Guidelines for Assessing 

Marine Mammal Stocks: 

Report of the GAMMS Workshop 

April 3-5,1996, Seattle, Washington 

Paul R. Wade* 

Robyn Angliss 

Office of Protected Resources 

National Marine Fisheries Se~ce 

Silver Spring, Maryland 

*Cwent address: 

National Marine Mammal Laboratory 

Alaska Fisheries Science Center 

National Marine Fisheries Service 

Seattle, Washington 

NOAA Technical Memorandum 

NMFS-OPR- 12 

February 1997 

U.S. Department of Commerce 

William M. Daley, Secretary 

National Oceanic and Atmospheric Administration 

D. James Baker, Under Secretary for Occam and Atmosphere 

National Marine Fisheries Service 

Rolland E. Schmittm, Assistant Administrator for Fisheries 
This document summarizes the discussion and recommendations of a workshop 

held in April 19% to review the guidelines being used to assess marine mammal populations as required by the Marine Mammal Protection Act. Included in 

this document is a copy of the final revised guidelines that resulted from the 

recommendations of the workshop. 

Suggested citation: 

Wade, Paul R., and Robyn P. Angliss. 1997. Guidelines for Assessing Marine 

Mammal Stocks: Report of the GAMMS Workshop April 3-5, 1996, Seattle, 

Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-1593 p. 
TABLE OF CONTENTS (clickable)

1.0 Introduction ............................................................ 1 

2.0 GAMMS workshop goals .................................................. 4 

3.0 GAMMS workshop description ............................................. 5 

4.0 Defining stocks for management under the MMPA ............................... 6 

4.1 Defining a stock ................................................... 6 

4.2 Known stock structure of marine mammals ............................... 7 

4.3 Consequences of incorrect stock decisions ............................... 8. 

4.4 Biological data important to management ................................ 9 

4.5 Discussion on the definition of stocks .................................. 10 

4.6 Trans-boundary species ............................................. 13 

4.7 Incomplete survey of a stock's range ................................... 13 

5.0 Annual human-caused mortality and serious injury .............................. 15 

5.1 Definition of mortality and serious injury ................................ 15 

5.2 Presentation of information about human-caused mortality in the SARs ........ 17 

5.3 The description of fisheries in the SARs ................................ 18 

6.0 Habitat issues .......................................................... 19 

7.0 Research on classifjhg stocks as strategic .................................... 20 

8.0 Calculation of PBRs ..................................................... 22 

8.1 Time period fiom which to use data on abundance and mortality .............. 22 

8.2 Combining estimates and Calculating CV of a product ...................... 24 

8.3 Problems associated with species which are difficult to identifj ............... 25 

8.4 Calculating PBR for declining species .................................. 26 

8.5 Changing recovery factors from default values ............................ 27 

8.6 Correction factors for deep diving whales ............................... 28 

8.7 Correction factors for pinniped counts .................................. 29 

9.0 Rehew. revision, and publication of the Stock Assessment Reports ................. 30 

9.1 Review and Revision .............................................. 30 

9.2 Annual schedule for revising and publishing the SARs ...................... 31 

9.3 Publication issues ................................................. 33 

9.4 Suggested forum for abundance and mortality estimate manuscripts ........... 34 

10.0 List of Fisheries ........................................................ 34 

1 1.0 Take reduction plans .................................................... 35 
12.0 Zero Mortality Rate Goal (ZMRG): proposed rule ............................. 36 

13.0 The regional Scientific Review Groups ...................................... 37 

13.1 SRG perspectives ................................................. 37 

13.2 The role of the SRGs .............................................. 38 

Acknowledgments .......................................................... 40 

Appendix 1 . summary of MMPA sections and regulations relevant to Stock Assessments .... 41 

Appendix 11 . Guidelines for preparing the Stock Assessment Reports PBR guidelines) ...... 52 

1 . General Guidelines ................................................. 53 

2 . Technical Details .................................................. :63 

3 . Descriptions of U.S. commercial fisheries ................................ 68 

4 . Recommendations of the GAMMS Workshop ............................ 71 

Appendix III . GAMMS workshop agenda, April 3.5. Seattle. WA ..................... 76 

Appendix N . GAMMS workshop documents ..................................... 79 

Appendix V . GAMMS workshop list of participants ................................ 80 

Appendix VI . GAMMS workshop working group meeting: definition of mortality and serious 

injury ............................................................. -81 

Appendix VII . Scientific Review Groups: proposed plan ............................. 83 

Appendix XIII . Proposed annual schedule for the review and revision of stock assessment 

reports ............................................................. 87 

Appendix IX . Statistical formulas and background ................................. 89 
'Guidelines for Assessing Marine Mammal Stocks: 

The GAMMS Workshop 

April 3-5,1996 

Seattle, WA 

gam 

(gam), n., v., gammed, gamaming. - n. 1. A herd or school of whales. 2. Eastern Nav Eng. Naut. 

a social meeting, visit, etc., as between whaling vessels at sea. -v.i. 3. (Of whales) to assemble into 

a herd or school. 4. Naut. (of the officers and crews of two whaling vessels) to visit or converse with 

one another for social purposes. 5. Eastern New Eng. To participate in a gam or social visit. 

1.0 Introduction 

1.1 Background 

The new section I 17 of the Marine Mammal Protection Act as amended in 1994 (MMPA) 

requires the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service 

(FWS) to prepare, in consultation with regional Scientific Review Groups, draft assessment 

reports for each stock of marine mammal that occurs in waters under U.S. jurisdiction. The 

agencies are to make these reports available for public review and comment and prepare final 

stock assessment reports based upon public comments and continued consultation with the 

Scientific Review Groups. 

The MMPA requires that each Stock Assessment Report (SAR) contain several items, including 

(1) a description of the stock, including its geographic range; (2) a minimum population 

estimate, a maximum net productivity rate, and a description of current population trend, 

including a description of the information upon which these are based; (3) an estimate of the 

annual human-caused mortality and serious injury of the stock and, for a strategic stock, other 

factors that may be causing a decline or impeding recovery of the stock, including effects on 

marine mammal habitat and prey; (4) a description of the commercial fisheries that interact with 

the stock, including the estimated number of vessels actively participating in the fishery and the 

level of incidental mortality and serious injury of the stock by each fishery on an annual basis, and 

an analysis stating whether the level is insignificant and is approaching a zero mortality and 

serious injury rate; (5) a statement categorizing the stock as strategic ormot, and why; and (6) an 

estimate of the potential biological removal level (PBR) for the stock, describing the information 

used to calculate it. 

A primary goal of the MMPA is to prevent any marine mammal stock fiom being reduced below 

its optimum sustainable population level, and to restore stocks that have been reduced below that 

level. A stock which has a level of human-caused mortality that is likely to cause the stock to be 

reduced or kept below its optimum sustainable population should be classified as "strategic".. A 

marine mammal stock is considered strategic if (A) its level of direct human-caused mortality 
exceeds the potential biological removal level; or (B) it is listed as a threatened or endangered 

species under the Endangered Species Act of 1973, or is designated as depleted under the 

MMPA; or (C) it is declining and is likely to be listed as a threatened species under the 

Endangered Species Act of 1973 within the foreseeable future. The consequences of being 

designated strategic include the formation of a take reduction team for each strategic stock which 

interacts with a category I or I1 fishery. These teams are required to develop a take reduction 

plan for each strategic stock, with an immediate goal of reducing the incidental mortality and 

serious injury to levels less than the PBR. 

Section 1 17 also requires the formation of three independent regional Scientific Review Groups 

(SRGs) representing Alaska, the Pacific Coast (including Hawaii), and the Atlantic Coast 

(including the Gulf of Mexico). The Secretary of Commerce established the groups after 

consulting with the Secretary of the Interior, the Marine Mammal Commission, Governors of 

affected adjacent coastal States, regional fishery and wildlife management authorities, Alaska 

Native organizations, Indian tribes, and fishing industry and environmental groups. Members of 

the groups must have expertise in marine mammal biology and ecology, populations dynamics and 

modeling, commercial fishing technology and practices, or marine mammal stocks taken under 

MMPA section 101(b). These groups advise the Secretary on stock assessments, uncertainties and 

research needed on stocks, impacts to stocks, and methods to reduce incidental mortality in 

fishing operations. 

Immediately after the amendments were signed into law on 30 April, 1994, NMFS and FWS held 

a workshop on 27-29 June at the Southwest Fisheries Science Center in La Jolla, CA, to draft 

guidelines for preparing the SARs (called the PBR guidelines). NMFS completed the draft SARs, 

including preliminary consultation with the three regional SRGs, and made the draft guidelines 

and the draft SARs available for public review and comment on 9 August, 1994 (59 FR 40527). 

The three SRGs held their first meetings jointly on 12-13 October, in Seattle, Wq along with 

NMFS and FWS personnel. The primary focus of that first meeting was to provide the agencies 

with comments and recommendations regarding the draft PBR guidelines. The public comment 

period on the draft SARs. ended on 1 December, and these comments were compiled, 

summarized, and distributed to field offices and the SRGs for review in late December. 

From December 1994, to February 1995, NMFS consulted extensively with the SRGs to discuss 

the review groups' and public's comments on the PBR guidelines and the individual draft SARs. 

The draft guidelines and SARs were modified in response to comments fiom the SRGs, the public 

(including non-governmental organizations such as the Humane Society of the U.S., the Center 

for Marine Conservation, and several Alaska Native organizations), and the Marine Mammal 

Commission. After discussions by NMFS scientists nationally, particularly authors of the SARs 

and members of the MMPA implementation task force, the PBR guidelines were finalized near the 

end of February, 1995. 

The revised SARs were submitted to NMFS headquarters in March 1995. These draft final 

reports were reviewed by NMFS headquarters staff fiom April to June, with a particular focus on 
ensuring that the PBR guidelines were consistently applied in all the reports. Additionally, the 

reports were sent to the regional SRGs for a final review. Some of the comments resulting fiom 

these reviews were incorporated into the final SARs, and NMFS published a notice of the 

availability of the final stock assessment reports and the final PBR guidelines in the Federal 

Register on 25 August 1995 (60 FR 44308). 

Between July and September, the 1995 marine mammal stock assessments and related information 

were published in the NOAA Technical Memorandum series. Three of those documents 

contained the final SARs prepared by NMFS in each of the three regions covered by Scientific 

Review Groups: Alaska (including the North Pacific) (Small and DeMaster 1995), the Atlantic 

coast (including the Gulf of Mexico) (Blaylock et al. 1995), and the Pacific coast (including 

Hawaii) (Barlow et al. 1995a). The fourth document contained the final PBR guidelines, a 

summary of the 1995 stock assessments, and the reports of the June 1994 PBR workshop and the 

October 1994 Joint Scientific Review Group (Barlow et al. 1995b). 

Concurrent with the development of the draft and final SARs, NMFS developed proposed and 

final regulations implementing section 11 8 of the MMPA (60 FR 3 1666; 60 FR 45086). These 

regulations allow U.S. commercial fisheries to unintentionally seriously injure and kill marine 

mammals provided that the fishers comply with certain provisions of the MMPA. The List of 

Fisheries, which NMFS must publish .at least annually, classifies fisheries into one of three 

categories based on the level of marine mammal incidental serious injury and mortality relative to 

the PBR level. Those fisheries with fiequent or occasional incidental mortality and serious injury 

levels of marine mammals are placed in Category I or 11, are subject to the registration 

requirements of the MMPq and must carry an observer if requested by NMFS. Furthermore, 

fisheries with frequent or occasional incidental mortality and serious injury of strategic stocks may 

be subjected to regulations which are recommended by Take Reduction Teams or are otherwise 

determined necessary by NMFS or FWS. Thus, the stock-specific incidental mortality 

information provided in the SARs, along with the PBR calculations, may have direct impacts on 

the management of marine mammal incidental mortality and serious injury in commercial fisheries. 

After the completion of the 1995 SARs and the recognition that the science provided in the SARs 

has direct management implications, NMFS recognized that a second workshop would be usehl 

to review the work done and set the course for the future. The MMPA gives specific rules 

regarding the review and revision of stock assessment reports. Therefore, it was necessary to 

establish some guidance for how the review and revision process will occur every year. 

Additionally, it was appropriate to review the 1995 final PBR guidelines to discuss possible 

improvements that could be made after the experience of preparing the 1995 reports. NMFS also 

wished to discuss in an open forum whether the structure and content of the information 

presented in the SARs could be modified slightly to reduce the amount of interpretation needed 

when making management recommendations. 

Therefore, a second workshop for April 1996 was planned. The focus of the workshop was to be 

potential modifications to the PBR guidelines, as well as the drafting, for the first time, of 
guidelines for the annual process of reviewing, revising, and producing the SARs. This document 

reports the findings of that workshop. 

2.0 GAMMS workshop goals 

The following were the stated goals established prior to the start of the workshop: 

Review stock assessment related processes and other relevant sections of the MMPA 

the proposed rule defining the Zero Mortality Rate Goal 

the final List of Fisheries and classification scheme 

strategic stocks: brief review of what is happening with Take Reduction Teams 

Review and discuss ways of defining stocks for management under the MMPA 

The workshop will spend considerable time reviewing the types of information that are 

relevant to defining stocks, to review what type of stock structures are to be expected, 

and to hold some discussion regarding the process by which stocks are defined. It may be 

useful to attempt to come to a consensus regarding how stocks should be defined for the 

stock assessments, going into more detail than is currently in the guidelines. 

Proposed additions and revisions to the guidelines for preparing stock assessment reports. 

Discussion of proposed additions and revisions are aimed at providing clearer guidance on 

particular parts of the SARs. Writing down specific guidelines can help ensure that these 

sections of the SARs are done in a consistent way nationally, and should also make the 

jobs of the SAR authors and the PBR table coordinator easier. The objective at the 

workshop will be to finalize these written sections which describe how to include the 

necessary information in the SARs. Areas to discuss include: 

Guidelines for combining abundance and mortality estimates fiom different years. 

Table for fisheries mortality information. 

Use of old abundance estimates. 

"Definition of Stocks" section 

Information on habitat, the descriptions of fisheries and the geographical range of 

stocks. 

Definition of "mortality and serious injury". 

Multiple species/stock complexes (such as beaked whales) 

Declining populations. 

Recovery factors for endangered whales 

Correction factors for abundance estimates. 

Guidelines for the annual stock assessment process 

Although guidelines for preparing the stock assessment reports have previously been 

completed, there are several issues that have to be addressed regarding the stock 
assessment process and how it will work fiom year to year. There are some specific issues 

that will require guidelines, and it is probably appropriate to draft guidelines for the entire 

process (the report guidelines can be viewed as one aspect of the guidelines for the entire 

process). Proposed items for the stock assessment process: 

Annual schedule for the stock assessment process 

Revision rules. 

Publication details. 

Availability of reports on which the SARs are based. 

Recommendations for frequency of monitoring, both abundance and mortality. 

Scientific Review Group role. 

3.0 GAMMS workshop description 

The workshop to review the Guidelines for Assessing Marine Mammal Stocks (GAMMS) was 

held April 3-5, 1996, in Seattle, WA. The workshop starled with a review of elements of the 

MMPA that are related to the stock assessment process. This included items legislated in the 

MMPA, and proposed and final rules that NMFS has written to implement the MMPA. These 

items are summarized in Appendix I. 

Several major areas of discussion were held at the workshop related to preparing the marine 

mammal stock assessments. These included defining stocks (4.0), the calculation and reporting of 

humancaused mortality (5.0), habitat issues (6.0), classifying stocks as strategic (7.0), calculating 

PBR (8.0), and reviewing, revising, and publishing the stock assessment reports (9.0). 

Recommendations made by the workshop participants were incorporated into the revised PBR 

guidelines (Appendix II). 

Also discussed at the workshop were other MMPA items that are directly affected by the results 

of the stock assessment reports. These included the List of Fisheries (10.0), take reduction plans 

(1 1.0), and the zero mortality rate goal (12.0). The perspective and role of the MMPAestablished Scientific Review Groups was also discussed (13.0). 

The workshop agenda is reproduced in Appendix 111. The documents used by the workshop are 

listed in Appendix IV. The workshop participants are listed in Appendix V. The report of a 

working group on the definition of mortality and serious injury is listed in Appendix VI. Other 

items tabled at the workshop are also presented in appendices. This includes a proposed plan 

defining the role of the Scientific Review Groups (Appendix VII), a proposed annual schedule for 

reviewing and revising the stock assessment reports (Appendix Vm), and, finally, a summary of 

statistical background and formula that are used in preparing the stock assessments (Appendix 

IX). 
4.0 Defining stocks for management under the MMPA 

The workshop discussions started with several presentations related to the issue of defining stocks 

for management under the MMPA. 

The workshop participants recognized that there are many different ways to define stocks. The 

appropriate stock definition depends upon the management goal. It was therefore recognized that 

a stock is a management unit, and does not necessarily have an exact definition in the real world 

divorced from a management goal. Populations in the real world exhibit a broad continuum of 

various levels of differentiation, making it difficult to choose a single universal definition of a 

biological stock that will be meaningful for all species and populations. Stocks are often defined 

as a unit that will preserve genetic diversity, but there are other possible definitions. Under the 

MMPA there is a clear mandate to maintain populations as a functioning element of the 

ecosystem, but there is no language to suggest that distinct genetic units should be the 

management unit. 

4.1 Defining a stock 

Dizon gave a presentation of the general principles and information used to identify stocks, and 

then gave a description of how inferences about stock structure can be drawn fiom genetic data. 

Under the U.S. Endangered Species Act, management is by "distinct population segment", which 

has been defined to be what is called an evolutionarily significant unit (ESU). ESUs must show a 

degree of isolation, be different and unique, and are intended to represent an evolutionary legacy. 

The management goals of the MMPA are different in several ways fiom the goals of the ESA. 

The workshop participants re-visited the language of the MMPA with respect to what it implies 

about the definition of stocks for management under the MMPA. The MMPA states in Section 

3(11): 

"The term 'population stock' or 'stock' means a group of marine mammals of the same 

species or smaller taxa in a common spatial arrangement, that interbreed when mature." 

This definition does not imply that a stock under the MMPA must represent an ESU. The phrase 

"that interbreed when mature" does not provide an exact definition, but does seem to imply 

something close to panrnixia. However, one might also conclude that if a single animal emigrated 

only once every 100 years between two adjacent spatial areas, these two populations could be 

considered to be interbreeding, in a different sense. 

Additional guidance is provided in the major goals of the MMPA (Section 2.2): 

Marine mammals "...should not be permitted to diminish beyond the point at which they 

cease to be a significant functioning element in the ecosystem of which they are a part, 

and, consistent with this major objective, they should not be permitted to diminish below 

their optimum sustainable population." 
The latter goal has been defined to mean maintaining populations above their maximum net 

productivity level (50 C.F.R. 216.3), often taken to be a population level between 50-70% of a 

known historical abundance level. However, if the maximum net productivity level was thought 

to be 50% of K, a population could decline to one-half of its initial population size and still be at 

their optimum sustainable population level, but if it was extirpated fiom one-half of its range, it 

could not be considered a significant fbnctioning element in the ecosystem in that portion of its 

range. Therefore, to define stocks to meet MMPA goals, one has to consider the demographic 

linkages between geographic areas, as well as the genetic linkages. Abundant populations with 

low levels of mixing (a few animals per year) may be genetically indistinguishable, but the level of 

mixing may not be sufficient to support the amount of human-caused mortality that occurs in one 

of the sub-populations. Thus, genetics alone may not provide sufficient data on which to base 

stock definitions to be assured of meeting management goals. 

Many types of data can provide information on stock structure, including distribution, population 

response, morphology, genetics, life history, and contaminants. Distribution and abundance data 

can give an indication of stock structure, such as high density areas separated by lower density 

areas. Different population responses (e.g., different trends in abundance) between geographic 

regions is an indicator of stock structure, as populations with different trends are not strongly 

linked demographically. 

Geographical differences in genetic or morphological data are strong indicators of stock structure. 

Concordance of genetic differences with geographic distribution infers isolation, and indicates that 

separate stocks are appropriate. Fixed genetic differences that are concordant with geographic 

distribution infers strong isolation (i.e., the next step is speciation). 

Current techniques allow sequencing information fiom almost any type of tissue. Microsatellite 

data may often be a more powerful tool than mitochondria1 DNA. 

An example shows the utility of current genetic techniques. Taxonomists have suggested that 

there were two types of bottlenose dolphin in the Atlantic and perhaps in the Gulf of Mexico: an 

inshore type and an offshore type. Recent mitochondria1 DNA studies found fixed haplotypic . differences between inshore and offshore animals in both the Atlantic and Gulf of Mexico. The 

data strongly support managing different inshore and offshore stocks in both locations. mshore 

animals were more similar genetically to offshore animals in the Indian ocean than they were to 

adjacent inshore animals. Genetic differences were also found between inshore animals in the 

Atlantic versus those in the Gulf of Mexico. Microsatellite DNA may be of use for further 

investigation into possible stock divisions within the inshore animals. 

4.2 Known stock structure of marine mammals 

Heyning provided an overview of what is known about marine mammal stock structure. The 

perspective of reviewing known information can provide guidance on what stock structure to 

expect for populations with little information currently available. For many marine mammal 

populations few data are available that can provide information about stock structure. One 
consistent trend is that as more information is collected, finer structure within populations has 

usually been seen. Unique units are often found within populations. Some species have 

particularly complicated stock structures, such as killer whales and sperm whales. For species 

with information available, stock structure has virtually always been found to be on a scale much 

less than that of an entire ocean, such as the Pacific. This is true for small cetaceans (summarized 

in Perrin and Brownell 1994), is probably also true for large cetaceans, and is true for many 

pinniped species (it was noted that northern elephant seals, which show little genetic variability, 

are an exception which may be anomalous because their population was recently reduced to 

extremely low numbers). 

4.3 Consequences of incorrect stock decisions 

The key difficulty in defining management stocks has been whether a manager should lump or . split adjacent populations. This is a particularly difficult and important decision when incidental 

fisheries mortality is concentrated in just one of the areas. 

Taylor demonstrated an interactive computer simulation (RISK) designed to illustrate the pitfalls 

of inappropriate stock definition. The program assumes that two stocks are inappropriately 

managed as a single stock. Although the user can input any scenario, four examples are provided 

to demonstrate specific points and Taylor went through these with the group. The program 

graphically shows the resulting population trajectories and the user can then change input to the 

program (such as the amount of dispersal between stocks) and view the resulting change. The 

first lesson is that inappropriate pooling can lead to overestimation of the abundance of animals 

available for "harvest". This can lead to depletion or elimination of the stock experiencing the 

high mortality. The user can then "find" (by entering different values) the dispersal rate which 

would meet management objectives. This critical dispersal rate is what would be required before 

a single stock definition would provide satisfactory results and would be the amount of mixing 

that geneticists would seek to find in stock definition studies. Other lessons demonstrated in the 

program are: 1) if there is unrecognized stock structure, then the level of the current population 

relative to historical numbers is important, 2) the type of mortality is important to the dynamics, 

where the types are mortality incidental to fishing operations (assumed to be a constant 

proportion of the population) and directed take (assumed to be a relatively fixed number of 

animals), and 3) in the case where a large population is exploited next to a small population, 

dispersal is always to the detriment of the small population. 

In situations where managers must decide between lumping or splitting adjacent areas, the most 

important information to know is the number of animals moving between areas in each year. 

Unfortunately, this is very difficult information to collect. Monitoring the movement of individual 

animals is often difficult and impractical. Identifllng genetic or morphological differences 

between areas will usually be strong evidence that animals do not move between areas in sufficient 

numbers to prevent the extirpation of one of these populations. However, the movement of small 

numbers of individuals between the populations could prevent any genetic or morphological 

differences, yet might still be insufficient to prevent the decline and extirpation of one of the 
populations. Therefore, one cannot conclude that one stock is the appropriate management unit 

based only on a lack of detection of genetic differences. Furthermore, the statistical power to 

detect a difference also needs to be considered to correctly interpret an observed lack of 

difference between two areas. 

It is recognized that in principle one should be able to relate dispersal rate to some sort of genetic 

measure. Actual estimation of dispersal rates from genetic data is difficult and requires that certain 

assumptions be made that are difficult to test. As dispersal increases genetic differentiation 

decreases. However, when abundance increases genetic differentiation will also decrease. In the 

situation where large populations have very little annual dispersal, finding significant differences 

will be very difficult. This difficulty arises because there are few genetic differences between 

populations, which makes finding these differences problematic. For example, Alaska harbor seals 

are so abundant that a dispersal rate of only about 10 animals per year between areas, which is a 

small number relative to the total population size, would make it difficult for genetic data to show 

population distinctness. 

Table 1 is provided to attempt to capture the important consequences of the above discussion by 

illustrating what the expected genetic and demographic distinctness will be between large 

populations and between small populations at different rates of dispersal between the populations. 

The important points can be summarized as follows. At very low ("rare") dispersal rates, one 

expects the populations to be both genetically and demographically distinct, and should thus be 

managed separately. At high dispersal rates, one expects the populations to be neither genetically 

nor demographically distinct, and should thus be managed as one unit. However, for either a 

scenario with large or small populations, there is a possible rate of dispersal that would be great 

enough to eliminate genetic differences between populations, but would not be sufficiently high to 

prevent the populations fiom being demographically distinct. The final point is that at some level 

of a low rate of dispersal, the genetic differences between two large populations will be eliminated 

but would not be between two small populations. The workshop participants agreed that it would 

be useful to have firther discussion on the definition of stocks, and consider revisions to the 

guidance given in the PBR guidelines. This discussion can be found in section 4.5. 

4.4 Biological data important to management . . 

Chivers summarized the type of biological data that are available and its importance to 

management. Fisheries observer programs, in addition to providing data from which to estimate 

mortality, also provide the largest source of tissue for genetic analyses. Furthermore, tissue 

samples can be used to identi@ species and stocks which can be difficult to identifjl when visually 

inspecting incidental catches in fishing gear at sea. Therefore, Chivers stressed that it is important 

to attempt to sample as many specimens as possible, which has been accomplished in some 

observer programs. For example, since 1994 about 90% of the observed kills in the CA drift 

gillnet fishery have been sampled. The genetics archive at the SWFSC in La Jolla currently has 

491 8 specimens representing 62 species of cetaceans and 7 species of pinnipeds. Reference to 

genetic sequences of voucher specimens allows the identification of species fiom small tissue 

samples. 
Observers have had difficulty identifjrlng some cetaceans, such as the two forms of Pelphinus 

(long and short beaked) and beaked whale species. It is not satisfactory to assess fisheries 

mortality for a multi-species group rather than for individual stocks, but the agency has been 

forced to do so currently for beaked whales, for example. Therefore, it is particularly important 

that observer programs acquire tissues samples from difficult to identi@ species. 

Table 1. A conceptual presentation of the expected genetic and demographic differences between sub-populations 

for diierent levels of dispersal of individuals between the sub-populations. The rates of dispersal have been defined 

specifically to illustrate several points, and note that they are relative terms only, as even the category of "high 

dispersal" may still represent only a few percent of the population per year. "Rare to no dispersal" is defined to be a 

level of dispersal that is low enough that genetic differences will be expected for any size of populations. "Low 

dispersal" is defined to be a rate of dispersal that is just suflicient to eliminate any genetic differences between two 

large sub-populations. "Moderate dispersal' is defined to be a rate of exchange that is just sufficient to eliminate any 

genetic differences between two small sub-populations. "High dispersal" is defined to be a rate of dispersal that is 

just sufficient to eliminate any demographic differences between two sub-populations. Finally, note that whether the 

sub-populations should be split for management or not is directly linked to whether they are demographically distinct 

or not. "Dernographcally distinct" is defined to mean that the exchange of individuals between the populations is not 

great enough to prevent the depletion of one of the populations when it experiences human-caused mortality that 

would certainly cause depletion ifthere was no exchange. 

Can a genetic Are the sub- Should the subdifference be populations populations be split 

detected? demographically for MMPA 

distinct? management? I 

Large sub-populations I 

rare to no dispersal yes Yes 

low dispersal I Yes Yes 

moderate dispersal I no 

yes Yes 

high dispersal 1 no no 

Small sub-populations I 

rare to no dispersal yes Yes 

low dispersal Yes Yes 

moderate dispersal I yes Yes 

high dispersal I no no 

4.5 Discussion on- the definition of stocks 

In general, the workshop participants agreed with the points made by the presenters. However, 

some of the participants pointed out that it was still unsatisfactory that there was no completely 

objective method for choosing a specific stock area in the face of uncertainty. Other participants 

noted that unless there is clear information that indicates two populations are isolated, there will 
almost always be some uncertainty in defining the appropriate stocks for management. However, 

the participants generally agreed that negative evidence (e.g., no differences found) should not 

automatically lead to lumping. Additionally, it was felt that there is clearly a difference between 

ESUs and MMPA management units. It was also noted that genetics are not the only criteria for 

stock differentiation and should not be necessary in all cases to differentiate stocks. 

The question still remains -- in an uncertain situation should the default be to split stocks or lump? 

It was concluded that a management unit is a human construct, and these units are best defined in 

a way that. will facilitate management. In particular, if human-caused mortality occurs in only a 

portion.of a species' geographic range, care should be taken to avoid making the type of mistakes 

in incorrectly lumping stocks that were shown, by simulations based on real scenarios, to lead to 

the depletion and potentially the extirpation of some population stocks. Clearly, situations where 

human impact hit certain segments of the population much harder than others should be carehlly 

scrutinized. It was concluded that splitting was to be preferred in situations where incorrectly 

lumping could lead to the depletion of a stock. Additionally, the participants agreed that stocks 

were expected in most cases to be on a scale smaller than entire ocean basins, sometimes much 

smaller, as shown for small cetaceans in Pemn and Brownell (1994). 

On the other hand, it was also felt by most participants that stocks should not be split into 

unreasonably small units. Some participants felt it might be appropriate to define some sort of 

minimum split that was reasonable. Others felt that it was probably best to not be too rigid in 

defining generic limits, as this could lead to problems. Case by case decisions are probably the 

best that can be done. 

Examples of expected stock areas include distinct oceanographic regions (e.g., Gulf of Alaska, 

California Current, Gulf of Mexico), semi-isolated habitat areas, and areas of higher density of a 

species that are separated by relatively lower density areas. 

It was noted that one could call a population one stock, but then allocate the PBR to geographic 

regions and not allow the whole PBR to be taken from one specific area. This type of strategy 

was used to deal with the difficult stock structure of bottlenose dolphins in the bays, sounds, and 

estuaries in the Oulf of Mexico (Blaylock et al. 1995). It was pointed out that this amounted to 

little more than a semantic difference, where the management units are termed something other 

than a stock, but it might be more acceptable to those who equate the word stock with an ESU. 

It was pointed out that in the management of terrestrial mammals, states usually use small areas as 

management units for permitted deer harvests to prevent deer populations fiom becoming 

depleted. The management units are understood to often be smaller units than the population, but 

the managers consider it an effective strategy for preventing population depletion and maintaining 

harvests. 

One difficult aspect of defining stocks is that little may be known about the natural distribution of 

many species, such as harbor porpoise, and the current distributions are likely human-induced 
distributions in many cases. In some cases it is uncertain whether areas of low density are the 

result of past activities of people or are due to how the species chooses to distribute itself. 

Some of the participants felt that in the absence of biological stock data it was inappropriate to 

define stocks to be the area of a fishery's operations. The PBR guidelines used for the 1995 stock 

assessment reports contained such language in the section that provided guidance on defining 

stocks. It was noted that the wording of that language did not adequately convey the true intent 

of the guidance, and it was further noted that there were no stocks that were created solely to be 

identical to the distribution of a fishery. Therefore, it was agreed that this section of the PBR 

guidelines should be revised, and that specific statement removed. 

The participants agreed that dramatic human-induced contractions in the range of a species should 

be viewed as a failure to meet the ecosystem goal ofthe MMPA, even if total population size is . still greater than MNPL. It was noted by one participant that it is difficult to define a stock's role 

as a hnctioning part of an ecosystem when the ecosystem in many cases is not clearly defined, but 

others noted that it is not necessary to filly define what the role is to recognize that the role will 

be missing if the population is gone. However, it was recognized by the participants that what 

constituted a dramatic contraction in range would be difficult to generically define for all species, 

as there was not believed to be intent to give protection to animals or groups of animals beyond 

the margins of their normal population range. 

The participants also discussed the merits of establishing some forum for the national review of 

difficult stock questions. Most of the participants felt that regional reviews, including the regional 

SRGs, were adequate. It was pointed out that it would be useful if the Alaska and Pacific SRGs 

held a common meeting to discuss the stock structure of species found in both regions. It was 

also pointed out that it would be entirely appropriate for an SRG to seek hrther help with 

problem stocks, such as inviting an expert(s) to a meeting or soliciting the opinion of a wider 

circle of scientists with appropriate expertise. 

A small working group @ion, Heyning, Taylor, Chivers) was formed to revise and clarify the 

section of the PBR guidelines describing the'definition of a stock. After reviewing a draft revision, 

the workshop participants agreed that the revision was helpful and should be included in the 

guidelines. The working group made a small number of additional edits to the draft revision after 

the workshop was completed. The resulting draft is incorporated into the revised draft guidelines 

in Appendix 11. 

Major points of agreementlaction items: 

Most of the currently defined stocks are appropriate. Some participants expressed concern 

about a few particular cases, such as having only one stock of harbor porpoise in Alaska. 

For MMPA management purposes, a stock is a management unit that in the best case delineates 

a demographically isolated biological population. It is recognized that delineated stocks often fall 
short of that ideal because of a lack of information and for other reasons. 

The revised definition of stocks section drafted by the working group is usefbl and helps clarify 

the intent of stock structure decisions. 

4.6 Trans-boundary species 

The PBR guidelines as currently written (Barlow et al. 1995) give advice on dealing with transboundary stocks: 

"In trans-boundary situations where a stock's range spans international boundaries or the 

boundary of the U.S. Exclusive Economic Zone (EEZ), the best approach is to establish 

an international management agreement for the species. In the interim, if a stock is 

migratory and it is reasonable to do so, the fraction of time in U.S. waters should be 

noted, and the PBR for U.S. fisheries should be apportioned fiom the total PBR based on 

this fraction. In a non-migratory situation, the PBR for U.S. fisheries should be calculated 

based on the abundance estimate of the stock residing in U.S. waters. For situations 

where a species with a broad pelagic distribution which extends into international waters 

experiences mortalities within the U.S. EEZ, PBR calculations should be based on the 

abundance in the EEZ area unless there is evidence for movement of individuals between 

the EEZ and offshore pelagic areas." 

Some specific trans-boundary stocks were discussed, such as harbor porpoise and common 

dolphins in the Atlantic which are both trans-boundary with Canada. For harbor porpoise, the 

abundance surveys cover both U.S. and Canadian waters, but because little is known about 

residency time of the animals in either the U,S or Canadian portion of their range, the guidelines 

were not followed for determining PBR. Mortality was summarized for only the U.S. side but the 

abundance used to calculate PBR was for the whole area. Some participants noted that the 

guidelines apparently allow for this type of departure in the face of uncertainty regarding time 

spent in each country's waters. Others felt that the PBR should be divided up between Canada 

and the U.S., but did not know how the allocation process should proceed. It is recognized that 

this should be done, but that it was a political issue, not a scientific issue. Alternately, some felt 

that an estimate of mortality in Canadian waters should be added to the U.S. mortality estimate 

for a total estimate of annual humancaused mortality, because this is what is mandated in Section 

1 17 and the abundance estimate that defines PBR is calculated from both U.S. and Canadian 

waters. 

4.7 Incomplete survey of a stock's range 

Management of several stocks is hampered by the possibility (for a variety of reasons) that a large 

portion of a stock's range has not been surveyed, and thus the current abundance estimate is too 

low by an unknown amount. The workshop'participants agreed that there was no scientific basis 

for extrapolating observed animal densities fiom a surveyed area into un-surveyed areas. 
Additionally, the participants agreed that there was no scientific basis for assuming that Nrnin could 

be considered to be a point estimate of abundance (which implies that the CV is 0.0) fiom a 

survey because the stock was known to have a distribution greater than the survey area (this was 

done for some stocks in the 1995 SARs). 

This situation occurs both for some transboundary stocks and for stocks solely within U.S. 

waters. Common dolphins in the Atlantic are noted as one stock for which abundance may be 

underestimated, as surveys over a decade ago (the CETAP surveys) indicated a seasonal 

movement of common dolphins out of U. S. waters in the summer, presumably into international 

and Canadian waters to the north and east. 

The participants discussed that in these cases it might be usefbl to calculate the minimum 

population size necessary to sustain the estimated level of fisheries mortality. This information 

could help in that there may be a perception that the PBR process has created a problem where 

none exists because abundance is under-estimated. Calculating the minimum number of animals 

needed to support a particular level of take makes the issue more concrete. For example, an N, 

of 45,000 would be necessary for the estimated mortality of 449 common dolphins to be below 

PBR, an abundance higher than any previous point estimates from . the . CETAP surveys. 

The workshop participants agreed that it would be helphl in most circumstances if the SAR 

included, where relevant, a map showing the survey area from which the abundance was 

calculated and any other additional information that is thought usehl, such as what areas outside 

the survey area could possibly be a part of the stock's range. It was noted that the reports are 

required to "...describe the geographic range of the affected stock, including any seasonal or 

temporal variation in such range; ..." Thus, this suggestion would help provide this mandated 

information. 

Major points of agreementlaction items: 

The only way of resolving uncertainty in abundance when a stock's range has not be completely 

surveyed is to improve the abundance estimate by doing more extensive surveys. Extrapolations 

of observed densities of dolphins into areas not surveyed would be usefbl for survey planning, but 

should not be used for calculating PBRs. Similarly, it is unacceptable to assume that the point 

estimate of abundance (rather than the 20th percentile) fiom the surveyed area can serve as a 

minimum abundance estimate for the entire stock 

Where appropriate because abundance is thought to be under-estimated, it would be usefbl to 

calculate the minimum population size necessary to sustain the estimated level of fisheries 

mortality. This information could optionally be included in the SAR. 

Each SAR should include a map showing the area within which the survey took place that led to 

the estimate of abundance. This map could, if appropriate, also include the survey tracklines, 

sightings of the stock during the survey, and the distribution of the stock outside the survey area. 
It was recognized that some abundance methodologies are not dependent upon surveys of the 

stock's range, and therefore this recommendation may not be appropriate in all SARs. For stocks 

for which transect surveys have not been done, it may be appropriate to include information about 

the stock's distribution fiom other sources, such as photo ID locations or other types of sighting 

information. 

5.0 Annual human-caused mortality and serious injury 

5.1 ~efinition of mortality and serious injury 

Under section 1 18 of the MMPA, fishers must report incidental +ries and mortalities of marine 

mammals, observer programs typically collect information on mortalities, but under section 1 18, 

NMFS must categorize fisheries based on incidental serious iniuries and mortalities. The 

workshop participants were asked to assist NMFS by addressing short- and long-term goals: 

Short-term. 

provide interim guidelines for determining which injuries are serious for use in this years 

SARs and in the 1997 LOF 

determine the most appropriate forum for addressing the injury/serious injury question 

Long-term 

How will NMFS interpret which of the injuries defined in the regulations are considered 

serious? 

How (and when) can NMFS modifjl data collected by observers to determine which 

injuries are serious? 

*How (and when) will information on serious injury be incorporated into SARs and the 

LOF process? 

In discussions, it was pointed out that it would be difficult at sea to distinguish between injuries 

that lead to mortality and injuries that do not, and that observers and fishermen should not be 

forced to try to make such determinations. It was agreed that observers and fishermen should 

both be asked to provide as complete a description of injuries as possible, and that the aid of a 

checklist helps. Some participants felt it appropriate in some situations to consider all injuries 

serious, such as the injury of large whales in gillnets. Others felt that such blanket statements may 

make the process lose credibility. It was also suggested that, in the absence of accurate 

information, considering 50% of all injuries to be serious may be more appropriate than 

considering 0% or 100% serious. However, many did not agree with any such generic proposals, 

as the types of injuries can differ substantially between fishing gear types and the species involved, 

and thus it was felt that determinations should be case-specific. It was proposed that the SRGs 

could convene meetings with invited experts to come up with guidelines to defining serious 

injuries in specific fisheries. One participant noted that this issue had been investigated for sea 

turtles, and involved scientists had concluded that only through experiments and the collection of 

specific data on the sutvival of injured individuals could such issues get resolved. 
Discussion raised the following points: 

The agency probably should not consider all injuries in a fishery as mortalities - this 

reduces the fisher's incentive to release animals and does not reflect current 

knowledge. 

Different Regionsfcenters provide observers with different guidelines for determining 

whether or not an injury is serious. In addition, different Centers incorporated 

injurylmortality in the SARs in different ways. Efforts should be made to reconcile 

these differences. 

Research is needed to determine what injuries should be considered serious. 

Because no consensus on the issue was reached, volunteers were solicited for a working group. 

The working group provided a report of their discussion back to the full workshop (Appendix 

W). 

After presentation of the working group report, there was general agreement fiom the workshop 

participants that assigning a probability of mortality to each injury would be preferable to either 

calling all injuries "serious injuries", or calling all injuries "not serious". However, there was 

considerable disagreement regarding what is the most appropriate forum to address the issue. 

It was noted that priorities could be set according to the total mortality of a stock relative to its 

PBR and 10% of its PBR when all injuries are assumed to lead to death. Stocks for which this 

assumption could lead to a strategic designation should be given the highest priority for research 

to determine which injuries are serious. It was fUrther recognized that for stocks with total 

known mortality greater than the PBR, this issue is not of priority now, but as mortality is 

decreased it may become increasingly important to resolve. 

It was suggested by the working group that a workshop should be held to gather people with 

appropriate expertise to attempt to produce guidelines. Although there was initially some support 

for convening a workshop to specifically address this subject, some participants indicated that in 

the absence of solid information, experts would be merely expressing opinions on which injuries 

were likely lethal, and thus they doubted the usefUlness of a workshop at this time. The 

participants agreed that there was little relevant information currently available on the probability 

that particular types of visible injuries are lethal for marine mammals. 

Major points of agreementtaction items: 

NMFS should circulate the definition of injury that is included in the regulations. To address 

this, the following is the regulatory text defining "injury" and "serious injury". Injury is defined 

specifically in the Code of Federal Regulations (C.F.R.): 

$229.2: "Injury means a wound or other physical harm. Signs of injury to a marine 

mammal include, but are not limited to, visible blood flow, loss of or damage to an 

appendage or jaw, inability to use one or more appendages, asymmetry in the 
shape of the body or body position, noticeable swelling or hemorrhage, laceration, 

puncture or rupture of eyeball, listless appearance or inability to defend itself, 

inability to swim or dive upon release from fishing gear, or signs of equiIibrium 

imbalance. Any animal that ingests fishing gear, or any animal that is released with 

fishing gear entangling, trailing, or perforating any part of the body will be 

considered injured regardless of the absence of any wound or other evidence of an 

injury. " 

"Serious injury means any injury that will likely result in mortality." 

A request should be made to all the regions to provide the list of injuries that are recorded by 

(1) observers in each observer program, and (2) by fishers on reporting forms. Additionally, it 

was requested that those who have analyzed observer data provide the definition of "serious 

injury" that has been used in a particular fishery, if it has been defined. 

Direct research on the survival of animals injured in fisheries would likely be the best (or even 

only) way to adequately define the difference between a serious injury (one leading to mortality) 

and a non-serious injury. 

If animals are injured in a fishery, but a determination has not been made as to whether the 

injuries are serious or not, then estimates of the number of animals injured should be presented in 

the Stock Assessment Reports along with the estimated mortality. This information could be 

provided in the fisheries table (see below) or within the text of the report. Where such an estimate 

of injury, when added to the estimate of mortality, is responsible for making the sum greater than 

PBR or 10% of PBR, this should be identified in the Report. 

If some injuries are currently considered "serious" and are thus counted as mortalities in the 

mortality estimation, this should be explicitly noted in the report. 

Some of the workshop participants recommended that NMFS convene a workshop on the 

definition of serious injury. Other participants argued that a workshop may not be p&icularly 

usehl at this time. 

5.2 Presentation of information about human-caused mortality in the SARs. 

The participants noted that information about fisheries bycatch was, in some cases, difficult to 

quickly access in the stock assessment reports. This was particularly true for stocks that interact 

with several fisheries. 

Major points of agreementfaction items: 

A new section should be added to the PBR guidelines which gives guidance about how to 

present information about annual mortality and serious injury (previously, no guidance was given). 
The PBR guidelines should explicitly state that the information in the reports is expected to 

include all pertinent information about incidental mortality that will subsequently be used to 

categorize fisheries in the List of Fisheries. 

Recommend adding a table summarizing incidental fisheries mortality and serious injury to the 

stock assessment report. Where "serious injury" is distinguished fiom "mortality" in a fishery, 

both numbers and their sum should be presented. All fisheries that are noted in the List of 

Fisheries as interacting with each stock should be in the table. 

A sample table be created and distributed to persons responsible for revising the stock 

assessment reports. 

5.3 The description of fisheries in the SARs 

Section 1 17 of the MMPA requires that the SARs : 

(b) "...describe commercial fisheries that interact with the stock, including (A) the 

approximate number of vessels actively participating in each fishery; . . .(C) seasonal 

or area differences in such incidental mortality and serious inju~y;. . . " 

Information about fisheries is required to be a part of the SARs. However, the workshop 

participants recognized that when a fishery interacts with several stocks, information about this 

fishery gets repeated in several reports. It was agreed that keeping the reports as concise as 

possible was important, but it was also important (and mandated) that the fisheries information be 

provided in the reports. Therefore, the participants agreed that if it was a helphl thing to do, 

redundant inforrnation about each fishery could be placed in an appendix to the stock assessment 

reports. This does not mean that fisheries information must be placed in an appendix, but 

optionally allows this to be done in cases where it is appropriate. Some participants felt that it 

may be better to place the fisheries information in a supplemental document, rather than in an 

appendix, to keep the overall size of the stock assessment report document to a minimum. It was 

agreed that this, too, was acceptable. However, such a supplement would need to be produced 

and distributed simultaneously to the stock assessment reports, as information about fisheries is 

required to be in the reports. 

Some participants felt that the most detailed information possible about fisheries should be 

included in the SARs. It was agreed that maps showing the location of fisheries would be helpful. 

Some participants felt this should be done for all fisheries known to take marine mammals, even 

category III fisheries, while others felt that it was only necessary to do this for Category I and I1 

fisheries. For Category I and I1 fisheries, such maps would be usefil for the take reduction teams. 

Such maps would additionally be usefbl for the SRGs and NMFS for assessing which unobserved 

Category I1 fisheries might have the greatest incidental mortality of marine mammals. The same 

was felt for some Category III fisheries, in that information regarding their location and size could 
help in judging whether an unobserved fishery should be investigated. The participants concluded 

that judgement should be used for category III fisheries, and recommendations from the SRGs 

would be helpfbl. 

Especially usehl information would include the distribution of fisheries effort (i.e., where the 

fishery fishes). If the exact location of fishing effort is not known, a rough indication of fishing 

areas and ports the fishery uses would be useful. For observed fisheries, it would also be usehl to 

have a map indicating where fishing activities were observed, and the location of marine mammal 

mortalities and injuries. 

It was recognized that this will initially be a large task, although some participants noted that such 

information was likely produced for other forums, such as for regional fisheries councils and for 

section 7 consultations under the ESA. Much of this information is available from NMFS 

regional offices, so it was recognized that getting this information into the SARs will require close 

cooperation between the NMFS science centers and the regional offices. Describing the 

distribution of fisheries, though a large task, is mandated in the MMPA, and was thought to be 

well worth the effort it will take to provide it. 

Major points of agreementfaction items: 

Additional information describing the geographical description of fisheries was both of great 

value and mandated by the MMPA. Where appropriate, an appendix or supplement should be 

added to the SARs that includes maps showing the location of fisheries with incidental mortality 

of concern. Ifpossible, the maps should show where the fishery operates (i.e., the estimated 

distribution of fishing effort). If the exact location of fishing effort is not known, a rough 

indication of fishing areas and ports used by the fishery would be usehl. For observed fisheries, it 

would also be usefbl to have a map indicating where fishing activities were observed, and the 

location of observed marine mammal mortalities and injuries. 

It was recommended that the NMFS Office of Protected Resources circulate a list of what 

fishery information would be use&] to include (see section 3 of Appendix 11, the PBR guidelines), 

and to provide the text of the Environmental Assessment if it would be helphl to those collecting 

fishery information. 

6.0 Habitat issues 

Consideration of marine mammal habitat concerns is specifically mandated in the MMPA, as there 

is a requirement that stock assessments: 

Sec 117 (a)(3) "estimate ..., for a strategic stock, other factors that may be causing a 

decline or impeding recovery of the stock, including effects on marine mammal habitat and 

prey; ..." 
Additionally, the regional Scientific Review Groups are asked to advise the agency on: 

Sec 117 (d)(E) "the actual, expected, or potential impacts of habitat destruction, including 

marine pollution and natural environmental change, on specific marine mammal species or 

stocks, and, for strategic stocks, appropriate conservation or management measures to 

alleviate such impacts;. . . . " 

Some public comments expressed the opinion that the 1995 SARs had not adequately addressed 

this issue. For ESA listed stocks, most of the required data has been put together for biological 

opinions, but is probably only organized in a convenient fashion for listed stocks that'have 

recovery plans. However, for non-listed strategic stocks (i.e., those stocks that are not listed 

under the ESA but that have estimated human-caused mortality greater than PBR), the SAR 

should at least make a statement that no information is available to suggest that habitat issues are 

likely to be causing a decline or impeding the recovery of the stock, if that is appropriate. It was 

suggested that information on contaminants, if available, should be included in the SARs. Habitat 

was recognized as being important to all species; therefore it was concluded that habitat issues 

should be included for stocks that are not strategic if the data indicate a potential problem. 

Major points of agreementlaction items: 

A statement about habitat issues should be included in the Status section of the Reports, or, if 

needed, in a separate section titled "Habitat issues". If data exist that indicate a problem, they 

should be summarized and included in the Reports. If there are no known habitat issues for a 

stock, that this should be explicitly stated, as consideration of habitat issues are mandated by the 

act. 

7.0 Research on classifying stocks as strategic 

Palka presented research investigating the probability of correctly classifjling a stock as strategic 

or not fiom a single estimate of abundance and a single estimate of bycatch. Two methods were 

compared, (1) classimng a stock as strategic when the ratio of the point estimate of bycatch to 

1 /2Rmax*Nrnin is greater than 1 .O, and (2) classifLing a stock as strategic when the ratio of an 

upper confidence limit (the I-s' percentile) of bycatch to %*Rmax*a lower confidence limit of an 

abundance estimate (the sh percentile) is greater than 1 .O. The first method is analogous to a PBR 

calculation without using the recovery factor, Fr. The second method was referred to as the 

percentile-percentile (P-P) method. Estimates of abundance and bycatch were assumed to be lognormally distributed in the analyses. The probability of making a correct classification was 

determined across a range of CVs for abundance and bycatch. For method 1, this probability 

surface was found to be non-symmetric, and non-monotonic when the ratio of bycatch to 

abundance was greater than %*Rmax. For the percentile-percentile method, the probability 

surface was found to be symmetric, but was also non-monotonic when the ratio of bycatch to 

abundance was greater than %*Rmax, although less-so than method 1. The results led Palka to 
conclude that one would have to know the true status of the stock to optimally allocate resources 

between estimating abundance and bycatch. An additional conclusion was that as bycatch is 

reduced, effort should change towards improving the CV of the abundance estimate at the 

expense of the CV of bycatch. 

Workshop participants noted that two previous analyses presented at the PBR workshop (Barlow 

et a1 1995) had found that when performance was measured by the probability of a population 

successfully obtaining OSP (which is the primary goal of the MMPA), the CV of bycatch was 

found to be much less important than the CV of abundance when bycatch is estimated every year, 

as is currently the case for all category I fisheries (see Wade 1994, Lerczak et al. 1994). Further, 

several participants commented that the analysis presented by Palka was flawed as the appropriate 

distribution for mortality data in the PBR approach was not used. The workshop participants 

noted that alternative methods for investigating bycatch should be encouraged and explored, but 

that the percentile-percentile method as presented could not be implemented. Partly this was 

thought to be true because the MMPA indicates that the true level of bycatch (and thus an 

unbiased point estimate) is to be compared to the PBR: "Sec 3(19) The term 'strategic stock' 

means a marine mammal stock-- (A) for which the level of direct human-caused mortality exceeds 

the potential biological removal level;. . . " Additionally, ignoring that difficulty, percentilepercentile could also not be implemented as presented because there had been no selection of a 

specific percentile to use, and no robustness trials were performed. The participants of the first 

PBR workshop (Barlow et al. 1995) concluded that simulation trials such as those in Taylor 

(1 993) could be used to judge the performance of proposed management schemes, and the 

workshop participants concluded that such an approach would be a useful evaluation of the 

proposed percentile-percentile method. 

It was noted that an easily understood and transparent management regime is important to the 

people who are being managed, a point that was also discussed at length in the first PBR 

workshop (Barlow et al. 1995). As a counterpoint, however, some participants noted that usekl 

scientific methods should not be discarded solely because they are complex and difficult to 

understand. Finally, some of the participants noted that the current PBR calculation method 

could similarly be implemented for case-specific CV's of abundance and mortality, as suggested in 

Lerczak (1994), but that the first PBR workshop participants had decided in favor of a more 

generic approach that covered a range of CV's, that could be adjusted as needed for particular 

cases. 

Wade presented an interactive computer simulation program termed MOKMAM (Monitoring kills 

of marine mammals). The program was designed to simulate abundance estimates and fisheries 

mortality estimates under a user-specified level of fisheries mortality. It provides a visual 

indication of how often a bycatch estimate will be greater than a calculated PBR over a specified 

time period, such as 10 to 40 years. An example given was that for a cetacean with a true Rmax 

of 0.04 and an MNPL of 0.5K. Under this scenario a fisheries bycatch of greater than 2% per 

year would cause the depletion of the population (and thus not meet the goal of the MMPA), 

while bycatch less than 2% would not cause depletion. The results indicated that for expected 
precision levels (CVs) of the abundance and mortality estimates, the probability of correctly 

classifjmg a stock with bycatch greater than 3% as strategic was very high. Conversely, the 

probability of correctly classifjrlng a stock with bycatch less than 1% as not strategic was also 

very high. Making the correct determination for bycatch levels between 1% and 3% depended 

upon the specified CVs and the exact level of bycatch; when bycatch was very close to 2% it, of 

course, becomes more difficult to distinguish between a bycatch level just greater than 2% and 

one just less than 2%. Although a population with bycatch just less than 2% will not become 

depleted, it will decline fiom an equilibrium level to a level very close to being depleted, and thus 

probably deserves close scrutiny. Furthermore, such a level of bycatch is not likely to be 

considered a level that is insignificant and approaching zero, and will therefore require 

consideration eventually. 

It was suggested by some of the workshop participants that hrther research along these lines, 

such as in Smith and Palka (WP-9) and Wade (WP-lo), would be useful. 

8.0 Calculation of PBRs 

A number of issues related to the calculation of PBR were felt to deserve hrther discussion after 

the experience of producing the first round of SARs. At the end of many specific discussions it 

was concluded that the PBR guidelines already contained sufficient guidance. However, there 

were minor areas where it was felt that some additional guidance might be helphl. 

Major points of agreementlaction items: 

The current PBR guidelines on calculating PBR are adequate and sufficient in most areas. It is 

recommended that minor changes to some sections of the guidelines be made. These changes are 

covered in the sections below. 

8.1 Time period fiom which to use data on abundance and mortality 

The participants discussed two issues related to this topic: (1) when estimates of abundance 

andlor mortality are available for several years, which should be used and how should they be 

combined, and (2) when no recent information has been collected, at what point does an old 

estimate become unreliable? 

Combining estimates of mortality and abundance from several years will improve the precision of 

the estimates, reduce the impact on a fishery of a single "bad" year, and create a more stable 

behavior for the management system. Potential problems from combining estimates across years 

would be the creation of a lag in the correct evaluation if a substantial trend exists in either 

abundance or mortality. In other words, if the mortality in a fishery declines substantially, 

averaging across years might prevent the recognition, for a few years, that a stock was no longer 

strategic, or the opposite. 
It was recognized that it would be appropriate to mathematically weight the most recent estimates 

more heavily than older estimates, although this may not be overly important if the "window" 

across which estimates are averaged is kept relatively short. 

8.1.1 Abundance estimates 

The point was raised about how to deal with situations where it is suspected that one might be 

seeing different portions of the population in different years, a possible explanation for the large 

differences in estimates seen between years for some populations, such as gray whales or Gulf of 

Maine harbor porpoise. Inter-annual oceanographic variability can, for some stocks, lead to 

distribution shifts, so that one is not seeing the whole population. If this represents the true 

situation for a stock, averaging across all years will yield an under-estimate of the true stock size, 

but conversely, arbitrarily throwing away low estimates will yield an over-estimate of the true 

stock size if the differences in estimates fiom year to year are only due to sampling variability. The 

difficulty lies in deciding when evidence supports the hypothesis that fewer animals were available 

to be surveyed in a year with a lower estimate. 

If estimates are combined, it is probably appropriate to use an inverse-variance weighted mean. 

Regarding what to do with old estimates, it was noted that the definition of N, states that there 

is assurance that "stock size is equal to or greater than the estimate" in the Act. At some point, 

with old estimates we lose this assurance. However, NMFS received public comments and 

comments fiom the SRGs expressing dis-satisfaction with the current guidelines which 

recommends ratcheting down the recovery factor by 10% every year after five years. It was 

suggested that an alternative would be to state that at some specified "age", abundance estimates 

become unreliable and at that point N,, and thus PBR, cannot be determined. The workshop 

participants agreed to this proposal, and also agreed to using eight years as the time period. Many 

of the participants were not willing to consider a longer time period, as it was pointed out that 

enonnous declines could occur over time periods longer than 8 years. For example, Steller sea 

lions were observed to decline at a rate of 10% over many years. A population starting at K that 

declines by 10% per year will be below 50% of K in 8 years. It was noted that for stocks for 

which it is possible to easily monitor trends in abundance but for which it is more difficult to 

estimate absolute abundance, that a longer period of time could elapse between absolute 

abundance estimates if one was contident that the'population had not declined in the mean time. 

Major points of agreement/action items: 

Confidence in the reliability of an abundance estimate declines with age. Therefore, estimates 

older that 8 years should not be used to calculate PBR. This is necessary to meet the requirement 

in the MMPA that Nrnin represent a level for which there is reasonable assurance that the true 

population is larger. The consequence of not being able to calculate a PBR for such stocks is that 

-PBR is unknown (not that PBR equals zero). A decision as to whether such stocks are strategic 

or not will be jointly decided case-by-case by NMFS or FWS and by the SRGs. This 

recommendation replaces the guidelines stating that recovery factors were "ratcheted down" as 
abundance estimates become older than 5 yrs. 

8.1.2 Fisheries mortality estimates 

The PBR guidelines as written contain no advice on what mortality estimates can or should be 

used. When combining years of data, it was suggested that we probably do not want to use a 

weighted mean for mortality. A weighted mean is appropriate when there is more than one 

estimate of a relatively constant value, but true mortality may itself vary substantially fiom year to 

year, and thus an unweighted mean will be a more appropriate measure of the average mortality 

during the specified time-period. 

In the 1995 SARs, the mean of 3 or 4 estimates of mortality were used for many stocks, when 

such data were available. It may not be appropriate to use more years of data than this, because if 

as many as 5 years of estimates were used, it is likely that the oldest estimate would be 6 or 7 

years old by the time the SAR was finalized. As a rough rule, as many years as necessary to 

achieve a reasonable CV (e.g., a CV of < 0.2-0.3) could be combined up to some maximum such 

as 5 years. It will be important to note whether external information gives evidence that true 

mortality may have changed substantially in recent years. For example, if fishing effort changed 

substantially, it may not be appropriate to use years prior to the change in the average. It is 

possible that the most appropriate years of data to use may differ between various fisheries, so 

each situation will have to be evaluated itself 

Regarding the use of old information, it was suggested that the guidelines should state some sort 

of time frame beyond which it is recognized that estimates are no longer relevant and useful, as 

the goal is to evaluate the current bycatch of fisheries. However, if the only information available 

becomes old, it should not automatically be assumed that the mortality no longer exists unless 

there is some compelling evidence to suggest that this is the case. It was recognized that in 

situations where the only information comes from logbook reports of mortalities, the MMPA 

reports can not be relied upon to necessarily give an accurate picture of current mortality, and so 

the use of old information may be appropriate. 

Major points of agreementlaction items: 

An unweighted mean should be used when averaging mortality over more than one year. 

A section giving guidance on what mortality estimates to use was drafted and added to the 

revised PBR guidelines. 

8.2 Combining estimates and Calculating CV of a product 

The workshop participants discussed a proposal to add a technical supplement to the PBR 

guidelines providing computational formulas for calculating the combined CV of a product, such 

as an abundance estimate and its correction factor, and for calculating the combined CV of a 

weighted mean, as might be used to combine abundance estimates. It was agreed that this would 

be a useful addition to the guidelines. 
Major points of agreement/action items: 

A new section was drafted to be added as a technical supplement to the PBR guidelines. 

8.3 Problems associated with species which are difficult to identify 

There are several situations in which incidental mortality occurs for cetaceans which are difficult 

to identif) to the species (or stock) level. This has caused greater uncertainty in assessing these 

stocks, as it is uncertain as to which stock to assign the mortality. Such situations include: 

Mesoplodon beaked whales (potentially 4 species) caught in the Atlantic drift gillnet fishery; 

Mesoplodon beaked whales (potentially 5 species) caught in the Pacific drift gillnet fishery; 

common dolphins (2 species) caught in the Pacific drift gillnet fishery; Pilot whales (2 species) 

caught in the Atlantic drift gillnet and longline fisheries; bottlenose dolphins (2 stocks which may 

deserve taxonomic distinction) caught in the Atlantic drift gillnet fishery and in Atlantic coastal 

gillnet fisheries; and spotted dolphins (potentially 2 species) caught in the Atlantic drift gillnet 

fishery. Other species also may be misidentified, such as a juvenile animal being mistaken for the 

adult of another smaller, species. 

This problem is perhaps most acute in the case of the beaked whales. Two strategies have been 

used to date to deal with this uncertainty. In the Pacific, Mesoplodon beaked whales have been 

treated as a single management unit, and all species are considered strategic because total 

Mesoplodon mortality exceeds the total Mesoplodon PBR. Under such circumstances it is 

certain that at least one of the species would have its PBR exceeded, if abundance and mortality 

could be calculated on a specieslstock level. For example, consider a hypothetical example where 

two species cannot be easily identified from each other. Suppose that species 1 should have a 

PBR of 100 and species 2 should have a PBR of 50. A combined PBR for the two species would 

be 150. Further suppose that the combined fisheries mortality for the two species is 15 1. It can 

be seen that there is no possible way to allocate the mortality of 15 1 between the two species 

without exceeding the PBR of species 1 (loo), or of species 2 (50), or of both. It can therefore 

be concluded that at least one of the species is a strategic stock. 

In the Atlantic, separate SARs have been written for the 4 Mesoplodon spp., but each species is 

evaluated as if the entire mortality was just of that species. Although abundance was not 

calculated for the 4 species due to the small number of sightings in surveys and the species 

identification problem, it is clear that, as in the Pacific, the total PBR that could be calculated for 

the 4 species would be exceeded by the total mortality. 

The workshop participants agreed that more work on identification of species should be done, 

including further research on strandings and other samples, and the collection of biopsies. 

However, it was pointed out that even the best observers do not routinely have the opportunity to 

identify Mesoplodon sightings to species, as such identification usually requires the animals to 

present themselves in a particular way (i.e., usually a clear view of the head of a male is 

necessary). Tissue samples collected by fisheries observers should eventually be able to determine 
what species are killed through genetic means if appropriate voucher material can be collected for 

all species. However, it will be difficult to improve identification during abundance surveys. It was 

suggested that a revised field guide for beaked whales would help with this issue and should be 

explored. Tissue materials (and particularly at least the head of beaked whales) are also important 

voucher materials for establishing what morphologically described species is associated with 

particular identified genetic sequences. 

It was noted that the ability to identlfy species of Kogza in the field is accepted in the Pacific SRG 

but disputed in the Atlantic SRG, despite many of the same observers being used. The agency's 

most experienced marine mammal observers note that they see the same identification characters 

in the Atlantic and Gulf of Mexico as they do in the Pacific, so that there is no reason that there 

could not be agreement nationally. It was suggested that this should be discussed between the 

Southeast, Northeast, and Southwest centers, as well as between the Atlantic and Pacific SRGs. 

Major points of agreementJaction items: 

The collection of biopsy samples and voucher material is strongly encouraged, particularly for 

species without such materials and other hard to identifjl species. In particular, voucher material 

is needed for these species ofMesopIodon beaked whales: M. carlhubbsi, M. ginkodens, M. 

densirostris, M. hectori, M. europaeus, M. mirus. 

National experts should be encouraged to revise a field guide to the identification of beaked 

whales and Kogza spp. 

8.4 Calculating PBR for declining species 

It was noted that 3 stocks are known to be declining: western stock of Steller sea lions 

(PBR=766, abundance= 43,200); Gulf of Alaska harbor seals (PBR not determined, abundance 

19,600); and Hawaiian monk seals (PBR=3.9, abundance 1,406). It is thought that none of these 

stocks are currently declining solely due to direct human-caused incidental mortalities. For Steller 

sea lions and monk seals, a PBR was calculated but since both are listed under the ESA, the SAR 

notes that the ESA takes precedence; particularly for monk seals this indicates that zero human 

related kills are authorized. 

It was suggested that there should be criteria for decreasing the recovery factor to account for 

declining populations. Of course, for endangered stocks such as monk seals the recovery factory 

is already at its lowest allowable value of 0.1. It was noted that takes of endangered marine 

mammals can be allowed as long as the take will have a negligible effect on the stock. Where take 

of a listed stock is known to occur (a total of 10 stocks), for only 3 of those stocks was NMFS 

able to determine that this take would have a negligible impact (central North Pacific stock of 

humpback whales, western and eastern stocks of Steller sea lions, 60 FR 45399 August 3 1 1995). 

Prior to 1994 a fishery could not be authorized to take an endangered marine mammal, but now 

the negligible impact standard in the MMPA can be used to support such an authorization. 
It was noted that future circumstances involving the decline of a stock not listed under the ESA 

may just@ not calculating a PBR, and such flexibility should be allowed if a new situation merits 

it. It was concluded that there was no need to revise the guidelines to account for the difficulties 

of declining populations, as sufficient flexibility to handle special circumstances exists as long as 

it is documented and justified in the SARs. 

8.5 Changing recovery factors fiom default values (particularly endangered whales) 

Some participants felt that a recovery factor of 0.1 may be too conservative for some populations 

of endangered whales. It was noted that many of these species were listed under the ESA in the 

early 1970s because no effective international management regime controlling the harvests of 

large whales was in place. Large whales may not currently be appropriately classified under the 

ESA in some cases. Some of the participants felt that this issue should be addressed through 

proposing the de-listing (or down-listing fiom endangered to threatened) of such stocks under the 

ESA, and that recovery factors for PBRs under the MMPA should not be altered to fix an 

incorrect classification under the ESA. Other participants noted that the de-listing process takes a 

long time, and felt that NMFS should be proactive and, if appropriate and justified by scientific 

evidence, ident@ stocks which should have their recovery factor increased. Further, where there 

was sufficient scientific evidence, it was suggested that NMFS should initiate the delisting 

process. There was consensus among the participants that candidate stocks should be identified 

and proposed for de-listing. There was not consensus as to what constituted sufficient evidence to 

increase the recovery factor or to propose de-listing. 

It was noted that in 3 examples, recovery factors for listed stocks had been altered relative to the 

default recovery factor in the existing PBR guidelines. The recovery factor for bowhead whales 

(listed as endangered) was raised from 0.1 to 0.5 because the population is thought to be 

increasing and a management scheme is in place for the subsistence harvest. The recovery factor 

for the western stock of Steller sea lions, listed as threatened, was decreased fiom 0.5 to 0.3 

because of the decline in the population and anticipation that the population may be listed as 

endangered in the future. The recovery factor for the eastern stock of Steller sea lions, listed as 

threatened, was increased from 0.5 to 0.75 on the recommendation of the Alaska SRG, because 

the population was thought to be stable. 

Similar reasoning was used to raise the recovery factor fiom 0.5 to 1.0 for un-listed stocks subject 

to subsistence harvest which were thought to be stable. One participant expressed dissatisfaction 

that there was no definition given for what represented a "stable" stock, and that no statistical 

criteria had been used to conclude that a stock was stable before increasing the recovery factor. 

There was some discussion as to whether changes to the recovery factor for endangered stocks 

should only occur after changes to their listing status under the ESA had been formally proposed. 

Most of the participants agreed that it was not appropriate to rigidly link recovery factor values to 

proposed changes under the ESA. However, some participants still felt that it was not appropriate 

to increase the recovery factor without sufficient evidence to also initiate the de-listing process, 

even if they are not formally linked. It was agreed that evidence that an endangered population 
was increasing was not sufficient evidence to increase the recovery factor, as endangered 

populations are expected to be increasing if their primary direct human-caused mortality (e.g., 

harvests) has ceased. The scientific justification for using a recovery factor of 0.1 is based on not 

significantly delaying the recovery time of an endangered population, so it is not appropriate to 

raise the recovery factor just because a population is increasing. It was noted that listed species 

should have recovery teams and recovery plans that specify criteria for de-listing, and that this is 

not the responsibility of MMPA processes or the SRGs. However, on a pragmatic level, it was 

noted that the SARs represent the first review in 11 years for some of these listed whale stocks. 

Some participants suggested we should be wary of effectively reclassifymg those stocks where 

recovery teams do not exist, and that we should set specific standards and not be arbitrary. It was 

hrther noted that takes of listed stocks can only be authorized if they have a negligible impact on 

the population. 

Major points of agreementlaction items: 

Clarification should be added to the guidelines that flexibility exists to change default recovery 

factors (such as for endangered species) on a case-by-case basis with carehl consideration of the 

information available for each stock. Such changes should be made in consultation with, and 

when appropriate should reflect the recommendations made by, the NMFS or FWS center(s) and 

region(s) responsible for the SARs and the relevant Scientific Review Group. Such changes 

should be justified by credible scientific evidence. It was acknowledged that this was a complex 

and difficult issue; therefore the evidence used to support any change to the recovery factor of an 

endangered species should be carehlly documented in the SAR. 

8.6 Correction factors for deep diving whales 

Barlow presented results from field monitoring of deep-diving whales in the Gulf of California, 

and preliminary work on estimating correction factors for abundance estimates from such data and 

other information. Beaked whales in particular are hard to see, and dive deeply, although little 

information is available about their actual dive times. It has been recognized that abundance for 

beaked whales and other deep-diving whales is under-estimated because during their dives they 

are unavailable to be seen. However, a lack of information has prevented the quantification of the 

amount of under-estimation. Therefore, research was conducted to visually monitor deep-diving 

species to investigate the fraction of time they spend at the surface, and are available to be seen. 

Preliminary results indicated that the most frequent dive durations were approximately 15-25 

minutes for Mesoplodon spp. and 20-35 minutes for Ziphius cavirostris. Dive patterns for Kogra 

spp. were highly variable (2-30 minutes), with most dives 20 minutes or less. Z.cavirostris spent 

approximately 1-3 minutes at the surface (or only about 10% of the time), while Mesoplodon spp 

and Kogra spent about 2 minutes at the surface. Sperm whales were problematic, as it was 

difficult to recognize sequential surfacings of individuals because of the presence of several 

groups of whales diving asynchronously. It was pointed out that such research can only take 

place under very good sea state conditions. 
The next step in estimating correction factors (through the parameter g(O), the probability of 

detecting a whale if it is at zero perpendicular distance from the ship's transect line) will be to 

model the searching behavior of observers (including the angle of acuity of the binoculars and the 

scan rate), the diving behavior of the whales, the detection probability for whales at given radial 

distances, and the speed of the vessel. 

Preliminary results indicated that correction factors for beaked whales will be on the order of 4 to 

8 times the abundance estimates from the surveys, but they will have large uncertainties associated 

with them (i.e., large CVs). It was cautioned that it is unknown whether these estimates would be 

applicable to other areas or to other similar species. The specific correction factors will only be 

applicable to abundance estimates from surveys using an identical height platform and identical 

searching methodology with 25x binoculars and teams of 3 observers. However, the dive time 

data could conceivably be adapted to estimates from other survey methodologies, but biases could 

occur if dive times differ in other regions or other times of year, which could be likely as the 

whales are often diving to the depth of target prey, which will itself vary. Therefore, it was 

agreed that these correction factors will give an indication of the amount of bias that might be 

found in other surveys but that it was unlikely to be appropriate to use them to actually correct 

abundance estimates from surveys of other species in other regions. 

8.7 Correction factors for pinniped counts. 

There are two primary kinds of correction factors for pinniped counts: correction for the fraction 

of animals hauled out, and corrections to scale pup counts to the total population size. One of the 

most difficult aspects of calculating such correction factors is estimating their variance. It was 

noted that several pinniped stocks in the reports had estimates of Nmin based on counts scaled by 

correction factors which assumed there was zero variance in the estimated correction factor 

because of this inability to properly estimate the variance. It was suggested that a default CV on 

the order of 0.2-0.3 (in the absence of an estimated CV) was probably a more appropriate default 

than assuming the CV was 0.0. The participants agreed that Mathews (WP-8) was a usehl 

summary of the difficulties in estimating correction factors for pinnipeds. 

Major points of agreementlaction items: 

Caution should be used when considering the application of correction factors for abundance 

estimates to stocks in other locations, or to other species. Additionally, caution should be used in 

applying correction factors in different situations in the same location (e.g., tidal state, season, 

time of day, etc.). The use of estimated correction factors without associated variance estimates 

is to be avoided. Where the use of such a correction factor is considered unavoidable, it is 

suggested that a default CV should be used that is greater than the 0.0 currently assumed for 

several stocks. 
9.0 Review, revision, and publication of the Stock Assessment Reports 

The relevant passage fiom the MMPA states: 

"Sec 117 (c) REVIEW AND REVISION. - 

(1) The Secretary shall review stock assessments in accordance with this subsection - 

(A) at least annually for stocks which are specified as strategic stocks; 

(El) at least annually for stocks for which significant new information is available; 

and 

(C) at least once every 3 years for all other stocks." 

The participants noted the use of the word "review" here; this implies that it is not necessarily 

' required that reports for the above stocks be revised if the review does not find revision 

necessary. 

9.1 Review and Revision 

The workshop participants discussed what constituted a review, and who should do the review. 

Within NMFS, the Science Centers in most cases have collected the data necessary for calculating 

PBR, and the Regional Offices in most cases are responsible for fisheries mortality data, although 

the Centers are also often involved in estimating mortality. In most cases, it is expected that the 

Science Centers will be the first to have new information when it becomes available, and so must 

initiate the review process, but the review should involve the NMFS Regional Offices as well. 

Additionally, the participants agreed that reviewing SARs was one of the primary responsibilities 

of the regional Scientific Review Groups, so that the review must be a joint process. It was 

concluded that NMFS Centers and Regions should initiate the process early on by summarizing 

new data and information that were not available for the previous SARs, and propose which 

reports need to be revised and what revisions will be necessary. This information should be 

passed on the SRGs as soon as possible. Then it is expected that the Centers, Regions, and SRGs 

will have a meeting to discuss the proposed revisions. It was noted that it was also clearly within 

the responsibility of the SRGs to suggest additional revisions that they consider necessary. For 

documentation purposes, it was noted that the minutes of the SRG meetings should indicate, 

when true, that stocks meeting the above criteria in Section 11 7(c) were reviewed (i.e., 

considered for revision). 

There was much discussion as to whether SARs for stocks with new information but no 

significant change in status should be revised every year. It was pointed out that many stocks will 

have an additional year of mortality data available every year, which will often not change any 

conclusions regarding the status of the stock. In response, it was noted that simply adding a few 

new estimates would not be overly burdensome, particularly once the process was well 

established. 

It was felt that the SARs were viewed by all involved parties as an important and useful resource, 

and that having the most current information possible in them was important. It was pointed out 
that the unavoidable lag time between field work, analysis, final results, and then the drafting and 

finalization of the SARs often makes information several years old (at best) by the time the SARs 

are published. The participants thus agreed that SARs should be revised whenever new ' 

information is available on the abundance, human-caused mortality, population growth rate, or 

stock structure of the population. It was agreed that it was best to revise the reports whenever 

new information was available, even if the new information did not affect whether the stock was 

strategic or not. For consistency and to avoid confbsion, it was also felt best to revise all reports 

with, for example, new mortality estimates, rather than just reports meeting the specific 

requirements of Section 1 17(c). It was also thought to be best to include any reports not revised 

so that each document is a complete set. 

Major points of agreementlaction items: 

A section would be added to the PBR guidelines to describe the annual review, revision, and 

publication of the SARs. 

b The review process leading to revision recommendations should be a joint consultation between 

the appropriate NMFS personnel (at both Centers and Regions) and the SRGs. 

The SARs should be revised whenever new information becomes available on abundance, 

mortality, R-, or stock structure. It is best to revise the SARs whenever new information is 

available, even if the new information does not affect whether the stock is strategic or not. 

Although it is anticipated that new estimates of mortality fiom a fishery observed for several years 

will often not change the classification of a stock, NMFS and FWS should still be encouraged to 

publish a revised SAR even if the only new information is a new estimate of mortality, in the 

interest of keeping the SARs as up to date as possible. 

9.2 Annual schedule for revising and publishing the SARs 

Wade and Angliss presented a proposed annual schedule for reviewing stocks, and drafting and 

finalizing the SARs. The categorization of many fisheries is tied to the calculated PBRs and 

annual mortality that are presented in the SARs. It was reported that many fishermen felt that the 

1995 SARs did not have the most recent information available in them. For example, the 1996 

List of Fisheries (LOF), which was finalized at the end of 1995, was based on the 1995 SARs, 

which in many cases only had information up through 1993 in them (some had 1994 data). 

However, NMFS was also criticized for basing categorizations on draft SARs, rather than on final 

SARs. Therefore, the proposed schedule was designed to attempt to have the categorizations in 

the LOF be based on as recent information as possible, while simultaneously satisfjing the 

objective of basing the proposed categorization on final SARs. 

At this point, the group agreed that the best schedule would be one that had field data fiom the 

previous year in the draft SARs in time for the LOF for the next year to be finalized by October 1. 

For example, abundance and fisheries mortality estimates fiom 1995 would be in draft SARs in 
the fall of 1996, which would be finalized in the spring of 1997, so that the information could be 

in the 1998 LOF that is finalized in the fall of 1997. 

It was speculated that in hture years it may be possible to accelerate this process if it is expected 

that few changes will occur fiom one year to the next. Accelerating the process by one year 

would require developing the SARs and the LOF simultaneously, rather than sequentially, 

something NMFS was criticized for doing in 1995. If few changes occur, it might be possible to 

think of a schedule that, for example, would have abundance and fisheries mortality estimates 

fiom 1995 incorporated into draft SARs and a proposed 1997 LOF in the late spring of 1996, 

with both the 1996 SARs and the 1997 LOF finalized in the fall of 1996. However, the workshop 

participants agreed that a schedule such as this would be too ambitious at this time. 

It was fbrther commented that the take reduction team process should be incorporated into this 

annual schedule, but this may be difficult due to the independent schedules of these teams. It was 

agreed that timely distribution of new information to the take reduction teams was important, and 

should not be a problem. 

One participant noted that there should be wording in the schedule showing why the time lags 

exist within the schedule, such as time necessary for analysis of data and peer review. It should 

also be understood that flexibility exists to incorporate some data later on in the process than 

called for by the schedule where it is thought to be important, although this should be kept to a 

minimum. It was suggested that the regions and centers could fine tune the schedule to fit their 

own needs, but establishing a target schedule will help the process and make clear what certain 

milestone dates are that can not be delayed, and why they occur when they do. It was hrther 

noted that good communications between the centers and regions will assist this process. 

The participants agreed to the proposed schedule, and suggested that more explanation of the 

process would be helpful. It also might be appropriate to expand the time line to incorporate 

other activities, such as those of the SRGs and regions. 

The representatives of all of the NMFS centers and regions agreed to attempt to meet the 

proposed schedule starting this year. The NMFS scientists responsible for revising the SARs 

agreed to complete revised drafts by Oct 1, 1996. 

It was noted that this was a schedule worked out by NMFS scientists, without consultation with 

FWS scientists until this workshop. It was also noted that formal communications regarding 

stock assessments were camed out between the Silver Spring and Washington, D.C. offices of the 

agencies, rather than between the field scientists writing the SARs. FWS scientists at the 

workshop noted that the proposed schedule was sensible, but that it may be hard for them to meet 

the NMFS schedule for various reasons. 
Major points of agreement/action items: 

A target annual time line for the stock assessment process was agreed upon (Appendix IX). It 

was agreed that in 1996, NMFS will attempt to meet a deadline of October 1 for completing draft 

revisions of SARs and making these draft SARs available for public comment. 

9.3 Publication issues 

The review and revision process is likely to lead to changes to some but not all of the SARs. 

There was discussion whether only SARs which have changed should be published, or whether all 

of the SARs should be published together in a single document every year. Publishing only 

revised SARs would save paper, cost, and time of the personnel responsible for writing, editing, 

and publishing the documents. Publishing all of the SARs every year, whether revised or not, will 

prevent confbsion as to which SAR is current for each stock, and keep all of the SARs in a single 

place for ease of reference and distribution. It was suggested that the SARs could be distributed in 

loose-leaf form to allow insertion of updated material. This idea was thought to be a sound idea 

for material circulated within the agency, but would be difficult to implement for documents 

circulated to the general public. Somewhat reluctantly, the participants agreed that all of the 

SARs should be published every time, as having all the most current information in a single place 

was thought to be a benefit that outweighed other considerations. 

There were several concrete suggestions for assisting this process. It was suggested that a 

summary of changes since the last publication be included in the document. It was noted again 

that the suggested appendix containing detailed information regarding fisheries, including maps of 

the location of fisheries, should also be included in this publication every year. Fisheries are 

known to be dynamic and subject to rapid changes in fishing location and methods, and so 

maintaining information as current as possible is important. Most participants felt fisheries 

information was best presented as an appendix. However, some participants felt that it may be 

most appropriate to publish the fisheries information in a supplementary document. It was noted 

that if this was done, both documents would have to be published and circulated simultaneously to 

meet the mandate of the MMPA. 

There was discussion regarding whether or not FWS and NMFS could publish their SARs 

together in the same regional documents. That would require being on the same time schedule. It 

was suggested that the SRGs write a letter to the head of both agencies to recommend this. It 

was suggested that whenever both agencies finalized their SARs, they could at that point be 

collated and released in a single final document. The workshop participants agreed that the two 

agencies should try to use a similar process for producing the SARs and that the agencies should 

push for joint publication. 

Major points of agreemedaction items: 

The majority of the workshop participants agreed that all of the SARs should be published 
every year. It was recognized as unfortunate that a certain amount of duplication and perhaps 

unnecessary waste of paper would take place, but any other scheme was thought to be potentially 

confusing. It was further noted that new estimates of mortality would likely be available every 

year for a large percentage of the stocks, and thus it will likely be good practice to revise the 

SARs for those stocks. Finally, it was agreed that keeping the SARs as up to date as possible 

would best serve NMFS and FWS constituents. It was also recommended that a last date of 

revision be printed at the top of the first page of each SAR, so it would be clear when each was 

last revised. 

NMFS and FWS should attempt to maintain the same schedule for reviewing, revising, and 

publishing the SARs, and if possible, publish the SARs in joint regional documents. 

9.4 Suggested forum for abundance and mortality estimate manuscripts 

The issue of where to publish information used to calculate abundance (and thus PBRs) and 

mortality estimates was discussed. It was recognized that in the interest of timely incorporation 

of new information, the SARs will often contain unpublished results. However, it was agreed that 

the SARs should not become a surrogate for publication of data in more appropriate places. It 

was also agreed that the agencies should attempt to limit the amount of "gray" literature that is 

used, and attempt to publish information in peer-review publications as much as possible. Also, it 

was recognized that it is .necessary to cite the primary source for information presented within the 

SARs. It was noted that the IWC annual reports were a good forum for the continual reporting 

of annual mortality estimates. It was also noted that the NOAA Technical Memorandums were an 

acceptable forum for the presentation of information not suitable for publication in a peer-review 

journal. , 

It may be appropriate to give a citation of some sort for every estimate of abundance and 

extrapolated mortality, even if these are only citations of unpublished manuscripts in progress or a 

"personal communication". The benefit of including such citations would be to try to avoid others 

from viewing the,SARs as the primary location of such estimates, and to minimize external 

citations to the SARs for such estimates. 

The methods and analyses that produce the estimates of abundance and mortality that are ysed 

in the SARs should be published in peer-reviewed scientific journals, where possible, or in a 

similar forum that is most appropriate, such as a NOAA Technical Memorandum. 

10.0 List of Fisheries 

The workshop participants agreed that a major problem in the classification of fisheries was the 

lack of information about the level of marine mammal incidental mortality in fisheries which do 

not have observer programs. The categorization process depends upon having an estimate of 

mortality, but only a small percentage of fisheries have observer programs which can provide such 

estimates. Fisheries without observer programs were categorized based on available information, 
mainly fiom direct evidence of mortalities such as those reported in logbooks, indirect evidence 

such as stranding information, and by analogy to similar fisheries which have observer data. 

Information similar to logbook data will continue to be collected, as the MMPA now requires all 

fishermen to report all marine mammal mortaIities that occur incidental to fishing operations. 

It was recognized that only through observer programs could fisheries mortality be hlly 

understood, and the main unresolved problem is how to decide when a fishery should be observed 

for the first time. In making these decisions, as much information as possible about each fishery is 

important to help determine the fisheries with the highest priorities for being observed. 

Major points of agreementlaction items: 

It is usefbl and important to include as much relevant information as possible about fisheries in 

the SARs. For fisheries without observer programs, information about the number of vessels, 

method of fishing, and area of operation are all important considerations in categorizing these 

fisheries. It would be beneficial to have this information documented in the SARs so that it would 

be subject to review by the centers, regions, and SRGs, as well as be readily available when the 

SARs are finalized. Therefore, it was concluded that the SARs should document all important 

information used to categorize fisheries in the List of Fisheries. 

It was recognized that, ideally, the List of Fisheries would be based on the incidental mortality 

information included in the SARs. However, if new sources of information become available that 

are not included in the SARs, this information may also be used.. 

11.0 Take reduction plans 

There was a short discussion on progress of take reduction teams (TRT) to date. Only four out 

of six of the TRTs had been formed, partially due to shortages in both manpower and funds, but 

also due to the lower priority of two of the teams. In prioritizing what teams needed to be formed, 

the team for Gulf of Maine harbor porpoise was given the highest priority along with the TRT 

teams for the drift gillnet fishery off each coast. The fourth team to be formed was that for 

impacts on endangered large whales (especially right whales). Lower priority was given to Alaska 

stocks because there were no stocks where incidental fisheries mortality exceeded PBR. 

Additionally, a TRT for mid-Atlantic states (take of bottlenose dolphins and harbor porpoise) was 

delayed as little evidence indicating the magnitude of mortality in specific fisheries was available, 

and therefore the TRT would not know which fisheries for which the take should be reduced, or 

by how much. 

It was noted that NMFS is not absolutely bound to follow the draft Take Reduction Plan 

submitted by a TRT, but that NMFS likely intended to implement draft plans provided they were 

consistent with the intent and provisions of the MMPA. Where consensus has not occurred, it 

was noted that NMFS will have to complete its own plan. NMFS is bound to follow a plan once it 
has been finalized. Some of the participants noted that it would be helpfbl for the TRTs to have 

confirmation fiom NMFS that indicates NMFS' intention to implement the plans developed by the 

Take Reduction Teams. 

Major points of agreement/action items: 

NMFS should c0nfini.l to the Take Reduction Teams NMFS' intention to implement the plans 

developed by the consensus of the Teams. 

12.0 Zero Mortality Rate Goal (ZMRG): proposed rule 

The proposed rule for the zero mortality rate goal was reviewed and discussed by the workshop , 

participants. The participants agreed that the proposed rule setting ZMRG as 10% of PBR was 

acceptable for most stocks. However, some felt that the rule resulted in an insignificant threshold 

that was felt to be too low in some cases, particularly for large whales listed as endangered that 

were not felt to be in imminent danger of extinction. It was felt that the PBR for endangered 

stocks was already set at a level that was thought, in one sense, to be insignificant to the recovery 

of the stock, so that 10% of that level was perhaps an overly conservative number. Additionally, 

where the total take of all fisheries is greater than 10% of PBR, individual fisheries are evaluated, 

at least initially, by whether their take is less than 1% of the PBR. Many participants questioned 

whether this number was overly conservative, although the intent is clear and well motivated to 

prevent insignificant takes fiom becoming significant in sum. 

Discussion noted that there were two points of view regarding the ZMRG for endangered stocks: 

(1) that such stocks are deserving of a higher standard because of their endangered status, and (2) 

that an insignificant level was insignificant for all stocks, including endangered stocks, and so 

endangered stocks did not need a more conservative level. 

A PBR calculated with a recovery factor of 0.5 represents a mortality level which will allow a 

population to recover to OSP, even under conditions of unknown problems with the estimates of 

abundance, mortality, R-, or stock structure. Thus, 1% of the PBR of an endangered stock is 

11500 of that mortality level that is estimated would allow recovery, and is 11100 of the mortality 

level that is estimated will not significantly delay the time to recovery. 

It was noted that the proposed definition for ZMRG is identical to the definition of a Category I11 

fishery, a rule that has already been finalized. It was agreed that it was sensible to keep this 

consistency, so it was noted that changing ZMRG would likely lead to a proposal to change the 

rules for categorizing fisheries. 

Some participants questioned whether it was the definition of ZMRG that should be discussed, or 

the recovery factor for endangered whales. It was noted that public comments went fiom the 

extremes of considering 10% of PBR too restrictive, to considering any level not restrictive 
enough unless it approached zero animals killed in a year. The language of the ZMRG section of 

the MMPA provides some indirect guidance on this issue. Section 1 18(b)(2) states "fisheries 

which maintain insignificant serious injury and mortality levels approaching a zero rate shall not be 

required to firther reduce their mortality and serious injury rate." This implies that it is possible 

for there to be a mortality level greater than zero that meets the ZMRG. 

Some participants suggested that NMFS initiate another proposal suggesting the ZMRG should 

be evaluated at 0.2% of N, for cetaceans , and 0.6% of N, for pinnipeds, except for 

endangered species which should be evaluated on a case by case basis to determine of their 

ZMRG should be set at a lower level. 

Major points of agreementlaction items: 

NMFS should reconsider finalizing the rule defining the Zero Rate Mortality Goal (which is in 

clearance within NMFS). The proposed rule defines ZMRG to be 10% of PBR, and when total 

fisheries mortality is greater than 10% of PBR, individual fisheries are said to meet ZMRG if their 

incidental mortality is less than 1% of PBR. The group agreed that ZMRG should, in principle, be 

less than PBR. A majority of the participants felt that the proposed rule was appropriate in most 

cases, and that 10% of a PBR calculated with a recovery factor of 0.5 was appropriate. However, 

some participants felt that 10% of PBR may be inappropriately low in the particular case of a 

whale stock listed as endangered which is not perceived to be in imminent danger of extinction 

(and thus perhaps inappropriately listed as endangered at this time). It was agreed that one 

possible solution would be to increase the recovery factor, and thus PBR, for such stocks where 

information warranted such an increase. The participants agreed that another solution would be 

to retain the proposed definition of ZMRG as 10% of PBR, but amend that definition to include 

the possibility of establishing ZMRG for endangered species on a case-by-case basis (to not 

exceed 10% of PBR calculated with a recovery factor of 0.5). The participants also suggested 

that a possible alternative for establishing ZMRG in a case-specific manner for endangered whales 

would be to define ZMRG as a % of N-, or as a % of the product (N,, x '/z R-), rather than as 

a percent of PBR. 

13.0 The regional Scientific Review Groups 

13.1 SRG perspectives 

The representatives of the three regional Scientific Review Groups (SRGs) gave their perspectives 

on the stock assessment process to date. As reported in Barlow et al. (1995), the SRGs had 

mostly agreed with the general guidelines used for calculating PBRs and producing the SARs. In 

general, the SRG members felt like part of process, and felt that their recommendations were 

listened to, and that the agency had often, although not always, been responsive to the SRGs. The 

SRGs felt that additional interaction between the Atlantic, Pacific, and Alaska groups would 

improve the availability of data sources. In general, the SRGs approved of the content of the 

SARs. Some SRG members thought it might be appropriate to allow more flexibility to put 
additional data into the SARs, such as more figures and tables. 

It was recognized that on some difficult issues the SRGs were not able to come to a consensus, 

but that it was useful to try to summarize conflicting points of view in the SRG meeting reports. It 

was also recognized that in spite of a lack of consensus fiom the SRG(s), some issues required 

action so that the agencies will be forced at times to make decisions without full agreement with 

the SRGs. For example, the Atlantic SRG did not reach a consensus on the proposed rule for 

ZMRG, the related 10% rule for no significant impact, or on the definition of serious injury. The 

Alaska SRG noted that their greatest difficulties came in defining stocks, and the use of correction 

factors for abundance estimates. The Pacific SRG noted that the assessment process was made 

more difficult because of mixed input from NMFS Regions, Centers, and headquarters offices and 

related internal communication problems within NMFS. There was agreement that consistency 

between NMFS and FWS was very important to the entire process. 

There was some discussion that the currently defined structure of some stocks found in California, 

Oregon, and Washington waters, and also Alaska waters may be less than ideal. There was some 

discussion that a joint meeting between the Pacific and Alaska SRGs to discuss the stock structure 

of overlapping species would be useful, which was agreed to by all of the workshop participants. 

Additionally, it was noted that within the Pacific SRG region there may be the need to reconsider 

and clam stock structure for some species between California and OregonIWashington (for 

example, the stock boundary at the California/Oregon border that is established for harbor 

porpoise and harbor seals). 

Major points of agreementlaction items: 

It was recommended that the Pacific and Alaska Scientific Review Groups hold a joint meeting 

with NMFS personnel responsible for marine mammal stock assessments fiom the Southwest, 

Northwest, and Alaska Centers and Regions to review stock structure for certain species. Certain 

species span the Pacific and Alaska SRG regions and it was felt that hrther discussion was 

necessary to clarifL stock structure between Alaska and WAIORICA (for example, killer whales). 

13.2 The role of the SRGs 

Wade presented a draft document that attempted to describe the role that the SRGs had played in 

the stock assessment process, and point the way towards the future role of the groups, as well as 

document some procedural issues regarding the functioning of the groups. The workshop 

participants agreed that the document was useful and approved it with minor modifications. In a 

post-workshop review, one SRG member suggested that the tenure of SRG members could be 

similar to Scientific advisors to the Marine Mammal Commission, which are 3 year terms that can 

be extended indefinitely. 
Major points of agreemedaction items: 

The proposed plan for the Scientific Review Groups (Appendix Vm) was considered a usefil 

guide to the role of the SRGs in the annual stock assessment process. 
Acknowledgments 

Dr. Howard Braham made available the facilities and support of the National Marine Mammal 

Laboratory for the workshop. Colleen Lee and Kathy Cunningham kindly provided support for 

many of the workshop participants. Sally Mivoch graciously provided her house for a workshop 

social event which was appreciated by all. 

Lt. Scott Hill is due a special thanks for acting as rapporteur of the workshop. The workshop 

report was greatly improved by the thorough review and comments provided by the participants 

of the workshop. The report was also greatly improved by comments from the MMPA Task 

Force and the regional Scientific Review Groups, particularly the carehl editing provided by 

Lloyd F. Lowry. Many thanks are due to Dr. Robert J. Hofinan of the Marine Mammal 

Commission for his comments on the report. Finally, Dr. Jeff Laake kindly provided the first draft, 

of what became the majority of the "Technical details" section of the PBR guidelines as well as 

Appendix IX (Statistical formulas and background). 
Appendix I. Summary of MMPA sections and regulations relevant to Stock Assessments 

This appendix summarizes parts of the written text of the U.S. Marine Mammal Protection Act 

(MMPA) that are relevant to the stock assessment process. Included here are the stated goals of 

the MMPq definitions of terms, and portions of Sec. 117 (Stock Assessments) and Sec. 118 

(Taking of Marine Mammals Incidental to Commercial Fishing Operations). Also included are 

some important interpretive definitions established by NMFS through the Federal Register. 

The Marine Mammal Protection Act was amended by Congress in 1994. These amendments 

included Sec. 1 17, which outlines the requirement that NMFS develop Stock Assessments for all 

marine mammal stocks which occur in U. S. waters and sets up three Scientific Review Groups to 

ensure that the assessments include the best available scientific information. These amendments 

also included Sec. 1 18, which replaced Sec. 1 14, and provides a new regime for managing 

incidental interactions between marine mammals and commercial fisheries. Secs. 1 17 and 1 18 are 

directly related, as the information provided in the SARs is necessary for NMFS to properly 

implement four major parts of Sec. 1 18: the List of Fisheries, Take Reduction Teams and Take 

Reduction Plans, and the progress of fisheries towards the Zero Mortality Rate Goal. In addition, 

information provided in SARs is also used to assess whether a permit can be issued to some 

commercial fisheries to incidentally seriously injure or kill endangered or threatened species (Sec. 

IOl(a)(S)(E). The overall goals of the MMPA are in Sec. 2, and definitions are provided in Sec. 

3. 

MMPA Sec. 2. Findings and Declaration of Policy (16 U.S.C. 1361') 

Management goals of the MMPA 

Sec. 2. (2) Marine mammals "...should not be permitted to diminish beyond the point at which 

they cease to be a significant functioning element in the e,cosystem of which they are a part, and, 

consistent with this major objective, they should not be permitted to diminish below their 

optimum sustainable population. Further measures should be immediately taken to replenish any 

species or population stock which has already diminished below that population." 

Sec. 2."(6) marine mammals have proven themselves to be resources of great international 

significance, esthetic and recreational as well as economic, and it is the sense of the Congress that 

they should be protected and encouraged to develop to the greatest extent feasible commensurate 

with sound policies of resource management and that the primary objective of their management 

should be to maintain the health and stability of the marine ecosystem. Whenever consistent with 

this primary objective, it should be the goal to obtain optimum sustainable population keeping in 

mind the carrying capacity of the habitat" 

'U.S.C. refers to a law established by the United States Congress. 
MMPA Sec. 3. Definitions (16 U.S.C. 1362) 

Depleted Stock 

Sec. 3. "(1) The term 'depletion' or 'depleted' means any case in which - 

(A) the Secretary, after consultation with the Marine Mammal Commission and the 

Committee of Scientific Advisors on Marine Mammals established under title II of this 

Act, determines that a species or population stock is below its optimum sustainable 

population;" 

Optimum sustainable population (0SP)- MMPA definition 

Sec. 3."(9) The term 'optimum sustainable population' means, with respect to any population 

stock, 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." 

Optimum sustainable population (0SP)-NMFS interpretive definition 

The definition of OSP above provided in the MMPA has been interpreted by NMFS (50 C.F.R. 

216.32) to mean the following: 

"Optimum sustainable population is a population size which falls within a range fiom the 

population level of a given species or stock which is the largest supportable within the ecosystem 

to the population level which results in maximum net productivity." 

"Maximum net productivity is the greatest annual increment in population numbers or biomass 

resulting fiom additions to the population due to reproduction and/or growth less losses due to 

natural mortality." 

Population stock 

Sec. 3."(11) The term 'population stock' or 'stock' means a group of marine mammals of the same 

species of smaller taxa in a common spatial arrangement, that interbreed when mature." 

Strategic stock 

Sec. 3. "(1 9) The term 'strategic stock' means a marine mammal stock - 

(A) for which the level of direct human-caused mortality exceeds the potential biological 

removal level; 

(B) which, based on the best available scientific information, is declining and is likely to be 

listed as a threatened species under the Endangered Species Act of 1973 within the 

foreseeable future; or 

2C.F.R. refers to a regulation established in the Code of Federal Regulations. 

42 
(C) which is listed as a threatened or endangered species under the Endangered Species 

Act of 1973 (16 U.S.C. 153 1 et seq.), or is designated as depleted under this Act." 

Potential Biological Removal Level (PBR) - MMPA definition 

Sec. 3."(20) The term 'potential biological removal level' means the maximum number of animals, 

not including natural mortalities, that may be removed fiom 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. 

(C) A recovery factor of between 0.1 and 1.0. " 

Net productivity rate 

Sec. 3."(26) The term 'net productivity rate' means the annual per capita rate of increase in a stock 

resulting fiom additions due to reproduction, less losses due to mortality." 

Minimum population estimate (7V-J 

Sec. 3."(27)The term 'minimum population estimate' means an estimate of the number of animals 

in a stock that - 

(A) is based on the best available scientific information on abundance, incorporating the 

precision and variability associated with such information; and 

(B) provides reasonable assurance that the stock size is equal to or greater than the 

estimate. " 

Potential Biological Removal (PBR) - NMFS' interpretive definition 

NMFS published proposed guidelines for calculating PBR, along with a notice of availability of 

draft stock assessment reports, on August 4, 1994 (59 FR 405273). The final definition for 

calculating PBR was published along with the notice of availability of final stock assessment 

reports on August 25, 1995 (60 FR 44308). The full guidelines for preparing the 1995 stock 

assessment reports was published in Barlow, J., S.L. Swartz, T.C. Eagle, and P. R. Wade, 1995 

(U.S. Marine Mammal Stock Assessments: Guidelines for Preparation, Background, and a 

Summary of the 1995 Assessments. U.S. Dep. Comer., NOAA Tech. Memo. NMFS-OPR-6, 

73 p). The MMPA defined PBR to be the product of a minimum population estimate (N,,,,,,), '/? 

the maximum net productivity rate 0, and a recovery factor (Fd. The final guidelines for 

calculating PBR defined those three terms as: 

'FR refers to the Federal Register. 
Nm= (1) the 20th percentile (lower 60% confidence limit) of the log-normal 

distribution resulting fiom a point estimate of abundance and its CV, or (2) 

a direct count of animals such as a count of hauled-out pinnipeds. 

%ux= (1) a default value of 0.04 for cetaceans and manatees and 0.12 for 

pinnipeds and sea otters, or (2) a reliable stock specific estimate can be 

used if available and accepted in a peer-review journal or accepted by a 

review groups such as a regional Scientific Review Group or the Scientific 

Committee of the International Whaling Commission. 

0.1 for stocks listed as endangered, 0.5 for stocks that are listed as 

threatened or depleted or are of unknown status if the CV of the mortality 

estimate is less than or equal to 0.3 (should be adjusted to 0.48 if CV=0.3- 

0.6, 0.45 if CV=0.6-0.8, and 0.4 if CV>0.8), and 1.0 for stocks known to 

. be within OSP. The PBR guidelines describe circumstances that allow 

hrther adjustments of the recovery factor. 

MMPA Sec. 117: Stock Assessments (16 U.S.C. 1386) 

Stock Assessment Reports (SAk) 

Sec. 1 17 (a)(l) NMFS shall ". .. prepare a draft stock assessment for each marine mammal stock 

which occurs in waters under the jurisdiction of the United States. Each draft stock assessment, 

based on the best scientific information available, shall - 

(1) describe the geographic range of the affected stock, including any seasonal or temporal 

variation in such range; 

(2) provide for such stock the minimum population estimate, current and maximum net 

productivity rates, and current population trend, including a description of the information 

upon which these are based; 

(3) estimate the annual .human-caused mortality and serious injury of the stock by source 

and, for a strategic stock, other factors that may be causing a decline or impeding recovery 

of the stock, including effects on marine mammal habitat and prey; 

(4) describe commercial fisheries that interact with the stock, including -- 

(A) the approximate number of vessels actively participating in each such fishery; 

(B) the estimated level of incidental mortality and serious injury of the stock by 

such fishery on an annual basis; 
(C) seasonal or areal differences in such incidental mortality and serious injury; 

@) the rate, based on the appropriate standard unit of fishing effort, of such 

incidental mortality and serious injury, and an analysis stating whether such level is 

insignificant and is approaching a zero mortality and serious injury rate; 

(5) categorize the status of the stock as one that either - 

(A) has a level of human-caused mortality and serious injury that is not likely to 

cause the stock to be reduced below its optimum sustainable population; or 

(B) is a strategic stock, with a description of the reasons therefor; and 

(6) estimate the potential biological removal level for the stock, describing the information 

used to calculate it, including the recovery factor." 

MMPA Sec. 118: Taking of marine mammals incidental to commercial fishing operations 

(16 U.S.C. 1387) 

Sec. 1 18 of the MMPA contains the following subsections: (a) in general, (b) zero mortality rate 

goal, (c) registration and authorization, (d) monitoring of incidental takes, (e) reporting 

requirement, (f) take reduction plans, (g) emergency regulations, (h) penalties, (i) assistance, 6) 

contributions, (k) consultation with Secretary of the Interior, and (1) definitions. A few of the 

relevant parts of Sec. 1 18 are given below. 

The goal of Sec 11 8 

Sec. 118 "(a) (I) Effective on the date of enactment of this section [April 30, 19941, and except 

as provided in section 114 and in paragraphs (2), (3), and (4) of this subsection, the provisions of 

this section shall govern the incidental taking of marine mammals in the course of commercial 

fishing operations by persons using vessels of the United States or vessel which have valid fishing 

permits issued by the Secretary in accordance with section 204(b) of the Magnuson Fishery 

Conservation and Management Act (16 U.S.C. 1824(b)). In any event it shall be the immediate 

goal that the incidental mortality or serious injury of marine mammals occumng in the course of 

commercial fishing operations be reduced to insignificant levels approaching a zero mortality and 

serious injury rate within 7 years after the date of enactment ofthis section [April 30, 20011." 

It should be noted that it is specifically stated that Sec. 118 does not govern the incidental taking 

of marine mammals in the purse seine fishery for yellowfin tuna in the eastern tropical Pacific 

Ocean or the incidental taking of California sea otters. 
The list of fisheries @.OF) - MPA definition 

Sec. 118 (c) (1) "The Secretary shall ... 

(A) publish in the Federal Register for public comment, for a period of not less than 90 

days, any necessary changes to the Secretary's list of commercial fisheries published under 

section 114(b)(l) ..., with respect to commercial fisheries that have - 

(i) fiequent incidental mortality and serious injury of marine mammals; 

(ii) occasional incidental mortality and serious injury of marine mammals; 

(iii) a remote likelihood of or no known incidental mortality and serious injury of 

marine mammals; 

(B) after the close of the period for such public comment, publish in the Federal Register a 

revised list of commercial fisheries ...; and 

(C) at least once each year thereafter.. .reexamine.. . the classification of commercial 

fisheries and other determinations required under subparagraph (A) and publish in the 

Federal Register any necessary changes." 

List of Fisheries @OF) - NMFS' interpretive definition 

Proposed and final regulations implementing Sec. 1 18 were published in the Federal Register in 

1995. The implementation of Sec. 1 18 relies on the information provided in the Stock 

Assessment Reports developed pursuant to Sec. 1 17. 

Under Sec 1 18, NMFS must classify all U.S. commercial fisheries based on the level of marine 

mammal serious injury and mortality that occurs incidental to each fishery. While all participants 

in all commercial fisheries must report incidental takes, fisheries that have a high or occasional 

level of serious injury or mortality are subject to more regulations than are fisheries that have a 

remote likelihood or no known incidental serious injuries or mortalities of marine mammals. 

Fisheries with high, occasional, or a remote likelihood of marine mammal serious injuries and 

mortalities are referred to as Category I, 11, and I11 fisheries, respectively. 

Under the old Sec. 114, the criteria used to classifjl commercial fisheries as having "high", 

"occasional", or "remote likelihood or no known" takes were based on a rate of cumulative 

marine mammal deaths (regardless of what stock of marine mammal) per 20 days. The final 

regulations implementing Sec. 1 18 defined the fishery classification criteria using a stock-specific 

approach, as the impact of fishery removals to individual stocks is likely more important than the 

total number of animals taken during an arbitrary period of time. 

The List of Fisheries, which NMFS must publish at least annually, evaluates U.S commercial 

fisheries based upon a two tiered, stock-specific approach that first addresses the total impact of 
all fisheries on each marine mammal stock and then addresses the impact of individual fisheries on 

each stock. This approach is based on the rate, in numbers of animals per year, of serious injuries 

and mortalities that occur incidental to commercial fishing relative to the Potential Biological 

Removal level (PBR) for each marine mammal stock. While the actual definitions of the fishery 

classification criteria can be found in the Federal Register notice published to announce the final 

regulations implementing Sec. 1 18, it is more convenient to consider the following approach to 

fishery evaluation: 

Tier 1: If the total annual mortality and serious injury across all fisheries that interact with 

a stock is less than or equal to 10 percent of the PBR of such a stock, then all fisheries 

interacting with this stock would be placed in Category III. Otherwise these fisheries are 

subject to the next tier to determine their classification. 

Tier ZCategory I: Annual mortality and serious injury of a stock in a given fishery is 

greater than or equal to 50 percent of the PBR level. 

Tier ZCategory II: Annual mortality and serious injury in a given fishery is greater than 1 

percent and less than 50 percent of the PBR level. 

Tier ZCategory III: Annual mortality and serious injury in a given fishery is less than or 

equal to 1 percent of the PBR level. 

Information used in the LOF includes descriptions of commercial fisheries, fishery-specific 

mortality and serious injury levels of marine mammals, and PBRs for those stocks taken in the 

fishery. 

Because information in the Stock Assessment Reports impact the List of Fisheries in two ways - 

via the PBR and the fishery-specific mortality level, changes in these values may change the 

classification of a commercial fishery. 

The regulatory requirements for Category I and II fisheries are essentially identical. Participants 

in fisheries placed in Category I or I1 must register in the Marine Mammal Assessment Program 

and pay the registration fee, and vessels must carry an observer if requested. All fishers, 

regardless of which fishery they participate in, must report incidental injuries and mortalities of 

marine mammals to NMFS within 48 hours of returning fiom a fishing trip. Aside from the 

mandatory reporting requirement, there are no further regulatory requirements for Category III 

fisheries: participants are not required to register and do not have to carry an observer if 

requested. Thus, there is an impact on the fishery if the classification changes from a 111 to a 

Category I or 11, and a corresponding decrease in regulatory requirements if a fishery changes 

fiom a Category I or 11 to a Category III. 
Zero Mortality Rate Goal - M'MPA definition 

Sec. 1 18 "(b) Zero Mortality Rate Goal- 

(1) Commercial fisheries shall reduce incidental mortality and serious injury of marine 

mammals to insignificant levels approaching a zero mortality and serious injury rate within 

7 years after the date of enactment of this section [April 30, 200 11. 

(2) Fisheries which maintain insignificant serious injury and mortality levels approaching a 

zero rate shall not be required to hrther reduce their mortality and serious injury rates. 

(3) Three years after such a date of enactment [April 30, 19971, the Secretary shall review 

the progress of all commercial fisheries, by fishery, towards reducing incidental mortality 

and serious injury to insignificant levels approaching a zero rate. The Secretary shall 

submit to ... the Senate and the ... House of Representatives a report setting forth the results 

of such review within 1 year after commencement of the review.. . . 

(4) If the Secretary determines after review under paragraph (3) that the rate of incidental 

mortality and serious injury of marine mammals in a commercial fishery is not consistent 

with paragraph (I), then the Secretary shall take appropriate action under subsection (f)." 

Note that subsection (f) describes the Take Reduction Plan process. Therefore, commercial 

fisheries not meeting the ZMRG after the review (due in 1998) will be required to have a Take 

Reduction Team formed to create a Take Reduction Plan designed to meet the ZMRG. 

Zero Mortality Rate Goal - NM. proposed interpretive definition 

Sec. 1 18 indicates that all fisheries should strive to attain the "Zero Mortality Rate Goal", 

(ZMRG) and requires that NMFS assess the progress of commercial fisheries towards this goal in 

a report initiated in April 1997 and presented to Congress by April of 1988. Congress did not, 

however, define this goal. 

A proposed definition of the ZMRG was included in the proposed implementing regulations for 

Sec. 1 18. The proposed definition published at that time was identical to the proposed definition 

of a Category 111 fishery4. The parallel definitions had the following advantages: 1) the List of 

Fisheries process would determine implicitly which fisheries had met the ZMRG, 2) the 

consideration of both individual and cumulative fishery impact to stocks would be considered in 

the ZMRG, and 3) the ZMRG would have a stock-specific approach and use PBR and mortality 

values provided through Sec. 117. In addition, the proposed definition would be based on 

measurable, quantifiable criteria and the definition would be conservative, as it would be 

synonymous with having a "remote likelihood or no known take". Using the proposed definition 

The final definition of a Category I11 fishery did not change substantially from the 

proposed definition. Thus, the Tier 1 -Tier 2 discussion of a Category 111 fishery included in the 

above List of Fisheries section is the same as the proposed definition of the ZMRG. 
for ZMRG, the information in the SARs used to determine whether a fishery should be classified 

in Category III also determines whether a fishery has met the ZMRG. 

NMFS received many comments on the proposed definition of the ZMRG. In order to evaluate 

the comments carefully, NMFS did not publish a final definition for ZMRG when the final 

implementing regulations for Sec. 1 18 were published late in 1995. The Federal Register notice 

announcing the final definition of ZMRG was removed fiom the clearance process when 

significant questions were raised during discussion about NMFS' approach at the GAMMS 

workshop in April of 1996. 

Take Reduction Plan goals - WPA definition 

Sec. 1 18 "(0 Take Reduction Plans. - 

(1) The Secretary shall develop and implement a take reduction plan designed to assist in 

the recovery or prevent the depletion of each strategic stock which interacts with a 

commercial fishery listed under subsection (c)(l)(A)(i) or (ii), and may develop and 

implement such a plan for any other marine mammal stocks which interact with a 

commercial fishery listed under subsection (c)(l)(A)(i) which the Secretary determines, 

after notice and opportunity for public comment, has a high level of mortality and serious 

injury across a number of such marine mammal stocks. 

(2) The immediate goal of a take reduction plan for a strategic stock shall be to reduce, 

within 6 months of its implementation, the incidental mortality or serious injury of marine 

mammals incidentally taken in the course of commercial fishing operations to levels less 

than the potential biological removal level established for that stock under section 117. 

The long-term goal of the plan shall be to reduce, within 5 years of its implementation, the 

incidental 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." 

Take Reduction Plans - NMFS implementation 

Under Sec. 1 18, NMFS is required to convene Take Reduction Teams (TRTs) for each strategic 

stock that interacts with a Category I or I1 fishery. Each team's primary objective is to develop a 

plan for reducing the fishery-specific incidental mortality and serious injury for each strategic 

stock. 

The coordination of the TRT process was initiated in 1995. Each team is to consist of individuals 

who represent the variety of interested or affected parties from the commercial and recreational 

fishing industry, appropriate Regional Fishery Management Councils, interstate fisheries 

commissions, academic and scientific organizations, state officials, native Alaskans or other 

Native Americans if appropriate, and environmental groups. A pilot study conducted through the 

NMFS Office of Protected Resources indicated that the parties likely to be involved in TRTs felt 
that all viewpoints would be equally represented at the table only if a professional facilitator not 

associated with NMFS conducted the TRT meetings. 

NMFS contracted a professional facilitation group with expertise in environmental dispute 

resolution in September of 1995. The contractor was responsible for compiling the team 

participants, convening six Take Reduction Teams, and facilitating their development of Take 

Reduction Plans in 1996. Take Reduction Teams have been formed or are planned for the 

following stocks or groups of stocks: Gulf of Maine harbor porpoise, Atlantic offshore cetaceans, 

Pacific offshore cetaceans, Atlantic baleen whales (humpback and right whales), Atlantic coastal 

bottlenose dolphins and harbor porpoise, and Alaska strategic stocks. 

Take Reduction Teams must develop Take Reduction Plans within 6 months of the team's 

formation. Once a plan has been developed, NMFS has 6 months in which to implement the plan. 

through publication of regulations in the Federal Register. NMFS will give the maximum weight 

possible to a plan that is developed by consensus of the TRT members. 

Stock Assessment Reports are used extensively during the TRT/TRP process, as these reports 

provide the best available information on the abundance, distribution, and fishery-specific 

incidental mortality of marine mammals. 

Incidental takes of ESA listed species - MMPA mandate 

Sec. 1 18 (a)(2) "In the case of incidental taking of marine mammals fiom species or stocks 

designated under this Act as depleted on the basis of their listing as threatened species or 

endangered species under the Endangered Species Act of 1973 (1 6 U. S.C. 153 1 et seq.), both this 

section and section' 10 1 (a)(5)(E) of this Act apply." 

Sec. 10 1 (a)(S)(E)(i) "....the Secretary shall allow the incidental, but not intentional, taking.. .in 

commercial fishery operations, of marine mammals from a species or stock designated as depleted 

because of its listing as an endangered or threatened species under the Endangered Species Act of 

1973 (16 U.S.C. 153 1 et seq.), if the Secretary, ... determines that - 

(I) the incidental mortality and serious injury fiom commercial fisheries will have a 

negligible impact on such species or stock; 

(11) a recovery plan has been developed or is being developed for such species or stock 

pursuant to the Endangered Species Act of 1973; and 

(In) where required under section 1 18, a monitoring program is established under 

subsection (d) of such section, vessels engaged in such fisheries are registered in 

accordance with such section, and a take reduction plan has been developed or is being 

developed for such species or stock." 
Negligible impact of ESA listed species - NMFS interpretive definition 

Sec. 101(a)(5)Q of the MMPA allows for the incidental serious injury and mortality of marine 

mammals listed as endangered or threatened under the ESA provided that the incidental mortality 

and serious injury will have a negligible impact on the affected species or stock. In order to 

determine whether commercial fishing activities are having a negligible impact on endangered or 

threatened species of marine mammals, NMFS evaluated the total number of all incidental serious 

injuries and mortalities due to commercial fishing for each stock, based on information included in 

the final SARs and the Environmental Assessment prepared to accompany the proposed 

implementing regulations for Sec. 1 18. 

Negligible impact, as defined in 50 CFR 228.3, is "an impact resulting from the specified activity 

that cannot be reasonably expected to , and is not reasonably likely to, adversely affect the species 

or stock through effects on annual rates of recruitment or survival." Because this definition is 

qualitative rather than quantitative, NMFS used both qualitative and quantitative guidelines to 

determine whether the take was negligible. NMFS determined that mortality and serious injury of 

the Central North Pacific stock of humpback whales and both stocks of Steller sea lions was 

negligible, and issued a general interim permit to fisheries that take only these stocks and no 

others listed as endangered or threatened. 

Citations of relevant Federal Register notices 

Proposed 1 18 regs/LOF for 1996: June 16,1995,60 FR 3 1666 

Final 1 18 regs: August 30, 1995,60 FR 45086 

Final LOF for 1996: December 28,1995,60 FR 67063 

Proposed LOF for 1997: July 16, 1996,61 FR 37035 

Final LOF for 1997: January 2, 1997,62 FR 33 

Taking of threatened & endangered 

marine mammals: August 3 1, 1995,60 FR 45399 

Draft SARs/PBR guidelines: August 4, 1994,59 FR 40527 

Final SARs/PBR guidelines: August 25,1995,60 FR 44308 

Other documents 

NMFS, 1995. Environmental Assessment of proposed regulations to govern interactions between 

marine mammals and commercial fishing operations under Sec. 1 18 of the Marine Mammal 

Protection Act. 137p. + appendices. 

NMFS, 1995. Assessment of fishery impacts on endangered and threatened marine mammals 

pursuant to Sec. 10 1 (a)(5)(E) of the MMPA. 2 1p. 
Appendix IL Guidelines for preparing the Stock Assessment Reports (PBR guidelines) 

The guidelines for preparing Stock ~ssessment Reports ("the PBR guidelines") were revised 

following discussions and recommendations of the GAMMS workshop in April, 1996. The 1996 

draft Stock Assessment Reports were prepared based on those revised guidelines. These revised 

PBR guidelines are included on the following pages. 
PBR Guidelines 25/97 

Guidelines for Preparing Stock Assessment Reports Pursuant 

to the 1994 Amendments to the Marine Mammal Protection Act 

1. General Guidelines 

Introduction 

Sec. 1 17 of the Marine Mammal Protection Act (MMPA) requires that the National Marine 

Fisheries Service (NMFS) and the Fish and Wildlife Service (FWS) develop Stock Assessment 

Reports (Reports) for all marine mammal stocks in waters under U.S. jurisdiction (U.S. waters). 

These Reports are to be based upon the best scientific information available. Reports are not 

required for stocks that have a remote likelihood of occumng regularly in U.S. waters (e.g., 

stocks for which only the margins of the range extends into U.S. waters or that enter U.S. waters 

only during anomalous current or temperature shifts). 

The MMPA requires Reports to include, among other things, information on how stocks were 

defined, a calculation of Potential Biological em oval (PBR), and an assessment of whether 

incidental fishery takes are "insignificant and approaching zero mortality and serious injury rate" 

These reports are to be reviewed annually for "strategic stocks" and for stocks for which new 

information is available, and at least once every three years for all other stocks. This document 

provides guidance for how these topics are to be addressed in the Reports. 

The MMPA provides some general guidance for developing the Reports; more detailed guidelines 

were developed at the PBR Workshop in June 1994 and were used in writing the original draft 

Reports. These original guidelines together with the draft PBR guidelines, were made available 

for public comment in August 1994 (59 FR 40527). Subsequently, the MMPA Scientific Review 

Groups met jointly in October 1994 to review the guidelines and to make recommendations for 

changes. These guidelines are based on the original PBR Workshop ,guidelines (see Barlow el al. 

1995) as modified according to public comments and on the consensus recommendations fiom the 

Scientific Review Groups, FWS, and NMFS staff. Further modifications were made based on 

recommendations of the GAMMS Workshop in April of 1996 (Wade and Angliss, 1997). It is 

anticipated that the guidelines themselves will be reviewed and changed based on additional 

scientific research and on experience gained in their application. In this regard, FWS and NMFS 

intend to convene a Stock Assessment Working Group, composed of scientists and managers 

fiom both agencies, to examine and recommend revision of the guidelines as part of the required 

1-year and 3-year revisions of the Reports. Furthermore, the guidelines in this document do not 

have to be followed rigidly; however, any departure from these guidelines must be discussed filly 

within any affected Report. 

The intent of these guidelines is to: (1) provide a uniform fiarnework for the consistent 
PBR Guidelines 2/5/97 

application of the amended MMPA throughout the country; (2) ensure that PBR is calculated in a 

manner that ensures meeting the goals of the MMPA, (3) provide guidelines for evaluating 

whether fishery takes are insignificant and approaching a zero mortality and serious injury rate; 

and (4) make the Government's approach clear and open to the public. Where the guidelines 

provided here are not incorporated into a particular Report, it was agreed that justification for the 

departure will be provided within the Report. Similarly, the Reports will explain when deviations 

are made fiom specific recommendations from the Scientific Review Groups. 

FWS and NMFS interpret the primary intent of the 1994 MMPA amendments and the PBR 

guidelines developed pursuant to the Act as a mechanism to respond to the uncertainty associated 

with assessing and reducing marine mammal mortality fiom incidental fisheries takes. 

Accordingly, this mechanism is increasingly conservative under increasing degrees of uncertainty. 

The MMPA requires the calculation of PBR for all stocks, including those that are considered 

endangered under the Endangered Species Act (ESA) and those which are managed under other 

authorities, such as the International Whaling Commission. However, in some cases allowable 

takes under these other authorities may be less than the PBR calculated under the MMPA owing 

to the different degrees of "risk" associated with, and the treatment of, uncertainty under each 

authority. Where there is inconsistency between the MMPA and ESA regarding the take of listed 

marine mammals, the more restrictive mortality requirement takes precedence. Nonetheless, PBR 

must still be calculated for these stocks, where possible, and discussed in the text of the Reports. 

As mandated in the MMPA, the PBR is calculated as "...the maximum number of animals, not 

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

that stock to reach or maintain its optimum sustainable population." Therefore, a PBR is an upper 

limit to removals that does not imply that the entire amount should be taken. 

Estimates of PBR, human-caused mortality, and classification as to whether a stock is "strategic" 

or "non-strategic" are required by Sec. 117 to be included in the Reports for all stocks of marine 

mammals in U.S. waters. However, it should be noted that the co-management of removals of 

marine mammals for subsistence purposes between the Federal government and Alaska Native 

organizations is specifically addressed in Sec. 119. In response to Sec. 119, NMFS and FWS are 

attempting to enter into cooperative agreements with Alaska Native organizations to conserve 

marine mammals and provide co-management of subsistence use by Alaska Natives. FWS and 

NMFS believe that it is appropriate to develop management programs for stocks subject to 

subsistence harvests through the co-management process provided that commercial fisheries takes 

are not significant and that the process includes a sound research and management program to 

identi@ and address uncertainties concerning the status of these stocks. Estimates of PBR and 

classification as to whether a stock is strategic will be determined fiom the analysis of scientific 

and other relevant information discussed during the co-management process. 
PBR Guidelines 2/5/97 

Definition of "Stock" 

"Population stock" is the fundamental unit of legally-mandated conservation. The MMPA defines 

population stock as "a group of marine mammals of the same species or smaller taxa in a common 

spatial arrangement, that interbreed when mature." To hlly interpret this definition, it is 

necessary to consider the objectives of the MMPA. In Sec. 2 (Findings and Declaration of 

Policy) of the MMPA it is stated that "...species and populations stocks of marine 

mammals ... should not be permitted to diminish beyond the point at which they cease to be a 

significant fbnctioning element in the ecosystem in which they are a part, and, consistent with this 

major objective, they should not be permitted to diminish below their optimum sustainable 

population." Further on in Sec. 2, it states "...the primary objective of their management should be 

to maintain the health and stability of the marine ecosystem. Whenever consistent with this . 

primary objective, it should be the goal to obtain an optimum sustainable population keeping in 

mind the carrying capacity of the environment." Therefore, stocks must be identified in a manner 

that is consistent with these goals. For the purposes of management under the MMPA, a stock is 

recognized as being a management unit that identifies a demographically isolated biological 

population. It is recognized that in practice, defined stocks may fall short of this ideal because of 

a lack of information, or for other reasons. 

Many types of information can be used to identifl stocks of a species: distribution and 

movements, population trends, morphological differences, genetic differences, contaminants and 

natural isotope loads, parasite differences, and oceanographic habitat differences. Evidence of 

morphological or genetic differences in animals fiom different geographic regions indicates that 

these populations are reproductively isolated. Reproductive igolation is proof of demographic 

isolation, and thus separate management is appropriate when such differences are found. Failure I 

to detect differences experimentally, however, does not mean the opposite. Dispersal rates, 

though sufficiently high to homogenize morphological or genetic differences detectable 

experimentally between putative populations, may still be insufficient to deliver enough recruits 

fiom an unexploited population (source) to an adjacent exploited population (sink) so that the 

latter remains a fbnctioning element of its ecosystem. Insufficient dispersal between populations 

where one bears the brunt of exploitation coupled with their inappropriate pooling for / 

management could easily result in failure to meet MMPA objectives. For example, it is common 

to have human-caused mortality restricted to a portion of a species' range. Such concentrated 

mortality (if of a large magnitude) could lead to population fragmentation, a reduction in range, or 

even the loss of undetected populations, and would only be mitigated by high immigration rates 

fiom adjacent areas. 

Therefore, carefil consideration needs to be given to how stocks are defined. In particular, where 

mortality is greater than a PBR calculated fiom the abundance just within the oceanographic 

region where the human-caused mortality occurs, serious consideration should be given to 
PBR Guidelines 2/5/97 

defining an appropriate management unit in this region. In the absence of adequate information 

on stock structure and fisheries mortality, a species' range within an ocean should be divided into 

stocks that represent defensible management units. Examples of such management units include 

distinct oceanographic regions, semi-isolated habitat areas, and areas of higher density of the 

species that are separated by relatively lower density areas. Such areas have often been found to 

represent true biological stocks where sufficient information is available. There is no intent to 

define stocks that are clearly too small to represent demographically isolated biological 

populations, but it is noted that for some species genetic and other biological information has 

confirmed the likely existence of stocks of relatively small spatial scale, such as within Puget 

Sound, WA, the Gulf of Maine, or Cook Inlet, AK. 

In trans-boundary situations where a stock's range spans international boundaries or the boundary 

of the U.S. Exclusive Economic Zone (EEZ), the best approach is to establish an international 

management agreement for the species. In the interim, if a stock is migratory and it is reasonable 

to do so, the fraction of time in U.S. waters should be noted, and the PBR for U.S. fisheries 

should be apportioned fiom the total PBR based on this fraction. In a non-migratory situation, 

the PBR for U.S. fisheries should be calculated based on the abundance estimate of the stock 

residing in U.S. waters. For situations where a species with a broad pelagic distribution which 

extends into international waters experiences mortalities within the U.S. EEZ, PBR calculations 

should be based on the abundance in the EEZ area unless there is evidence for movement of 

individuals between the EEZ and offshore pelagic areas. 

PBR Elements 

The 1994 amendments to the MMPA mandate that, as part of the Reports, PBR estimates must 

be developed for each marine mammal stock in U.S. waters. The PBR is defined as "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." PBR is, therefore, calculated as the product of three elements: the minimum 

population estimate (+I,,,,,,); half the maximum net productivity rate (0.5 R a; and a recovery 

factor (F,). The guidelines for defining and applying each of these three elements are described 

below. Further specific guidance on the calculation of PBR is provided in part 2 (Technical 

Details) of this document. 

Minimum Population Estimate (N,,,) 

N, is defined in the MMPA amendments as an estimate of the number of animals in a stock that: 

"(A) is based on the best available scientific information on abundance, incorporating the 

precision and variability associated with such information; and, 
PBR Guidelines 2/5/97 

(B) provides reasonable assurance that the stock size is equal to or greater than the 

estimate." 

Consistent with these MMPA definitions, N, should be calculated such that a stock of unknown 

status would achieve and be maintained within OSP with 95% probability. Population simuiations 

have demonstrated (Wade 1994) that this goal can be achieved by defining N,, as the 20th 

percentile of a log-normal distribution based on an estimate of the number of animals in a stock 

(which is equivalent to the lower limit of a 60% Ztailed confidence interval): 

where N is the abundance estimate and CV(N) is the coefficient of variation of the abundance 

estimate. If abundance estimates are believed to be biased, appropriate correction factors should 

be applied to obtain unbiased estimates of N. In such cases, the coefficient of variation for N 

should include uncertainty in the estimation of the correction factor. In cases where a direct 

count is available, such as for many pinniped stocks, this direct count could alternatively be used 

as the estimate of N,. Other approaches could also be used to estimate N,, if they provide the 

same level of assurance that the stock size is equal to or greater than that estimate. 

Clearly, projections of current abundance estimates become less dependable with time after a 

survey has occurred. When abundance estimates become many years old, at some point estimates 

will no longer meet the requirement that they provide reasonable assurance that the stock size is 

presently greater than or equal to that estimate. Therefore, unless compelling evidence indicates 

that a stock has not declined since the last census, the minimum population estimate of the stock 

should be considered unknown if 8 years have transpired since the last abundance survey of a 

stock. Eight years was chosen, in part, because a population that declines at 10% per year from 

carrying capacity would be reduced to less than 50% of its original abundance after 8 years. A 

10% decline per year over at least 8 years represents the greatest decline observed for a stock of 

marine mammals in U.S. waters. If N, is unknown, then PBR cannot be determined, but this is 

not equivalent to considering PBR equal to zero. If there is known or suspected human-caused 

mortality of the stock, decisions about whether such stocks should be declared strategic or not 

should be made on a case-by-case basis. Stocks for which N,, becomes unknown should not 

move from "strategic" to "not-strategic", or v.v., solely because of an inability to estimate N,. 

Maximum Rate of Increase (R,,,d 

One-half R- is defined in the MMPA as "one-half of the maximum theoretical or estimated 'net 

productivity rate' of the stock at a small population size", where the term "net productivity rate7' 

means "the annual per capita rate of increase in a stock resulting from additions due to 

reproduction, less losses due to natural mortality." 
PBR Guidelines 2/5/97 

Default values should be used for R- in the absence of stock-specific measured values. To be 

consistent with a risk-averse approach, these default values should be near the lower range of 

measured or theoretical values (or 0.12 for pinnipeds and sea otters and 0.04 for cetaceans and 

manatees). Substitution of other values for these defaults should be made with caution, and only 

when reliable stock-specific information is available on R- (e-g., estimates published in peerreviewed articles or accepted by review groups such as the MMPA Scientific Review Groups or 

the Scientific Committee of the International Whaling Commission). 

Details on rounding and precision, and on averaging more than one estimate of abundance to 

calculate N-, can be found in part 2 of this document. 

Recovery Factor (F,) 

The MMPA defines the recovery factor, F, , as being between 0.1 and 1 .O. The intent of Congress 

in adding F, to the definition of PBR was to ensure the recovery of populations to their OSP 

levels, and to ensure that the time necessary for populations listed as endangered, threatened, and 

depleted to recover was not significantly increased. The use of F, less than 1.0 allocates a 

proportion of expected net production towards population growth and compensates for 

uncertainties that might prevent population recovery, such as biases in the estimation of N, and 

R- or errors in the determination of stock structure. Population simulation studies demonstrate 

that the default F, for stocks of endangered species should be 0.1, and that the default F, for 

depleted and threatened stocks and stocks ofunknown status should be 0.5. The default status 

should be considered as "unknown". Stocks known to be within OSP (e.g., as determined from 

quantitative methods such as dynamic response or back-calculation), or stocks of unknown status 

that are known to be increasing, or stocks that are not known to be decreasing taken primarily by 

aboriginal subsistence hunters, could have higher F, values, up to and including 1 .O, provided that 

there have not been recent increases in the levels of takes. Recovery factors for listed stocks can 

be changed fiom their default values, but only after carehl consideration and where available 

scientific evidence confirms that the stock is not in imminent danger of extinction. Values other 

than the defaults for any stock should usually not be used without the approval of the regional 

Scientific Review Group, and scientific justification for the change should be provided in the 

Report. 

The recovery factor can be adjusted to accommodate additional information and to allow for 

management discretion as appropriate and consistent with the goals of the MMPA. For example, 

if human-caused mortalities include more than 50% females, the recovery factor should be 

decreased to compensate for the greater impact of this mortality on the population (or increased if 

less than 50% female). Similarly, declining stocks, especially ones that are threatened or depleted, 

should be given lower recovery factors, the value of which should depend on the magnitude and 

duration of the decline. The recovery factor of 0.5 for threatened or depleted stocks or stocks of 

unknown status was determined based on the assumption that the coefficient of variation of the 
PBR Guidelines 2/5/97 

mortality estimate is equal to or less than 0.3. If the CV is greater than 0.3, the recovery factor 

should be decreased to: 0.48 for CVs of 0.3 to 0.6; 0.45 for CVs of 0.6 to 0.8; and 0.40 for CVs 

greater than 0.8. 

Recovery factors could also be increased in some cases. If mortality estimates are known to be 

relatively unbiased because of high observer coverage, then it may be appropriate to increase the 

recovery factor to reflect the greater certainty in the estimates. Thus, in an instance where the 

observer coverage was 100% and the observed fishery was responsible for virtually all fishery 

mortality on a particular stock, the recovery factor for a stock of unknown status might be 

increased from 0.5 (reflecting less concern about bias in mortality, but continued concern about 

biases in other PBR parameters and errors in determining stock structure). Recovery factors of 

1.0 for stocks of unknown status should be reserved for cases where there is assurance that N-, 

R-, and the kill are unbiased and where the stock structure is unequivocal. 

Annual human-caused mortality and serious injury 

The Reports should contain a complete description of what is known about current human-caused 

mortality and serious injury. Information, about incidental fisheries mortality should be provided, 

including sources such as observer programs, logbooks, fisher's reports, strandings, and other 

sources, where appropriate. It is expected that this section of the Reports will include all 

pertinent information that is subsequently used to categorize fisheries under Sect. 1 18. Therefore, 

any additional information that is anticipated to be used to categorize a fishery should be provided 

here. 

In general, the most recent appropriate information about annual human-caused mortality and 

serious injury ("annual mortality") should be used. If mortality estimates are available for more 

than one year, a decision will have to be made about how many years of data should be used to 

estimate annual mortality. There is an obvious trade-off between using the most relevant 

information (the most recent data) versus using more precise information (pooling across a 

number of years). It is recognized that it is inappropriate to give one specific rule defining which 

years of data should be used, as this depends upon the quality and quantity of data available in 

each case. It is suggested that mortality estimates could be averaged over as many years 

necessary to achieve a CV of less than or equal to 0.3, but should usually not be averaged over a 

time period of more than the most recent 5 years for which data have been analyzed. However, 

information that is more than 5 years old should not be ignored if it is the most appropriate 

information available in a particular case. Also, in some cases it may not be appropriate to 

average over as many as 5 years even if the CV of an estimate is greater than 0.3. For example, if 

it is known that within the last 5 years the amount of total fishing effort has changed substantially, 

or the mortality rate per unit of fishing effort has changed substantially, it will probably be most 

appropriate to use only the most recent relevant data to most accurately reflect the current level 

of annual mortality. When mortality is averaged over years, it is recommended that an un- 
PBR Guidelines 2/5/97 

weighted average be used, as it is possible and likely that true mortality varies from year-to-year. 

A summary of incidental fisheries mortality and serious injury should be presented in a table, 

providing the name of the fishery, the current number of vessels, and for each appropriate year, 

observed mortality, estimated extrapolated mortality and serious injury and its CV, and percent 

observer coverage in that year, with the last column providing the average annual mortality 

estimate for that fishery. Information should be provided (in either the table or the text) about the 

number of mortalities and the number of injuries, and what injuries are considered "serious" (i.e., 

leading to mortality), if any. For fisheries without observer programs, information about 

incidental mortality fiom logbooks, fisher's reports, strandings, and other sources should be listed 

instead, where appropriate. Such information should be presented in brackets to distinguish it 

fiom actual estimates of total mortality in the fishery. All fisheries listed as interacting with the 

stock in the List of Fisheries should be listed in the table with as much information as possible. 

Further guidance, including a sample table, is provided in the third section of these guidelines. 

It is often difficult to determine if an injury is serious or not. Stocks which have estimated known 

mortality (not including injuries) that is less than PBR but have tota1,estimated mortalities and 

injuries that is greater than PBR (or similarly which have estimated known mortality that is less 

than 10% of PBR but have total estimated mortalities and injuries that is greater than 10% of 

PBR) should be clearly identified. Research to determine which injuries are serious will be 

necessary for such stocks. If injuries have been determined to be serious, the Report should 

indicate how this determination was made. 

There is a general view that marine mammal mortality information fiom logbook or fisher report 

data can only be considered as a minimum estimate of mortality, although exceptions may occur. 

Logbook or fisher report information can be used to determine whether the minimum mortality is 

greater than the PBR (or greater than 10% of the PBR), but it should not be used to determine 

whether the mortality is less than the PBR (or 10% of the PBR). Logbook data for fisher reports 

should not be used as the sole justification for determining that a particular stock is not strategic 

or that its mortality and serious injury rate is insignificant and approaching zero rate. 

Further guidance on averaging human-caused mortality across years and across different sources 

of mortality can be found in part 2 (Technical Details) of this document. 

Mortality Rates 

Sec. 1 18 of the 1994 MMPA Amendments reaffirmed the goal set forth in the Act when it was 

enacted in 1972 that the take of marine mammals in commercial fisheries is to be reduced to 

insignificant levels approaching zero mortality and serious injury rate, and hrther requires that 

this goal be met within 7 years of enactment of the 1994 Amendments (April 30,2001). This 

fisheries-specific goal is referred to as the "zero mortality rate goal" (ZMRG). The Stock 
PBR Guidelines 2/5/97 

Assessment Reports are not the vehicle for publishing determinations as to whether a specific 

fishery has achieved the ZMRG. A review of progress towards the ZMRG for all fisheries is 

required to be submitted to Congress by April 30, 1998. 

However, Sec. 117 of the amended MMPA does require that stock assessment reports include 

descriptions of fisheries that interact with (i.e., kill or seriously injure) marine mammals, and these 

descriptions must contain "an analysis stating whether such level is insignificant and is 

approaching a zero mortality and serious injury rate." As a working definition for the Reports, 

this analysis should be based on whether the total mortality for a stock in all commercial fisheries 

with which it interacts is less than 10% of the calculated PBR for that stock. The following 

wording is recommended: 

"The total fishery mortality and serious injury for this stock is (or is not) less than 10% of the 

calculated PBR and, therefore, can (or cannot) be considered to be insignificant and approaching 

a zero mortality and serious injury rate. " 

Status of Stocks 

This section of the Reports should present a summary of 4 types of "status": 1) legal status 

under the MMPA and ESA, 2) status relative to OSP (within OSP, depleted, or unknown), 3) 

designation of strategic or non-strategic, and 4) a summary of trends in abundance and mortality. 

The MMPA requires a determination of a stock's status as being either strategic or non-strategic 

and does not allow for a category of unknown. If abundance or human-related mortality levels 

are truly unknown (or if the fishery-related mortality level is only available from logbook data), 

some judgement will be required to make this determination. If the human-caused mortality is 

believed to be small relative to the stock size based on the best scientific judgement, the stock 

could be considered as non-strategic. If human-caused mortality is likely to be significant relative 

to stock size (e.g., greater than the annual production increment) the stock could be considered as 

strategic. In the complete absence of any information on sources of mortaIity, and without 

guidance from the Scientific Review Groups, the precautionary principle should be followed and 

the default stock status should be strategic until information is available to demonstrate otherwise. 

The MMPA requires for strategic stocks a consideration of other factors that may be causing a 

decline or impeding recovery of the stock, including effects on marine mammal habitat and prey. 

Therefore, such issues should be summarized in the Status section for all strategic stocks. If 

substantial issues regarding the habitat of the stock are important, a separate section titled 

"Habitat Issues" should be used. If data exist that indicate a problem, they should be summarized 

and included in the Report. If there are no known habitat issues or other factors causing a decline 

or impeding recovery, this should be stated in the Status section. 
PBR Guidelines 2/5/97 

References 

Barlow, J., S.L. Swartz, T.C. Eagle, and P. R. Wade. 1995. U.S. Marine Mammal Stock 

Assessments: Guidelines for Preparation, Background, and a Summary of the 1995 

Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 p. 

Dizon, A. E., C. Lockyer, W. F. Perrin, D. P. DeMaster, and J. Sisson. 1992. Rethinking the 

stock concept: a phylogeographic approach. Conserv. Biol. 6(1):24-36. 

Pemn, W. F., and R. L. Brownell, Jr. 1994. A brief review of stock identity in small marine 

cetaceans in relation to assessment of driftnet mortality in the North Pacific. Rep. Int. 

Whal. Comm. Spec. Iss. 15:393-401. 

Wade, P.R. 1994. Managing populations under the Marine Mammal Protection Act of 1994: a 

strategy for selecting values for N&, the minimum abundance estimate, and F, the 

recovery factor. U.S. Dep. Commer., NOAA, Natl. Mar. Fish. Serv., Southwest Fish. Sci. 

Cent. Admin. Rep. LJ-94-19,26 p. 

Wade, P. R. and Angliss, R. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of 

the GAMMS Workshop, April 3-5, 1996, Seattle, WA. In prep. 
PBR Guidelines 2/5/97 

2. Technical Details 

In this section, technical details are given for making appropriate calculations of PBR and 

mortality. The first section provides details on precision and rounding issues. The second section 

provides details for combining more than one abundance estimate for calculating Nm. The third 

section contains details for calculating the estimate of annual human caused mortality and its 

associated variance. 

Precision and Rounding 

The following rules on precision and rounding should be applied when calculating PBR and other 

values: 

(a) N (the abundance estimate), CV(N), R ,, and F, should be reported in the Report to 

whatever precision is thought appropriate by the authors and involved scientists, so long 

as what is reported is exactly what the PBR calculation is based on. 

(b) PBR should be calculated from the values for (a) to full precision, and not be 

calculated fiom an intermediary rounded off N-. However, N, should be reported as a 

rounded integer. 

(c) PBR and mortality should be reported with one decimal place if they are below 10. 

Otherwise, PBR and mortality should be reported as a rounded integer. 

(d) If PBR and mortality round to the same integer, the Report will report both values to 

the precision necessary to determine which is larger. This would also be done if 10% of 

PBR and mortality round to the same integer. 

Computation of Average Abundance and its Variance 

When estimates of abundance are available for more than one year or fiom more than one source 

in the same year, it may be appropriate to combine those estimates into an average abundance for 

the time period in question. It was agreed that a weighted mean was probably the most 

appropriate average to use, where the weights are equal to the inverse of the associated variance: n 

where: 
PBR Guidelines 2/5/97 

The variance of a weighted mean of several abundance estimates is calculated as: 

var (a) 

Finally, the variance is parameterized as a CV in the provided equation for calculating N-. The 

CV is calculated as: 

Computation of Average Human-Caused Mortality and its Variance 

When estimates of human-caused mortality and serious injury (called here "mortality") are 

available for more than one year and/or from more than one source, such as a fishery, it is 

necessary to calculate an estimate of the mean annual mortality along with its associated variance 

(or CV). The following section provides guidelines for doing this. For convenience, the section 

refers to averaging the incidental by-catch of fisheries, but the guidelines apply equally well to 

estimates of human-caused mortality from other sources. 

Calculatine the overall mean annual bv-catch 

First, it was agreed that it was most appropriate for the bycatch estimates from a fishery to be 

averaged UN-WEIGHTED across years, as the true bycatch might be different in each year, and 

thus is not stationary. This is just the simple average of the available estimates of by-catch. If 

estimates are available fiom more than one fishery, a mean annual by-catch fiom each fishery 

should be calculated first, and then the annual mean from each fishery should be summed to 

calculate an overall estimate of the mean annual by-catch. 

Calculatine the coefficient of variation {CV) of the mean annual bv-catch of a single fishery 

There are two potential methods for calculating the CV or variance of the mean annual by-catch 

of a single fishery. Method 1 involves using standard statistical formulas for combining the 

variances of the individual yearly by-catch estimates (assuming they are available). Method 2 

involves estimating the variance empirically from the 2-5 years of point estimates of by-catch, 

which is done by calculating the standard deviation of the 2-5 mortality estimates and dividing it 

by the square root of n, where n is the number of years available. Both methods are valid. 

However, two points favor Method 1. 

First, because the true bycatch might be different in each year, and thus is not stationary, 

estimating the variance using Method 2 above could over-estimate the true variance of the 

estimates of bycatch, and this positive bias would be related to how much the bycatch truly varied 

from year to year independent of observation error. 
PBR Guidelines 2/5/97 

Second, Method 1 is likely to give a more precise estimate of the variance because it has more 

degrees of fieedom. Using Method 2 involves estimating the variance fiom a sample size ofjust 

2-5, and ignores the information that is known about the precision of each individual estimate. 

Obviously, Method 2 is the only method that can be used if there are no estimates of the variance 

of the bycatch estimates available. Method 1 is the recommended method if the estimates of bycatch in each year do have an estimated variance (or CV). 

lwud.l 

Table 1 outlines the computations needed for estimates of average by-catch mortality by f fisheries 

operating over n years. Table 2 gives an example computation for f=3 fisheries operating over a 

horizon of n=3 years and all of the estimates are non-zero. Most variance estimators will provide 

an estimate of 0 for the variance when the estimated mortality is zero; however, the true variance 

is non-zero. In this case, a more realistic estimate of the variance can be developed by averaging 

the variances for those years which have a positive variance. The variance computations in Table 

1 are simply modified by dividing by the square of the number of years with a non-zero variance. 

The computation of the average is unaffected with the zero included in the average (Table 3). In 

certain circumstances a fishery may have been operating but was not monitored for mortality. 

Missing estimates should be dropped both fiom the calculation of the average and the variance 

(Table 4). 

lmhKL2 

In Method 2 the only change is in how the variance is calculated for the estimate of average bycatch mortality for each fishery over n years. In Method 2 the variance of the average by-catch is 

estimated empirically from the several point estimates of by-catch available fiom different years. 

This is done by calculating the variance of those estimates and dividing it by n, where n is the 

number of years used in calculating the average: 

The above formula would thus be substituted for the formula for var(m,.) presented in Table 1. 

The second step of combining variances across fisheries is identical to Method 1. 

PBR Guidelines 2/5/97 

Table 2 Example computation of average mortality and its variance for 3 fisheries over 3 years. 

Year 

Fishery 1 2 3 Average 

1 m 10 3 19 10.67 

v 4 2 8 1.56 

2 m 2 13 6 7.00 

v 2 14 4 2.22 

3 m 6 33 5 14.67 

v 8 23 4 3.89 

Total m 32.33 

Table 3. Example computation of average mortality and its variance for 3 fisheries over 3 years when some estimates 

are zero. 

Year 

Fishery 1 2 3 Average 

1 m 10 0 19 9.67 

v 4 0 8 3 .OO 

2 m 2 13 6 7.00 

v 2 14 4 2.22 

3 m 0 0 5 1.67 

v 0 0 4 4.00 

Total m 18.33 

Table 4. Example computation of average mortality and its variance for 3 fisheries 'over 3 years when some estimates 

are zero and others are missing. 

Year 

Fishery 1 2 3 Average 

1 m 0 19 9.50 

v 0 8 8.00 

2 m 2 6 4.00 

v 2 4 1 .so 

3 m 0 0 5 1.67 

v 0 0 4 . 4.00 

Total m 15.17 
PBR Guidelines 2/5/97 

3. Descriptions of U.S. commercial fisheries 

Fisheries table in each stock assessment report 

Sample incidental fisheries mortality table to be included in stock assessment reports. Each 

fishery noted as interacting with a stock should be included in the table, even iflittle information is 

available. Information on the number of incidental injuries and which injuries should be 

considered serious should be provided in either the table or the text, if appropriate. See 

discussion in 5.2 of Wade and Angliss (1997). 

Table 5. Summary of incidental mortality of stock - due to commercial fisheries fiom 1990 through 1994 and 

calculation of the mean annual mortality rate. Mean annual mortality in brackets represents a minimum estimate fiom 

logbooks or MMPA reports. 

'Note -- numbers indicated with an asterisk are optional -- dB< 

Current 

Fishery 

Name ' 

:s have been expressed in dill 

Mean 

Annual 

Mort. 

14 

(0.32) 

2 

(0.24) 

1.4 

(0.15) 

14.5 

(0.42) 

3 1.9 

(O.=) 

[2.75]' 

[> .5]' 

[2 11' 

z 34.2' 

Range of 

Observer 

Coverage 

53-74% 

Observed 

Mort. (in 

given yrs.) 

13, 13, 15, 

4,9 

Estimated 

Mort. (in 

given y rs.) 

13, 19,21, 

6, 1 1 

groundfish trawl fishery 1 1 90-94 1 490 obs 

data 

groundfish trawl fishery 2 90-94 490 obs 

data 

longline fishery 1 90-94 1064 obs 

data 

drift gillnet fishery 1 90-9 1 509 obs 

data 

Observer program total 

II set gillnet fishery 1 1 90-93 1 I20 I log 

book 

set gillnet fishery 2 90-93 1187 1% 

book 

longline fishery 2 94 213 mmpa 

reports 

Minimum total annual 

mortality - -- 

'~he name should be consistent with fishery names in the List of Fisheries. 
PBR Guidelines 2/5/97 

General information about a fishery (not stock-specific) 

Information to ~rovide 

As discussed at the GAMMS workshop, information on U.S. commercial fisheries should be 

included either within each SAR, as an appendix, or as a companion document. Information on 

U.S. commercial fisheries was collected during the preparation of the Environmental Assessment 

for the proposed regulations implementing Sec. 1 18 (NMFS, 1994). The following information, 

which was provided for each fishery whenever possible, has direct relevance to managing 

incidental serious injuries and mortalities of marine mammals: 

Fishery naw: A description of those fisheries that are classified in Category I or II in the LOF, 

and those fisheries in Category 111 that have experienced incidental mortality and serious injury of 

marine mammals should be provided. The Category of the fishery in the List of Fisheries should 

be specified in the text. 

flumber of permitholders: NMFS is required by the MMPA to provide the number of 

permitholders in each fishery included in the List of Fisheries. Information on the number of 

permitholders in federal fisheries can often be found in recent amendments to Fishery 

Management Plans. Information on fisheries that occur within state waters but are managed via 

an interstate commission may be found in interstate fishery management plans. Information on 

state fisheries that are managed by individual states can typically be found by contacting the state 

office responsible for licensing commercial fishing vessels. 

Number of active ~ermitholders: Because not all licensed commercial fishers participate actively 

in each fishery, the number of active permitholders may be different than the number of actual 

permitholders in a fishery. This is particularly true for fisheries that operate in state waters. 

Total effort: Provide an estimate of the total fishing effort, in the number of hours fished, for each 

fishery. This information is typically available only for fisheries that are both federally managed 

and observed. 

omaphic ranec: Provide a description of the geographic range of the fishery. The description 

of the geographic range of the fishery should include any major seasonal changes in the . distribution of the fishing effort. 

Seasons: Describe the seasons during which the fishery operates. 

Gear twe: Describe the gear type used in the fishery as specifically as possible. Include mesh 

size, soak duration, trawl type, depth of water typically fished, etc if the information is available. 

Rermlations: Indicate whether the fishery is managed through regulations issued by the federal 

government, interstate fishery commissions, individual states, or treaty. 
PBR Guidelines 2/5/97 

Management type: Indicate what types of fishery management techniques are used to manage the 

fishery. Some examples include limited entry, seasonal closures, and gear restrictions. 

Comments: Include any additional relevant information on the fishery. 

Sources of information on U.S. commercial fisheries 

The sources of information provided in the Environmental Assessment are fisted in the 

bibliography and on page A21 and A22. In general, good sources of current information on a 

particular fishery include recent amendments to federal Fishery Management Plans or interstate 

fishery management plans, and annual reports of Fishery Management Councils or interstate 

fishery management commissions. Some information may be found on federally managed fisheries 

in the recent issue of Our Living Oceans (NMFS, 1995). In addition, each Fishery Management 

Plan has a individual who is the point of contact in the NMFS Regional Offices. 

Much information on the geographic ranges of fisheries, seasonal changes in the distribution of 

effort, etc, was obtained by interviewing key state fishery management personnel. Telephone 

numbers for Fishery Management Councils, various state Marine Fisheries Cornmissions, and 

various state Fish and Wildlife Commissioners can be found in the most recent Conservation 

Directory published by the National Wildlife Federation (1-800-477-5560; cost per copy is $25.00 

+ $3.50 shipping and handling, please allow 3-6 weeks for delivery -- OR request a copy of the 

relevant pages fiom FPR2). 
PBR Guidelines 2/5/97 

4. Recommendations of the GAMMS Workshop 

The following recommendations pertaining to the Stock Assessment Reports (SARs) were made 

by the participants of the Guidelines for Assessing Marine Mammal Stocks (GAMMS) Workshop 

held 3-5 April, 1996. Where appropriate, these recommendations were explicitly incorporated 

into the current PBR guidelines. Numbers refer to the applicable section of the workshop report. 

4.5 Discussion on the definition of stocks 

Most of the currently defined stocks are appropriate. Some workshop participants expressed 

concern about a few particular cases, such as having only one stock of harbor porpoise in Alaska. 

For MMPA management purposes, a stock is a management unit that in the best case delineates 

a demographically isolated biological population. It is recognized that delineated stocks often fall 

short of that ideal because of a lack of information and for other reasons. 

The revised "definition of stocks" section drafted by a working group at the workshop is usehl 

and helps clarify the intent of stock structure decisions, and should be incorporated into the PBR 

guidelines. 

4.7 Incomplete survey of a stock's range 

The only way of resolving uncertainty in abundance when a stock's range has not be completely 

surveyed is to improve the abundance estimate by doing more extensive surveys. Extrapolations 

of observed densities of animals into areas not surveyed would be usehl for survey planning, but 

should not be used for calculating PBRs. Similarly, it is unacceptable to assume that the point 

estimate of abundance (rather than the 20th percentile) fiom the surveyed area can serve as a 

minimum abundance estimate for the entire stock. 

In some cases, because abundance is thought to be under-estimated, it would be usehl to 

calculate the minimum population size necessary to sustain the estimated level of fisheries 

mortality. This information could optionally be included in the SARs. 

Each SAR should include a map showing the area within which the survey took place that led to 

the estimate of abundance. This map could, if appropriate, also include the survey tracklines, 

sightings of the stock during the survey, and the distribution of the stock outside the survey area. 

It was recognized that some abundance methodologies are not dependent upon surveys of the 

stock's entire range, and therefore this recommendation may not be appropriate in all SARs. For 

stocks for which transect surveys have not been done, it may be appropriate to include 

information about the stock's distribution fiom other sources, such as photo ID locations or other 

types of sighting information. 

5.1 Definition of mortality and serious injury 

NMFS should circulate the definition of injury that is included in the regulations. To address 
PBR Guidelines 2/5/97 

this, the following is the regulatory text defining "injury" and "serious injury". Injury is defined 

specifically in the C.F.R. (final regulations for implementation of Section 1 18): 

"Injury means a wound or other physical harm. Signs of injury to a marine 

mammal include, but are not limited to, visible blood flow, loss of or damage to an 

appendage or jaw, inability to use one or more appendages, asymmetry in the 

shape of the body or body position, noticeable swelling or hemorrhage, laceration, 

puncture or rupture of eyeball, listless appearance or inability to defend itself, 

inability to swim or dive upon release fiom fishing gear, or signs of equilibrium 

imbalance. Any animal that ingests fishing gear, or any animal that is released with 

fishing gear entangling, trailing, or perforating any part of the body will be 

considered injured regardless of the absence of any wound or other evidence of an 

injury. " 

"Serious injury means any injury that will likely result in mortality." 

Direct research on the survival of animals injured in fisheries would likely be the best (or even 

only) way to adequately define the difference between a serious injury (one leading to mortality) 

and a non-serious injury. 

If animals are injured in a fishery, but a determination has not been made as to whether the 

injuries are serious or not, then estimates of the number of animals injured should be presented in 

the SARs along with the estimated mortality. This information could be provided in the fisheries 

table (see below) or within the text of the SAR. Where such an estimate of injury, when added to 

the estimate of mortality, is responsible for making the sum greater than PBR or 10% of PBR, this 

should be identified in the SAR. 

5.2 Presentation of information about human-caused mortality in the SARs. 

A new section should be added to the PBR guidelines which gives guidance about how to 

present information about annual mortality and serious injury (previously, no guidance was given). 

The PBR guidelines should explicitly state that the information in the SARs is expected to 

include all pertinent information about incidental mortality that will subsequently be used to 

categorize fisheries in the List of Fisheries. 

A table summarizing incidental fisheries mortality and serious injury should be added to the 

SAR. Where "serious injury" is distinguished fiom "mortality" in a fishery, both numbers and 

their sum should be presented. All fisheries that are noted in the List of Fisheries as interacting 

with each stock should be in the table. 

A sample table for reporting information about incidental mortality and serious injury in 

commercial fisheries should be created and distributed to persons responsible for revising the 
PBR Guidelines 2/5/97 

SARs. 

5.3 The description of fisheries in the SARs 

Additional information describing the geographical description of fisheries was both of great 

value and mandated by the MMPA. Where appropriate, an appendix or supplement should be 

added to the SARs that includes maps showing the location of fisheries with incidental mortality 

of concern. If possible, the maps should show where the fishery operates (i.e., the estimated 

distribution of fishing effort). If the exact location of fishing effort is not known, a rough 

indication of fishing areas and ports used by the fishery would be usehl. For observed fisheries, it 

would also be useful to have a map indicating where fishing activities were observed, and the 

location of observed marine mammal mortalities and injuries. 

It was recommended that the NMFS Office of Protected Resources circulate a list of what 

fishery information would be usehl to include, and to provide the text of the Environmental 

Assessment if it would be helphl to those collecting fishery information. 

6.0 Habitat issues 

A statement about habitat issues should be included in the Status section of the SARs, or, if 

needed, in a separate section titled "Habitat issues". If data exist that indicate a problem, they 

should be summarized and included in the SARs. If there are no known habitat issues for a stock, 

that this should be explicitly stated, as consideration of habitat issues are mandated by the act. 

8.0 Calculation of PBRs 

The current PBR guidelines on calculating PBR are adequate and sufficient in most areas. It is 

recommended that minor changes to some sections of the guidelines be made. These changes are 

covered in the sections below. 

8.1 Time period from which to use data on abundance and mortality 

Confidence in the reliability of an abundance estimate declines with age. Therefore, estimates 

older that 8 years should not be used to calculate PBR. This is necessary to meet the requirement 

in the MMPA that Nmin represent a level for which there is reasonable assurance that the true 

population is larger. The consequence of not being able to calculate a PBR for such stocks is that 

PBR is unknown (not that PBR equals zero). A decision as to whether such stocks are strategic 

or not will be jointly decided case-by-case by NMFS or FWS and by the SRGs. This 

recommendation replaces the guidelines stating that recovery factors were "ratcheted down" as 

abundance estimates became older than 5 yrs. 

An unweighted mean should be used when averaging mortality over more than one year. 

A section giving guidance on what mortality estimates to use was drafted and added to the 

revised PBR guidelines. 
PBR Guidelines 2/5/97 

8.2 Combining estimates and Calculating CV of a product 

A new section was drafted to be added as a technical supplement to the PBR guidelines. 

8.3 Problems associated with species which are difficult to identifj 

The collection of biopsy samples and voucher material is strongly encouraged, particularly for 

species without such materials and other hard to identifjl species. In particular, voucher material 

is needed for these species ofMesoplodon beaked whales: M. carlhubbsi, M. gznkodens, M. 

densirostris, M. hectori, M. europaeus, M. mirus. 

National experts should be encouraged to revise a field guide to the identification of beaked 

whales and Kogza spp. 

8.5 Changing recovery factors from default values (particularly endangered whales) 

Clarification should be added to the guidelines that flexibility exists to change default recovery 

factors (such as for endangered species) on a case-by-case basis with carefbl consideration of the 

information available for each stock. Such changes should be made in consultation with, and 

when appropriate should reflect the recommendations made by, the NMFS or FWS center(s) and 

region(s) responsible for the SARs and the relevant Scientific Review Group. Such changes 

should be justified by credible scientific evidence. It was acknowledged that this was a complex 

and difficult issue; therefore the evidence used to support any change to the recovery factor of an 

endangered species should be carefilly documented in the SAR. 

8.7 Correction factors for pinniped counts. 

Caution should be used when considering the application of correction factors for abundance 

estimates to stocks in other locations, or to other species. Additionally, caution should be used in 

applying correction factors in different situations in the same location (e.g., tidal state, season, 

time of day, etc.). The use of estimated correction factors without associated variance estimates 

is to be avoided. Where the use of such a correction factor is considered unavoidable, it is 

suggested that a default CV should be used that is greater than the 0.0 currently assumed for 

several stocks. 

9.1 Review and Revision 

A section would be added to the PBR guidelines to describe the annual review, revision, and 

publication of the SARs. 

The review process leading to revision recommendations should be a joint consultation between 

the appropriate NMFS personnel (at both Centers and Regions) and the SRGs. 

The SARs should be revised whenever new information becomes available on abundance, 

mortality, &, or stock structure. It is best to revise the SARs whenever new information is 

available, even if the new information does not affect whether the stock is strategic. Although it is 
PBR Guidelines 2/5/97 

anticipated that new estimates of mortality from a fishery observed for several years will often not 

change the classification of a stock, NMFS and FWS should still be encouraged to publish a 

revised SAR even if the only new information is a new estimate of mortality, in the interest of 

keeping the SARs as up to date as possible. 

9.2 Annual schedule for revising and publishing the SARs 

A target annual time line for the stock assessment process was agreed upon. It was agreed that 

in 1996, NMFS will attempt to meet a deadline of October 1 for completing draft revisions of 

SARs and making these draft SARs available for public comment. 

9.3 Publication issues 

The majority of the workshop participants agreed that all of the SARs should be published 

every year. It was recognized as unfortunate that a certain amount of duplication and perhaps 

unnecessary waste of paper would take place, but any other scheme was thought to be potentially 

confusing. It was hrther noted that new estimates of mortality would likely be available every 

year for a large percentage of the stocks, and thus it will likely be good practice to revise the 

SARs for those stocks. Finally, it was agreed that keeping the SARs as up to date as possible 

would best serve NMFS and FWS constituents. It was also recommended that a last date of 

revision be printed at the top of the first page of each SAR, so it would be clear when each was 

last revised. 

NMFS and FWS should attempt to maintain the same schedule for reviewing, revising, and 

publishing the SARs, and if possible, publish the SARs in joint regional documents. 

9.4 Suggested forum for abundance and mortality estimate manuscripts 

The methods and analyses that produce the estimates of abundance and mortality that are used 

in the SARs should be published in peer-reviewed scientific journals, where possible, or in a 

similar forum that is most appropriate, such as a NOAA Technical Memorandum. 

10.0 List of Fisheries (Section 1 18) 

It is useful and important to include as much relevant information as possible about fisheries in 

the SARs. For fisheries without observer programs, information about the number of vessels, 

method of fishing, and area of operation are all important considerations in categorizing these 

fisheries. It would be beneficial to have this information documented in the SARs so that it would 

be subject to review by the centers, regions, and SRGs, as well as be readily available when the 

SARs are finalized. Therefore, it was concluded that the SARs should document all important 

information used to categorize fisheries in the List of Fisheries. 

It was recognized that, ideally, the List of Fisheries would be based on the incidental mortality 

information included in the SARs. However, if new sources of information become available that 

are not included in the SARs, this information may also be used. 
Draft February 13,1997 

Appendix III. GAMMS workshop agenda, April 3-5, Seattle, WA 

............................................................................................................... 

Wednesday: 9:OO-520 pm ............................................................................................................... 

Introduction 

(5 min) Welcome (Balsiger) 

(5 min) Introduction (Wade) 

(20 min) Logistics, Agenda, and Ground-rules (Angliss) 

Background information presentations 

(5 Final List of Fisheries categorization rule (Angliss) 

(5 min) Final ZMRG rule (Eagle) 

(20 min) Strategic stocks: brief review of what is happening with Take Reduction Teams 

(Beach/Lagomarsino/Wang) 

(30 min) SRG perspectives (Brault/Heyning/Straley/Hild) 

(15 min) Break (10:30-10:45) 

Stock structure 

(15 min) Introduction: what sort of stock structure should we expect? (Presentation: 

Heyning) (30 min) Review of relevant types of information available for making stock decisions, 

especially genetic data (Presentation: Dizon) 

(30 min) 

(30 min) 

(70 min) 

(30 min) 

(60 min) 

(30 min) 

(20 min) 

(10 min) 

(20 min) 

The stock decision process (Presentation: Taylor) 

Presentation and exercises running a simulation model showing the consequences 

of stock structure decisions. Participants are encouraged to bring a lap-top 

PC if possible (group exercise: Taylor) 

Working Lunch (12:30-1:40) 

Review of available and needed data for making stock decisions (Presentation: 

Chivers). 

Should the "Definition of Stocks" section be revised, supplemented, or left alone? 

Are the current guidelines adequate? (Discussion: DeMaster) 

Discussion of specific problems in defining stocks for trans-boundary species 

(Discussion: Waring) 

Break (3:30-350) 

Do we need a very specific description of the geographic range of each stock in 

the SARs (i.e., define specific borders of stock area) (Discussion: group) 

How should stocks be reviewed, would review at a national level help for stocks of 

difficult species? (Discussion: group) 

Fisheries, mortality estimates and other information 
Draft February 13, 1997 

(30 min) Definition of "mortality and serious injury" (Discussion: Angliss) 

(10 min) Proposed fisheries table to be included in each SAR (Discussion: Wade) 

(20 min) Geographic description of fishing effort and incidental mortality for category I and 

I1 fisheries: a proposed supplement to the SARs (Discussion: 

WadeIAngliss) 

5:20pm Social and Dinner 

After dinner Working groups on stock structure if necessary 

Thursday: 9:OO-5:30pm 

(30 min) Working group report and discussion 

(20 min) Habitat and other issues for strategic stocks: suggestions for meeting the required 

description of other factors that may be causing a decline or impeding 

recovery of a strategic stock, including effects on marine mammal habitat 

and prey (Discussion: Eagle) 

PBR calculations: monitoring over multiple years 

(30 min) Sampling Implications of the Performance of Marine Mammal By-Catch 

Management Based on "Potential Biological Removals" (Presentation: 

Palka) 

(30 min) Detecting mortality levels that will lead to depletion, with implications for 

monitoring frequency and interpretation of the mortality/PBR ratio 

(Presentation: Wade) 

(20 min) Break (1050-11:lO) 

(30 min) Monitoring kill of marine mammals computer demonstration (Group exercise: 

Wade) 

(10 min) Combining estimates: weighted means and their CVs (Presentation: Palka) 

(20 min) "Aging" of PBR when no new data is available (Presentation and discussion: 

Hobbs) 

(70 min) Lunch (12:OO-1: 10) 

(40 min) Guidelines for combining abundance and mortality estimates, and for monitoring 

frequency (Discussion: Laake) 

PBR Calculations: Detailed Guidelines 

(10 min) Calculating the CV of a product (e.g., combining the CVs of an abundance 

estimate and its associated correction factor (Presentation and discussion: 

Laake) 

(30 min) Calculating PBRs for multiple species/stock complexes (such as beaked whales) 

(Discussion: WaringBarlow) 

(30 min) Calculating PBR for declining populations (Discussion: DeMaster) 
Draft February 13, 1 997 

(20 min) Break (3 : 10-3 :30) 

(30 min) Recovery factors for endangered whales (Discussion: BeachLagomarsino) 

(30 rnin) Correction factors for deep-diving whales (Presentation and discussion: Barlow) 

(30 min) (maybe) Correction factors for pinnipeds, haul-out counts and pup counts 

(Mathews paper) 

(30 min) Free time for working groups, or to catch up on business 

5:30pm Dinner 

After dinner Working groups if necessary 

................................................................................................................ 

Friday: 8: 00-12: 00am 

- -~ ---------- ~ ----------- ~ -- 

(30 min) Working groups report and discussion 

The annual process for assessing marine mammal stocks 

(40 min) Annual schedule for the stock assessment process (Presentation and discussion: 

WadeIAngliss) 

(20 min) Break (9:30-950) 

(40 min) Review and Revision rules (Discussion: Wade). 

(10 min) Publication issues (Discussion: Eagle) 

(10 min) Target guidelines for the availability of reports on which the SAR estimates are 

based 

(20 min) SRG role (Discussion: Wade) 

Wrap-up 

(30 min) Discussion of assignment of krther tasks, including workshop report. 

1 1 :40am End 
Draft February 13, 1997 

Appendix TV. GAMMS workshop documents 

Working Papers 

Taylor, B. 1995. Defining "populations" to meet management objectives. NMFS-SWFSC Ad 

Min LJ-95-03 (also in press as NOAA Tech. Rep.). GAMMS-WP-1 

Taylor and Dizon. 1996. The need to estimate power to link genetics and demography for 

conservation. Conservation Biology. In press. GAMMS-WP-2 

Draft annual schedule for the stock assessment process (WadeIAngliss). GAMMS-WP-3 

Draft Scientific Review Group Plan (Wade). GAMMS-WP-4 

Atlantic Scientific Review Group report excerpt. GAMMS-WP-5 

Alaska Scientific Review Group report excerpt and letter fiom L.Lowry. GAMMS-WP-6 

Pacific Scientific Review Group excerpt. GAMMS-WP-7 

Mathews, E.A. Marine mammal stock assessment reviews: comments on the use of correction 

factors in calculations of N-. GAMMS-WP-8 

Palka, D. and Smith, T Sampling Implications of the Performance of Marine Mammal By-Catch 

Management Based on "Potential Biological Removals". GAMMS-WP-9 

Wade. The probability of correctly detecting a level of human-caused mortality great enough to 

cause the depletion of a marine mammal population. GAMMS-WP-10 

Background Papers 

Wade. Calculating sustainable thresholds for the human-caused mortality of cetaceans and 

pinnipeds. To be submitted to Marine Mammal Science. GAMMS-BP- 1 

Lerczak, Hobbs, and DeMaster. Incorporating uncertainty in maximum kill levels for long-lived 

vertebrates. Submitted to J. Wild. Manag. GAMMS-BP-2 

Mange1 et al. 1996. Principles for the conservation of wild living resources. Ecological 

Applications. In press. GAMMS-BP-3 

Taylor, Chivers, and Dizon. Using geneteic data to define management units for marine 

mammals. Submitted as NOAA Tech. Rep. GAMMS-BP-4 

Pemn and Brownell. 1994. A brief review of stock identity in small marine cetaceans in relation 

to assessment in driftnet mortality in the North Pacific. Rep. Int. Whal. Comrnn (Spec Iss 

15):393-401. GAMMS-BP-5 

Barlow, Swartz, Eagle, and Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines 

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. 

Comer., NOAA Tech. Memo. NMFS-OPR-6,73p. GAMMS-BG-6 (not provided to 

NMFSISRGs as they should already have one - will be available at workshop) 

Gerrodette, T. Draft Ad Min report. A comparison of mortality limits for eastern tropical Pacific 

dolphins under the declaration of Panama and under Potential Biological Removal (PBR) 

management. GAMMS-BP-7 
Draft February 13, 1997 

Appendix V. GAMMS workshop list of participants 

NMFS 

Doug Beach (NER) 

Gordon Waring (NEC) 

Debra Palka (NEC) 

Kathy Wang (SER) 

Larry an sen (SEC) 

Irma Lagomarsino (SWR) 

Jay Barlow (SWC) 

Susan Chivers (SWC) 

Andy Dizon (SWC) 

Barbara Taylor (SWC) 

Brent Norberg (NWR) 

Bridget Mansfield (AKR) 

Linda Shaw (AKR) 

Douglas DeMaster (AKC) 

Scott Hill (AKC) 

Rod Hobbs (AKC) 

Jeff Laake (AKC) 

Tom Loughlin (AKC) 

Robyn Angliss (FPR) 

Tom Eagle (FPR) 

Paul Wade (FPR) 

Non-NMFS 

Carl Benz (FWS-Ventura) 

Carol Gorbics (FWS-Anchorage) 

Judy Zeh (Mar. Mam Commission) 

Solange Brault (Atlantic SRG) 

John Heyning (Pacific SRG) 

Jan Straley (Alaska SRG) 

Carl Hiid (Alaska SRG) 

Joe Blum (Alaska SRG) 
Draft February 13,1997 

Appendix VI. GAMMS workshop working group meeting: definition of mortality and 

serious injury 

. . Partici~antx 

Joe Blum 

Doug Beach 

Larry Hanson 

Solange Brault 

Bridget Mansfield 

Kathy Wang 

Debbie Palka 

Robyn Angliss 

The working group recommended the following: 

b Instead of deciding which injuries are serious, assign a probability that an injury will be 

serious to each injury as defined in the 118 regulations. b Conduct research to better determine the probability that an injury would be serious. 

Current studies that could address this issue are 1) photographs of scars collected during 

photo-id studies, 2) retrieval and sampling of carcasses resulting from the drift gillnet 

fishery (NEC study). b Include the following table in each SARS: 

If killed plus injured is > than PBR, the SAR should make a general statement about the 

importance of the number of injured animals in a management context. 

Fishery 

Fishery X 

Fishery Y 

b What is the most appropriate forum to address the definition of serious injury? 

-- GAMMS Workshop 

-- MMPA Task Force 

-- Separate workshop: HQ funded? 

-- goals of workshop: 1) information transfer 

2) definition of serious injury 

5The working group recommended that this table be included. Recommendations 

endorsed by the GAMMS workshop participants are detailed at 5.1 and 5.2 of the workshop 

report. 

# killed 

observedl 

extrapolated 

observed 

extrapolated 

# injured 

describe injuries 

# released alive & 

uninjured 
Draft February 13, 1 997 

3) research ideas 

4) improve field data collection 

-- observer data consistency 

-- stranding data 

-- workshop should be held between late summer - mid-September to allow 

for research priorities to be accounted for in the 1997 FY budget cycle 
Draft February 13, 1 997 

Appendix MI. Scientific Review Groups: proposed plan 

Scientific Review Groups: a summary of their purpose, structure, and future role 

NMFS must consult with the Secretary of the Interior, the Marine Mammal Commission, 

Governors of affected adjacent coastal States, regional fishery and wildlife management 

authorities, Alaska Native organizations, Indian tribes, and resource user (fishing industry and 

environmental) groups and appoint members to each of three Scientific Review Groups (Pacific, 

including Hawaii; Atlantic, including the Gulf of Mexico; Alaska). The groups will advise the 

Secretary regarding the following information: 

(a) information in stock assessment reports, 

(b) uncertainties and research needed regarding information on marine mammal stocks and the 

impact of fishing operations on these stocks, 

(c) research needed to identifl appropriate gear technology to reduce incidental mortality and 

injury of marine mammals, 

(d) the actual, expected, or potential impacts of habitat destruction on marine mammal stocks, 

and, for strategic stocks, appropriate conservation or management measures to alleviate 

such.impacts, and 

(e) other issues that the Secretary or groups consider appropriate. 

Members of the groups must have expertise in marine mammal biology and ecology, populations 

dynamics and modeling, commercial fishing technology and practices, or marine mammal stocks 

taken under MMPA Sec. 101(b) (the Alaska Native exemption). 

There are three Scientific Review Groups (SRGs) consisting of approximately 11 members each. 

These groups are convened and organized out of each of the following Science Centers: Alaska, 

Southwest and Northeast/Southeast. These Centers are responsible for contacting SRG members 

when meetings are to be held, identifjhg and coordinating lodgings and travel accommodations, 

providing materials requiring SRG consultation, and assisting in facilitating communication 

between SRG members and documentation of recommendations. NMFS, through the Centers, 

will provide travel, hotel and meeting-location expenses. Headquarters budgeted $30K for each 

team in the first year (FY95) and $20K in the second year (FY96). 

In their first year of existence, the SRGs reviewed proposed guidelines for stock assessment 

reports and the reports themselves. In doing so, the SRGs have advised on marine mammal stock 

structure, population estimates, population status and trends, annual removals, and uncertainties 

in available information and data. Now that the first round of stock assessments (1995) have been 

completed, it is time to establish what the role of the SRGs will be in FY96 and beyond. This 

includes some logistical issues such as how often the groups should meet and how long members 
Draft February 13, 1 997 

should serve. Therefore, at this point it is desirable to attempt to formalize the expected future 

role of the SRGs and their interaction with NMFS. The SRGs were established for specific 

purposes that are outlined in the MMPA. Therefore, it is important for the agency to make 

recommendations to the SRGs as to how they can most effectively help the agency implement the 

PBR-based management scheme defined by the 1994 amendments to the MMPA. It is also 

recognized that the SRGs are specifically identified in the MMPA as independent review groups, 

and it is hrther noted that the MMPA states that the groups shall advise the Secretary on any 

issue which the Secretary or the groups consider appropriate. 

The following is a list of recommendations that the agency will make to the SRGs to 

define their future role. 

(1) Review of revised stock assessments. 

This role will continue. Stock assessments are required to be revised (a) annually for strategic 

stocks, (b) annually for stocks with significant new information, and (c) at least once every 3 

years for all other stocks. 

(2) Review of any changes to the PBRlStock assessment guidelines 

The SRGs provided such a review at the Seattle joint SRG meeting. This role will continue. The 

SRGs will be asked to review and comment on fbture changes to the guidelines. 

(3) Prioritized list of recommended research to improve the stock assessments. 

The SRGs should provide to their NMFS coordinator a written list of recommended research, 

ranked in order of importance. The three SRGs have to some extent provided this advice already, 

whether verbally during meetings or in written form in meeting reports. It is proposed that this be 

made more formal, where each SRG would be requested to provide a written list of recommended 

research in their meeting report. Such a list is most usefbl to the agency if the various research 

areas are ranked in order of importance, or at least put into ranked bins of importance. These 

recommendations have and will be useful to the agency, both for program reviews at the Centers 

and for the allocation of MMPA research funds annually. 

(4) Review of research recommended in take reduction plans. 

The SRGs are asked to advise on "research needed to identify modifications in fishing gear and 

practices likely to reduce the incidental mortality and serious injury of marine mammals in 

commercial fishing operations". The take reduction plans that result from the take reduction 

teams are likely to contain recommendations for research on bycatch reduction measures. The 

SRGs should review these take reduction plans to stay informed, and it may be appropriate for 

them to comment on the plans. Specifically, as a SRG, they should comment on research 

recommended in the Take Reduction Plans. The SRGs may not consider it necessary for all their 

members to review every take reduction plan, as there may be considerable overlap of people 

between the take reduction teams and the SRGs. In such a case, an explicit SRG review of the 

take reduction plans may be unnecessary. In conclusion, NMFS should request that the SRGs 
Draft February 13, 1 997 

review take reduction plans and comment on research recommended in the plans. 

(5) Identify important habitat issues. 

The SRGs are asked to advise on "the actual, expected, or potential impacts of habitat 

destruction, including marine pollution and natural environmental change, on specific marine 

mammal species or stocks, and, for strategic stocks, appropriate conservation or management 

measures to alleviate such impacts". They could accomplish this task by identifjrlng important 

habitat issues for protecting strategic stocks. 

This is a fairly broad charge to the SRGs, and it is hard to suggest specific topics on this subject 

that would be usehl for the SRGs to evaluate. However, the Marine Mammal Commission's 

comments on the drafi stock assessments @ec 1, 1994) do contain numerous references to 

needing more information on habitat issues, and Sec. 117 does state that the stock assessments 

should contain information on "...other factors that may be causing a decline or impeding recovery 

of the stock, including effects on marine mammal habitat and prey". Therefore, a specific task that 

could be requested of the SRGs would be to identify important habitat issues for strategic stocks. 

Actually, this may not take long. Presumably, any ESA or MMPA listed stock should have habitat 

issues addressed in their recovery/conservation plan, but no plan exists for several species. 

However, in some circumstances it may be usehl to get the SRGs perspective on these habitat 

issues. Certainly, non-listed strategic stocks with human-caused mortality greater than PBR (or 

listed stocks that do not have a recovery/conservation plan in place or in draft form, or for stocks 

currently declining but not listed) would benefit from a consideration of important habitat. For 

such stocks that have a known or suspected source of mortality other than fisheries interaction or 

subsistence harvest, the SRGs could attempt to identifjl important habitat to protect that could 

prevent such mortality. 

(6) Logistics 

a.) 1-2 meetings per year for each complete SRG is appropriate and may be sufficient, but 

flexibility should be allowed when issues warrant further attention. Meetings of subgroups may be 

needed to address specific issues. 

In the first year of their existence, the three groups met 2 or 3 times each. However, one meeting 

was devoted entirely to reviewing the PBR guidelines. Although these are certain to be modified 

in the future, they are unlikely to require such extensive review in the future. Furthermore, the 

groups spent the bulk of the rest of their time reviewing stock assessments. This workload should 

be somewhat less in the future as there will not be 153 new assessments to review each year, and 

even many of the revised assessments may actually change very little. Therefore, one meeting per 

year may be sufficient, and 2 meetings per year is certainly appropriate and probably useful. Three 

meetings in a fiscal year may be necessary at times, as needs arise, particularly if a group has not 

met for several months prior to the start of a new fiscal year. 

b.) Members should have open-ended tenures. 
Draft February 13, 1997 

Although it might be desirable to have a limited tenure to gain even broader representation on the 

groups over time, the reality is that there is limited expertise in certain areas, so it is not clear that 

it would be desirable to replace all 10-12 members at some point in the fhture. It may be desirable 

to rotate a few new people in occasionally to broaden the representation. For now, most people 

seem fairly satisfied with the composition of the groups. 

c.) When replacement members are needed, the SRGs should submit recommendations for 

replacements to their coordinator. If the relevant Centers and Regions have suggestions for 

replacements, they should ask the SRGs to comment on those nominees, also. 

The power to appoint people to the SRGs clearly resides with the Secretary, who is supposed to 

consult a long list of people before making their decision. However, it is a reasonable courtesy to 

ask the SRG for suggestions for replacements, given that they will be the ones who have to work 

with the new members, and they may have a better idea than anyone else about what kind of 

expertise they are most lacking and that they would like to have represented on the group. 

(7) Reports and minutes of SRG meetings. 

For the SRGs to be effective, their advice should be provided in a written form in a timely fashion. 

SRG meetings usually include NMFS personnel fiom Science Centers who are responsible for 

writing stock assessment reports and/or personnel who have done the research that goes into the 

stock assessment reports. Specific advice relevant to stock assessment reports has been (and 

should continue to be) provided verbally at meetings and in reports communicated to the NMFS 

contact person. It is also important for the advice of the SRGs to be communicated more broadly 

to the agency. Therefore; it is also requested that SRG reports and minutes continue to be 

provided to the F/PR SRG contact. FPR will take responsibility for distributing the reports to a 

broader audience within NMFS, including Regional Directors and Science Center Directors. 
Draft February 13, 1997 

Appendix XIU. Proposed annual schedule for the review and revision of stock assessment 

reports. 

The following schedule ensures that final Stock Assessment Reports (SARs) are available for the 

development of the proposed List of Fisheries for the upcoming year. Thus, the List of Fisheries 

for 1998, which is developed during 1997, will be based on marine mammal abundance and 

incidental mortality information through 1995. Including more recent marine mammal abundance 

and incidental mortality information is not possible as it requires 1 year to analyze survey 

information and collect and analyze mortality information from observer programs. 

June - Sept. Prepare draft SARs. Centers are responsible for coordinating reviews by the 

Regional offices. 

September 21 Draft PBR table information due at FPR. 

October 1 FR notice of availability published, including draft PBR table. Public comment 

period starts (90 days). 

Draft SARs completed and distributed to SRGs, MMPA task force members, and 

HQ for review. It is anticipated that prior to this date, an initial in-house review of 

information to be included in the SARs would have taken place involving the 

appropriate center and regional personnel. Ideally, preliminary abundance and 

mortality estimates from the previous summer field season will be available by this 

time (leaving 9 months for preliminary analysis of mortality data, probably over a 

year for abundance data). 

[Preliminary mortality estimates may suggest revisions to the LOF, which can 

initiate initial discussions of such changes within NMFS.] 

Oct-Dec. SRG review of draft SARs. Optionally, SRG meetings with NMFS SAR authors 

to discuss draft SARs. 

HQ organizes NMFS technical review of draft SARs. 

[Any preliminary mortality estimates which become available which suggest a 

change is needed to LOF should be passed along as soon as possible to regional 

offices, MMPA task force, and HQ LOF contact.] 

Jan 1 SRG and HQ review and comments due to SAR authors. 

Public comment period ends. 
Draft February 13,1997 

Jan 7 F/PR distributes public comments to SAR authors and SRGs. 

Feb 1 Revised PBRMortality table information due at F/PR. F/PR assembles table and 

distributes nationally within NMFS. 

Ideally, final abundance and mortality estimates from the previous year (leaving 13 

months for analysis of mortality data, probably longer for analysis of abundance 

data) will be incorporated into these revised PBRMortality estimates. 

[Draft List of Fisheries can be constructed at this point, leaving 8 weeks to 

accomplish before April 1 publication] 

Feb 15 Revised SARs (draft final) due incorporating comments from public, SRGs, and 

NMFS HQ and regions. The expectation is that the final published SAR will not 

differ substantially fiom this version. Revised SARs distributed back to SRGs, 

MMPA task force, and HQ for final inspection of incorporation of comments. 

March 15 Final PBRMortality table information due at FPR. 

April 1 SARs finalized, due at FPR for availability for distribution to public. 

FR notice of availability published with final PBRMortality table. 

Final SARs submitted to publication process (possibly as NOAA tech memos). 

[Proposed LOF for next year based on final SARs published in FR for public 

comment. Necessary deadline to meet Oct. 1 finalization deadline.] 

April-Oct [LOF review process] 

October 1 FOF finalized, published in FR. Necessary deadline to allow sufficient time for 

registration process by end of calendar year.] 
Draft February 13, 1997 

Appendix M. Statistical formulas and background 

Coefficient of Variation (CV) 

The CV of an estimate is simply the standard error of the estimate divided by the estimate itself 

The CV of an estimate (2) is: 

where Se(2) is the standard error of the estimate. Note that: 

se(ji)=J- . 

Therefore, the squared coefficient of variation, CV2, is simply: 

cv2 (2) = var (8) 

ji2 

Variance of the product of a constant and a variable 

The variance of the product of a constant (c) and an estimated variable (2) is the square of the 

constant multiplied by the variance of the estimate: 

Variance of the sum of two independent variables 

The variance of the sum of two variables is simply the sum of their variances (if they are 

independent): 

For example, when summing mortality estimates from two fisheries, the variance of the sum is just 

the sum of the variances. The standard error (square root of the variance) of the sum can then be 

converted into a CV of the sum by dividing it by the sum. 

Variance of the un-weighted mean of several variables 

The mean of several variables can be thought of as the sum of those variables multiplied by a 

constant (i.e., lln), so that the variance of such a mean can be calculated from combining the two 

above equations. Therefore, the variance of the mean of several estimates is the sum of their 

variances divided by the square of the number of estimates: 
Draft February 13, 1997 

var(8,) var(2,) var (An) r(mean of Al,ji,, . . .) = + +. . . n2 n2 n2 i =l n2 = 2 var(Ri) 

This is the formula that can be used, for example, to calculate the variance of the mean mortality 

of a single fishery across several years. 

Wei~hted mean of several estimates and its associated variance 

The weighted mean of several estimates is calculated by summing the products of the estimates 

and their respective weights, and dividing the total by the sum of the weights. For example, using 

the inverse of the respective variances as the weights results in: 

n 

man 2 . . . = w 2, , i =l 

The variance of a weighted mean of several estimates will be the sum of the variances multiplied 

by the square of the weights. For example, a weighted mean using the inverse of the estimated 

variances as the weights will have as its variance: 

A weighted mean should be used for combining more than one abundance estimate into a single 

abundance estimate. 
Draft February 13, 1997 

Variance of a product of independent estimates !approxi& 

An approximate variance for a product or ratio can be derived by the delta method which is based 

on a second order Taylor series expansion. See pages 7-9 in Seber(1973) for a derivation of the 

delta method. For a product of independent random variables an estimator for the exact variance 

is also available (Goodman 1960) but the approximation is sufficiently close in most situations. 

For products and ratios, a simplification is achieved by expressing the variance formula in terms of 

coefficient of variation (CV). Using the above notation for the product(? 9) and ratio(Y9) of 

independent estimates, the delta method approximations for the CV2(? 9) and CV2(Y?) are 

identical and expressed as: 

Therefore, the CV of a product can be calculated as: 

It can also be expressed in terms of the variances. Using the definition in (I), we get: 

var (2p) = CV~ (29) A2p2 = var (A) P2 + var (p) A2 , 

and likewise, 

The formula for calculating the variance of a product is usefil for calculating the variance for a 

single abundance estimate that has been multiplied by a correction factor. 1f the values being 

multiplied are statistically independent, then it can be seen above that the CV of the product is the 

square root of the sum of the squared individual CV's of each component, such as the CV of the 

un-corrected abundance estimate and the CV of the correction multiplier. 

nce of a product of independent random variables (exact) 

For a product of independent random variables, the estimator for the variance (Goodman 1960) 

is: 
Draft February 13, 1997 

which can also be expressed in terms of squared CV's as: 

CV2(jiP) = cv2(2) + cv2(p) - CV2(8) cv2(p) . 

The estimator derived by Goodman (196Q) is often incorrectly given with an addition of the 

product of variances rather than a subtraction. This error is made because it should be added for 

the variance of a product of independent variables but for the estimator of the variance it must be 

subtracted. However, as shown below, if either the CV(2) or the CV(9) is less than 0.3, the 

approximation given in (2) is only slightly larger (<4%) than (3) if the estimates are truly 

independent. 

Ratio of equations (2) and (3) for various combinations of CVfor 9 andj. 

Variance of a product of correlated random variables 

A direct application of the delta method for products and ratios in which ii and 9 are correlated 

yields the following formulas expressed in terms of CV2 : 

and 

cv2(2/p) = cv2(2) + cv2(p) - 2pCV(ji)CV(P) , 

where p is the correlation between 2 and 9. 
Draft February 13, 1997 

Literature Cited 

Goodman, L. 1960. On the exact variance of products. American Statistical Association Journal 

55: 708-713. 

Seber, G.A.F. 1973. The Estimation of Animal Abundance. Griffin & Co., Ltd, London. 506p.