

visibility. In these instances, animals may be caught but released before being brought on board,

without the observer’s knowledge or before the observer is able to make a positive species

identification.
38

Another source of bias is known as the “observer effect”. The observer effect is the

change in fishing behavior caused by having an observer onboard a vessel. This can result in

avoidance of known “hot spots,” reduced fishing effort, or extra attention paid to the quick

release of live animals. This may also result in interference with observer sampling by the crew

or intimidation of the observer in order to prevent observers from making accurate estimates for

observed hauls. When it is reported, such interference and intimidation can be addressed by

observer program managers and enforcement officials. The management regime can affect both

the nature and magnitude of the observer effect. For example, if there are bycatch limits that can

either close a fishery or trigger time and area closures, fishermen will have a greater incentive to

take actions that result in an observer effect bias.

The observer effect can be difficult to measure and account for. Although increases in

observer coverage may increase the accuracy of bycatch estimates by decreasing the chances that

observed operations are not representative of all operations, this is not recommended without

first attempting to quantify this effect through some other, independent assessment of fishing

activity. This could include analysis of data from logbooks, landings reports, Vessel Monitoring

Systems (VMS), or electronic monitoring programs. In some cases, a compliance program will

be needed to decrease some of the bias introduced by the observer effect.

It can be difficult to determine how representative the observed catch and effort are of

total catch and effort in a fishery and how accurate the observer estimates are for the sampled

catch. It is more difficult to do either for new programs or programs with low levels of coverage,

where knowledge is limited regarding the unobserved portion of the fleet.

Determining the accuracy of observer data can be difficult unless there are methods for

validating these data. Walsh et al. (2002) evaluated data collected by observers in the Hawaii

longline fishery against auction house data and found that, overall, occurrences of errors were

low, and errors either in the misidentification of pelagic species or in the enumeration of

abundantly caught fish were more likely to occur due to inexperience in either the job or the

fishery, or the poor performance of a single individual. Walsh et al. (2002) concluded that the

relatively small number of errors in the Hawaii observer data set increased the usefulness of these

data in verifying the accuracy of logbook data.

Where bias cannot be eliminated through adherence to strict sampling protocols, it must

be accounted for by measuring the extent of the bias and incorporating this into analysis of the

data.

The adequacy of samples obtained in an observer or other bycatch data collection

program must be viewed in terms of both the precision and accuracy of the resulting bycatch

estimates. The accuracy of an estimate is the difference between the mean of the sample and the

true population value. The precision of an estimate is essentially how repeatable an observation

would be if a number of independent trials were to be conducted. The mean square error (MSE)

of an estimate is composed of two additive elements, the variance of the estimate and the square

of the bias (Cochran 1977, pp. 15-16). It is possible to partition considerations related to the

accuracy and precision of bycatch estimates, but a full evaluation requires estimates of both

elements. Obtaining independent estimates to assess bias fully can be particularly difficult but

should be carefully pursued.

Babcock et al. (2003) examine important issues related to the potential for bias in bycatch

estimates derived from observer programs due to factors such as non-random sampling and

changes in fishing tactics when observers are onboard (the “observer effect”). The difficulty in

obtaining a strictly random sample is evident in many observer programs where logistical
39

constraints in scheduling and variable levels of cooperation are common. Often, sampling has

been undertaken on an opportunistic basis, particularly during the initial stages of development

of an observer program. The potential for changes in the behavior of fishermen when observers

are onboard must be recognized. Avoidance of areas where bycatch might be high and changes

in trip duration or other aspects of fishing operations when observers accompany the vessel can

result in bias in estimates of bycatch. Babcock et al. (2003) recommend that comparisons of

observed and unobserved vessel trips be routinely made to check for potential bias. Possible

checks based on widely available information include comparisons between observer-reported

information and the landed component of the catch for the fleet as a whole (e.g., Liggens et al.

1997, Sampson 2002). Such comparisons should be implemented in all observer programs,

although it must be recognized that these checks cannot ensure that bias in bycatch estimates is

not present. Comparisons of factors such as trip duration, tow or haul duration, fishing location,

and catch-per-unit-effort and other metrics characterizing a fishing trip made between observed

and unobserved trips can also provide important checks on the adequacy of sampling. These

comparisons will often necessarily be made against self-reported information from the fishing

fleet, and appropriate care must be taken in interpretation.

Babcock et al. (2003) recommend that 20% of all fishing trips for common species and

50% of all trips capturing “rare” bycatch species be sampled. They note that, “The required level

of coverage, however, could be much higher or much lower for a particular fishery depending on

the size of the fishery, distribution of catch and bycatch, and spatial stratification of the fishery.” 

The proportion of hauls that are sampled during an observed trip and the proportion of the catch

in the observed hauls that are sampled, not just the proportion of trips that are sampled, should

be considered in any discussion of the actual or desired observer coverage level.

In this report, we focus on the coefficient of variation of the estimated bycatch rather than

percentage coverage and maintain that the coefficient of variation is a more relevant measure. 

The proportion of trips covered does, however, directly enter into the calculation of precision

through the finite population correction factor. When bias is present, the mean square error

should be used as the measure of variability.

Babcock et al. (2003) further state that increasing the percentage coverage of trips reduces

the likelihood of an observer effect. In essence, it is argued that, as the level of coverage is

increased for a specific vessel, the cost of altering fishing tactics when an observer is on the

vessel is increased; therefore, the net incentive to alter fishing tactics is decreased. Although

there is substantial uncertainty concerning both the extent of this behavior and the change in

behavior that would be associated with a given increase in observer coverage, the expectation is

that both would tend to vary by fishery, if not by vessel or fisherman. Fishery specific research

would be necessary to provide the information necessary to determine whether an increase in

coverage can be justified in terms of a reduction in this type of observer effect. It may be

possible to test for such behavioral change in observer programs in which increases in the

coverage level have occurred over time.

4.3.1.4 Cost and Logistics in Observer Programs

Observer programs can be one of the most expensive monitoring methods available for

estimating bycatch. Direct expenses include the cost of recruiting and training observers, salaries

and benefits (including premium pay while at sea and on-call pay while waiting for a vessel to

depart), contractor profit, travel costs, gear and equipment, and insurance (which can be up to

30% of the cost of a sea day). Some programs also provide a food allowance to the observer or

the vessel while the observer is deployed at sea ($20 to $25/day). The Southeast shrimp trawl

observer program pays $150/day to fishermen for time and shrimp lost due to testing of gear. 
40

Indirect expenses include the salaries and benefits of NMFS employees that oversee the largelycontracted workforce, sampling design and data analytical support, data entry, and database

design and maintenance. Currently, direct expenses may range from $350 to $2,000 per sea day. 

Increased costs are associated with observation of seasonal fisheries, fisheries operating in

remote areas, low effort fisheries that require 100% coverage, fisheries with unpredictable levels

of effort, and fisheries that have fishermen embarking unpredictably out of any number of ports.

Because observer programs are expensive, their use has been limited to date to fisheries

with known or suspected high levels of bycatch. This creates gaps in knowledge where bycatch

may be occurring but is not being documented. Inconsistencies in funding from year to year can

also affect sampling effort over time, creating disparate data sets, and introducing additional

sources of bias.

Currently, the majority of NMFS observer programs are government funded. Notable

exceptions include the observer programs for the North Pacific groundfish fishery, the at-sea

Pacific whiting fishery, and the Atlantic scallop fishery operating in closed areas. Consideration

should be given to how much NMFS should pay and how much specific fleets should pay (in the

form of fees or payments), and whether fisheries should be provided with incentives for having

vessels pay, as in the case of the closed area scallop fishery, where vessels that participate in the

fishery are able to offset observer costs with increased harvest and gross revenues which are

provided by having access to areas that are otherwise closed.

The logistics associated with implementing observer programs and deploying observers

can be substantial. Considerations include procurement of observer services, observer training,

moving observers around, minimizing down time, and deployment of observers in highly mobile

fisheries or fisheries operating out of many ports. Experience in deployment of observers can

minimize logistical difficulties. NMFS has effectively implemented observer programs in each

region of the United States. The National Observer Program in the NMFS Office of Science and

Technology provides a forum for sharing experiences and addressing logistical as well as policy

issues to increase the efficiency and effectiveness of observer programs nationwide. 

Realizing the potential for timely access to observer data can increase the benefits of an

observer program relative to other data collection methods. Real-time access by fishermen to

observer data in the North Pacific groundfish fishery has resulted in reduced bycatch of Pacific

halibut and, consequently, longer fishing seasons; and real-time access by fishery managers

allows for inseason management of groundfish quotas in terms of total catch and of nongroundfish bycatch quotas. Real-time access by fisheries managers to observer data collected in

the Pacific at-sea whiting fishery allows for in-season management and minimization of Pacific

salmon bycatch. 

More widespread sharing of bycatch data could help reduce bycatch and keep bycatchlimited fisheries open longer. However, the proprietary nature of observer data may limit its

effectiveness in pursuing collaborative approaches to mitigation that involve sharing of data with

fishery groups or non-governmental organizations.

Fadely (1999) argued that in the case of some Alaska fisheries where strandings or other

information confirm fishing-related mortality of marine mammals, the best use of funds may be

in outreach efforts to mitigate bycatch, rather than the collection of precise data on the level of

bycatch occurring. Due to limited funds for the deployment of observers in the Gulf of Mexico

shrimp otter trawl fishery, the design of the sampling program is geared more towards

monitoring the effectiveness of gear modifications in reducing turtle and finfish bycatch than for

bycatch estimation.
41

4.3.1.5 Safety in Observer Programs

The safety of observers is a significant factor that should be considered in any expansion

of observer coverage. Fishing is widely recognized as one of the most dangerous professions

(U.S. Dep. of Labor 2002). While a high level of safety training is provided in all NMFS

observer training programs, NMFS is limited in its ability to ensure the safety of an observed

vessel, beyond requiring the vessel to take reasonable actions to ensure the health and safety of

an observer. In 1998, NMFS published a final rule implementing the Observer Health and Safety

regulations, in response to a directive in the MSA that required NMFS to:

Promulgate regulations, after notice and opportunity for public comment, for fishing

vessels that carry observers. The regulations shall include guidelines for determining—

(1) when a vessel is not required to carry an observer on board because the facilities of

such vessel for the quartering of an observer, or for carrying out observer functions, are so

inadequate or unsafe that the health or safety of the observer or the safe operation of the

vessel would be jeopardized; and

(2) actions which vessel owners or operators may reasonably be required to take to render

such facilities adequate and safe. 

The Observer Health and Safety regulations specify that observers are not required to

board an unsafe vessel (as defined by the lack of a U.S. Coast Guard safety decal or other license

certifying the presence of certain safety equipment onboard). In most programs, observers are

instructed during training not to deploy on a vessel that does not have a current vessel safety

decal. However, this has not been a consistent policy in all NMFS observer programs. Even if a

safety decal is present, observers may judge a vessel to be unsafe and may refuse to board the

vessel. On the other hand, observers have significant incentives to deploy on questionable

vessels or risk losing a deployment opportunity (and the associated pay for that deployment). 

These regulations are in the process of being revised to require that all observed vessels

display a current and valid safety decal, submit to and pass a pre-trip safety check, and maintain

safe conditions at all times an observer is onboard. Additional measures that could be

implemented include the requirement that each vessel in an observed fishery show proof that it

has a current and valid safety decal as a term and condition of receiving or renewing a federallyissued fishing permit or license, and that unobservable vessels not be allowed to participate in a

fishery that has a mandatory observer coverage requirement. However, this policy may favor

larger vessels that can accommodate observers and exclude smaller vessels that cannot pass

minimum safety and accommodation requirements.

The placement of government-employed observers on fishing vessels involves significant

risk to the government, and over time this risk has been transferred to contracted observer service

providers. NMFS is pursuing policy and legislative alternatives for addressing this risk, in close

cooperation with observer service providers, observer representatives, fishing vessel owners and

operators, the insurance industry, and risk management professionals (NMFS 2002b and 2003).

4.3.1.6 Observer Programs Summary

Observer programs are a reliable source of data for estimating bycatch. The precision and

accuracy of bycatch estimates are determined by sample size and the design and execution of a

robust sampling scheme. Identifying and accounting for sources of bias is critical, as are

measures to increase both the cost effectiveness and safety of observers.
42

Figure 2. The components of a digital

video monitoring system (courtesy

Archipelago Marine Research)

4.3.2 Digital Video Cameras

The use of video cameras to monitor at-sea fishing operations is a relatively new

technique, and has only been used in select fisheries to date. The methodology involves

mounting one or more tamper-proof digital video cameras in various areas on a fishing vessel’s

deck or hull, and recording all or a portion of the fishing activities. An overview of the

methodology being used by the primary developers of this technology, Archipelago Marine

Research, can be found at: http://www.archipelago.ca/em-techno.htm. The components of a

digital video monitoring system (also called an electronic monitoring system, or EM) are

illustrated in Figure 2.

This technology can be used to monitor fishing activities to augment, or where

appropriate, replace onboard observers. It can monitor such factors as the time and area of

fishing, the use of special fishing requirements (e.g., tori lines), compliance with onboard catch

handling requirements, and species caught and/or discarded. It was determined to be a promising

option for assessing bycatch of seabirds in the Pacific halibut fishery off Alaska (Geernaert, et al.

2001). This technology has been applied on an experimental basis in at least three federallymanaged fisheries: the Pacific halibut longline fishery off Alaska, the Alaska groundfish trawl

fishery and the Pacific whiting trawl fishery. It is also being used extensively in several

Canadian fisheries.

A recently completed pilot program in the Pacific halibut longline fishery off Alaska has

found video cameras to be extremely useful in compliance monitoring (Shannon Fitzgerald,

Alaska Fisheries Science Center, pers. comm.). Video cameras also recognized 91% of seabirds

intentionally placed on the longline, with 64% of these identified to species. Reporting on a pilot

study to determine the feasibility of electronic monitoring (EM) of seabird interactions with trawl

third-wire cables in the groundfish fisheries off Alaska, McElderry et al. (2004) concluded that:

(1) EM could effectively monitor seabird interactions with trawl third-wire cables; (2) the EM

system provided imagery of sufficient quality to detect the presence, abundance, and general

behavior of seabirds during most daylight fishing events; (3) EM-based imagery was also able to

detect third-wire cable entanglements of seabirds

although it was not possible to determine the cause

of these entanglements; (4) EM imagery was not

very useful for seabird enumeration and species

identification: (5) in regard to monitoring seabird

interactions with trawl third-wire cables, EM would

be suitable for monitoring the use and effectiveness

of mitigation measures; and (6) EM is more

efficient and effective than observers for monitoring

seabird interactions with the trawl third-wire cables

as many hours can be recorded and the imagery can

be replayed at a controllable viewing speed and

because observers have a variety of functions to

perform, it is impractical to have an observer

monitor these interactions for more than a small

fraction of the time a vessel is fishing. The EM 

system used in this pilot study included two closed

circuit television cameras, GPS, hydraulic and

winch sensors, and on-board data storage. 

The cost of video monitoring includes the

cost of the equipment (three-five cameras per vessel
43

and a computer with a removable hard drive), installation of cameras on vessels, and post-cruise

analysis of the video stream. The estimated cost to equip 10 vessels for 60 days, including

analysis of video, is approximately $90,000 (Howard McElderry, Archipelago Marine Research,

pers. comm.). The equipment cost could be lower on a per day basis if the units were installed

for a longer time period; however, the costs of analyses per day of video are more fixed. The

units are somewhat tamper-proof, using the same safeguards as security cameras mounted in

public areas. However, no camera is completely tamper-proof.

Concerns among fishermen regarding the widespread application of video monitoring are

significant, and include the confidentiality of the images collected, and the potential for lawsuits

if video monitoring records injuries to crew or other mishaps. These issues must be addressed,

and policies and procedures for the disposition of electronic images must be established before

NMFS can proceed with full implementation of a video monitoring program. However, the

potential for application of this technology to enhance current monitoring capabilities warrants

its continued testing and application in U.S. fisheries.

4.3.3 Digital Observers

Digital observer technology takes the use of video cameras for monitoring fishing

activities one step further to using a digital scanner to record images of individual fish for

electronic species identification and for length/frequency estimates. The scanner records several

images of a fish as it passes through the scanner on a conveyor belt, and uses the best of these

images to make its predictions and calculations. The primary developer of this technology is

Digital Observer LLC of Kodiak, Alaska, for use in Alaska groundfish fisheries. Although this

technology is still in a pilot phase, it appears to be software and hardware intensive. Further

testing needs to be done to determine its potential utility for specific fisheries and/or gear types,

and associated costs. 

4.3.4 Alternate Platforms and Remote Monitoring

In instances when the safety of observers aboard fishing vessels is an issue or when

logistics of placing observers aboard fishing vessels is insurmountable, the use of small vessels

to observe fishing operations may be an option. Government-owned or leased vessels to observe

fishing operations remotely have been employed in a few U.S. fisheries to monitor bycatch. 

Sampling may target the fishery as a whole, or only those vessels that would otherwise be

difficult to sample using an onboard observer. 

Alternate platforms and remote monitoring may be considered a form of observer

coverage: the only difference being where the observer is deployed and the costs of doing so. 

Therefore, many of the issues mentioned in Section 4.3.1 also apply here.

Alternate platforms were used in the California drift gillnet fishery from 1993-1995, but

were abandoned due to safety concerns, cost, and sampling limitations (Price, et al. 1999). The

NEFSC currently is operating an alternate platform observation program to monitor bycatch of

sea turtles in the Chesapeake Bay pound net fishery. The sampling design uses a combination of

fishery-wide sampling on a regular schedule, with more intensive sampling of problematic nets

on a more frequent basis (Michael Tork, NMFS Northeast Fisheries Science Center, pers.

comm.).

Alternate platforms were used extensively in monitoring the Kodiak salmon set gillnet

fishery in Alaska in 2002 (Amy Van Atten, NMFS Northeast Fisheries Science Center, pers.

comm.). Two large chartered vessels (greater than 100 feet) were used to transport observers
44

from land sites to boats and from boat to boat and to provide housing for observers when

necessary. Nine smaller boats (approximately 30 feet), operated by experienced commercial

fishermen, were used to observe 10% of the overall effort. In some cases, the smaller boats were

also used to transfer observers to commercial skiffs that were tending gear. 

The advantages of the smaller boats in this instance were that: (1) observers did not have

to depend on the fishermen to pick them up and drop them off; (2) once the behavior of

fishermen was better understood, the observer would not have to make prior arrangements with

the fishermen, they would just be at the net waiting for them; (3) if one fisherman decided not to

fish or if they had mechanical difficulties, the observer had the flexibility to get to the next

permit scheduled for coverage; (4) observers did not have to rely on or have to share the

fishermen's limited resources; (5) it was easier to keep track of the location of observers; (6) by

using their own small boats, observers did not have to judge whether the commercial fishing boat

would be safe and safely operated by the fisherman; and (7) the observers had a better view of the

fish being picked by being slightly in front of the fishing boat. Disadvantages were that the small

boat skippers that have local knowledge of the area and the fishery needed to be hired and

properly trained in safety precautions and in sampling procedures. Typically, the best vessel

operators were usually retired or ex-commercial fishermen (thus, there may be some perceived

conflict of interest). However, using small boats was more costly than just placing observers

onboard the commercial boats. Also, small boat operators ran the risk of damaging someone

else's fishing gear or affecting their catch by scaring fish (liability concerns).

In general, the use of alternate platforms should be evaluated in fisheries where there are

concerns about unsafe vessels or inadequate accommodations, or where it is more efficient to

observe fishing operations remotely due to the nature of the fishery. However, it should be noted

that there may be similar safety and cost concerns whether observers are deployed on alternate

platforms or on fishing vessels.

4.4 Stranding Networks

“Strandings” is the term used to describe when marine mammals or sea turtles swim or

float into shore and become "beached" or stuck in shallow water. Stranding “networks” have

been established throughout the country to monitor the rate of strandings on beaches and to

facilitate communication and reporting of stranding events. Typically, sampling is opportunistic

and is dependent on the frequency of strandings in an area, the frequency of beach monitoring by

network volunteers or others to report stranding events, the availability of network volunteers to

respond to a stranding event, and the experience and training of network volunteers.

Marine mammal or sea turtle stranding networks have been established in all U.S. coastal

states, and are authorized through Letters of Authority from NMFS regional offices. Many are

supported by federal funds to assist in the provisioning of sampling equipment to network

volunteers, to provide training in necropsy methods and sampling and archival procedures, and

for timely entry and analysis of stranding data. 

Marine mammal stranding networks in the United States make up one facet of a broader,

more comprehensive program called the Marine Mammal Health and Stranding Response

Program (MMHSRP), established in the late 1980s in response to growing concern about marine

mammals washing ashore in U.S. waters. The MMHSRP goals are to: facilitate collection and

dissemination of data; assess health trends in marine mammals; correlate health with available

data on physical, chemical, environmental, and biological parameters; and coordinate effective

responses to unusual mortality events. More information on the MMHSRP can be found at:

http://www.nmfs.noaa.gov/strandings.htm.
45

Only a small proportion of the animals that strand can be reliably attributed to fishing

interactions, and fewer still can be attributed to specific fisheries. Hohn and Martone (2001)

noted that: (1) from 1997-2000, 424 bottlenose dolphins were reported stranded in North

Carolina; (2) for 95 of those, it was determined that cause of death was due to interaction with a

fishery (on most of these carcasses line or net marks were detected); (3) for the majority of

strandings (n=238), it was not possible to determine whether the mortality was human-caused;

and (4) only 73 strandings were attributed to natural mortality. Therefore, more of the standings

were determined to be due to fishery interactions than due to natural causes. Similarly, in a

sample of 66 stranded harbor porpoise recovered from the mid-Atlantic from 1993-1995, 21 had

signs of entanglement in fishing gear. Further analyses for the Bottlenose Dolphin Take

Reduction Team by Hohn et al. (2001) determined that fisheries interactions in particular could

be attributed to 24 of the 605 bottlenose dolphins reported stranded along the Atlantic coast or in

the estuaries of South Carolina, Georgia, and Florida. However, for the majority of strandings

(63%), it was not possible to determine whether the mortality was human-caused. This prompted

recommendations by the Bottlenose Dolphin Take Reduction Team to increase observer

coverage in Southeast and Mid-Atlantic fisheries to verify the level of fishing-related mortality

and the specific fisheries and gear types responsible.

Similar efforts have been made to determine the relationship between sea turtle strandings

and fishing operations. Epperly et al. (1996) compared the number of sea turtles stranded on

beaches in the vicinity of Cape Hatteras to the estimated number taken in the winter trawl fishery

for summer flounder from November 1991 to February 1992. They found that stranded sea

turtles represented a maximum of 7–13% of the estimated fishery-induced mortalities. This

suggests that not all turtles that died as a result of fishing operations washed ashore and are

included in the standings data, due to such factors as distance from shore at the time of

interaction, currents, weather, and the frequency with which beaches are monitored for stranding

events. This highlights the limits to using stranding data as a sole indicator of fishing-related

mortality, and as a means of estimating bycatch. 

Stranding events can nevertheless be used to drive management actions. For example, an

increase in strandings annually in waters off Virginia in May and June prompted a pilot study to

investigate the occurrence and entanglement of sea turtles in pound net gear. The data from this

and other small-scale studies, as well as inferences from strandings data, eventually led to the

issuance of mesh size restrictions for pound net leader lines in the Chesapeake Bay (67 FR

41196, June 17, 2002). These restrictions were followed by a prohibition on the use of certain

pound net leaders from May 6 to July 15 each year in Virginia waters of the Chesapeake Bay (69

FR 24997, May 4, 2005). In February 2003, NMFS issued regulations to require larger openings

on turtle excluder devices (TEDs) to ensure that leatherback turtles, as well as larger loggerheads

and green turtles, could escape. The impetus for the larger opening requirements was based in

part on new information showing that 33–47% of stranded loggerheads and 1–7% of stranded

green turtles are too large to fit through the current TED openings (68 FR 8456, Feb. 21, 2003).

In summary, the use of stranding data can provide indications of where fishing-related

mortality may be occurring and direct further observations, but should not be the sole source of

information used to make management decisions.

4.5 Summary

At-sea observations of fishing operations, fishery-independent data collection, logbooks,

landings reports, port samplers, and stranding networks all may be used to obtain data to estimate

bycatch. Each has specific advantages and disadvantages. Data collected from at-sea

observation programs (which usually are observer programs) provide better estimates of bycatch

rates than do data from either fishery-independent surveys or self-reporting. Combined with

reliable estimates of total fishing effort or landed catch, bycatch rate estimate from observation

programs can be used to estimate total bycatch levels in a fishery. Sources of bias must be
46

acknowledged and addressed, and efforts made to limit biases wherever possible. Efforts should

be made to increase the safety of observed vessels and to increase the cost-effectiveness of

observers in order to increase the viability of observer programs as a management tool. Stability

in observation program funding is also needed.

Where possible, analyses should be undertaken to compare logbook data to data from atsea observations. Self-reporting in logbooks can be a useful adjunct to at-sea observation

programs, but these should be subject to ground-truthing periodically. Typically, relying solely

on self-reporting of bycatch will result in poor information on which to base management

decisions. 

Better information regarding the portion of the fleet without observers, perhaps through

the use of electronic monitoring (e.g., digital video cameras or digital observers) and electronic

logbooks, would be helpful in improving the estimates of total bycatch. More emphasis should

be placed on testing, evaluating, and implementing these technologies to augment, or where

appropriate, replace onboard observers. At the same time, NMFS should strive to resolve issues

of confidentiality and liability associated with electronic monitoring.

Continual efforts should be made to improve the integration of various fishery-dependent

and fishery-independent data sources to ensure these data sets are used effectively in providing an

accurate and comprehensive portrayal of what level of bycatch is occurring in each fishery and

why. The implementation of the Fisheries Information System (FIS) (NMFS 1998b) is an

appropriate mechanism for providing the framework for a more integrated and coordinated

system to increase the accessibility and sharing of data. The FIS's mission is to create an

umbrella program that coordinates techniques to gather and disseminate data nationally while

accounting for the unique characteristics of regional commercial and recreational fisheries. The

FIS provides a context for the design, development, and implementation of data collection and

data management programs for fishery-dependent statistics nationwide to improve the timeliness

and accuracy of data.

Periodic reviews of the monitoring methods employed in each fishery should be

implemented to ensure that the proper methods are being used to estimate bycatch, taking into

consideration the known or expected level of bycatch, the nature of the bycatch, the fisheryspecific characteristics of the fishermen and their fishing vessels, and the need to obtain precise

and accurate estimates of bycatch.
47

5. Estimation of Bycatch

5.1 Definition of Bycatch and Precision

Bycatch for the purposes of this report is defined as the discarded catch of any living

marine resource plus unobserved mortality due to a direct encounter with fishing gear. As

mentioned in the Introduction, this definition is based on the bycatch definition that appears in

Managing the Nation’s Bycatch (NMFS 1998a), but it does not include retained incidental catch

as a component of bycatch.

Unobserved mortality due either to direct encounters with fishing gear before it is

retrieved or to mortality resulting from lost or abandoned gear is not easily estimated. With the

exception of the case in which discard mortality rates are known to be very close to 100%, it is

also difficult to estimate the mortality associated with fish or other species that are discarded at

sea. If estimates can be made, the typical method is to multiply the number of discards (or

encounters) by a rate of post-encounter mortality (by appropriate strata). Monitoring procedures

are designed to determine the number of discards, but additional experiments are needed to

determine post-release survival rates, encounter rates that do not result in catch, and the survival

rates after such encounters. The experiments include such studies as: in situ survival

experiments in traps; tagging of discarded fish to compare tag-return rates from fish released

using standard fishery practices versus those released using experimental procedures; underwater

observation; and electronic tagging and tracking. For example, a post-hooking survival study

conducted as part of the experiments in the North Atlantic to evaluate sea turtle mitigation

measures in the distant waters, pelagic longline fishery provided helpful data on the fate of

hooked turtles. Estimates of post-encounter mortality are virtually always inferred from

experimental programs. Therefore, a scientific effort that is qualitatively different from bycatch

monitoring is required. 

In this report, the discussion of bycatch precision will relate only to the discard portion of

the bycatch because unobserved mortality cannot be determined using a catch or discard

monitoring program. In addition, the discussion is focused principally on bycatch in commercial

fisheries because total catch, including landed and discarded catch for most recreational fisheries,

is estimated from statistical surveys in which precision is an important design component.

Furthermore, when the notion of “precision” is discussed in this document, we are

generally referring to the extent to which bycatch estimates are likely to vary in repeated

sampling. More specifically, our standard measure of precision will be the coefficient of

variation, which is given by the ratio of the square root of the variance of the bycatch estimate

(i.e., the standard error) to the estimate, itself. By using this measure, one is able to compare the

variances of distributions that have large differences in their means or units of measurement. For

example, a coefficient of variation (CV) of 30% implies that the size of the standard error is 30%

as large as the estimate. Smaller coefficients of variation indicate greater precision: a 0% CV

means that there is no variance in the sampling distribution, and thus no estimation error if the

estimator is unbiased. Alternatively, CVs of 100% or greater have poor precision with the

standard errors being equal to or larger than the estimate. In fisheries surveys, CVs of 20-50%

for estimates of abundance of a stock are the norm for the dominant commercial species. 

However, the survey CVs for some commercially important species and for many non-target

species can be considerably higher. In addition, a bycatch estimate with a CV of 20-30% may

provide a very tight estimate in absolute terms or relative to other sources of fishing mortality

when bycatch is small.
48

The variance of an estimate depends upon the underlying variation of the biological and

fisheries processes and the number of data points or observations used in making an estimate

(denoted by the sample size, n). For example as noted above, for large samples the precision

(CV) of an estimate is inversely proportional to the square root of the size of a sample. Since

larger sample sizes usually imply larger survey costs, this demonstrates that reductions in the CV

will require additions to both sample size and budgets – an important planning consideration. 

Often, it will be desirable to partition the observations into strata that are relatively

homogeneous. Such strata will often be defined by the distribution patterns of the species caught

and the patterns of fishing effort in space and time. They will also often involve partitioning by

gear type and season. If it is possible to define strata with homogeneous characteristics, the

precision of the estimates within strata will be higher and the overall CV will be lower. Changes

in the sample size within strata will also affect the CV. In general, it will be desirable to increase

the sample size in strata with higher variability. 

Additionally, it should be noted that in this report the precision to be discussed will be

that related to annual estimates of bycatch, not seasonal or monthly estimates. This focus was

chosen because the requirements for within-year precision are much more data and logistically

demanding, and because, at a minimum, effective bycatch monitoring and management require

estimates on an annual basis. Accordingly, the focus of the discussion will be on the CV of

annual estimates of discards and the sample sizes associated with annual estimates of discards

with varying levels of precision. However, there are instances in which the management needs

are more rigorous, especially when more detailed estimates are needed to determine how to

reduce bycatch and how far to reduce it. In those instances, the CVs of bycatch estimates for

specific areas and time periods may be relevant. In addition, there are circumstances (such as

rare or protected species) where the absolute precision in numbers of animals is more appropriate

than the CV of the estimate (see Appendix 4).

5.2 Estimation from At-Sea Observations

Fishery-dependent estimation of at-sea discards involves the observation of fishing

activities as they occur on the ocean. Typically, at-sea observation will involve human observers

placed on the fishing vessel or on an alternate platform. However, as noted in Section 4,

technologies other than observers may exist to obtain the at-sea observations. From the

standpoint of estimation and sampling design, it does not matter how the observation is made;

what matters is the measurement reliability and the cost of that observation. We recognize that in

most cases under current technology, human observers will be the most effective method of

obtaining at-sea observations. However in this report we will often refer to observations, to

emphasize that observations may be obtained in a variety of ways other than with human

observers.

The development of a sampling strategy for estimation of bycatch based on an at-sea

observation program entails first clearly defining the objectives of the sampling program and

selecting a sampling strategy designed to meet these objectives. Further critical requirements

include the specification of the sampling frame from which to draw samples, the sample

selection procedures, the designation of sampling strata and allocation strategies, and the

identification of appropriate estimators. An explicit statement of the objectives of the program is

a critical step in devising effective sampling procedures. For example, an at-sea observer

program designed with the objective of estimating fishery discards may be quite different from

one designed to assess incidental takes of protected species, particularly if the latter represents

rare events. When there are multiple objectives for an observer program, the program design

often will need to address competing objectives and the optimal design cannot be determined

unless weights have been assigned to the various objectives. Basically, when there are multiple
49

Specify Objectives

Construct Sampling 

Frame

Choose Sampling

Design

Choose Vessel/Trips

For Sampling

Choose Hauls within

Trips for Sampling

Select Biological

Subsamples

Figure 3. Steps in developing a sampling

strategy to estimate bycatch using at-sea

observations

objectives, it becomes much more difficult to clearly define the objective (including the weights

to be used), to identify the appropriate sample design, and to identify the desired level of

precision for each estimate.

Ideally, the statement of the objectives of the program will entail not only the

identification of the critical bycatch issues for the program (e.g., fishery discards and the

incidental take of protected species), but also the desired level of precision for the estimates. The

latter will entail consideration of the acceptable level of risk associated with uncertainty in the

bycatch estimates and the cost of improving precision.

The specification of a probability-based sample selection scheme, while difficult under

some circumstances in at-sea programs, is a critical step in avoiding potential biases that can

develop with non-representative sampling based on ad hoc sample selection. The selection of

sampling strata for each fishery is essential both in distributing the sampling effort over relevant

spatial and temporal domains and in increasing precision of the estimates when relatively

homogeneous strata can be defined. The choice of allocation strategies for sampling effort

among strata will depend in part on the state of development of the sampling program. The

choice of estimators for bycatch and its variance will depend on the nature of the available

information and the objectives of analysis but will often involve some form of a ratio estimator

where information on total landed catch and/or effort is used as an auxiliary variable. For

situations in which each haul of the gear cannot be observed, it will be further necessary to select

hauls within fishing trips to sample according to a specified probability sampling scheme. 

Finally, either when additional biological samples are to be collected to evaluate certain factors

(e.g., the collection of size composition data and the collection of structures for age

determination), or when it is not feasible to sample the entire haul, strategies for the selection of

a subsample will be required. Each of these issues

is described in further detail below (see also

Figure 3).

There are several distinct stages and steps

in the evolution of an at-sea sampling program. 

The initial step in fisheries for which no at-sea

coverage has been attempted is the establishment

of a program to collect baseline information on the

fishery and fishing practices used therein with

particular emphasis on bycatch rates and factors

affecting bycatch (Table 3). Typically this will

involve the establishment of initial strata defined

by time and area (see below) and the deployment

of observers or other observation systems within

each spatial and temporal unit. Because this is an

exploratory effort, it is likely that a uniform

allocation of sampling effort among strata will be

useful unless ancillary information is available to

guide more targeted sampling. The baseline study

can be viewed as a preliminary pilot program. We

recognize that a more intensive pilot study will

often follow the baseline phase (or may be

implemented directly in instances where no

existing observer coverage has been deployed but where sufficient auxiliary information exists to

develop a more detailed sampling program). It is anticipated that a full pilot program will permit

refined estimates of variance as the basis for developing an enhanced sampling strategy. We
50

Table 3. Developmental levels (stages) for observation programs.

Observer

Program Level

 Definition

None No systematic program exists for bycatch data collection

Baseline An initial effort including at-sea monitoring to assess whether a

systematic program is needed to estimate bycatch is completed. 

Pilot An at-sea monitoring program that obtains information from

relevant strata (time, area, gear) for design of a systematic program

to estimate bycatch with the ability to calculate variance estimates

has been done.

Developing A program in which an established stratification design has been

implemented and alternative allocation schemes are being evaluated

to optimize sample allocations by strata to achieve the recommended

goals of precision of bycatch estimates for the major species of

concern.

Mature A program in which some form of an optimal sampling allocation

scheme has been implemented. The program is flexible enough to

achieve the recommended goals of precision of bycatch estimates

for the major species of concern considering changes in the fishery

over time.

identify a developing program as one in which a well-defined stratification scheme has been

established based on known fishery characteristics and where an evaluation of alternative

strategies has been made to develop an optimal allocation scheme to provide the highest possible

precision and accuracy for a given observation program budget. Finally, we identify a mature

sampling program as one in which an optimal allocation scheme has been implemented and the

target levels of precision are being met for the species of major concern.

The developmental levels of observation programs as defined in Table 3 were used to

classify the progress each fishery is making toward bycatch monitoring goals (see Section 6).

5.2.1 Sample Selection

The development of a sampling frame is a critical first step in the selection of samples in

any observer program. The importance of establishing a well-defined probability sampling

scheme cannot be overemphasized. Although an ad hoc sample selection procedure potentially

can provide valid results, it generally will be impossible to ensure the estimates are free of biases

due to non-representative sampling. The development of a probability-based sampling scheme

requires definition of the units available for sampling. In most instances, this will involve a

sampling frame comprising the vessels actively engaged in the fishery. Following the

designation of sampling strata and decisions concerning the allocation of samples within strata

(described below), a random sample is drawn from the list of vessels operating within the spatial

and temporal units defined. It is recognized that differing degrees of cooperation and willingness

to accommodate observers are often encountered. In addition, it may not be possible to make a

trip on a selected vessel because the vessel may not be operating during the specified time

periods due to maintenance schedules or other considerations. Accordingly, it will be necessary

to draw samples randomly until the target sampling levels within strata are attained. The

procedure would involve randomly selecting vessels to be sampled, contacting the vessel owner

or captain to ascertain whether a trip will be made within the specified time frame and whether

an observer can be accommodated, and continuing until the number of trips designated for that
51

stratum meets the target levels. If necessary, fishermen should be reminded of requirements in

the MSA and MMPA to accommodate observers when requested unless justifiable extenuating

circumstances exist. Such emphasis should reduce difficulties and potential biases introduced by

non-cooperation of different vessel owners or captains. However, observer bias, or the observer

effect, would still be a factor under the random selection of vessels for a single trip, or several

trips, especially if this sample represents a small portion of the vessel’s total trips. If the captain

has an incentive to have bycatch underestimated, the estimate can have a substantial negative

bias.

The considerations above pertain to cases in which an attempt is being made to sample

fishing trips as the unit of observation. Vessels are chosen randomly to meet the goal of

sampling a specified number of trips. In some cases, a vessel itself might be of direct interest

because of requirements attached to fishing permits, as in some Alaska fisheries. In this case, a

random choice of the trips to be sampled for each vessel is desirable and again, the potential for

bias will be minimized if timing of sampling trips aboard particular vessels is not left to the

discretion of the vessel owner or captain. 

For cases in which all hauls cannot be observed during a fishing trip, a sample scheme for

selecting hauls will be necessary. Given an initial estimate of how many hauls will be made

during the trip, several approaches are possible. A systematic sample with random start points

can be employed in which a choice of which haul to sample initially is randomly made and then

every nth haul is sampled thereafter. For example, if it is anticipated that every other haul could

be sampled, a random draw could be made of the first three hauls and then alternate hauls

sampled. However, if the expectation is that fishing practices differ when the crew know that a

haul will be sampled, systematically choosing alternative hauls may introduce bias. 

Consideration of factors potentially affecting bycatch should enter into the decision of how to

distribute the sampling. For example, it may be desirable to sample throughout the day and night

periods to avoid biases that would result from differential bycatch rates by diurnal period in a

fishery that operates on a 24-hour basis. In this case, consideration of the haul time and duration

between hauls will be critical.

An alternative strategy is to make an initial random selection to determine which hauls to

sample for the duration of the trip (taking care to select more than the expected number of hauls),

possibly stratified by time of day. Although this design allows for the spacing of sampling by

observers to allow adequate sample processing, rest periods, and other factors, this design may be

less desirable than some form of systematic sampling.

Selection of a sub-sample of a haul either for biological information such as size

composition or when it is not feasible to sample the entire haul will depend on the operational

procedures onboard the vessel. For example, when the catch is placed on a conveyor belt system

for culling, observers can readily select samples randomly from throughout the entire catch to

avoid potential biases associated with clustering of individuals with similar characteristics (e.g.,

size) in different portions of the catch. If sorting and culling is done directly on deck, it will be

desirable to select samples randomly from different portions of the catch and to do so before

sorting and culling occur.

There are often difficulties in implementing these procedures. For example, if the list of

active vessels is stable, selecting vessels using a probability sampling scheme is reasonable. But

if not, this may mean that a two-stage sampling design is required with the vessel as the primary

sampling unit and trip as the secondary sampling unit. If vessels are selected with equal

probability and an equal number of trips are selected with equal probability for each selected

vessel, trips from different vessels will have different probabilities of being selected, unless all
52

vessels do the same number of trips. If the specified time period is short enough that a vessel

makes, at most, one trip during the time period, then trips are selected with equal probability. 

However, if several vessels depart about the same time, there might not be a sufficient number of

observers to place one onboard each vessel. If selected trips are determined when an observer is

available, trips may have an unequal probability of being sampled. Furthermore, each time

period needs to be treated as a stratum since randomization is restricted within the time period. 

Thus, while it is easy to recommend an equal probability sample, it can be very difficult to

obtain.

5.2.2 Sampling Strata

Spatial and temporal variation in bycatch levels will typically dictate the use of area-time

designations for sampling strata in observer programs. In instances where the fishery involves

multiple gear types and fishing strategies, it will be more important to employ appropriate strata

for each gear type and fishing strategy. The specification of geographical strata will often be

linked to predefined statistical areas used for assessment purposes for the stocks under

consideration. Under some circumstances, these area designations will also be linked to ports in

which observers are stationed and from which vessels depart to fish in particular statistical areas. 

The choice of strata should entail consideration of defining relatively homogeneous sampling

units with respect to the occurrence of bycatch. Under certain conditions, there may be a need

for post-stratification evaluation. However, caution is needed because post stratification often

leads to very biased estimates with purportedly small standard errors. In some instances, a

reevaluation of the stratification will be needed. In the Northwest, depth strata cannot be

predefined because different tows of a trip are operating in several depth strata. The depth is a

primary factor of distribution of some species. This situation will pose difficulty for sample

allocation as the fishing depth is not clearly defined a priori. The number of strata to be

employed also entails consideration of the level of overall sampling effort possible given funding

constraints. A large number of strata will typically mean that the sample sizes within strata will

be low, resulting in relatively high within-stratum variances; this should be avoided.

The choice of temporal strata will be tailored to the characteristics of the individual

fishery. The within-year sampling units will generally be defined at the quarterly level or at finer

scales (e.g., monthly or weekly) depending on how the fishery is prosecuted and consideration of

the temporal variability in bycatch rates as a function of recruitment and seasonal distribution

patterns. Although no generic guidelines can be established to apply to all regions, it is

important that the entire fishing season be covered.

5.2.3 Sample Allocation

In the initial stages of observer program development, a uniform allocation of sampling

effort likely will be necessary to permit specification of the fishery bycatch characteristics. 

Sample sizes would be equal for each stratum in this phase for baseline studies and potentially

for pilot study programs unless additional information to guide allocation strategies is available.

In instances where more detailed information on the fishery is available in terms of

fishing effort, catch, and/or bycatch, alternative allocation strategies can be considered. For

example, allocating sampling effort to strata in proportion to the fishing effort or overall catch

within these spatial and temporal units can be an effective strategy since discards can be expected

to vary in proportion to total catch and/or effort. This can be particularly effective where the

variability in bycatch increases as the bycatch level increases as will often be the case.

An optimum allocation scheme would entail identification of strata within which high

variability in bycatch occurs and placing additional sampling effort in these strata to minimize
53

the variance for a specified funding level. Because different strata may exhibit higher levels of

variability over time, it can be expected that an optimum allocation scheme would have to be

adjusted to meet existing conditions. Typically, a specified budget level is comprised of fixed

costs (e.g., administrative costs, data management and analytical services) and variable costs

related to at-sea operations. The allocation of sampling units to strata is made in a way that

minimizes the overall variance given constraints on these costs and the need to address sources

of bias.

For multispecies fisheries or when the bycatch includes fish and other living marine

resources, in general it will be impossible to specify a bycatch sampling plan that will be optimal

for each of the species caught. In this report we have focused on optimizing the sampling design

for the total bycatch of fish and the bycatch by species of protected species (e.g., marine

mammals and ESA-listed species). However, it is recognized that it may be necessary to

concentrate on particular species to meet identified management and conservation goals. This

may require targeted supplemental sampling to meet needs for overfished species or protected

species.

5.2.4 Estimators

As noted above, funding limitations, observer program costs, safety considerations, and

logistical constraints typically result in it being neither physically nor economically feasible to

monitor all fishing effort, catch and bycatch and to do so without measurement error. Therefore,

a way of estimating the bycatch for some representative portion of the fishery must be obtained

and this result then expanded to the fishery as a whole to estimate the total bycatch. In most

cases, this is accomplished by measuring the bycatch in relation to some easily and reliably

measured factor for the fishery as a whole.

The two factors that have been used most often as ‘auxiliary’ variables in estimating

bycatch are the retained (landed) portion of the catch and the amount of fishing effort. For

example, if we choose a unit of observation (say a fishing trip) and directly measure the amount

discarded and the amount landed of one or more species on a number of representative fishing

trips, we have a way of estimating the total bycatch using information on the observed trips and

the total landed catch from the fishery. For the observed trips, we can take the amount discarded

and divide this by the amount landed to form a ratio. We then have an estimate of the amount

discarded per unit of landed catch. If we then multiply this ratio by the total landed catch for the

fishery, we can generate an estimate of the total amount discarded. Alternatively, we could use

the fishing effort (say number of hours towed or number of traps set adjusted for fishing time) as

the auxiliary variable if we have an estimate of the total effort for the fishery. 

In recognition of the fact that bycatch can vary considerably by fishery sector, time

period, and area, the fishery is often partitioned (or stratified) by these factors. Stratification of

this type can be an important factor in increasing the precision of estimates of bycatch. In this

case, the estimates of bycatch would be computed at the stratum level and then summed over

strata to obtain the totals. Special considerations hold for estimating the bycatch of non-target

species. For bycatch of protected species, the ratio of the number of individuals of the protected

species to the landed portion of the targeted catch or the amount of fishing effort is often used.

The choice of the appropriate sampling unit (e.g., haul or trip) will be dictated by

logistical considerations and an evaluation of the statistical properties of the observations. In

instances where the bycatch rates are not independent among hauls within a fishing trip, it may

be desirable to consider the trip as the unit of observation. For example, we may commonly

encounter situations where the bycatch of a particular species is consistently high during a fishing
54

trip and the bycatch among hauls would not be independent. This creates statistical problems

because the effective sample size that we have to work with may be much smaller as a result of

this lack of independence. In effect, under these conditions, each haul is repeating the same

information instead of providing entirely new information. We therefore need to take this

directly into account or use the trip as a whole as a unit of observation.

Often, estimates of the bycatch using the ratio estimator approach above are made on a

species by species basis (e.g., the ratio of the discarded to the landed portion of the catch for the

species is determined and multiplied by the total catch for that species to get the total amount

discarded). However, we might as easily estimate the total amount discarded over all species

using a ratio estimator in one stage and then estimate the proportion of each species contributing

to the total bycatch in a separate stage. The bycatch for each species is then given by the product

of the total bycatch and the proportion of each species contributing to the bycatch.

Estimation of rare events presents special challenges. For example, if sampling bycatch

of certain threatened or endangered species is a primary goal, sampling designs specifically

developed for estimating the occurrence of rare events may be required. It is possible that quite

large sample sizes will be required to obtain sufficiently large effective sample sizes to detect

rare events and to develop unbiased estimates of the bycatch. If the rare events exhibit some

form of clustering in space and time, it may be effective to utilize an adaptive sampling design in

which once an event is detected, additional samples are allocated in the region surrounding the

observed event as quickly as possible. However, the potential advantages and disadvantages of

an adaptive sampling design need to be considered. If the chance of such an event can be

predicted based on previous occurrences at specified times and locations, the initial sampling

effort can be allocated accordingly with additional sampling effort deployed in temporal and

spatial proximity to any observed events. 

The statistical properties of ratio estimators and the assumption underlying the method

must be carefully considered. In the following, we will distinguish between ‘structural’ bias that

may result from non-representative sampling (including the observer effect described above) and

‘statistical’ bias that results from the characteristics of the estimators themselves. We have

implicitly assumed that each unit of observation (say a fishing trip) has an equal probability of

being selected for sampling. This is not a reasonable assumption for all observer programs. 

Making this assumption when it is false will likely result in a structural bias and underscores the

importance of obtaining representative samples that reflect the fishery as fully as possible. As

noted earlier, in observer programs, every attempt should be made to obtain random samples

from the fishery and to check for possible observer effects reflecting changes in fishing practices

when observers are on board the vessel. 

 The ratio estimator also assumes that there is a simple linear relationship between the

‘response’ variable (bycatch) and an auxiliary variable such as the landed portion of the catch. 

When sample sizes are low, ratio estimators can be statistically biased. Ensuring adequate

sample sizes in each stratum (e.g., a particular gear, area, and time combination) is important. 

Usually, at least 20-30 samples (e.g., trips or other units of observation) per stratum would be

desirable. The statistical bias in ratio estimates can also be estimated (and corrected) using

resampling methods such as the bootstrap technique (for an application to salmon bycatch, see

Turnock and Karp 1997). In this method, we would repeatedly take a large number of random

sub-samples by computer from a set of observed fishing trips and determine the bycatch ratio and

the sampling distribution of these estimates.
55

5.2.5 Sample Size Requirements

The sample size required to achieve a desired CV for the bycatch estimate can be

specified given an initial estimate of the sample variance based on a pilot study or previous

bycatch sampling. Given an appropriate stratification scheme in which the bycatch is as

consistent as possible within strata, the key issue is how to distribute the available sampling

effort among the strata. Often, we are interested in obtaining the most precise estimate possible

under a given cost constraint. The optimum allocation of samples will depend on the variability

in each stratum, the cost of obtaining samples for each stratum, and the bycatch level for each

stratum (often based on a previous estimate). In general, we will want to put higher sampling

effort in strata where the bycatch is most variable to reduce the overall variance. We also wish to

ensure that the sample size is sufficiently large that ‘statistical’ bias is not a problem and that we

can test other assumptions such as a linear relationship between the bycatch and the auxiliary

variable. In some instances, the ‘structural’ bias resulting from the observer effect can be

reduced either by increasing sample size or by changing the distribution of sample sizes.

5.2.6 Accuracy and Bias

The discussion of sampling design has primarily addressed precision, that is, the amount

of random error that occurs in estimates due to the variability among observations. However,

accuracy is also a concern, specifically, are the vessels and hauls that are being observed

representative of those that are not? Issues related to representativeness, bias and accuracy were

discussed in Section 4.3.1.3 Accuracy and Bias in Observer Programs. Accuracy is difficult to

address in statistical designs of observation programs. The act of observation often alters

behavior and there is not a clear-cut way of determining whether the changes in behavior are

significant. Therefore, indirect methods of comparison should be instituted where possible. For

example, the areas, times and catch of target species sometimes may be compared between

observed and unobserved vessels to determine if fishing operations are statistically similar (for

example, Walsh et al. 2002). This kind of verification check should be made periodically.

5.3 Precision of Bycatch Estimates

Precision requirements for bycatch estimates depend upon the management procedures

for which the estimates are being used. Additionally, there are a number of issues about

statistical sampling that impede our ability to obtain precise estimates. In this section the issues

relating to precision are discussed and recommendations for precision goals are presented and

discussed.

5.3.1 Management Uses of Bycatch Estimates

The precision requirements for bycatch estimates depend upon the management uses to

which the estimates are being put. What are managers doing with the bycatch estimates?

Typically there are three primary uses for bycatch estimates. One use is when the

estimates of bycatch of a particular species are incorporated into the analyses by which the status

of that species or resource is being evaluated, (i.e., into the stock assessment). A second use is

for direct management purposes, such as determining either if bycatch has exceeded a bycatch

quota or when it will exceed the quota. A third use is to utilize bycatch estimates in order to

guide management on actions that might be taken to mitigate bycatch.
56

Catch at Age, Size,

Sex

Population Model

Management Quantities;

TAC’s, PBR’s, Population Size and

Mortality Estimates

Fishery-Independent

Surveys;

Indices of Abundance

Ancillary Fishery

Dependent

Information

Landings 

Age/Size Composition

Discard

Age/Size Composition

Catch at Age, Size,

Sex

Population Model

Management Quantities;

TAC’s, PBR’s, Population Size and

Mortality Estimates

Fishery-Independent

Surveys;

Indices of Abundance

Ancillary Fishery

Dependent

Information

Landings 

Age/Size Composition

Discard

Age/Size Composition

Figure 4. Schematic diagram of a stock assessment

with inputs of relevant data (including bycatch) and

outputs of management quantities.

5.3.1.1 Assessment Uses

An assessment of a population or

stock of a living marine resource results in

estimates of management-related quantities

(e.g., total allowable catches (TACs) for

fishery resources, potential biological

removals (PBRs) for marine mammals,

incidental take statements for endangered

species). Uncertainty in a stock assessment

and in the resulting estimates of

management-related quantities will depend

upon a number of factors. Contributions to

the uncertainty in a species’ TAC or PBR

include: (1) the magnitude and precision

of the bycatch estimates of that species; (2)

the magnitude and precision of the

estimates of other sources of mortality

(directed catch, natural mortality); (3) the

precision of the estimates of survey indices

or direct estimates of abundance; (4) the

precision of the estimates of the biological distribution of the species (for example, age and sex

distribution and spatial-temporal distribution); and (5) the status of the resource relative to the

management quantities. Figure 4 shows the structure of a general stock assessment. Thus, the

precision of bycatch estimates may not be the limiting factor in the precision of estimates of

TACs or PBRs. Often other factors are more important. Exceptions occur when the bycatch is

large relative to the overall catch of that stock. The relationship between the precision of the

assessment components (including the precision of the bycatch estimate) and the precision of

management quantities such as TACs or PBRs is addressed in Appendix 2.

Generally, one wishes to increase the precision for all components of an assessment of a

stock, not just for the bycatch of that stock. Additionally, one would invest more heavily in

activities that would more efficiently reduce uncertainty in the management quantities, and that

may or may not be the bycatch component (Powers and Restrepo 1993). Nevertheless, we strive

to obtain a balance in which estimates of management quantities are reasonably precise (Fogarty

and Gabriel, unpub. ms.). The Atlantic States Marine Fisheries Commission (ASMFC) (1997)

recommended that precision of the estimates of bycatch of a stock be in the order of a 20-30%

CV, recognizing the importance of the various assessment components.

5.3.1.2 Monitoring Relative to Management Standards

A second management use of bycatch estimates is direct comparison of the estimate with

some management standard, such as the PBR for a marine mammal stock (Barlow 1999), or with

other sources of mortality,. An example of a management standard might be some upper limit on

bycatch that managers are trying to avoid exceeding. Thus, the precision of the bycatch estimate

directly relates to the probability that the true bycatch level (not the estimated level) is or is not

below the limit. An example of a comparison with another source of mortality might be when

allocations of a TAC are being made between the catch and bycatch of a species; and in that case,

the precision of both the bycatch and the catch directly relate to the probability that one source of

catch is larger than the other. In both of these examples, precision relates to straightforward

statistical comparisons of bycatch with some standard or other source of mortality. Precision

requirements depend upon how sure the manager wants to be that the bycatch is below that

standard. A simple rule of thumb is that, if you want to be about 84% sure that the “true”
57

bycatch level is below some standard, the bycatch estimate must be less than or equal to the

standard divided by (CV + 1). For example, if the CV is 0.5, the estimate of bycatch would have

to be no more than two-thirds of the standard for one to be about 84% sure that the “true”

bycatch level is below the standard. Similarly, if you want to be about 98% sure that the “true”

bycatch level is below some standard, then the bycatch estimate must be less than or equal to the

standard divided by [(2 x CV) + 1]; with a CV of 0.5, the estimate of bycatch would have to be

no more than one half of the standard for one to be about 98% sure that the “true” bycatch level

is below the standard. With a CV of 0.2, the estimate of bycatch would have to be no more than

83% or 71% of the standard, respectively, for one to be about 84% or 98% sure that the “true”

bycatch level is below the standard. Clearly, with higher precision (lower CVs), one can manage

closer to the standard and still be confident of not exceeding management targets. Indeed, that is

the goal of efficient statistical designs–to be able to make more efficient and flexible

management decisions. Note that these rules of thumb assume that estimates result from normal

distributions. More formal analyses would be needed for most comparisons, including those in

which there is uncertainty concerning what the value of the management target should be.

5.3.1.3 Developing Mitigation Plans

The third management use of bycatch estimates is to structure a mitigation program (i.e.,

the estimates are used to design measures to reduce bycatch). For example, bycatch estimates

might inform managers whether it is more likely that closing an area will reduce bycatch

mortality more or less than requiring a gear modification; or requiring changes in gear

deployment versus instituting quotas. From a statistical standpoint, this is the same use of the

data as discussed in the previous Section (Section 5.3.1.2 Monitoring Relative to Management

Standards). However, the difference is that these decisions are often focused on finer spatial and

temporal scales than what is usually used for annual bycatch estimates. The managers may wish

to know (and compare) bycatch estimates for one area versus another, or one month versus

another. Requirements for finer scales results in requirements for additional sampling in order to

maintain comparable precision. 

5.3.2 Precision of Bycatch Estimates from Fisheries

The discussion above focuses on the precision of bycatch estimates taken from a single

stock of fish or a single stock of a protected resource and the management uses of these

estimates. Clearly, there is a need for single-species estimates for use in assessments and for

other management needs. However, a single fishery may have bycatch of more than one stock of

fish or protected resource, sometimes from many stocks. Therefore from a practical standpoint,

often the entire fishery needs to be monitored, not just selected species within the bycatch. Thus,

if standards of precision for bycatch estimation are established for the aggregate fish bycatch in a

fishery, the relationship between the precision of the estimate of fish bycatch from a fishery (i.e.,

the bycatch of all fish species or stocks aggregated) and the precision of the estimates of the

individual stocks within the bycatch needs to be understood.

When estimating catch or bycatch from fisheries data, survey or observation programs

usually are designed to address estimations of the bycatch of multiple species, rather than being

designed specifically for the estimate of the bycatch of an individual species. The reasons for

this are: (1) more than one species is of concern to managers; (2) the species that are of little

concern today may be of great concern in the future; and (3) sampling designs can be more

efficient when directed at more than one species. Therefore, observations are often designed to
58

0.00 0.50 1.00 1.50 0.00 0.25 0.50 0.75 1.00

CV of Bycatch Estimate of Species i

Total Bycatch=10,000

Total Bycatch=1,000

Total Bycatch=100

CV of Total Bycatch=.05

0.00 0.50 1.00 1.50 0.00 0.25 0.50 0.75 1.00

CV of Total Bycatch=.30

0.00 0.50 1.00 1.50 0.00 0.25 0.50 0.75 1.00

Proportion

CV of Bycatch Estimate of Species i

CV of Total Bycatch=.50

0.00 0.50 1.00 1.50 0.00 0.25 0.50 0.75 1.00

Proportion 

CV of Total Bycatch=0.75

Figure 5. Precision of estimates of bycatch of an individual

species (species I) as a function of the total bycatch aggregated

over all species, the CV of the total aggregate bycatch and the

proportion of the total that species I represents.

obtain bycatch estimates of the aggregate of all fish species combined with a specified precision. 

However, if the bycatch estimate for each species is given by the product of the estimate of total

bycatch and the estimate of the

proportion of each species

contributing to the bycatch, the

precision of the bycatch

estimate of an individual

species will be less, sometimes

considerably less, when a

species comprises a small

percentage of the aggregate (see

Figure 5 and Appendix 3). In

this case, the precision of

bycatch estimates for an

individual species deteriorates

disproportionally when the

proportion is below 10-15%. 

This is especially so when the

aggregate bycatch is small. 

This suggests that some

pragmatism might be required

in specifying precision

requirements, particularly when

there are multiple bycatch

species of concern in a fishery.

5.4 Precision Goals for Estimating Bycatch from a Fishery

The appropriate precision standards for the estimates of bycatch depend on the

management objectives, the management uses of the estimates, the precision of other information

used with the bycatch estimates to make management decisions, and the cost of increasing the

precision of the bycatch estimates. Ideally, standards of precision would be based on the benefits

and costs of increasing precision. More often though, managers specify the available budget for

estimating bycatch and then scientists determine the precision that can be achieved for that

budget. In either case, the precision will be a function of a number of fishery-specific factors. 

For these reasons, this report specifies precision goals, rather than precision standards.

These CV goals are the levels of precision that NMFS will strive to achieve. However, it

is important to recognize that: 

• The goals may in some instances exceed minimum statutory requirements.

• There are intermediate steps in increasing precision that may not immediately

achieve the goals but that represent progress nonetheless.

• There are circumstances in which higher levels of precision may be desired,

particularly when management is needed on fine spatial or temporal scales.

• There are circumstances under which meeting these precision goals would not be

an efficient use of public resources.
59

• Funding and logistical constraints, safety considerations and additional objectives

for observer programs may prevent the attainment of these goals.

• When a numeric limit is set for a bycatch species, the uncertainty associated with

setting that limit and the methods used for addressing that uncertainty are two of

the factors that determine the appropriate CV for the bycatch estimate for that

species.

• If CVs of 20-30% for individual fishery species can be obtained and are needed

for management, then this precision should be encouraged.

• In some instances decreasing bias (including that caused by the observer effect)

will be more important than increasing precision.

• The absolute precision (in numbers of animals) may be more appropriate than the

percent precision for some protected species (see Appendix 4 for technical

comments on this issue).

• Flexibility is needed when setting CV targets for specific fisheries and bycatch

species.

• A decision to accept lower precision should be based on analyses and

understanding of the implications of that decision.

If bycatch is being monitored principally in order to manage a fishery within bycatch

limits, an alternative to CV goals is to set the bycatch limits based on a management regime that

incorporates uncertainty. For example, the management of marine mammal bycatch in

commercial fisheries in U.S. waters is based on the product of a conservative estimate of

abundance, an estimate of maximum net production, and a recovery factor. The product of these

three parameters is referred to as the Potential Biological Removal (PBR) level. The estimate of

abundance for a given stock is based on the 20th percentile of the distribution for abundance. 

This value was selected based on the results of computer simulations that indicated such an

approach would meet specific management objectives. In this case, as the CV of the estimate

increases, the limit on bycatch for the marine mammal species of interest decreases in a

predictable manner. Therefore, managers can determine the costs and benefits associated with

various levels of the CVs on both the abundance estimate and the bycatch estimate and allocate

funding appropriately to improve either or both estimates.

The precision of bycatch estimates for protected species is often not the most important

factor in determining the precision of an assessment of that protected species or stock. The

reason for this is that often the absolute magnitude of the take of that species is small. Thus,

assessments often are driven more by the precision of abundance surveys or population estimates

and associated information than by that of bycatch. However, the evaluation of bycatch relative

to allowable takes is important in the management of protected species (Barlow 1999). Precision

goals for protected species should emphasize this aspect of management. Precision of 20-30%

CVs on the bycatch of many protected species or stocks would mean that managers would know

that the bycatch estimate reflects the actual bycatch occurrence with a reasonably high

probability. However, as noted above, the absolute precision (in numbers of animals) may be

more appropriate than the percent precision for protected species for which the allowable take is

very few animals.
60

Precision Goals for a Fishery

Protected Species

For marine mammals and other protected species, including seabirds and sea

turtles, the recommended precision goal is a 20-30% CV for estimates of

bycatch for each species/stock taken by a fishery.

Fishery Resources

For fishery resources, excluding protected species, caught as bycatch in a

fishery, the recommended precision goal is a 20-30% CV for estimates of

total discards (aggregated over all species) for the fishery; or if total catch

cannot be divided into discards and retained catch then the goal is a 20-30%

CV for estimates of total catch.

Precision goals for the bycatch of the fishery resources (excluding protected species)

within a fishery should recognize that often there are a number of species within the aggregate

bycatch. If the precision of the aggregate has a CV of 20-30%, then the CV of an individual

species within that aggregate will have a comparable CV unless the aggregate is small and the

proportion of the total that that species represents is also small (see Figure 5 and Appendix 3). 

However, as noted above, the precision of bycatch estimates for an individual species

deteriorates disproportionately when a species accounts for less than 10-15% of the total bycatch. 

The deterioration is more rapid when the aggregate bycatch is small. This means that the bycatch

of all but the most abundant species could fall into this category, especially as the number of

bycatch species encountered in a fishery increases. If the aggregate and the proportion are

sufficiently small, then the bycatch of that species will be on the order of a few animals. If

bycatch of a few animals is significant to a population, then that population probably falls within

the protected species realm and the CV recommendation for protected species would apply.

The role that bycatch plays in the CV of the management quantities derived from an

assessment of a fishery resource can be varied. A CV of 20-30% on a TAC is a useful

management goal (Powers and Restrepo 1993). Additionally, the ASMFC recommended a target

20-30% CV for both finfish and protected species (ASMFC 1997). Hence, a 20-30% CV for the

bycatch estimate is a useful goal.

Note that in some instances, management is focused on monitoring total catch of a fishery

resource of which bycatch is an important component. In this case, the sampling design has been

structured to estimate total catch including bycatch. In these situations the precision of the

bycatch component is not easily teased out. However, in these instances a goal of 20-30% CV

for the total catch including bycatch appears to be sufficient.

5.5 Other Factors That May Affect Observer Coverage Levels

Although the precision goals for estimating bycatch are important factors in determining

observer coverage levels, other factors are also considered when determining actual coverage

levels. These may result in either lower or higher levels of coverage than that required to achieve

the precision goals for bycatch estimates.

Factors that may justify lower coverage levels include lack of adequate funding,

incremental coverage costs that are disproportionately high compared to benefits, and logistical
61

considerations such as lack of adequate accommodations on a vessel, unsafe conditions, and lack

of cooperation by fishermen.

Factors that may justify higher coverage levels include incremental coverage benefits that

are disproportionately high compared to costs and other management-focused objectives for

observer programs. The latter include total catch monitoring, in-season management of total

catch or bycatch, monitoring bycatch by species, monitoring compliance with fishing regulations,

monitoring requirements associated with the granting of Experimental Fishery Permits, or

monitoring the effectiveness of gear modifications or fishing strategies to reduce bycatch. In

some cases, management may require one or even two observers to be deployed on every fishing

trip. Increased levels of coverage may also be desirable to minimize bias associated with

monitoring rare events (such as takes of protected species), or to encourage the introduction of

new “standard operating procedures” for the industry that decrease bycatch or increase the ease

with which it can be monitored.

63

6. Status of At-Sea Observation Programs

At-sea observation programs for fishery dependent data include observer programs,

electronic monitoring programs (e.g., the use of digital video cameras and digital observers) and

a combination of the two. As electronic monitoring technology is improved and as the associated

policy issues are addressed, the use of electronic monitoring is expected to increase. Often it will

be used to complement observer programs, but in some cases it will be used either as a substitute

for an observer program or as a method of expanding at-sea observations for a fishery with an

observer program. However, the following survey of observation programs focuses on observer

programs because they currently are the principal element of the at-sea observation programs for

marine fisheries.

6.1 A Survey of Observation Programs

The National Working Group on Bycatch (NWGB) reviewed U.S. fisheries to determine

the level of existing bycatch monitoring. Each fishery was assigned a bycatch monitoring level

(i.e., type) classification of: None, Baseline, Pilot, Developing or Mature as defined in Table 3

(recognizing the precision goals established in Section 5). The level of the bycatch program and

other information that is designed to assist in setting priorities for improving observer programs

are presented in Tables 4.1-4.6. The additional information includes: (1) the recommended next

level in the development of the observer program; (2) an estimate of the number of at-sea

observer days needed to achieve the next level (typically estimates were not available if the next

level is a developing or mature program); (3) the vulnerability of the fishery to the bycatch of fish

(excluding protected species), marine mammals and other protected species, that is, ESA-listed

species (excluding marine mammals), other sea turtles and other seabirds. The vulnerability

classification are defined and discussed in Section 7.

There should be a clear understanding of the list of fisheries used in Tables 4.1-4.6 and,

specifically, the definition of what is meant by the term “fishery”. The definition of a fishery is

inherently subjective (e.g., which gears are grouped), but in this context a “fishery” would be a

logical unit for which a sampling program might be designed. However, this approach results in

differences both within and between regions. This should be understood by the reader,

particularly when interpreting summary statistics derived from Tables 4.1-4.6. For example, the

fisheries of the Southeast (Table 4.2) include a large number of relatively small coastal fisheries,

as well as very large fisheries, such as the Gulf of Mexico shrimp trawl fishery. Thus, the

implications of having or not having a bycatch monitoring program are clearly different between

the Gulf shrimp trawl fishery and smaller coastal fisheries. This imbalance of implications

occurs within all regions. To some extent this imbalance is addressed by assigning bycatch

“vulnerabilities” to each fishery (this is done in Section 7). However, vulnerability does not

address the economic or political factors that one may wish to consider when developing bycatch

monitoring programs.

Also, the reader should note that recreational fisheries are not included within Tables 4.1-

4.6. Most of the private recreational and charterboat fisheries are monitored through the Marine

Recreational Fishing Statistics Survey in which estimates of bycatch (discards) are made. Thus,

in these recreational fisheries, there currently is a bycatch reporting procedure, albeit based on

self-reporting (with some of the problems inherent in self-reporting, noted in Section 4).

Additionally, some state fisheries were included either if they were classified as MMPA

Category I or Category II fisheries or if there were ESA concerns. Using this procedure, the

NWGB examined the status of each fishery. The evaluations in Tables 4.1–4.6 were made by the

NWGB in consultation with numerous NMFS experts.
64

Given the different emphasis placed on the fisheries examined in this report, it is

important that the Regional Teams established in the National Bycatch Strategy review their

constituent fisheries with the aim of identifying additional state and interstate jurisdictional

fisheries and recreational fisheries that might be important for bycatch monitoring. Additional

fisheries requiring monitoring are identified in the Regional Bycatch Implementation Plans that

can be found at: http://www.nmfs.noaa.gov/bycatch.htm

A total of 84 fisheries were classified in Tables 4.1-4.6. Of these, 5% have a Mature

observer program, 20% have a Developing program, 10% have a Pilot program, 29% have a

Baseline program, and 37% do not have a program (None). The summary statistics are in Table

5. In considering these summary statistics, it is critical to note the caveats in Section 6.1 about

the definition of a “fishery” and that there are differences both within and between regions. 

6.2 Enhancement of Observer Programs

6.2.1 Criteria for Enhancing Observer Programs

Section 5 presented a discussion of precision goals. It was noted there that the goals are

levels of precision that NMFS strives to achieve, but that for a variety of reasons flexibility is

needed when setting CV targets for specific fisheries and bycatch species. Given this

understanding, the NWGB used the following procedure for examining options for enhanced

observer programs.

The NWGB reviewed each fishery and determined the “next step” of sampling program

development needed, that is, moving from None to a Baseline or Pilot program, moving from a

Baseline to a Pilot program, moving from a Pilot to a Developing program, and moving from a

Developing to Mature program (see Tables 4.1-4.6). In a few instances, it is suggested that the

sampling program be maintained (for example, for some Mature sampling programs or for

fisheries that are being phased out). The NWGB could not make quantitative, fishery by fishery,

sampling recommendations for Pilot, Developing and Mature programs. The data may exist to

do this, but the NWGB had neither the time nor expertise for these analyses. Such analyses may

be more appropriately undertaken at the regional level. Additionally, Developing or Mature

sampling programs imply optimization of sampling which, in turn, depends on budget constraints

and precision goals. This sampling plan and optimization process should be done for each of the

Developing and Mature sampling programs.

Additionally, initial effort should be made to establish baseline or pilot-level information

for every fishery such that statistically rigorous sampling plans can be developed. At this stage, it

is not expected that all fisheries will achieve the 20-30% precision goals, but rather that

information will become available to both plan for the attainment of those goals and to do it in an

efficient manner. The information may be used to identify the cost of achieving the precision

goal. In developing quantitative advice for coverage of observer programs, the guidance of the

ASMFC’s Atlantic Coastal Cooperative Statistics Program (ACCSP) was noted: observer

programs should obtain a minimum of 2% coverage until CVs can be calculated, and then target

20-30% CVs for both finfish and protected species (ASMFC, 1997). The programs should utilize

proportional sampling across all gear types and fisheries, recognizing some prioritization as

need (statutory requirements) and data (high bycatch areas) dictate. Recognizing the

importance of evaluating sampling programs through intermediate steps, the NWGB suggests the

following sampling criteria for each fishery (Table 6).
65

Table 4.1. Survey of Southwest Region fishery-specific at-sea observer programs, including current program level, recommendedenhancements and bycatch vulnerability.

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Coastal Pelagic Species(Coastwide)

Pacific sardine northern

anchovy pacific

mackerel jack mackerel

market squid

Purse seine lamparanet drum net

None Pilot 130 days Low Moderate Moderate

Drift Gillnet Fishery Swordfish, sharks

(thresher, mako)

Drift gillnet, largemesh

Mature Maintain - Moderate Moderate High

Surface Hook and Line Albacore Troll None Baseline 420 days Low Low LowPelagic Longline Swordfish, tuna Single main line Pilot Developing 900 days to

achieveprecisiongoals

Moderate Moderate High

Coastal Purse Seine Tuna Purse seine None Pilot 15 days Moderate Moderate ModerateHarpoon Swordfish Harpoon None Baseline 15 days Low Low Low

The program level (stage) classifications are defined in Table 3. A dash (-) indicates that an estimate of the number of sea days neededfor the next level was not available. The vulnerability classification are defined and discussed in Section 7. The other protected speciesare ESA species (excluding marine mammals), other sea turtles and other seabirds.
66

Table 4.2 Survey of Southeast Region fishery-specific at-sea observer programs, including current program level, recommended

enhancements and bycatch vulnerability.

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Gulf of Mexico ReefFish FMP

42 species in FMP Bottom longline Baseline Pilot 490 days High Low Moderate

South Atlantic SnapperGrouper FMP 73 species in FMP Bottom longline Baseline Pilot 112 days High Low ModerateGulf of Mexico ReefFish FMP

42 species in FMP Handline Baseline Pilot 1,680 days High Low Moderate

South Atlantic SnapperGrouper FMP 73 species in FMP Handline Baseline Pilot 1,932 days High Low ModerateMigratory CoastalPelagic FMP - Gulf ofMexico

King/Spanish mackerel Trolling None Baseline 168 days Low Low Moderate

Migratory CoastalPelagic FMP - SouthAtlantic

King/Spanish mackerel Trolling None Baseline 1,260 days Low Low Moderate

Crab Trap/Pot (StoneCrab Fishery)

Stone crabs Pot None Baseline 350 days Low Low Low

Crab Trap/Pot (BlueCrab Fishery) Gulf ofMexico

Blue crabs Pot None Baseline 2,500 days Low Moderate Low

Crab Trap/Pot (BlueCrab Fishery) SouthAtlantic

Blue crabs Pot None Baseline 1,200 days Low Moderate Low

Crab Trap/Pot (GoldenCrab Fishery)

Golden crab Pot None Baseline 14 days Low Low Low
67

Table 4.2 (Continued)

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Directed Shark Gillnet Large coastal and small

coastal shark aggregates

Drift gillnet/strike

gillnet

Mature Maintain No change Moderate Moderate Moderate

South Atlantic snappergrouper FMP 73 species in FMP Trap Baseline Maintain fishery being

phased-out

High Low Low

Gulf of Mexico ReefFish FMP

42 species in FMP Trap Baseline Maintain fishery

being

phased-out

High Low Low

 Lobster Trap Caribbean spiny lobster Pot None Baseline 230 days Low Low LowGulf of Mexico - ShrimpTrawl 

Brown, white, pink

shrimp

Trawl Pilot Developing 8000 days High Low High

Southeastern Atlantic -Shrimp Trawl 

Brown, white, pink

shrimp; rock shrimp

Trawl Pilot Developing 4,000 days High Low Moderate

Fish Trawl (Paired /Single)

Butterfish, squid Trawl None Baseline 50 days Low Low Low

Pelagic Longline Fishery Tuna, swordfish Surface longline Developing Mature 1,700 days High High HighSurface Trawl Jellyfish Trawl None Baseline 7 days Low Low ModerateInshore Gillnet Bluefish, Spanish

mackerel, weakfish,

butterfish, southern

flounder, spot, kingfish

Gillnet Pilot Developing 820 days Moderate Moderate High
68

Table 4.2 (Continued)

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

NC Coastal Gillnet(State and FederalWaters)

Striped bass, monkfish,

spot, croaker, bluefish,

weakfish, Spanish

mackerel, king mackerel,

kingfish

Gillnet Pilot Developing 117 days Moderate High High

NC Pound-net Southern flounder Pound net Baseline Pilot 66 days Low Moderate HighSoutheastern Atlantic -Flynet

Croaker, weakfish Trawl Baseline Pilot 35 days Moderate Low Moderate

Atlantic MenhadenPurse-Seine Fishery

Atlantic menhaden Purse seine None Baseline 25 days Low Low Low

Gulf Menhaden PurseSeine Fishery Gulf menhaden Purse seine Baseline Pilot 226 days Low Moderate LowGulf of Mexico - CastNet (W. Florida)

Shrimp Cast net None None 0 days Low Low Low

Southeastern Atlantic -Cast Net (Florida,Georgia, North Carolina)

Brown, white, pink and

other marine shrimp

Cast net None None 0 days Low Low Low

Gulf of Mexico - BeamTrawl (Florida-WestCoast) NMFS landingdata.

Pink shrimp Beam trawl Baseline Baseline 75 days Low Low Low

Gulf of Mexico -Skimmer Trawls

Brown, white, pink,

seabob and other marine

shrimp

Skimmer trawl None Baseline 438 days Low Low Low

Southeastern Atlantic -Skimmer Trawls -

White shrimp Skimmer trawl None Baseline 36 days Low Low Low
69

Table 4.2 (Continued)

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Gulf of Mexico (AllStates) - Butterfly Nets

Brown, white, pink,

seabob and other marine

shrimp

Butterfly net None Baseline 51 days Low Low Low

Southeastern Atlantic(NC, E FL) - ButterflyNets

Brown, pink and other

marine shrimp

Butterfly net None Baseline 6 days Low Low Low

NC Haul/Beach Seine Striped bass, weakfish,

spot, striped mullet

Multifilament seine;

monofilament

gillnet/seine

Baseline Pilot 12 days Moderate Moderate Moderate

NC Long-Haul Seines Spot, weakfish, Atlantic

croaker

Seine Baseline Pilot 8 days Moderate Moderate Moderate

NC Stop Nets Striped mullet Multifilament

anchored net and

multifilament beach

seine

Baseline Pilot 100 days Moderate Moderate Moderate

Black Sea Bass PotFishery

Black sea bass Pot/traps None Baseline 50 days Moderate Moderate Low

Winter Fluke (Flounder)Trawls

Flounder Trawls Baseline Pilot 91 days Moderate Low Moderate

The program level (stage) classifications are defined in Table 3. A dash (-) indicates that an estimate of the number of sea days neededfor the next level was not available. The vulnerability classification are defined and discussed in Section 7. The other protected speciesare ESA species (excluding marine mammals), other sea turtles and other seabirds.
70

Table 4.3. Survey of Northwest Region fishery-specific at-sea observer programs, including current program level, recommendedenhancements and bycatch vulnerability.

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

West Coast Mid-WaterTrawl for Whiting, AtSea Processing

Pacific whiting Pelagic trawl Mature Maintain - Low Low High

West Coast Mid-WaterTrawl for Whiting,Shoreside Processing

Pacific whiting Pelagic trawl Pilot Maintain - Low Low High

West Coast GroundfishBottom Trawl 

Flatfish, rockfish,

roundfish, assorted

skates/sharks

Bottom trawl, large

(>8" dia.) and small

(<8") footrope

Developing Mature - High Low Moderate

West Coast GroundfishNon-trawl Gear

Sablefish, rockfish,

greenling, assorted

roundfish

All non-trawl gear:

hook-and-line, net

gear, pot gear

Developing Mature - High Low Low

West Coast SalmonTroll, Non-Tribal Ocean

Salmon Troll hook-and-line

gear

Baseline Baseline - Moderate Low Low

West Coast PacificHalibut Longline, NonTribal

Pacific halibut Longline None Baseline 4 Moderate Low Low

The program level (stage) classifications are defined in Table 3. A dash (-) indicates that an estimate of the number of sea days neededfor the next level was not available. The vulnerability classification are defined and discussed in Section 7. The other protected speciesare ESA species (excluding marine mammals), other sea turtles and other seabirds.
71

Table 4.4. Survey of Alaska Region fishery-specific at-sea observer programs, including current program level, recommendedenhancements and bycatch vulnerability.

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Pacific HalibutIndividual Fishing Quota

Pacific halibut Hook and line

(mainly longline)

None Pilot 115 days Moderate Low Moderate

BSAI Groundfish Trawl Pollock, Pacific cod,

flatfish, rockfish, Atka

mackerel

Trawl Developing Mature - High Moderate Moderate

BSAI GroundfishLongline

Pacific cod, flatfish,

sablefish

Longline Developing Mature - Moderate Low Moderate

BSAI Groundfish Pot Pacific cod, sablefish,

rockfish

Pot Developing Mature - Low Low Low

BSAI Groundfish Jig Pacific cod, rockfish Jig None Baseline 3 days Low Low LowGOA Groundfish Trawl Pollock, Pacific cod,

flatfish, rockfish

Trawl Developing Mature - Moderate Low Moderate

GOA GroundfishLongline

Pacific cod, sablefish,

rockfish

Longline Developing Mature - Moderate Low Moderate

GOA Groundfish Pot Pacific cod Pot Developing Mature - Low Low LowGOA Groundfish Jig Pacific cod, rockfish,

sablefish, flatfish

Jig None Baseline 14 days Low Low Low

Select State ManagedSalmon

 Salmon Drift and set gillnet

and purse seine

NoneBaseline * Baseline- Pilot * >600 days Low ** Moderate Low ***

The program level (stage) classifications are defined in Table 3. A dash (-) indicates that an estimate of the number of sea days neededfor the next level was not available. The vulnerability classification are defined and discussed in Section 7. The other protected speciesare ESA species (excluding marine mammals), other sea turtles and other seabirds. *The current design classification and , therefore, thenext step varies by area and gear. ** Note that, with one exception, controlling the bycatch of fish, non-marine mammal ESA species

and seabirds in these state managed salmon fisheries is not a stewardship responsibility of NMFS. The exception is the bycatch of ESAlisted Pacific Northwest salmon stocks. The Northwest Region has the lead for protecting those stocks.
72

Table 4.5. Survey of Northeast Region fishery-specific at-sea observer programs, including current program level, recommendedenhancements and bycatch vulnerability.

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

New England LargeMesh Otter Trawl

Gadoids, flatfish,

monkfish

Otter trawl Developing Mature - Moderate Low Low

New England SmallMesh Otter Trawl

Gadoids, herring, small

pelagics, dogfish

Otter trawl Developing Mature - Moderate Low Low

New England Gillnet Gadoids, flatfish,

dogfish

Demersal gillnet Developing Mature - Moderate High Moderate

New England DemersalLongline

Gadoids, dogfish Longline Baseline Pilot 50 days Moderate Low Low

Gulf of Maine ShrimpTrawl

Northern shrimp Otter trawl Baseline Pilot 36 days Moderate Low Low

Georges Bank ScallopDredge

Sea scallop Mechanical dredge Developing Mature - Moderate Low High

Mid-Atlantic LargeMesh Otter Trawl

Summer flounder, black

sea bass, scup

Otter trawl Developing Mature - Moderate Low Moderate

Mid-Atlantic SmallMesh Otter Trawl

Squid, mackerel,

butterfish

Otter trawl Pilot Developing - Moderate High Moderate

Mid-Atlantic Longline Tilefish Longline Baseline Pilot 50 Moderate Low LowMid-Atlantic Gillnet Monkfish, dogfish Gillnet Developing Mature - Moderate High High
73

Table 4.5 (Continued)

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Mid-Atlantic/S. NewEngland Small Pelagics

Herring, mackerel Midwater trawl Pilot Developing - Low Moderate Moderate

Gulf of Maine SmallPelagics

Herring, mackerel Midwater trawl Baseline Pilot 75 days Low Moderate Moderate

Mid-Atlantic ScallopDredge

Sea scallop Dredge Developing Mature - Moderate Low High

Lobster/Crab Trap Lobster, cancer crab, red

crab

Traps None Baseline 100 days Low High Low

Other Pots Cancer crab, red crab,

whelk, black sea bass

Traps Baseline Pilot 80 days Low Moderate Low

Pound Nets Croaker, drum,

weakfish, flounder

Fish trap Baseline Pilot 40 days Moderate Moderate Moderate

Weirs Herring Fish trap None Baseline 30 days Moderate Moderate ModerateHydraulic Dredge Surf clams, ocean

quohogs

Hydraulic dredge Baseline Pilot 30 days Low Low Low

The program level (stage) classifications are defined in Table 3. A dash (-) indicates that an estimate of the number of sea days neededfor the next level was not available. The vulnerability classification are defined and discussed in Section 7. The other protected speciesare ESA species (excluding marine mammals), other sea turtles and other seabirds.
74

Table 4.6. Survey of Pacific Island Region fishery-specific at-sea observer programs, including current program level, recommended

enhancements and bycatch vulnerability.

Fishery Target species Gears Program

level

Next Level Sea days

needed for

next level

Vulnerability by type of bycatch

Fish Marine

Mammals

Other

protected

species

Pelagic Longline Tuna, mahimahi, other Longline Developing Mature - Moderate Moderate HighPelagic Hook-and-Line(Rod and Reel)

Tuna, mahimahi, other Hook and line None Baseline - Low Low Low

Pelagic Handline Tuna, mahimahi, other Handline None Baseline - Low Low LowNWHI Crustaceans Spiny and slipper lobster Traps Baseline Pilot - Moderate Moderate LowNWHI Bottomfish Snapper, carangids Handline None Pilot - Moderate Moderate LowPelagic Purse Seine Tuna Purse seine Mature Maintain - Moderate Low ModeratePrecious Corals Stony corals Tangle nets None Baseline - Low Low Low

The program level (stage) classifications are defined in Table 3. A dash (-) indicates that an estimate of the number of sea days neededfor the next level was not available. The vulnerability classification are defined and discussed in Section 7. The other protected speciesare ESA species (excluding marine mammals), other sea turtles and other seabirds.
75

Table 5. Frequency and percent of observer programs by level (i.e., stage)*.

Frequency

Current Observer

Program # Fisheries # None # Baseline # Pilot # Developing # Mature

Southwest 6 4 0 1 0 1

Southeast 37 17 14 4 1 1

Northwest 6 1 1 1 2 1

Alaska 10 3 1 0 6 0

Northeast 18 2 7 2 7 0

Pacific Islands 7 4 1 0 1 1

Total 84 31 24 8 17 4

Percent

Current Observer

Program Fisheries None Baseline Pilot Developing Mature

Southwest 100% 67% 0% 17% 0% 17%

Southeast 100% 46% 38% 11% 3% 3%

Northwest 100% 17% 17% 17% 33% 17%

Alaska 100% 30% 10% 0% 60% 0%

Northeast 100% 11% 39% 11% 39% 0%

Pacific Islands 100% 57% 14% 0% 14% 14%

Total 100% 37% 29% 10% 20% 5%

* The five program level classifications are defined in Table 3. 

Percent coverage levels were put into the criteria to move the programs up through the

initial stages of the process, but were purposely not suggested for the more advanced stages. In

the initial expansion of any sampling program, a certain level of coverage must be established to

determine the next developmental steps in the process. Using the coverage level standards

developed by the ACCSP, it was determined that a 2% coverage level would allow each of the

programs to develop up to the pilot stage of sampling. This level of coverage would allow

enough data to be collected for coverage levels and stratification designs to be developed to

move the programs up through the more advanced sampling levels. However, for fisheries with a

large amount of effort (a large number of vessel-sea days), a simple 0.5-2% rule may be

prohibitively expensive and statistically wasteful. Therefore, it is recommended that in the

Baseline and Pilot stages of a program that sample sizes not exceed 100 per strata or an overall

coverage of 0.5-2%, whichever is smaller. This sampling level would allow initial evaluation

and planning to occur for Developing and Mature observer programs. Sampling would then

either increase or decrease depending on the design characteristics chosen. 

Fixed or recommended percentage coverage levels for the advanced stages are not

appropriate, since the amount and allocation of the coverage levels are developed by statistical

methodologies and will differ from fishery to fishery and region to region. A fishery with a few

abundant, but evenly distributed, bycatch species will have a very different sampling design than

a fishery with many uncommon bycatch species with patchy distributions. At the mature stage of

development, the two programs will have very different percentage levels of coverage.
76

6.2.2 Enhanced Sample Sizes and Costs

Of the fisheries reviewed in Tables 4.1-4.6, 60% were suggested as candidates for “next

step” improvement to a Baseline or Pilot sampling program. Using the quantitative sampling

criteria of Table 6, estimates were made of the number of observed sea days (observed trips or

observed participants) that are needed to move sampling programs from None to Baseline or

None to Pilot. 

Estimates of cost per observation day are quite variable between fisheries and between

regions. Estimates vary from $350 to $2,000 per observation day (at-sea day) (or $450-2,000 per

day if all program costs are prorated to a cost per day basis). The reasons for the variation

include: logistical difficulties for observers to join trips (lengthy travel, onshore travel costs),

insurance, food, data entry, quality control, training, analytical costs and program management. 

Differences in these factors arise from differences in who pays for these various costs, whether

the program is large enough for economies of scale and the geography of the fishery.

Cost estimates for Baseline and Pilot observer programs were not made. Cost estimates

to establish baseline or pilot-level information for all fisheries can be made, based on knowledge

of the fisheries. Additionally, costs associated with Developing and Mature programs may be

obtained. It is foreseeable that sampling programs that are in advanced stages could call for

either more or less sampling coverage when optimized for changing budgets and/or precision

goals. However, it is expected that in general more precision (and, thus, larger budgets) will be

required.
77

Table 6. Sampling criteria for enhanced observer programs.

From:

Current

Program

To: 

Enhanced

Program

Improvement Criteria

None Baseline 0.5-1% coverage of total effort preferably distributed across

initial time/area/gear strata. There should be a minimum

sample size of three per strata. Maximum sample sizes for

Baseline and Pilot programs should be 100 per strata until

quantitative designs can be developed. Focus on definition of

relevant strata and the determination of the likelihood of a

bycatch problem. Recommend uniform sampling allocation.

None Pilot 0.5-2% coverage of total effort distributed across refined

time/area/gear/vessel strata. There should be a minimum

sample size of three per strata. Maximum sample sizes for

Baseline and Pilot programs should be 100 per strata until

quantitative designs can be developed. Recommend uniform

allocation or alternative more efficient allocations (e.g.,

proportional allocations) based on available data. This

approach to skip baseline would be for fisheries where a

perceived bycatch problem has been noted from nonsystematic observation.

Baseline Pilot 1-2% coverage of total effort distributed across refined

time/area/gear/vessel strata. There should be a minimum

sample size of three per strata. Maximum sample sizes for

Baseline and Pilot programs should be 100 per strata until

quantitative designs can be developed. Recommend uniform

allocation or alternative more efficient allocations (e.g.,

proportional allocations) based on available data.

Pilot Developing Stratified random designs have been established and optimal

sampling allocations are developed, implemented and

evaluated. Strategy for meeting recommended precision goals

is established

Developing Mature An optimal sampling allocation scheme has been implemented. 

It is periodically re-evaluated considering changes in the

fishery over time. Precision goals are being met. 

79

7. Vulnerability of Fisheries to Adverse Impacts of Bycatch

Each fishery was rated in terms of its “vulnerability” to adverse impacts on bycatch

species (either existing or expected to arise in the future). The assignment of ratings was

designed to provide guidance for priority-setting in developing strategies for addressing bycatch

issues. Vulnerability criteria might include such factors as the degree of overfishing of target

species, life history characteristics of target and bycatch species and the spatial-temporal patterns

of the bycatch and target species.

When examining the impact of fishing on a species or stock of fish, the metric that is

most often used is the Spawning Potential Ratio (SPR), that is, the contribution to reproductive

potential of a cohort of animals over its lifetime when undergoing fishing relative to that

contribution when no fishing is occurring. In order to calculate SPR, one needs age-specific rates

of natural mortality, fishing mortality, fecundity and growth. In many cases, fishing mortality

rates that result in an SPR of 35–40% are approximations of the fishery mortality rate at

maximum sustainable yield. When examining bycatch impacts on a species or stock, the SPR

concept may be expanded to look at the reproductive potential (1) when there is bycatch

mortality and no target fishing relative to when there is neither bycatch nor target fishing; (2)

when there is both bycatch and target fishing relative to no fishing; and (3) when there is both

bycatch and target fishing relative to when there is just target fishing. The first calculation

examines the risk to the population of bycatch alone; the second looks at the total risk to the

population under all fishing mortality; and the third addresses the relative, incremental risk

imposed by bycatch beyond that of the target fisheries. Ideally, these calculations would be made

for every bycatch species within a fishery and then fisheries could be assigned vulnerability

based on those risks. For example, bycatch of species x might be assigned High vulnerability if

SPR with both target and bycatch fishing was below 40%, or if SPR with bycatch alone was

reduced to, say, 50%. The results by species or stock could be grouped in categories within a

fishery to assign vulnerability to the fishery as a whole.

However, the number of species for which this can be done is limited due to the lack of

data. For example, the required data are available for few non-target species such as many deepwater coral species. Therefore, a more qualitative approach was used. Each fishery was assigned

a “vulnerability” of High, Moderate, or Low for bycatch of the fishery resources, for the bycatch

of marine mammals and for the bycatch for other protected species (i.e., ESA-listed species

(excluding marine mammals), other sea turtles and other seabirds). Endangered and threatened

marine mammals were included in the marine mammal category, rather than the “other protected

species” category since regulatory procedures for both types of marine mammals are defined

similarly. The vulnerability issues are similar for the species included in “other protected

species” category. No attempt was made to weight vulnerability among the three resource types. 

The criteria used to define High, Moderate and Low vulnerability for these three resource groups

are presented below.

7.1 Vulnerability Criteria for Fishery Resources

Regional experts within NMFS were polled and asked to address five questions for each

of the fisheries within their region (see Tables 4.1-4.6):

Does uncertainty in bycatch estimates contribute in an important way to application of

management constraints such as TACs, PBRs, days at sea, the minimum stock size

threshold (MSST), the maximum fishing mortality rate threshold (MFMT), etc.? For

example, if bycatch is a large proportion of the total catch, and/or if the precision of the
80

inputs to stock assessment models is much better than that of the bycatch, then

uncertainty contributes in an important way.

Is there a high discard or bycatch rate or amount relative to total catch? Indicate whether

this is a current management concern due to the absolute amount of discard or rate.

Does the bycatch of this fishery cause significant mortality of any species listed as

overfished? For example, if the mortality affects an overfished species' rebuilding

schedule, then the mortality is significant.

Are the target species of this fishery undergoing overfishing or overfished?

Does the bycatch impact other fishery allocations? For example, do levels of bycatch

taken in the fishery result in lower catch limits, closures, etc. in other fisheries or sectors?

The experts were also asked to provide their own overall rating for the fishery and to provide

comments on the reasons for that rating. The five questions were designed to address risks to the

bycatch species taken in the fishery, risks to target species of the fishery, constraints on

management imposed by uncertainty in the bycatch, and allocation impacts imposed on other

fisheries. Answers to these questions were grouped according to the number of positive

responses and were compared to the overall judgement on vulnerability of the fishery by the

regional expert. Fisheries were assigned High, Moderate or Low vulnerability based on the

number of affirmative responses to the five questions. Note that for many non-target species and

some target species, there is insufficient stock assessment and bycatch information to determine

bycatch vulnerability for a specific fishery.

7.2 Vulnerability Criteria for Marine Mammals

Vulnerability criteria for marine mammals in individual fisheries have already been

established by the MMPA (16 U.S.C. 1387 (c)(1)(A)) and codified in regulations at 50 CFR

229.2. The resulting ranking of marine mammal vulnerability for each fishery is identified in the

annual List of Fisheries which categorizes fisheries based on the level of incidental mortality and

serious injury the fishery causes relative to a marine mammal stock’s potential biological

removal level (PBR). A Category I fishery is one that results in frequent incidental mortality and

serious injury of marine mammals and by itself is responsible for the annual removal of 50% or

more of any stock’s PBR level. A Category II fishery is one that results in occasional incidental

mortality and serious injury of marine mammals. A Category II fishery, collectively with other

fisheries, is responsible for the annual removal of more than 10% of any marine mammal stock’s

PBR and by itself responsible for the annual removal of between 1% and 50% of any stock’s

PBR. A Category III fishery is one that has a remote likelihood or no known incidental mortality

and serious injury of marine mammals and that (1) collectively with other fisheries is responsible

for the annual removal of 10% or less of any marine mammal stock’s PBR, or (2) by itself is

responsible for the annual removal of 1% or less of any marine mammal stock’s PBR. The

Category of a fishery that takes marine mammals is based upon a procedure that is analogous to

the SPR metric mentioned above, except that usually there is no targeted take of marine

mammals.

Thus, the MMPA Category of a fishery was the basis for assigning vulnerability:

Category I fisheries were assigned High vulnerability, Category II fisheries were assigned

Moderate vulnerability and Category III fisheries were assigned Low vulnerability. Additionally,

fisheries that NMFS is evaluating with respect to a Category I or II classification, but that are

currently listed as Category III, were assigned Moderate vulnerability in this report. 
81

7.3 Vulnerability Criteria for Other Protected Species, Including Seabirds

The vulnerability of other protected species, (i.e., ESA-listed species (excluding marine

mammals), other sea turtles and other seabirds) in individual fisheries was assigned based upon

the relative seriousness of the impact of bycatch on the species’ recovery. 

Where authorization of the fishery required a formal Section 7 consultation and the result

of the Biological Opinion was a jeopardy finding within the last 3-5 years, or where the

Biological Opinion has been challenged and is being reevaluated by NMFS (e.g., New England

scallop fishery), vulnerability of other protected species was rated High for that fishery. Where

authorization of the fishery required a formal Section 7 consultation, but the result of the

Biological Opinion was No Jeopardy and an incidental take statement exists and is being

complied with, vulnerability of other protected species was rated Moderate for that fishery. 

Where authorization of a fishery did not require formal consultation and no incidental take

statement was needed, vulnerability of other protected species was rated as Low for that fishery. 

As noted above, the vulnerability issues are similar for the species included in the “other

protected species” category. 

In the future, the USFWS’s list of “species of concern” will be used to identify seabird

species for which bycatch vulnerability is Moderate. The purpose of this list is to highlight

potential conservation issues and concerns before species get listed. This list is maintained by

the USFWS Division of Migratory Bird Management and is available at:

http://migratorybirds.fws.gov/reports/bcc2002.pdf

7.4 Bycatch Vulnerability of Fisheries

Vulnerability classifications for each fishery are given in Tables 4.1-4.6. Summaries of

the classification statistics are presented below and in Table 7.

• 1% of these fisheries are rated as having a High vulnerability for bycatch of all

three resource types (fishery resources, marine mammals and other protected

species).

• 6% of these fisheries are rated High for bycatch of two or more of the three

resource types.

• 31% of these fisheries are rated High for bycatch of one or more of the three

resource types (thus, 69% are rated Moderate or Low for all three resources).

• 6% of these fisheries are rated High for bycatch of one or more of the three

resource types AND have a suggested “next step” sampling program of baseline or

pilot.

• 15% of these fisheries are rated High for bycatch of fishery resources (85% are

rated Moderate or Low).

• 7% of these fisheries are rated High for bycatch of marine mammals (93% are

rated Moderate or Low).

• 15% of these fisheries are rated High for bycatch of other protected species

including seabirds and sea turtles (85% are rated Moderate or Low).
82

• 26% of these fisheries are rated as having a Low vulnerability for bycatch for all

three resource types.
83

Table 7. Frequency summary of vulnerability classifications per NMFS Region

Frequency

Vulnerability Number of Fisheries High Fish High MM High OPS High in 1 or more High in 2 or 3 High in All 3 Low in All 3 High in 1 or more AND next step program is baseline or pilot

Southwest 6 0 0 2 2 0 0 2 0Southeast 37 9 2 5 12 3 1 12 5Northwest 6 3 0 2 4 1 0 0 0Alaska 10 1 0 0 1 0 0 4 0Northeast 18 0 4 3 6 1 0 1 0PacificIslands 7 00 1 1 0 0 3 0Total 84 13 6 13 26 5 1 22 5

_____________________________________________________________________________MM = marine mammalsOPS = other protected species

85

8. Strategies to Address Bycatch

The best method(s) to address the bycatch problem(s) in a particular fishery will depend

on fishery-specific factors including: the nature and source of the bycatch problem(s) in the

fishery, the information required and available to effectively and efficiently implement a

solution, and the expected net benefits of a particular solution.

8.1 The Nature and Source of the Bycatch Problem

Bycatch mortality can decrease the sustainability of a fishery and the net benefits

provided by that fishery. It can do this in four ways. First, if bycatch mortality is not monitored

adequately, it increases the uncertainty concerning total fishing-related mortality, which in turn

makes it more difficult to assess the status of stocks of fish and other bycatch species, to set the

appropriate optimum yields and overfishing levels for fish stocks, to determine acceptable levels

of bycatch for other bycatch species, and to ensure that the optimum yields are attained, that

overfishing does not occur and that the acceptable levels of bycatch for other species are not

exceeded. Second, the discards themselves can have adverse effects on other species. Third,

bycatch mortality precludes some other uses of living marine resources. For example, juvenile

fish that are subject to bycatch mortality will not contribute directly to the growth of that stock

and to future catch. Nor can they be available as prey for depleted stocks and other species. 

Bycatch is a wasteful use of living marine resources if it precludes a higher valued use of those

resources. Fourth, in the absence of management measures designed to reduce bycatch, there

will typically be too much bycatch, that is, the overall net benefit to the Nation from that fishery

can be increased by decreasing bycatch. However, without adequate information concerning the

biological, ecological, social, and economic effects of a set of bycatch management measures, the

measures can be ineffective and inefficient and in some cases the measures will decrease the net

benefits derived by the Nation from the use of living marine resources.

If the problem is due principally to uncertainty concerning fishing-related mortality,

improved bycatch monitoring systems should be considered and may be sufficient to solve the

bycatch problem. A strategy for developing an adequate bycatch monitoring program is to

progress, as necessary, from the current program to a Mature bycatch monitoring program. For

some fisheries the progression would be from basically no independent at-sea observations of

fishing operations, to a Baseline program, to a Pilot program, to a Developing program, and

finally to a Mature at-sea monitoring program.

At each level, the monitoring program could rely on at-sea observers, electronic

monitoring, or a combination of the two. The best mix of these two methods for independent atsea observations will vary by fishery, by the bycatch species of most concern, and over time. The

information provided by each type of program will be used in determining if it is appropriate to

implement a more extensive monitoring program, the priority for doing so, and the nature of the

enhancements that should be made when enhancements are necessary. Due both to changes in

circumstances in fisheries and technological progress in monitoring methods, a periodic review

of the monitoring program will be required to identify the appropriate changes. 

In some cases, a less extensive program may demonstrate that the bycatch problems in a

fishery are minimal and do not justify the progression to a Mature monitoring program. In some

other cases, the initial monitoring program may demonstrate that there is a substantial bycatch

problem, that the cost of a Mature monitoring program would be prohibitive, but that there are

relatively low cost methods for substantially reducing bycatch. This could occur, for example, if

the bycatch of a species of concern is a very rare event and the effectiveness of the bycatch

reduction methods is expected to be similar for the very rare species and some species that are
86

more easily monitored. In other cases, an initial monitoring program may provide information

that would justify a rapid progression to a Mature monitoring program.

If the problem is principally adverse effects on other species due to the discards

themselves, it may be possible to solve the problem effectively and efficiently by controlling the

temporal and spatial distribution of discards or by prohibiting the discard of whole fish.

If the problem is excessive human-induced mortality for a particular stock and there are

several sources of that mortality, the merits of reducing the alternative sources of mortality

should be considered. For example, in the case of overfishing, the solution could be to decrease

the catch or bycatch of that stock or both. The appropriate choice will depend on the marginal

net benefit of each of these two uses of the stock that is being overfished. Similarly, in the case

of protected species, additional methods for increasing or maintaining their populations also

should be considered. These additional methods may include decreasing other sources of

mortality and improving habitat. The extent to which each method should be used for a specific

protected species depends on the marginal cost of providing protection with each of the feasible

methods.

If it is determined that there is too much bycatch in a fishery (i.e., the overall net benefit

to the Nation from that fishery can be increased by decreasing bycatch), there are two general

types of solutions. Regulations can be developed and implemented that prohibit fishermen from

fishing in ways that result in too much bycatch. For example, regulations can prohibit fishing in

specific times or areas, they can require the use of specific gear or gear modifications, and they

can restrict the use of catch or the level of bycatch. Alternatively, regulations can be developed

and implemented to eliminate or decrease incentives (i.e., externalities) that result in fishermen

taking too much bycatch. Typically, much of the benefit of reducing bycatch accrues to others,

not to the fisherman who modifies fishing practices to decrease bycatch. The benefits others

receive are external to the fisherman’s decision making process; therefore, from society’s

perspective, the fisherman does not do enough to reduce bycatch. The externalities are the

source of the excess bycatch problem, and in some cases decreasing the externalities will be the

appropriate solution. But that will require holding individual fishermen accountable for their

bycatch, and the monitoring required to do that may not be feasible.

The MSA specifies that bycatch be minimized to the extent practicable. Generally, there

will be some practical limitations on how much bycatch can be reduced within feasible fishery

operating procedures. There may be uncertainty or a misunderstanding concerning the extent to

which it is practicable to reduce bycatch. Thus, in these instances there needs to be a full and

complete public debate of the options and ramifications of bycatch reduction including research

and outreach programs that decrease the uncertainty and increase the general understanding of

the effects of specific methods of decreasing bycatch.

8.2 Information Needed to Implement an Effective and Efficient Solution to the Bycatch

Problem for the Fishery

With sufficient information, fishery managers could identify the best way for each fishing

operation to decrease its bycatch. The difficulty is that fishery managers have relatively limited

and usually static information. Individual fishermen usually have more complete and more

timely information concerning methods for decreasing bycatch, but as noted above, they may

lack the appropriate incentives. In selecting the management approach that will be used to

decrease bycatch, it is important to be realistic about information deficiencies and the difficulty

of providing the correct incentives to fishermen.
87

Research concerning the response of fish and other bycatch species to fishing gear and

fishing operations can assist in developing effective and efficient methods for reducing bycatch

and bycatch mortality. Such research is also necessary to determine the extent to which a change

in gear or fishing practices decreases bycatch as opposed to, for example, just replacing discard

mortality with unobserved fishing mortality. In many cases, the information needed to

implement effective and efficient bycatch solutions can result from cooperative research with the

commercial and recreational fishing industry.

8.3 Expected Net Benefits

Although the information required to precisely estimate the net benefits of alternative

solutions will seldom be available, an effort should be made to consider both the benefits and

costs of the alternative strategies, where the benefits and costs are broadly defined to address the

biological, ecological, social, and economic effects of bycatch and bycatch management. Such

an approach is required for good stewardship and to meet federal regulatory mandates, including

those in the MSA, the MMPA, the ESA, the National Environmental Policy Act, the Regulatory

Flexibility Act, and Executive Order 12866. Outreach and public debate to obtain information

concerning the benefits and costs of the alternatives can be done through the Council and NMFS

processes that may be used to develop and evaluate alternatives. In general, more complete

information concerning the biological, ecological, social, and economic effects of bycatch and

methods for reducing bycatch are required to develop more effective and efficient methods for

managing bycatch. As more efficient methods for reducing bycatch are developed, further

reductions in bycatch will become practicable.

8.4 Setting National Priorities for Improving Bycatch Monitoring

The Magnuson-Stevens Act requires a standardized reporting methodology for bycatch

(see Appendix 5). There are a variety of standardized methodologies that can be used to meet

this requirement. As noted in previous sections, there are tradeoffs between the quality of the

bycatch estimates and the bycatch monitoring costs either when choosing among methodologies

or when choosing sample sizes. The cost of improving the quality of the bycatch estimates will

decrease as the methodologies are improved. For example, such improvements will result from

improving either sample designs or observation technologies. However, the tradeoffs will

remain and for each fishery the appropriate choice between the cost and quality of bycatch

estimates will depend on the importance of improving the quality of the estimates. That will be

determined by a variety of factors. For example, if the expected level of bycatch is very low

compared to other sources of fishing mortality and if the populations of the bycatch species are

healthy, a low-cost reporting methodology that provides estimates with low precision may be

appropriate. Conversely, if bycatch is thought to account for a large part of the fishing mortality

of a species that is overfished, better bycatch estimates and higher bycatch monitoring costs are

justified.

Typically, the recommended precision goals for bycatch estimates cannot be met without

an at-sea observation program. In most cases with the current technologies, such programs will

include at-sea observers. Therefore, this section focuses on setting priorities for implementing

and improving observer programs.

Fisheries that have bycatch vulnerability rated as High for one or more of the three types

of bycatch are high priority candidates for additional funding to improve the observer programs. 

There are 26 such fisheries in Tables 4.1-4.6 (2 in the Southwest, 12 in the Southeast, 4 in the

Northwest, 1 in Alaska, 6 in the Northeast and 1 in the Pacific Islands). Estimates of sampling
88

requirements needed to maintain or bring these fisheries up to the required precision goals in

Developing and Mature programs have not been made for all of the fisheries.

There are no observer programs for 37% of the fisheries in Tables 4.1-4.6. However, few

of these fisheries have been classified as having a High bycatch vulnerability for one or more of

the three types of bycatch species (fish, marine mammals and other protected species, including

seabirds and sea turtles). These few fisheries are high priority candidates for Baseline or Pilot atsea observer programs. 

The remaining fisheries in Tables 4.1-4.6 have a bycatch vulnerability rating of Low or

Moderate for all three types of bycatch. The observer program classifications for these fisheries

range from None to Developing programs. These fisheries are lower priority candidates for

either implementing an observer program or improving the existing program. There are 58 such

fisheries in Tables 4.1-4.6. Since these remaining fisheries have bycatch ratings of only Low or

Moderate vulnerability, the Baseline or Pilot programs could be conducted using an annual

rotation (perhaps, three-year) unless results indicated that more mature sampling programs

should be developed.

As at-sea observer programs are implemented and improved, it may become clearer that

there are minor bycatch problems in some fisheries and unexpectedly severe bycatch problems in

other fisheries. In the latter case, the development of effective and efficient actions to decrease

bycatch may require more extensive programs than are required to meet the recommended

precision goals for bycatch estimates.
89

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by A. Didier and V. Cornish, NOAA Technical Memorandum NMFS-OPR-14. p. 9-11.

Cochran. W.G. 1977. Sampling Techniques. J. Wiley and Sons, New York.

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estimate bycatches? In: Proceedings of the International Conference on Integrated Fisheries

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Hoag, S. H. 1975. Survival of halibut released after capture by trawls. International Pacific

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Carolina, 1997-2000. Prepared for the Dolphin-Fishery Interaction Workshop. Available from

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Hohn, A.A., B. Mase, J. Litz, W. McFee, and B. Zoodsma. 2001. Characterization of humancaused strandings of bottlenose dolphins along the Atlantic Coast from South Carolina to

Southern Florida, 1997 – 2000. Draft paper prepared for the Bottlenose Dolphin Take Reduction

Team. Available from, NMFS, Southeast Fisheries Science Center, 75 Virginia Beach Dr. 

Miami FL 33194.

IPHC (International Pacific Halibut Commission). 2003. Area 2A Sport Halibut Seasons at-aglance. Available at: www.iphc.washington.edu.halcom.sport/2asportglance.htm

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estimates of retained and discarded catches from a multispecies trawl fishery. Fisheries

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Mayo, R.K., A.M. Lange, S.A. Murawski, M.P. Sissenwine, and B.E. Brown. 1981. Estimation

of discards in mixed trawl fisheries off the Northeast Coast of the United States, based on bottom

trawl survey catches. Northeast Fisheries Science Center Laboratory Reference Document 81-18.

Mayo, R.K., L. O’Brien, and N. Buxton. 1992. Discard estimates of American plaice

Hippoglossoides platessoides, in the Gulf of Maine Northern Shrimp Fishery and the Gulf of

Maine-Georges Bank large-mesh otter trawl fishery. Stock Assessment Workshop Research

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McElderry, H., J. Schrader, D. McCullough, J. Illingworth, S. Fitzgerald, and S. Davis. 2004. 

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pilot study. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-147, 39 p. Available at:

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NMFS (National Marine Fisheries Service). 1998a. Managing the Nation’s bycatch: priorities,

programs and actions for the National Marine Fisheries Service. National Marine Fisheries

Service, 192 p. Available at: http://www.nmfs.noaa.gov/bycatchplanonline.pdf

NMFS (National Marine Fisheries Service). 1998b. Report to Congress on the Proposed

Implementation of a Fishing Vessel Registration and Fisheries Information System. Submitted to

the Committee on Resources of the House of Representatives and the Committee on Commerce,

Science, and Transportation of the Senate. 80 p.

NMFS (National Marine Fisheries Service). 2001. Marine fisheries stock assessment

improvement plan. Report of the National Marine Fisheries Service National Task Force for

Improving Stock Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-F/SPO-56, 69

p., 25 appendices.

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on Fishing Technology: Report of First Meeting, March 6-7, 2002. Pascagoula, MS, 48 p. 

(Available at www.nmfs.noaa.gov/bycatch.htm) 
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NMFS (National Marine Fisheries Service). 2002b. Fisheries Observers Insurance, Liability, and

Labor Workshop, June 12-14, 2001; Technical Memorandum. Prepared by MRAG Americas,

Tampa, FL; edited by D. Hansford and V. Cornish, NMFS Office of Science and Technology.

NMFS (National Marine Fisheries Service). 2003. Plan to manage risks and minimize liabilities

associated with the deployment of contracted fisheries observers. Prepared by D. Cox, Quantech,

Inc. and R. Goldberg, Schnader Harrison Segal & Lewis, NOAA Contract No. 50-DGNF-1-

90089. 

NMFS (National Marine Fisheries Service). 2004. NMFS Fisheries Observer Coverage Level

Workshop: Defining a Basis Workshop, July 29–31, 2003; Summary Report. Prepared by

MRAG Americas, Tampa, FL, and Iowa State University; edited by Graeme Parkes and Mark S.

Kaiser, MRAG Americas and Iowa State University. Available at:

http://www.nmfs.noaa.gov/by_catch/CoverageWorkshopFinalRevised.pdf

NRC (National Research Council). 1999. Sharing the Fish: Toward a National Policy on

Individual Fishing Quotas. National Academy Press, Washington, DC, 422 p.

NRC (National Research Council). 2000. Improving the Collection, Management, and Use of

Marine Fisheries Data. National Academy Press, Washington, DC. 222 p.

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data. In: 22nd Northeast Regional Stock Assessment Workshop: Stock Assessment Review

Committee consensus summary of assessments. NEFSC Reference Document 96-13; 242 p.

NWFSC (Northwest Fisheries Science Center), West Coast Groundfish Observer Program: Initial

data report and summary analyses. 2003. Northwest Fisheries Science Center, 2725 Montlake

Boulevard East, Seattle, WA 98112. Available at:

http://www.nwfsc.noaa.gov/research/divisions/fram/Observer/narjan03.pdf

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Price, T. 1999. The California drift gillnet fishery. In: Development of a process for the longterm monitoring of MMPA Category I and II commercial fisheries. Edited by A. Didier and V.

Cornish, NOAA Technical Memorandum NMFS-OPR-14. p. 23-25.

Powers, J.E. and V.R. Restrepo. 1993. Evaluation of stock assessment research for Gulf of

Mexico king mackerel: benefits and costs to management. North American Journal of Fisheries

Management. 13:15-26.

RecFIN 2003. RecFIN MRFSS Estimates. www.psmfc.org/recfin/forms/est.html

Sampson, D. 2002. Final report to the Oregon Trawl Commission on analysis of data from the

at-sea data collection project. Oregon State University. Newport, OR.

Turnock, B.J. and W.A. Karp. 1997. Estimation of salmon bycatch in the 1995 pollock fishery

in the Bering Sea/Aleutian Islands - A comparison of methods based on observer sampling and

counts of salmon retained by fishing vessel and processing plant personnel. An Alaska Fisheries

Science Center report prepared for the North Pacific Fishery Management Council, 32 p.

U.S. Department of Labor, Bureau of Labor Statistics. 2002. Injuries, Illnesses, and Fatalities. 

http://www.bls.gov/iif/home.htm
92

Walsh, W.A. 2000. Comparison of fish catches reported by fishery observers and in logbooks of

Hawaii-based commercial longline vessels. NMFS Southwest Fisheries Science Center,

Honolulu Laboratory, Administrative Report H-00-07, 45 p.

Walsh, W.A., P. Kleiber, and M. McCracken. 2002. Comparison of logbook reports of

incidental blue shark catch rates of Hawaii-based longline vessels to fishery observer data by

application of a generalized additive model. Fisheries Research 58:79-94.

Williams, G.H., C.C. Schmitt, S.H. Hoag, and J.D. Berger. 1989. Incidental catch and mortality

of Pacific halibut, 1962-1986. Technical Report 23. 94 p. Available at: 

http://www.iphc.washington.edu/halcom/pubs/techrep/tech0023.pdf
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Appendix 1. 

Definition of Bycatch Terms 

(from NMFS 1998a)

Bycatch Discarded catch of any living marine resource plus retained incidental catch and

unobserved mortality due to a direct encounter with fishing gear.

Discarded catch Living marine resources discarded whole at sea or elsewhere, including those

released alive.

Incidental catch Catch that is not part of the targeted catch. This includes retained nontargeted

catch and discarded catch. Examples are finfish catch in shrimp fishery that may be sold or kept

for personal use, juvenile pollock catch that now must be retained in the Alaska pollock fishery,

and seabird catch in the Pacific longline tuna/swordfish fishery that must be discarded.

Target catch Catch of a species, a particular size or sex, or an assemblage of species that is

primarily sought in a fishery, such as shrimp in a shrimp fishery or mature female fish in a roe

fishery. The definition of targeted catch within a fishery is not static, for example in a

multispecies fishery, the mix of species targeted and caught may be quite variable and may

change over time.

Total catch Retained catch plus discarded catch.

Landings Portion of the total catch that is brought ashore.

Total fishing-related mortality Mortality of living marine resources due to a direct encounter

with fishing gear.

Bycatch mortality* All mortality of living marine resources associated with discarded catch plus

unobserved mortality.

Unobserved mortality** Mortality of living marine resources due to a direct encounter with

fishing gear that does not result in the capture of that species by a fisherman. This includes

mortality due to lost or discarded fishing gear, as well as live releases that subsequently die.

Regulatory discards Catch that is required by regulation to be discarded.

Discretionary discards Catch that is discarded because of undesirable species, size, sex, or

quality, or for other reasons, including economic discards as defined in the Magnuson-Stevens

Act.

Prohibited species A species for which retention is prohibited in a specific fishery.

Protected species Any species that is subject to special conservation and management measures

(e.g., Marine Mammal Protection Act, Endangered Species Act, and Migratory Bird Treaty Act).

Living marine resources Any animal or plant life that spends part of its life in coastal or ocean

waters.
94

*The definition of “bycatch mortality” as published in NMFS 1998a was incomplete and should

have read as follows: All mortality of living marine resources associated with discarded catch

and retained incidental catch plus unobserved mortality.

**The definition of “unobserved mortality” as published in NMFS 1998a should not have

included the phrase “as well as live releases that subsequently die.”
95

CV Other Catch = 0.8

CV Survey = 0.2

CV Other Catch = 0.2

CV Survey = 0.2

CV Other Catch = 0.6

CV Survey = 0.6

CV Other Catch = 0.2

CV Survey = 0.5

Appendix Figure 2-1. Diagram of hypothetical precision in the estimate of

management quantities such as TAC or PBR as a function of the precision of estimates

of the catch other than bycatch (other catch), the other assessment information such as

survey indices (survey), the CV of bycatch, and the proportion of catch that is bycatch.

Appendix 2. 

A Characterization of the Relationship Between the Precision of the Assessment

Components and the Precision of Management Quantities

In order to develop an explanatory and qualitative characterization of the relationship of

the precision of components within an assessment with the precision of the management

quantities estimated by that assessment, the following approximation was utilized:

(CVTAC or PBR)

2

 = (CVCatch)

2

 + (CVFopt/F)

2

 + (CVCatch)

2

 (CVFopt/F)

2

where Fopt/F is the ratio of the desired exploitation rate to the present exploitation rate and

CVcatch. is the precision of the total catch of a stock (not just the bycatch). The precision of the

total catch of a stock depends upon the precision of the estimate of bycatch of that stock, the

precision of the “other catch” (all the other catch other than bycatch) and the proportion of the

total catch of a stock that comes from bycatch (Pbycatch):

(CVcatch)

2

 = (CVbycatch Pbycatch )2 + [CVother catch (1-Pbycatch )]2

The precision of the Fopt/F ratio can be approximated by

(CVFopt/F)

2

 = (CVCatch)

2

 + (CVsurvey)

2

 + (CVCatch)

2

 (CVsurvey)

2

where (CVsurvey)

2

 is the precision of an arbitrary variable denoting all the factors of an assessment

other than catch (e.g., the survey index of abundance). Combining the above equations leaves an

expression of the precision of the management quantities as a function of the precision of the

assessment, the precision of the bycatch, the precision of the other catch and the proportion of the
96

catch comprised of bycatch. The relationships given are very broad approximations not meant to

be exact. Nevertheless, they provide useful examples for discussions of precision requirements

arising from the assessment evaluation of management quantities (see Appendix Figure 2-1).
97

Appendix 3. 

Precision of a Bycatch Estimate of an Aggregate of Species and the Precision of Estimates

of Individual Species within the Aggregate

When the bycatch estimate for each species is given by the product of the estimate of total

bycatch and the estimate of the proportion of each species contributing to the bycatch, the

relationship between the precision of an estimate of bycatch of an individual species and the

precision of the estimate of bycatch of the aggregate of all species may be approximated by:

(CVspecies)

2

 = (CVagg )2 + [ (1 - Pspecies)/ (xagg Pspecies)] [ 1 + (CVagg )2 ]

where Pspecies is the proportion of the total aggregate bycatch (agg) that an individual species

comprises and CVagg is the precision of the aggregate estimate (xagg). This relationship assumes

that proportional encounters are random which often is not the case (i.e., individual species

cluster with others of the same species). Therefore, the above relationship may underestimate the

CV of an individual species in an actual application.

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Appendix 4. 

Comments on Precision Requirements for Rare-event Species

The same sampling and estimation methods may not be appropriate for all bycatch

monitoring programs. Most of the discussions and formulas in this report assume that (1) a

normal distribution is appropriate when computing the confidence intervals for the estimated

bycatch, (2) an equal probability sample within strata is practical, and (3) the bias of the ratio

estimator is negligible. In some fisheries where these assumptions do not hold, the use of the

coefficient of variation to specify a precision goal, the estimator, and the sampling design that are

discussed in this report are not appropriate. In fisheries in which the bycatch of protected species

is extremely rare, this creates problems. Below are more details concerning the guidelines given

in this report and the problems faced with the observer programs for these fisheries.

When designing a bycatch monitoring program, it seems that the goal should be either to

specify a maximum allowable difference, absolute or relative, between the estimate and the true

value and a small probability that the error may exceed the maximum allowable difference or to

minimize the cost of obtaining specific criteria with respect to the confidence interval for an

estimate of bycatch. To meet either objective the confidence interval, not just the CV, of the

estimate needs to be considered.

If using an unbiased estimator with a normal distribution, the CV provides a

straightforward measurement related to the distance between the estimate and the upper and

lower bound of the confidence interval. However, there are situations when a biased estimator is

more efficient than an unbiased estimator (the biased estimator has a smaller mean square error),

or it is unreasonable to assume the normal distribution. For example, the bycatch of protected

species is extremely rare in the Hawaii longline and bottomfish fisheries. Because of the extreme

rarity, even for a large sample of trips, say over 100, the Finite-Central Limit Theorem does not

apply and assuming the normal distribution would result in inaccurate confidence intervals (the

lower bound of the confidence interval would be a negative number). For the species where

bycatch is extremely rare, the distribution of the estimated total is likely not symmetrical, but has

a long right-hand tail. In such cases where exceeding allowed takes is a concern, then the focus

should be on the distance between the estimate and the upper bound of the confidence interval. 

For example, take the loggerhead, leatherback or green sea turtle bycatch in the Hawaiian

longline fishery. In order to obtain a CV of between 20% and 30% for these species, sampling of

900 to 1,000 trips (80% to 90% coverage) may be required. Is this worth the expense? If the

estimated total bycatch is small, such as five individuals, do we really need to achieve a standard

error of 1 to 2 individuals to monitor bycatch? If jeopardy is such a fine line that four turtle takes

do not jeopardize the population but five takes do, then 100% coverage may be needed. 

Also, CV is undefined if no bycatch is observed and the estimated total bycatch is zero. 

Not only is there a problem with dividing by zero, but it is unclear how best to estimate the

standard error when no bycatch has been observed. The objective of an observer program might

be to monitor a protected species bycatch; however, even with 100% coverage, we might not

expect to observe any bycatch of this species. With what level of uncertainty should we estimate

zero bycatch? This should be defined by management.

5

 Category I and II fisheries include both federally and state managed fisheries.

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Appendix 5.

NMFS Objectives, Protocol, and Recommended Precision Goals 

for Standardized Bycatch Reporting Methodologies

The MSA, ESA, MMPA, and international agreements identify NMFS's stewardship

responsibilities to monitor and reduce bycatch. The 1996 amendments to what is now titled the

MSA defined the term “bycatch” and required that it be minimized to the extent practicable. 

Bycatch, as defined by the MSA (16 U.S.C. § 1802 (2)), “means fish which are harvested in a

fishery, but which are not sold or kept for personal use, and includes economic discards and

regulatory discards. Such a term does not include fish released alive under a recreational catch

and release fishery management program.” National Standard 9 of the MSA requires that

“conservation and management measures shall, to the extent practicable, (A) minimize bycatch

and (B) to the extent bycatch cannot be avoided, minimize the mortality of such bycatch” (16

U.S.C. § 1851(9)). Section 303 of the MSA expands on this requirement somewhat, stating that

fishery management plans (FMPs) are required to “establish a standardized reporting

methodology to assess the amount and type of bycatch occurring in the fishery” (16 U.S.C. §

1853(11)). The MSA requirement for a standardized bycatch reporting methodology (SBRM) for

each FMP fishery is intended to address only the bycatch of fish, where “fish” is defined by the

MSA to mean "finfish, mollusks, crustaceans, and all other forms of marine animal and plant life

other than marine mammals and birds" (16 U.S.C. § 1802(12)).

Based on its stewardship responsibilities defined elsewhere in the MSA and in other laws,

including the MMPA and ESA, NMFS believes that: (1) the SBRM for each FMP fishery should

address the bycatch of marine mammals and seabirds, as well as fish and sea turtles, and (2) an

effective and efficient SBRM should be established for each federally managed fishery and for

each other fishery that either takes ESA-listed species that are under NMFS jurisdiction or is an

MMPA Category I or II fishery.5

 Such an SBRM will improve the bycatch estimates for each

fishery, which will improve both the estimates of total catch and the scientific basis for making

the often interdependent decisions concerning the reductions in bycatch to be attained and the

methods to be used to attain those reductions.

This document identifies the SBRM objectives, protocol, and recommended precision goals that

NMFS has established to meet its stewardship responsibilities for monitoring bycatch. The

actions that are being taken by NMFS and the Fishery Management Councils to further reduce

bycatch are addressed elsewhere.

NMFS has established the following SBRM objectives:

• The development and documentation of an effective and efficient SBRM for each

federally managed fishery and for each other fishery that either takes ESA-listed species

that are under NMFS jurisdiction or is an MMPA Category I or II fishery, where the

documentation of a SBRM includes the responsibilities of each entity involved in

collecting and using data to estimate bycatch or total catch, as well as well-defined goals

and objectives with associated performance criteria.

• The periodic review of the SBRM for each of these fisheries.
102

• The development of more effective and efficient methods, including electronic

monitoring, for estimating bycatch or total catch.

The combination of data collection and analyses that is used to estimate bycatch in a fishery

constitutes the SBRM for that fishery. For example, an at-sea observer program, effort and

landings data collection, and analyses to estimate overall bycatch can constitute an SBRM. 

NMFS, working with the Regional Fishery Management Councils and other management

agencies, has implemented some or all of the elements of an SBRM for each federally managed

fishery and for each other fishery that either takes ESA-listed species that are under NMFS

jurisdiction or is an MMPA Category I or II fishery.

To assist in meeting these objectives, NMFS has established the following protocol for SBRMs:

• Deploy at-sea observers in most cases as part of the preferred method for collecting

bycatch data due to the effectiveness of at-sea observer programs.

• Use other at-sea observations technologies (i.e., electronic monitoring) as appropriate to

complement observer programs. 

• Use the appropriate sampling design as determined by the objectives of and the level and

sources of funding for the observer program and other monitoring programs, where the

objectives include providing a scientific and statistically valid basis for estimating

bycatch or total catch.

• Use the appropriate models for combining observer data with effort, landings, and/or

other data to obtain accurate estimates of total bycatch or total catch.

• Use appropriate methods to identify and decrease sources of bias.

• Address the goal of achieving recommended levels of precision (20-30% CV) in

estimating bycatch or total catch.

• Adhere to standards established by NMFS to ensure the integrity and quality of the data

collected in NMFS-approved observer programs, other data that are used in estimating

bycatch or total catch, and the resulting estimates of bycatch or total catch.

• Where appropriate, use other monitoring methods for estimating bycatch (e.g., using data

from experimental tows, fishery-independent survey data, data from electronic

monitoring technology, strandings data, or self-reported data) instead of at-sea observers. 

• Emphasize outreach to industry and other constituents and encourage their participation

in the development of SBRM goals, objectives and implementation plans.

At-sea observer program sampling designs should be formulated to achieve precision goals for

the least amount of observation effort, while also striving to increase accuracy. These designs

require the development of appropriate sampling strata and sampling allocation procedures. The

overall design of a bycatch monitoring program should address the potential for observer effect

bias and recognize that the overall management regime can affect the magnitude of this bias. An

observer effect bias exists either if fishing practices change for trips or hauls that are observed or

if crew members take actions to prevent accurate catch or bycatch estimates for observed hauls. 

In some cases, additional compliance resources will be needed to decrease the latter source of

bias.

Observer sampling programs are driven by recommended precision goals that address

management needs for estimating management quantities such as allowable catches through a

stock assessment, for evaluating bycatch relative to a management standard such as allowable

take, and for developing mitigation mechanisms. The recommended precision goals for

estimates of bycatch are defined in terms of the coefficient of variation (CV) of each estimate. 
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The recommended precision goals for estimates of bycatch, in general, are as follows:

Protected Species

For marine mammals and other protected species, including seabirds and sea

turtles, the recommended precision goal is a 20-30% CV for estimates of bycatch

for each species/stock taken by a fishery.

Fishery Resources

For fishery resources, excluding protected species, caught as bycatch in a fishery,

the recommended precision goal is a 20-30% CV for estimates of total discards

(aggregated over all species) for the fishery; or if total catch cannot be divided

into discards and retained catch then the recommended goal for estimates of total

catch is a CV of 20-30%.

These CV goals are the levels of precision that NMFS will strive to achieve. However, it is

important to recognize that:

• The goals may in some instances exceed minimum statutory requirements.

• There are intermediate steps in increasing precision that may not immediately

achieve the goals but that represent progress nonetheless.

• There are circumstances in which higher levels of precision may be desired,

particularly when management is needed on fine spatial or temporal scales.

• There are circumstances under which meeting these precision goals would not be

an efficient use of public resources.

• Funding and logistical constraints, safety considerations and additional objectives

for observer programs may prevent the attainment of these goals.

• When a numeric limit is set for a bycatch species, the uncertainty associated with

setting that limit and the methods used for addressing that uncertainty are two of

the factors that determine the appropriate CV for the bycatch estimate for that

species.

• If CVs of 20-30% for individual fishery species can be obtained and are needed

for management, then this precision should be encouraged.

• In some instances decreasing bias (including that caused by the observer effect)

will be more important than increasing precision.

• The absolute precision (in numbers of animals) may be more appropriate than the

percent precision for some protected species (see Appendix 4 for technical

comments on this issue).

• If bycatch is being monitored principally in order to manage a fishery within

bycatch limits, an alternative to the above CV goals is to set the bycatch limits

based on a management regime that incorporates uncertainty (see Section 5.4).

• Flexibility is needed when setting CV targets for specific fisheries and bycatch

species.

• A decision to accept lower precision should be based on analyses and

understanding of the implications of that decision.
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NMFS recognizes that when there are multiple objectives for an observer program, the objective

of better estimates of bycatch or total catch needs to be balanced with other program objectives to

obtain an optimal sampling design.

To assist both in establishing an effective and efficient SBRM for each federally managed fishery

and for each other fishery that either takes ESA-listed species that are under NMFS jurisdiction

or is an MMPA Category I or II fishery and in periodically reviewing the SBRM for each of these

fisheries, NMFS will work cooperatively with stakeholders to:

• Identify the appropriate mix of methods to be used to estimate bycatch or total catch;

• Develop the sample design for at-sea observation programs;

• Determine the precision of the estimates of bycatch or total catch;

• Identify and decrease sources of bias, including the observer effect bias; and

• Identify the appropriate sample size(s).

NMFS recognizes that many of the characteristics of an appropriate SBRM will be determined by

a variety of factors that are both fishery- and time-specific. Therefore, the SBRMs that result

from these cooperative efforts often will differ by fishery and vary over time, and the standards

that are established as part of the SBRM protocol will reflect regional and fishery-specific

differences.

In many instances, NMFS will establish, review and improve SBRMs collaboratively with the

Regional Fishery Management Councils, MMPA Take Reduction Teams, other fishery

management agencies, the fishing industry, the environmental community, university or private

sector researchers, and other stakeholders. In most cases, a NMFS Regional Office and/or

Science Center will take the lead and be principally responsible for implementing the SBRM

objectives and protocol for specific fisheries.

The ability of NMFS to improve the SBRMs by implementing its SBRM objectives, protocol and

precision goals will depend on the funding and staffing resources that will be available. 

Therefore, NMFS will pursue adequate, stable and equitable sources of funding for the

following: (1) the research and analysis that are necessary to implement a more effective and

efficient SBRM for each fishery, and to periodically evaluate each SBRM and determine how to

improve it in a cost-effective manner; (2) enhanced bycatch monitoring programs; and, if

necessary, (3) additional monitoring methods or compliance resources to address the observer

effect bias.

In general, NMFS should be expected to use funds appropriated by Congress or, if authorized,

money collected from the fishing industry to pay for the bycatch monitoring required under the

MSA, MMPA and ESA.

It is unlikely that adequate funding will be available to immediately identify and implement the

appropriate SBRM enhancements for each fishery. Therefore, NMFS will use an efficient and

equitable mechanism for allocating the funds that are made available, on a discretionary basis,

through the federal budget process. The ability of NMFS to implement these objectives will also

depend on how effectively it can use outreach programs to develop better methods for estimating

bycatch or total catch and to obtain the assistance of fishermen and other stakeholders in

improving these estimates. 

In summary, the establishment of these objectives, protocol, and recommended precision goals

for SBRMs is an important element of a National Bycatch Strategy that includes improving the

bycatch or total catch estimates for each federally managed fishery and for each other fishery

that either takes ESA-listed species that are under NMFS jurisdiction or is an MMPA Category I

or II fishery in accordance with the requirements of the MSA and the other stewardship
105

responsibilities of NMFS, while taking into account the substantial differences that occur among

fisheries and over time.

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Appendix 6.

Acronyms Used in this Report

ABC acceptable biological catch

ACCSP Atlantic Coastal Cooperative Statistics Program

AFSC Alaska Fisheries Science Center

ASMFC Atlantic States Marine Fisheries Commission

BDTRT Bottlenose Dolphin Take Reduction Team

BRD bycatch reduction device

BSAI Bering Sea/Aleutian Islands area 

CPS coastal pelagic species

CPUE catch-per-unit-of-effort

CV coefficient of variation

DGN drift gillnet

EEZ Exclusive Economic Zone

EM electronic monitoring system

ESA Endangered Species Act

ETP Eastern Tropical Pacific Ocean

FAO Food and Agriculture Organization of the United Nations

FIS Fisheries Information System

FMP fishery management plan

GAM generalized additive model

GLM generalized linear modeling

GOA Gulf of Alaska

HMS highly migratory species

IATTC Inter-American Tropical Tuna Commission

ICCAT International Commission for the Conservation of Atlantic Tunas

IFQ individual fishing quota

IPHC International Pacific Halibut Commission

IPOA international plan of action

MARFIN Marine Fisheries Initiative grants programs.

MFMT maximum fishing mortality rate threshold

MMHSRP Marine Mammal Health and Stranding Response Program

MMPA Marine Mammal Protection Act 

MRFSS Marine Recreational Fisheries Statistics Survey

MSA Magnuson-Stevens Fishery Conservation and Management Act

MSE mean square error

MSST minimum stock size threshold

MUS management unit species

NEFSC Northeast Fisheries Science Center

NMFS National Marine Fisheries Service or NOAA Fisheries

NOAA National Oceanic and Atmospheric Administration

NPFMC North Pacific Fishery Management Council

NRC National Research Council

NWFSC Northwest Fisheries Science Center

NWGB National Working Group on Bycatch

NWHI Northwestern Hawaiian Islands

OY optimum yield

PacFIN Pacific Fisheries Information Network

PSMFC Pacific States Marine Fisheries Commission 

PBR potential biological removal

RecFIN Recreational Fisheries Information Network

RPA reasonable and prudent alternatives
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SBRM standardized bycatch reporting methodology

S-K Saltonstall-Kennedy grants programs.

SPR spawning potential ratio

TAC total allowable catch

TED turtle excluder device

TRP take reduction plan

USCG United States Coast Guard

USFWS U.S. Fish and Wildlife Service

VMS vessel monitoring systems

VTR vessel trip report

WCGOP West Coast Groundfish Observer Program

WPFMC Western Pacific Fishery Management Council