Northeast Fisheries Science Center Reference Document 11-11

52nd Northeast Regional 

Stock Assessment Workshop

(52nd SAW): 

Assessment Summary Report

by Northeast Fisheries Science Center
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Northeast Fisheries Science Center Reference Document 11-11

US DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Northeast Fisheries Science Center

Woods Hole, Massachusetts

July 2011

52nd Northeast Regional 

Stock Assessment Workshop

(52nd SAW): 

Assessment Summary Report

by Northeast Fisheries Science Center

NOAA National Marine Fisheries Service, 166 Water St., Woods Hole, MA 02543. 
Northeast Fisheries Science Center Reference Documents

This series is a secondary scientific series designed to assure the long-term documentation and 

to enable the timely transmission of research results by Center and/or non-Center researchers, 

where such results bear upon the research mission of the Center (see the outside back cover for 

the mission statement). These documents receive internal scientific review, and most receive 

copy editing. The National Marine Fisheries Service does not endorse any proprietary material, 

process, or product mentioned in these documents.

All documents issued in this series since April 2001, and several documents issued prior to 

that date, have been copublished in both paper and electronic versions. To access the electronic 

version of a document in this series, go to http://www.nefsc.noaa.gov/nefsc/publications/. The 

electronic version is available in PDF format to permit printing of a paper copy directly from 

the Internet. If you do not have Internet access, or if a desired document is one of the pre-April 

2001 documents available only in the paper version, you can obtain a paper copy by contacting 

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corporate (i.e., non-individualized) authorship, then contact the Center’s Woods Hole Laboratory Library (166 Water St., Woods Hole, MA 02543-1026).

Editorial Treatment: To distribute this report quickly, it has not undergone the normal technical and copy editing by the Northeast Fisheries Science Center’s (NEFSC’s) Editorial Office 

as have most other issues in the NOAA Technical Memorandum NMFS-NE series. Other than 

the four covers and first two preliminary pages, all writing and editing have been performed by 

the authors listed within. This report was reviewed by the Stock Assessment Review Committee, a panel of assessment experts from the Center for Independent Experts (CIE), University 

of Miami.

Information Quality Act Compliance: In accordance with section 515 of Public Law 106-

554, the Northeast Fisheries Science Center completed both technical and policy reviews for 

this report. These predissemination reviews are on file at the NEFSC Editorial Office.

This document may be cited as:

Northeast Fisheries Science Center. 2011. 52nd Northeast Regional Stock Assessment 

Workshop (52nd SAW) Assessment Summary Report. US Dept Commer, Northeast 

Fish Sci Cent Ref Doc. 11-11; 51 p. Available from: National Marine Fisheries Service, 

166 Water Street, Woods Hole, MA 02543-1026, or online at http://www.nefsc.noaa.

gov/nefsc/publications/
52nd SAW Assessment Summary Report iii

Table of Contents 

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

Outcome of Stock Assessment Review Meeting .........................................................................2 

Glossary ........................................................................................................................................3 

A. SOUTHERN NEW ENGLAND/MID-ATLANTIC (SNE/MA) WINTER 

FLOUNDER ASSESSMENT SUMMARY FOR 2011 ...................................................11

State of Stock .............................................................................................................................11 

Projection ...................................................................................................................................11 

Catch ...........................................................................................................................................11 

Catch and Status Table ...............................................................................................................12 

Stock Distribution and Identification .........................................................................................12 

Data and Assessment ..................................................................................................................12 

Biological Reference Points .......................................................................................................13 

Fishing Mortality ........................................................................................................................13 

Recruitment ................................................................................................................................13 

Spawning Stock Biomass ...........................................................................................................13 

Special Comments ......................................................................................................................13 

References ..................................................................................................................................14 

Figures ........................................................................................................................................15 

B. GEORGES BANK (GBK) WINTER FLOUNDER ASSESSMENT SUMMARY FOR 

2011 .....................................................................................................................................27

State of Stock .............................................................................................................................27 

Projections ..................................................................................................................................27 

Catch ...........................................................................................................................................27 

Catch and Status Table ...............................................................................................................28 

Stock Distribution and Identification .........................................................................................28 

Data and Assessment ..................................................................................................................28 

Biological Reference Points .......................................................................................................29 

Fishing Mortality ........................................................................................................................29 

Spawning Stock Biomass ...........................................................................................................29 

Recruitment ................................................................................................................................29 

Special Comments ......................................................................................................................30 

References .................................................................................................................................30 

Tables ........................................................................................................................................31 

Figures .......................................................................................................................................32 

C. GULF OF MAINE (GOM) WINTER FLOUNDER ASSESSMENT SUMMARY 

FOR 2011 ............................................................................................................................36

State of Stock .............................................................................................................................36 

Projections ..................................................................................................................................36 

Catch ...........................................................................................................................................36 
52nd SAW Assessment Summary Report iv

Catch and Status Table ...............................................................................................................37 

Stock Distribution and Identification .........................................................................................37 

Data and Assessment ..................................................................................................................37 

Biological Reference Points .......................................................................................................38 

Fishing Mortality ........................................................................................................................38 

Recruitment ................................................................................................................................38 

Spawning Stock Biomass ...........................................................................................................38 

Special Comments ......................................................................................................................38 

References ..................................................................................................................................39 

Figures ........................................................................................................................................40 

 Appendix: Terms of Reference ................................................................................................48

 
52nd SAW Assessment Summary Report 1

SAW-52 ASSESSMENT SUMMARY REPORT 

 Introduction 

The 52nd SAW Assessment Summary Report contains summary and detailed technical 

information on three stock assessments reviewed in June 2011 at the Stock Assessment 

Workshop (SAW) by the 52nd Stock Assessment Review Committee (SARC-52): three stocks of 

winter flounder (Pseudopleuronectes americanus) from Southern New England/Mid-Atlantic, 

Georges Bank, and Gulf of Maine. The SARC-52 consisted of 3 external, independent reviewers 

appointed by the Center for Independent Experts [CIE], and an external SARC chairman from 

the NEFMC SSC. The SARC evaluated whether each Term of Reference (listed in the 

Appendix) was completed successfully based on whether the work provided a scientifically 

credible basis for developing fishery management advice. The reviewers’ reports for 

SAW/SARC-52 are available at website: http://www.nefsc.noaa.gov/nefsc/saw/ under the 

heading “SARC 52 Panelist Reports”. 

An important aspect of any assessment is the determination of current stock status. The 

status of the stock relates to both the rate of removal of fish from the population – the 

exploitation rate – and the current stock size. The exploitation rate is the proportion of the stock 

alive at the beginning of the year that is caught during the year. When that proportion exceeds 

the amount specified in an overfishing definition, overfishing is occurring. Fishery removal rates 

are usually expressed in terms of the instantaneous fishing mortality rate, F, and the maximum 

removal rate is denoted as FTHRESHOLD. 

Another important factor for classifying the status of a resource is the current stock level, 

for example, spawning stock biomass (SSB) or total stock biomass (TSB). Overfishing 

definitions, therefore, characteristically include specification of a minimum biomass threshold as 

well as a maximum fishing threshold. If the biomass of a stock falls below the biomass threshold 

(BTHRESHOLD) the stock is in an overfished condition. The Sustainable Fisheries Act mandates 

that a stock rebuilding plan be developed should this situation arise. 

As there are two dimensions to stock status – the rate of removal and the biomass level – 

it is possible that a stock not currently subject to overfishing in terms of exploitation rates is in an 

overfished condition, that is, has a biomass level less than the threshold level. This may be due to 

heavy exploitation in the past, or a result of other factors such as unfavorable environmental 

conditions. In this case, future recruitment to the stock is very important and the probability of 

improvement may increase greatly by increasing the stock size. Conversely, fishing down a stock 

that is at a high biomass level should generally increase the long-term sustainable yield. Stocks 

under federal jurisdiction are managed on the basis of maximum sustainable yield (MSY). The 

biomass that produces this yield is called BMSY and the fishing mortality rate that produces MSY 

is called FMSY. 

Given this, federally managed stocks under review are classified with respect to current 

overfishing definitions. A stock is overfished if its current biomass is below BTHRESHOLD and 

overfishing is occurring if current F is greater than FTHRESHOLD. The table below depicts status 

criteria. 
52nd SAW Assessment Summary Report 2

BIOMASS

 B <BTHRESHOLD BTHRESHOLD < B < BMSY B > BMSY 

EXPLOITATION 

RATE 

F>FTHRESHOLD 

Overfished, overfishing is 

occurring; reduce F, adopt and 

follow rebuilding plan 

Not overfished, overfishing is 

occurring; reduce F, rebuild 

stock 

F = FTARGET <= 

FMSY 

F<FTHRESHOLD 

Overfished, overfishing is not 

occurring; adopt and follow 

rebuilding plan 

Not overfished, overfishing is 

not occurring; rebuild stock 

F = FTARGET <= 

FMSY 

Fisheries management may take into account the precautionary approach, and overfishing 

guidelines often include a control rule in the overfishing definition. Generically, the control 

rules suggest actions at various levels of stock biomass and incorporate an assessment of risk, in 

that FTARGETS are set so as to avoid exceeding FTHRESHOLDS. 

Outcome of Stock Assessment Review Meeting 

Based on the Review Panel reports (available at http://www.nefsc.noaa.gov/nefsc/saw/

under the heading “SARC 52 Panelist Reports”), the SARC review committee concluded that for 

the SNE/MA winter flounder assessment all Terms of Reference were addressed satisfactorily. 

The statistical catch-age model used for SNE/MA assessment is considered to be a scientifically 

credible approach and provides a reasonable basis for fisheries management advice. In 2010, this 

stock was overfished but overfishing was not occurring. 

The Terms of Reference for the GBK winter flounder assessment were satisfactorily addressed. 

The VPA model used was a scientifically credible approach and provides a reasonable basis for 

fisheries management advice. A statistical catch-age model should be considered for the GBK 

stock as there may be more uncertainty here associated with catch and discards than would be 

appropriate for the assumption of true known catches as is made in a VPA analysis. In 2010 the 

GBK winter flounder stock was not overfished and overfishing was not occurring. 

The Terms of Reference for the GOM winter flounder assessment were partially addressed. The 

GOM statistical catch-age model could not account for conflicting trends in the catch and survey 

information, and was not accepted. However, the accepted fall back analysis of the area-swept 

method provides a reasonable gauge of overfishing status and provides time trends in biomass. 

Overfishing does not appear to be taking place in 2010. It was not possible at the meeting to 

determine whether or not the stock is overfished. 

For all of these assessments, the SARC felt that the discussion of stock vulnerability could have 

addressed biological issues more directly (e.g., life history, longevity, fecundity, productivity, or 

whether the species or stock is overly susceptible to fishing or environmental conditions). While 

the length-based calibrations between vessels were informative and appeared appropriate, this 

method might be considered for additional peer review. A method was developed for combining 

information on winter flounder across regions to help inform the spawner-recruit relationships 

used in developing projections and biological reference points (for details on the method see the 

Review Panel Summary Report and the Appendix of the Stock Assessment Report). 

 
52nd SAW Assessment Summary Report 3

Glossary 

ADAPT. A commonly used form of 

computer program used to optimally fit a 

Virtual Population Assessment (VPA) to 

abundance data. 

ASAP. The Age Structured Assessment 

Program is an age-structured model that uses 

forward computations assuming separability 

of fishing mortality into year and age 

components to estimate population sizes 

given observed catches, catch-at-age, and 

indices of abundance. Discards can be 

treated explicitly. The separability 

assumption is relaxed by allowing for fleetspecific computations and by allowing the 

selectivity at age to change smoothly over 

time or in blocks of years. The software can 

also allow the catchability associated with 

each abundance index to vary smoothly with 

time. The problem’s dimensions (number of 

ages, years, fleets and abundance indices) 

are defined at input and limited by hardware 

only. The input is arranged assuming data is 

available for most years, but missing years 

are allowed. The model currently does not 

allow use of length data nor indices of 

survival rates. Diagnostics include index 

fits, residuals in catch and catch-at-age, and 

effective sample size calculations. Weights 

are input for different components of the 

objective function and allow for relatively 

simple age-structured production model type 

models up to fully parameterized models. 

ASPM. Age-structured production models, 

also known as statistical catch-at-age 

(SCAA) models, are a technique of stock 

assessment that integrate fishery catch and 

fishery-independent sampling information. 

The procedures are flexible, allowing for 

uncertainty in the absolute magnitudes of 

catches as part of the estimation. Unlike 

virtual population analysis (VPA) that tracks 

the cumulative catches of various year 

classes as they age, ASPM is a forward 

projection simulation of the exploited 

population. ASPM is similar to the NOAA 

Fishery Toolbox applications ASAP (Age 

Structured Assessment Program) and SS2 

(Stock Synthesis 2) 

Availability. Refers to the distribution of 

fish of different ages or sizes relative to that 

taken in the fishery. 

Biological reference points. Specific values 

for the variables that describe the state of a 

fishery system which are used to evaluate its 

status. Reference points are most often 

specified in terms of fishing mortality rate 

and/or spawning stock biomass. The 

reference points may indicate 1) a desired 

state of the fishery, such as a fishing 

mortality rate that will achieve a high level 

of sustainable yield, or 2) a state of the 

fishery that should be avoided, such as a 

high fishing mortality rate which risks a 

stock collapse and long-term loss of 

potential yield. The former type of reference 

points are referred to as “target reference 

points” and the latter are referred to as “limit 

reference points” or “thresholds”. Some 

common examples of reference points are 

F0.1, FMAX, and FMSY, which are defined later 

in this glossary. 

B0. Virgin stock biomass, i.e., the long-term 

average biomass value expected in the 

absence of fishing mortality. 

BMSY. Long-term average biomass that 

would be achieved if fishing at a constant 

fishing mortality rate equal to FMSY. 

Biomass Dynamics Model. A simple stock 

assessment model that tracks changes in 

stock using assumptions about growth and 

can be tuned to abundance data such as 

commercial catch rates, research survey 

trends or biomass estimates. 

Catchability. Proportion of the stock 

removed by one unit of effective fishing 

effort (typically age-specific due to 
52nd SAW Assessment Summary Report 4

differences in selectivity and availability by 

age). 

Control Rule. Describes a plan for preagreed management actions as a function of 

variables related to the status of the stock. 

For example, a control rule can specify how 

F or yield should vary with biomass. In the 

National Standard Guidelines (NSG), the 

“MSY control rule” is used to determine the 

limit fishing mortality, or Maximum Fishing 

Mortality Threshold (MFMT). Control rules 

are also known as “decision rules” or 

“harvest control laws.” 

Catch per Unit of Effort (CPUE). 

Measures the relative success of fishing 

operations, but also can be used as a proxy 

for relative abundance based on the 

assumption that CPUE is linearly related to 

stock size. The use of CPUE that has not 

been properly standardized for temporalspatial changes in catchability should be 

avoided. 

Exploitation pattern. The fishing mortality 

on each age (or group of adjacent ages) of a 

stock relative to the highest mortality on any 

age. The exploitation pattern is expressed as 

a series of values ranging from 0.0 to 1.0. 

The pattern is referred to as “flat-topped” 

when the values for all the oldest ages are 

about 1.0, and “dome-shaped” when the 

values for some intermediate ages are about 

1.0 and those for the oldest ages are 

significantly lower. This pattern often varies 

by type of fishing gear, area, and seasonal 

distribution of fishing, and the growth and 

migration of the fish. The pattern can be 

changed by modifications to fishing gear, 

for example, increasing mesh or hook size, 

or by changing the proportion of harvest by 

gear type. 

Mortality rates. Populations of animals 

decline exponentially. This means that the 

number of animals that die in an "instant" is 

at all times proportional to the number 

present. The decline is defined by survival 

curves such as: Nt+1 = Nte

-z 

where Nt is the number of animals in the 

population at time t and Nt+1 is the number 

present in the next time period; Z is the total 

instantaneous mortality rate which can be 

separated into deaths due to fishing (fishing 

mortality or F) and deaths due to all other 

causes (natural mortality or M) and e is the 

base of the natural logarithm (2.71828).To 

better understand the concept of an 

instantaneous mortality rate, consider the 

following example. Suppose the 

instantaneous total mortality rate is 2 (i.e., Z 

= 2) and we want to know how many 

animals out of an initial population of 1 

million fish will be alive at the end of one 

year. If the year is apportioned into 365 days 

(that is, the 'instant' of time is one day), then 

2/365 or 0.548% of the population will die 

each day. On the first day of the year, 5,480 

fish will die (1,000,000 x 0.00548), leaving 

994,520 alive. On day 2, another 5,450 fish 

die (994,520 x 0.00548) leaving 989,070 

alive. At the end of the year, 134,593 fish 

[1,000,000 x (1 - 0.00548)365] remain alive. 

If, we had instead selected a smaller 'instant' 

of time, say an hour, 0.0228% of the 

population would have died by the end of 

the first time interval (an hour), leaving 

135,304 fish alive at the end of the year 

[1,000,000 x (1 - 0.00228)8760]. As the 

instant of time becomes shorter and shorter, 

the exact answer to the number of animals 

surviving is given by the survival curve 

mentioned above, or, in this example: 

Nt+1 = 1,000,000e-2 = 135,335 fish 

Exploitation rate. The proportion of a 

population alive at the beginning of the year 

that is caught during the year. That is, if 1 

million fish were alive on January 1 and 

200,000 were caught during the year, the 

exploitation rate is 0.20 (200,000 / 

1,000,000) or 20%. 
52nd SAW Assessment Summary Report 5

FMAX. The rate of fishing mortality that 

produces the maximum level of yield per 

recruit. This is the point beyond which 

growth overfishing begins. 

F0.1. The fishing mortality rate where the 

increase in yield per recruit for an increase 

in a unit of effort is only 10% of the yield 

per recruit produced by the first unit of 

effort on the unexploited stock (i.e., the 

slope of the yield-per-recruit curve for the 

F0.1 rate is only one-tenth the slope of the 

curve at its origin). 

F10%. The fishing mortality rate which 

reduces the spawning stock biomass per 

recruit (SSB/R) to 10% of the amount 

present in the absence of fishing. More 

generally, Fx%, is the fishing mortality rate 

that reduces the SSB/R to x% of the level 

that would exist in the absence of fishing. 

FMSY. The fishing mortality rate that 

produces the maximum sustainable yield. 

Fishery Management Plan (FMP). Plan 

containing conservation and management 

measures for fishery resources, and other 

provisions required by the MSFCMA, 

developed by Fishery Management Councils 

or the Secretary of Commerce. 

Generation Time. In the context of the 

National Standard Guidelines, generation 

time is a measure of the time required for a 

female to produce a reproductively-active 

female offspring for use in setting maximum 

allowable rebuilding time periods. 

Growth overfishing. The situation existing 

when the rate of fishing mortality is above 

FMAX and when fish are harvested before 

they reach their growth potential. 

Limit Reference Points. Benchmarks used 

to indicate when harvests should be 

constrained substantially so that the stock 

remains within safe biological limits. The 

probability of exceeding limits should be 

low. In the National Standard Guidelines, 

limits are referred to as thresholds. In much 

of the international literature (e.g., FAO 

documents), “thresholds” are used as buffer 

points that signal when a limit is being 

approached. 

Landings per Unit of Effort (LPUE). 

Analogous to CPUE and measures the 

relative success of fishing operations, but is 

also sometimes used a proxy for relative 

abundance based on the assumption that 

CPUE is linearly related to stock size. 

MSFCMA. (Magnuson-Stevens Fishery 

Conservation and Management Act). U.S. 

Public Law 94-265, as amended through 

October 11, 1996. Available as NOAA 

Technical Memorandum NMFS-F/SPO-23, 

1996. 

Maximum Fishing Mortality Threshold 

(MFMT, FTHRESHOLD). One of the Status 

Determination Criteria (SDC) for 

determining if overfishing is occurring. It 

will usually be equivalent to the F 

corresponding to the MSY Control Rule. If 

current fishing mortality rates are above 

FTHRESHOLD, overfishing is occurring. 

Minimum Stock Size Threshold (MSST, 

BTHRESHOLD). Another of the Status 

Determination Criteria. The greater of (a) 

1⁄2BMSY, or (b) the minimum stock size at 

which rebuilding to BMSY will occur within 

10 years of fishing at the MFMT. MSST 

should be measured in terms of spawning 

biomass or other appropriate measures of 

productive capacity. If current stock size is 

below BTHRESHOLD, the stock is overfished. 

Maximum Spawning Potential (MSP). 

This type of reference point is used in some 

fishery management plans to define 

overfishing. The MSP is the spawning stock 

biomass per recruit (SSB/ R) when fishing 

mortality is zero. The degree to which 

fishing reduces the SSB/R is expressed as a 

percentage of the MSP (i.e., %MSP). A 

stock is considered overfished when the 
52nd SAW Assessment Summary Report 6

fishery reduces the %MSP below the level 

specified in the overfishing definition. The 

values of %MSP used to define overfishing 

can be derived from stock-recruitment data 

or chosen by analogy using available 

information on the level required to sustain 

the stock. 

Maximum Sustainable Yield (MSY). The 

largest average catch that can be taken from 

a stock under existing environmental 

conditions. 

Overfishing. According to the National 

Standard Guidelines, “overfishing occurs 

whenever a stock or stock complex is 

subjected to a rate or level of fishing 

mortality that jeopardizes the capacity of a 

stock or stock complex to produce MSY on 

a continuing basis.” Overfishing is 

occurring if the MFMT is exceeded for 1 

year or more. 

Optimum Yield (OY). The amount of fish 

that will provide the greatest overall benefit 

to the Nation, particularly with respect to 

food production and recreational 

opportunities and taking into account the 

protection of marine ecosystems. MSY 

constitutes a “ceiling” for OY. OY may be 

lower than MSY, depending on relevant 

economic, social, or ecological factors. In 

the case of an overfished fishery, OY should 

provide for rebuilding to BMSY. 

Partial Recruitment. Patterns of relative 

vulnerability of fish of different sizes or 

ages due to the combined effects of 

selectivity and availability. 

Rebuilding Plan. A plan that must be 

designed to recover stocks to the BMSY level 

within 10 years when they are overfished 

(i.e. when B < MSST). Normally, the 10 

years would refer to an expected time to 

rebuilding in a probabilistic sense. 

Recruitment. This is the number of young 

fish that survive (from birth) to a specific 

age or grow to a specific size. The specific 

age or size at which recruitment is measured 

may correspond to when the young fish 

become vulnerable to capture in a fishery or 

when the number of fish in a cohort can be 

reliably estimated by a stock assessment. 

Recruitment overfishing. The situation 

existing when the fishing mortality rate is so 

high as to cause a reduction in spawning 

stock which causes recruitment to become 

impaired. 

Recruitment per spawning stock biomass 

(R/SSB). The number of fishery recruits 

(usually age 1 or 2) produced from a given 

weight of spawners, usually expressed as 

numbers of recruits per kilogram of mature 

fish in the stock. This ratio can be computed 

for each year class and is often used as an 

index of pre-recruit survival, since a high 

R/SSB ratio in one year indicates aboveaverage numbers resulting from a given 

spawning biomass for a particular year class, 

and vice versa. 

Reference Points. Values of parameters 

(e.g. BMSY, FMSY, F0.1) that are useful 

benchmarks for guiding management 

decisions. Biological reference points are 

typically limits that should not be exceeded 

with significant probability (e.g., MSST) or 

targets for management (e.g., OY). 

Risk. The probability of an event times the 

cost associated with the event (loss 

function). Sometimes “risk” is simply used 

to denote the probability of an undesirable 

result (e.g. the risk of biomass falling below 

MSST). 

Status Determination Criteria (SDC). 

Objective and measurable criteria used to 

determine if a stock is being overfished or is 

in an overfished state according to the 

National Standard Guidelines. 

Selectivity. Measures the relative 

vulnerability of different age (size) classes 

to the fishing gears(s). 
52nd SAW Assessment Summary Report 7

Spawning Stock Biomass (SSB). The total 

weight of all sexually mature fish in a stock. 

Spawning stock biomass per recruit 

(SSB/R or SBR). The expected lifetime 

contribution to the spawning stock biomass 

for each recruit. SSB/R is calculated 

assuming that F is constant over the life span 

of a year class. The calculated value is also 

dependent on the exploitation pattern and 

rates of growth and natural mortality, all of 

which are also assumed to be constant. 

Stock Synthesis (SS). This application 

provides a statistical framework for 

calibration of a population dynamics model 

using a diversity of fishery and survey data. 

SS is designed to accommodate both age 

and size structure and with multiple stock 

sub-areas. Selectivity can be cast as age 

specific only, size-specific in the 

observations only, or size-specific with the 

ability to capture the major effect of sizespecific survivorship. The overall model 

contains subcomponents which simulate the 

population dynamics of the stock and 

fisheries, derive the expected values for the 

various observed data, and quantify the 

magnitude of difference between observed 

and expected data. Parameters are searched 

for which will maximize the goodness-of-fit. 

A management layer is also included in the 

model allowing uncertainty in estimated 

parameters to be propagated to the 

management quantities, thus facilitating a 

description of the risk of various possible 

management scenarios. The structure of SS 

allows for building of simple to complex 

models depending upon the data available. 

Survival Ratios. Ratios of recruits to 

spawners (or spawning biomass) in a stockrecruitment analysis. The same as the 

recruitment per spawning stock biomass 

(R/SSB), see above. 

TAC. Total allowable catch is the total 

regulated catch from a stock in a given time 

period, usually a year. 

Target Reference Points. Benchmarks 

used to guide management objectives for 

achieving a desirable outcome (e.g., OY). 

Target reference points should not be 

exceeded on average. 

Uncertainty. Uncertainty results from a 

lack of perfect knowledge of many factors 

that affect stock assessments, estimation of 

reference points, and management. 

Rosenberg and Restrepo (1994) identify 5 

types: measurement error (in observed 

quantities), process error (or natural 

population variability), model error (misspecification of assumed values or model 

structure), estimation error (in population 

parameters or reference points, due to any of 

the preceding types of errors), and 

implementation error (or the inability to 

achieve targets exactly for whatever reason) 

Virtual population analysis (VPA) (or 

cohort analysis). A retrospective analysis of 

the catches from a given year class which 

provides estimates of fishing mortality and 

stock size at each age over its life in the 

fishery. This technique is used extensively 

in fishery assessments. 

Year class (or cohort). Fish born in a given 

year. For example, the 1987 year class of 

cod includes all cod born in 1987. This year 

class would be age 1 in 1988, age 2 in 1989, 

and so on. 

Yield per recruit (Y/R or YPR). The 

average expected yield in weight from a 

single recruit. Y/R is calculated assuming 

that F is constant over the life span of a year 

class. The calculated value is also dependent 

on the exploitation pattern, rate of growth, 

and natural mortality rate, all of which are 

assumed to be constant. 
52nd SAW Assessment Summary Report 8

Figure 1. Offshore depth strata sampled during Northeast Fisheries Science Center bottom trawl 

research surveys. 

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52nd SAW Assessment Summary Report 9

Figure 2. Inshore depth strata sampled during Northeast Fisheries Science Center bottom trawl 

research surveys. 

 

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52nd SAW Assessment Summary Report 10

Figure 3. Statistical areas used for reporting commercial catches. 
52nd SAW 11 A. Southern New England Winter Flounder

A. SOUTHERN NEW ENGLAND / MID-ATLANTIC (SNE/MA) WINTER FLOUNDER 

ASSESSMENT SUMMARY FOR 2011 

State of Stock: In 2010 the SNE/MA winter flounder stock was overfished but overfishing was 

not occurring. The current assessment provides a new assessment model, a new assumption for 

the instantaneous natural mortality rate (M), and new biological reference points. The 

recommended biological reference points are FMSY = FTHRESHOLD = 0.290, SSBMSY = BTARGET = 

43,661 mt, 1/2 SSBMSY = BTHRESHOLD = 21,831 mt, and MSY = 11,728 mt. The 2010 estimate of 

Spawning Stock Biomass (SSB) is 7,076 mt, 16% of BTARGET and 32% of BTHRESHOLD. The 2010 

estimate of fishing mortality (F, ages 4-5) is 0.051, 18% of FTHRESHOLD (Figures A1-A3). 

Given the new model and assumptions in the current assessment, comparison of the 2010 

estimates of SSB and F estimates with the existing 2008 GARM III reference points (NEFSC 

2008) is not appropriate. The existing biological reference points from the 2008 GARM III 

assessment are F40% = FTHRESHOLD = 0.248, SSB40% = BTARGET = 38,761 mt, 1/2 SSB40% = 

BTHRESHOLD= 19,381 mt, and MSY40% = 9,742 mt. 

Projections: Projections of future stock status were made based on the current assessment 

results using mean weight, maturity, and fishery selectivity patterns at age estimated for the most 

recent 5 years in the assessment (2006-2010) to reflect current conditions in the stock and 

fishery. Recruitment was projected using the stock-recruitment model for the MSY-based BRPs. 

The projections assumed the FMP Framework 44 fishing year (May 1) catch of 842 mt would be 

landed as a calendar year (Jan 1) catch in 2011. A catch of 842 mt in 2011 is projected to provide 

median F in 2011 = 0.100 and median SSB in 2011 = 9,177 mt. Projections at F = 0.000 in 2012-

2014 indicate less than a 1% chance that the stock will rebuild to SSBMSY = 43,661 mt by 2014. 

Catch: Commercial fishery landings reached an historical peak of 11,977 metric tons (mt) in 

1966, then decreased through the 1970s, peaked again at 11,176 mt in 1981, and then steadily 

decreased to 2,128 mt in 1994. Commercial landings then increased to 4,556 mt in 2001 but have 

decreased since then to only 174 mt in 2010 (Figure A4). The Proportional Standard Error (PSE) 

of commercial landings has averaged less than 1%. Recreational fishery landings peaked in 

1984 at 5,510 mt, but decreased substantially thereafter, with only 28 mt estimated for 2010. The 

PSE of the recreational landings has averaged about 27%. Commercial fishery discards for 1981 

to 1993 were estimated from length frequency data from the NEFSC and MADMF trawl 

surveys, commercial port sampling of landings at length and Fishery Observer sampling of 

landings and discards at length. The Standardized Bycatch Reporting Method (SBRM) has been 

used for estimation of SNE/MA winter flounder commercial fishery discards for 1994 and later 

years. Commercial fishery discard losses peaked in the early 1980s at 1,000-1,500 mt per year 

and then decreased to less than 200 mt per year since 1997. A discard mortality rate of 50% was 

applied to the commercial live discard estimates. The PSE of the commercial fishery discards has 

averaged 27%. Recreational fishery discard losses peaked in 1984-1985 at about 700,000-

750,000 fish or 150-200 mt and then decreased to less than 100,000 fish or 20 mt per year since 

2000. A discard mortality rate of 15% was applied to recreational live discard estimates. The 

PSE of the recreational discards has averaged 30%. 

 
52nd SAW 12 A. Southern New England Winter Flounder

Catch and Status Table (weights in 000s mt, recruitment in millions, arithmetic means): 

SNE/MA Winter Flounder 

Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Max1 Min1 Mean1

 

Commercial landings 4.6 3.1 2.3 1.6 1.3 1.7 1.6 1.1 0.3 0.2 11.1 0.2 3.9 

Commercial discards <0.1 0.1 0.2 0.1 0.1 0.2 0.1 0.1 0.2 0.2 1.5 <0.1 0.5 

Recreational landings 0.5 0.2 0.3 0.2 0.1 0.1 0.1 0.1 0.1 <0.1 5.5 <0.1 1.4 

Recreational discards <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 

Catch used in 

assessment 5.1 3.4 2.8 1.9 1.6 2.0 1.9 1.3 0.5 0.4 15.8 0.4 5.9 

 

Spawning Stock 

Biomass2 8.1 6.0 5.6 4.9 4.5 5.2 6.2 5.9 5.7 7.1 20.1 3.9 8.0 

Recruitment (age 1) 15.1 7.4 7.5 15.6 14.2 8.3 7.5 13.5 8.7 8.7 71.6 7.4 25.2 

F (ages 4-5) 0.70 0.63 0.55 0.46 0.37 0.42 0.34 0.24 0.09 0.05 1.16 0.05 0.65 

1: Over the period 1981-2010 

2: On March 1 annually 

Stock Distribution and Identification: Winter flounder (Pseudopleuronectes americanus) is a 

demersal flatfish species commonly found in North Atlantic estuaries and on the continental 

shelf. The species is distributed between the Gulf of St. Lawrence, Canada and North Carolina, 

U.S., although it is not abundant south of Delaware Bay. Information from tagging, meristics, 

and life history studies suggest extensive mixing occurs among the localized Southern New 

England and Mid-Atlantic populations, and so the populations in the region are combined into a 

single stock complex for assessment purposes. Within the SNE/MA stock complex, winter 

flounder undergo annual migrations from estuaries, where spawning occurs in the late winter and 

spring, to offshore shelf areas of less than 60 fathoms (110 meters). The current SNE/MA stock 

complex extends from the coastal shelf east of Provincetown, MA southward along the Great 

South Channel (separating Nantucket Shoals and Georges Bank) to the southern geographic 

limits of winter flounder off Delaware. 

Data and Assessment: The age-structured assessment model for SNE/MA winter flounder has 

changed from an ADAPT VPA model to an ASAP SCAA model (NFT 2011). A new value for 

natural mortality has been adopted, changing from M = 0.20 to M = 0.30 for all ages and years. 

New biological reference points have therefore also been estimated, with FMSY, SSBMSY, and 

MSY now based on a stock-recruitment model. Indices of recruitment and stock abundance 

from the NEFSC winter, spring, and fall, Massachusetts spring, Rhode Island spring, University 

of Rhode Island, Connecticut spring, Delaware and New Jersey trawl surveys were used in the 

ASAP calibration. 
52nd SAW 13 A. Southern New England Winter Flounder

Biological Reference Points (BRP): FMSY, SSBMSY, and MSY were estimated from a stockrecruitment model using a range of values for steepness (slope of the stock recruitment curve 

near the origin) which was consistent with the stock-recruitment data. It is anticipated that 

steepness should be similar between the three stocks. Therefore, when computing the BRPs, 

values of steepness were chosen which were constructed to be as similar as possible between 

stocks, while also providing good fits to the stock recruitment data for each stock. For the 

SNE/MA stock, steepness was set at 0.6. These BRP estimates are direct MSY based estimates. 

The recommended biological reference points for SNE/MA winter flounder are FMSY = 

FTHRESHOLD= 0.290, SSBMSY = BTARGET = 43,661 mt, 1/2 SSBMSY = BTHRESHOLD = 21,831 mt, and 

MSY = 11,728 mt. For comparison, F40% computed using the same biological and fishery 

characteristics is 0.327, with SSB40% = 29,045 mt and MSY40% = 8,903 mt (Figures A5-A7). 

Fishing Mortality: During 1981-1993, fishing mortality (F ages 4-5) varied between 0.61 

(1982) and 0.95 (1993) and then decreased to 0.47 by 1999. Fishing mortality then increased to 

0.70 by 2001, and then decreased to 0.05 in 2010, generally tracking the decrease in fishery catch 

(Figure A8). The fishery selectivity pattern during 1981-1993 was estimated to be 0.01 at age 1, 

0.24 at age 2, 0.75 at age 3, was fixed at 1.00 at age 4, was estimated at 1.00 at age 5, 0.99 at age 

6, and 1.00 at age 7+. The pattern during 1994-2010 was estimated to be 0.01 at age 1, 0.19 at 

age 2, 0.70 at age 3, was fixed at 1.00 at age 4, was estimated at 0.97 at age 5, 0.89 at age 6, and 

0.67 at age 7+. There is an 80% probability that F for ages 4-5 in 2010 was between 0.04 and 

0.06 (Figure A9). Retrospective analysis for the 2003-2010 terminal years indicates retrospective 

error in fishing mortality ranged from -38% in 2006 to -13% in 2009. 

Recruitment: Recruitment at age 1 decreased nearly continuously from 71.6 million age-1 fish 

in 1981 (1980 year class) to 7.5 million fish in 2002 (2001 year class). Recruitment has 

averaged 10.5 million during 2003-2010 (Figure A10). Retrospective error in recruitment at age 

1 ranged from +78% in 2005 (2004 year class) to -11% in 2009 (2008 year class). 

Spawning Stock Biomass: SSB decreased from 20,100 mt in 1982 to a record low of 3,900 mt 

in 1993 and then increased to 8,900 mt by 2000. SSB has varied between 4,500-8,000 mt during 

2001-2009 and was 7,076 mt in 2010 (Figure A10). There is an 80% probability that SSB in 

2010 was between 6,433 mt and 8,590 mt (Figure A11). Retrospective error in SSB ranged from 

+42% in 2004 to +12% in 2009. 

 

Special Comments: A considerable source of vulnerability for SNE/MA winter flounder is the 

continued weak recruitment and low reproductive rate (e.g., recruits per spawner). Recruitment 

estimates for the last decade are lower than those predicted by the stock recruitment model 

(Figures A5 and A12). If the weak recruitment and low reproductive rate continues, productivity 

and rebuilding of the stock will be less than projected. 

Stock-recruit modeling suggests that warm winter temperatures can have a negative effect on 

recruitment of SNE/MA winter flounder. 

 
52nd SAW 14 A. Southern New England Winter Flounder

References: 

NEFSC. 2008. Assessment of 19 Northeast groundfish stocks through 2007. Report of the 3rd

Groundfish Assessment Review Meeting (GARM III), Northeast Fisheries Science 

Center, Woods Hole, Massachusetts. August 4-8, 2008. NEFSC Ref Doc. 08-15. 884 p. 

NOAA Fisheries Toolbox (NFT) 2011. Age Structured Assessment Program (ASAP), version 

2.0.21. [Internet address: http://nft.nefsc.noaa.gov/ASAP.html ]. 
52nd SAW 15 A. Southern New England Winter Flounder

SNE/MA Winter flounder stock status

Spawning Stock Biomass (000s mt)

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50

Fishing Mortality (F ages 4-5)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1/2 SSBMSY = 

Bthreshold = 

21,831 mt

FMSY = Fthreshold = 0.290

SSBMSY = 

Btarget = 

43,661 mt

SAW 52

A1. 2011 SAW 52 stock status in 2010 for SNE/MA winter flounder with respect to 

MSY-based BRPs; error bars on SSB and F are 80% confidence intervals. 

 
52nd SAW 16 A. Southern New England Winter Flounder

A2. Estimated trend in Fishing Mortality and associated BRPs for SNE/MA winter flounder. 

ASAP CAT10 is the 2011 SAW 52 final assessment model. The MSY-based BRP is 

recommended for stock status determination. 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

Fishing Mortality (age 4-5)

Year

SNE/MA Winter Flounder

ASAP CAT10 FMSY F40%
52nd SAW 17 A. Southern New England Winter Flounder

A3. Estimated trend in Spawning Stock Biomass (SSB) and associated BRPs for SNE/MA 

winter flounder. ASAP CAT10 is the 2011 SAW 52 final assessment model. The MSY-based 

BRP is recommended for stock status determination. 

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

SSB (metric tons)

Year

SNE/MA Winter Flounder

ASAP CAT10 SSBMSY SSB40%
52nd SAW 18 A. Southern New England Winter Flounder

SNE/MA Winter flounder

Landings and Discards

Year

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

000s mt

0

2000

4000

6000

8000

10000

12000

14000

16000

Comm Land 

Comm Disc

Rec Land

Rec Disc

Total Catch

A4. Commercial landings (1964-2010), commercial discards (1981-2010), recreational landings 

(1981-2010), recreational discards (1981-2010), and total fishery catch (1981-2010) for 

SNE/MA winter flounder. 

 
52nd SAW 19 A. Southern New England Winter Flounder

A5. Final stock-recruitment model for SNE/MA winter flounder. Spawning stock is in mt; 

recruitment is in thousands of age-1 fish. 
52nd SAW 20 A. Southern New England Winter Flounder

A6. Comparison of fishing mortality versus total yield relationship for stock-recruitment model 

based BRPs (FMSY, MSY) and yield per recruit model based BRPs (F40%, MSY40%). 

 
52nd SAW 21 A. Southern New England Winter Flounder

A7. Comparison of fishing mortality versus SSB relationship for stock-recruitment model based 

BRPs (FMSY, SSBMSY) and yield per recruit model based BRPs (F40%, SSB40%). 
52nd SAW 22 A. Southern New England Winter Flounder

Year

1960 1970 1980 1990 2000 2010

000s mt

0

5

10

15

20

F (age 4-5)

0.0

0.5

1.0

1.5

Total Catch and Fishing Mortality

Total Catch

F (age 4-5)

SNE/MA Winter flounder

Comm. Land.

A8. Total catch (landings and discards, 000s mt), commercial landings (000s mt) and 

fishing mortality rate (F, age 4-5) for SNE/MA winter flounder.
52nd SAW 23 A. Southern New England Winter Flounder

A9. MCMC distribution of the estimate of the 2010 Fishing Mortality of SNE/MA winter 

flounder. 
52nd SAW 24 A. Southern New England Winter Flounder

Recruitment and Biomass Year

1980 1985 1990 1995 2000 2005 2010

SSB (000s mt)

0

5

10

15

20

25

Recruitment (age 1, millions)

0

10

20

30

40

50

60

70

SSB and Recruitment

Recruitment

SSB

SNE/MA Winter flounder

A10. Spawning stock biomass (SSB, 000s mt, solid line) and recruitment (millions of fish at 

age-1, vertical bars) for SNE/MA winter flounder.
52nd SAW 25 A. Southern New England Winter Flounder

A11. MCMC distribution of the estimate of the 2010 Spawning Stock Biomass (SSB) of 

SNE/MA winter flounder. 
52nd SAW 26 A. Southern New England Winter Flounder

A12. Time series trend in Recruits per Spawner (R/S) for SNE/MA winter flounder; most recent 

years are on the right side of the plot. 
52nd SAW B. Georges B 27 ank Winter Flounder 

B. GEORGES BANK WINTER FLOUNDER ASSESSMENT SUMMARY FOR 2011 

State of Stock: In 2010, the stock was not overfished and overfishing was not occurring, based 

on the new biological reference point (BRP) estimates of: FMSY (FTHRESHOLD) = 0.42, SSBMSY

(BTARGET) = 10,100 mt, and 1/2 SSBMSY (BTHRESHOLD) = 5,050 mt, MSY = 3,700 mt. The 2010 

estimate of spawning stock biomass (SSB) is 9,703 mt, which is well above the BTHRESHOLD and 

at 96.1% of the BTARGET. The 2010 estimate of fishing mortality (average F on ages 4-6) is 0.15 

and is well below the FTHRESHOLD of 0.42 (Figure B1). There was an 80% probability that the 

2010 average F was between 0.12 and 0.21 and that the 2010 SSB estimate was between 7,304 

mt and 12,578 mt. 

Given the new model and assumptions in the current assessment, comparison of the 2010 

estimates of SSB and F with the existing reference points is not appropriate. The BRPs derived 

from the 2008 assessment (NEFSC 2008) were: F40% (FTHRESHOLD) = 0.26, SSB40% (BTARGET) = 

16,000 mt, 1/2 SSB40% (BTHRESHOLD) = 8,000 mt, and MSY40% = 3,500 mt. 

Projections: A projection of future stock status was made based on the VPA results using mean 

weights, maturity, and fishery selectivity patterns at age estimated for the most recent 5 years 

(2006-2010) to reflect current conditions in the stock and fishery. Stochastic projections were run 

for 2011-2017 because rebuilding of the stock, with at least 75% probability, is required by 2017. 

Recruitment was projected using the results from a Beverton-Holt stock-recruitment model, 

which fixed steepness (h) at 0.78, resulting in an FMSY estimate of 0.42. The projections assumed 

the FMP Framework 44 fishing year (May 1) catch of 2,118 mt would be landed as a calendar 

year (Jan 1) catch in 2011. 

The projection results indicate that rebuilding to SSBMSY (= 10,100 mt) is expected to be 

achieved with 76% probability in the current year (2011), assuming a 2011 catch of 2,118 mt. 

Catch: Total landings during 1964-2010 were predominately from the U.S groundfish trawl 

fishery, with lesser amounts reported by the USSR (during 1965-1977), for the U.S scallop 

dredge fishery, and as bycatch in the Canadian bottom trawl fisheries for cod and haddock (1-

24% of the total). Total landings reached a peak of 4,500 mt in 1972, and averaged 3,200 mt 

during 1973-1984, but then declined to their lowest level (780 mt) in 1995 (Figure B2). 

Following an increase to 3,100 mt in 2003, landings declined to 800 mt in 2007. Landings were 

1,000 mt in 2008 and 1,300 mt in 2010. During 1995-2010, the proportional standard error (%) 

due to the allocation of Georges Bank winter flounder landings to Statistical Areas using Vessel 

Trip Reports, ranged between 0.7 and 1.3%. 

U.S. discards during 1989-2010 were estimated using the Standardized Bycatch Reporting 

Methodology (Wigley et al. 2007) and were hindcast for 1964-1988. Discards for the Canadian 

scallop dredge fleet were estimated by the CA Division of Fisheries and Oceans for 2004-2010 

and were hindcast for 1982-2003. Discards from the Canadian groundfish trawl fleet were not 

available. During the assessment period, 1982-2010, total discards of winter flounder averaged 

15% of the total landings. Discards were higher during 1982-1991 than thereafter and were 

primarily from U.S. fisheries (i.e., primarily from the large mesh (≥ 5.5 in. codend mesh size)

fleet during 1964-1975 and the scallop dredge fleet during 1976-2010). However, after 1991, 
52nd SAW B. Georges B 28 ank Winter Flounder 

discards were primarily from the Canadian scallop dredge fishery. Total discards have slowly 

increased since 1995. The precision (CVs) of U.S. discard estimates for 1992-2010 ranged 

between 0.09 and 0.49 (average = 0.26), but the precision of the Canadian estimates is unknown. 

Catches during 1964-2010 and were dominated by landings from the U.S. groundfish bottom 

trawl fleet. Catches increased during 1964-1972, reaching a peak of 4,600 mt in 1972, but then 

declined to 2,000 mt in 1976 (Figure B3). During 1977-1984 catches ranged between 3,300 and 

4,300 mt then gradually declined to a time series low of 800 mt in 1995. Catches increased again 

to 3,300 mt in 2003 then declined to 1,000 mt in 2007, followed by a slight increase to 2,000 mt 

in 2009. Total catch in 2010 was 1,500 mt. Catches prior to 1964 were likely higher because U.S. 

landings alone reached a peak of 4,100 mt in 1945, close to the 1964-2010 peak catch of 4,600 

mt and without accounting for discards or landings from international fleets. 

 

Catch and Status Table (weights in 000s mt, recruitment in millions, arithmetic means): 

Georges Bank Winter flounder 

Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Max1 Min1 Mean1

 

U.S. landings 1.7 2.1 2.8 2.7 2.0 0.8 0.8 0.9 1.7 1.3 4.0 0.7 2.1 

CA landings 0.5 0.2 0.3 0.2 0.1 0.1 <0.1 <0.1 <0.1 <0.1 0.5 <0.1 0.1 

Total 2.2 2.3 3.1 2.9 2.1 0.9 0.8 0.9 1.7 1.3 4.5 0.8 2.3 

U.S. discards <0.1 <0.1 <0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.3 <0.1 0.1 

CA discards 0.2 0.2 0.2 0.1 0.1 0.1 <0.1 0.1 0.3 0.1 0.3 <0.1 0.1 

Total 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.4 0.2 0.5 0.1 0.2 

U.S. catch 1.7 2.1 2.8 2.8 2.1 0.9 1.0 1.0 1.8 1.4 4.3 0.7 2.2 

CA catch 0.7 0.4 0.5 0.3 0.2 0.2 <0.1 0.1 0.3 0.1 0.7 0.0 0.2 

Total 2.4 2.5 3.3 3.1 2.3 1.1 1.0 1.1 2.1 1.5 4.3 0.8 2.4 

Spawning Stock 

Biomass2

 10.7 10.2 9.5 5.5 5.3 5.9 6.2 6.5 7.9 9.7 17.4 26.3 1.2 10.7 

Recruitment (age 1) 9.0 7.3 6.1 5.5 5.6 10.5 15.6 18.8 4.0 22.5 3.4 4.0 0.2 9.0 

F (ages 4-6) 0.52 0.55 0.85 0.63 0.56 0.20 0.21 0.23 0.23 0.15 7.9 13.4 0.5 0.52 

1

 During 1964-2010 for landings (includes pre-2001 USSR landings), discards (no CA discards available prior to 1982) and catches; during 1982-

2010 for F, SSB and R 

2

 On April 1 annually 

Stock Distribution and Identification: Winter flounder (Pseudopleuronectes americanus) is a 

demersal flatfish species commonly found in North Atlantic estuaries and on the continental 

shelf. The species is distributed between the Gulf of St. Lawrence, Canada and North Carolina, 

U.S., although it is not abundant south of Delaware Bay. On Georges Bank, winter flounder are 

generally found at depths less than 82 m (Collette and Klein-MacPhee 2002). Tagging studies 

(e.g., Howe and Coates 1975) indicate that there is limited mixing of fish among the three 

current stock units, with about 1%-3% between the GOM and SNE/MA, about 1% between GBK 

and SNE/MA, and <1% between GOM and GBK. Meristics studies based mainly on fin ray 

counts also indicate a separate Georges Bank stock (Kendall 1912; Perlmutter 1947; Lux et al 

1970). Growth and maturity studies also support the distinction of at least three stock areas (Lux 

1973; Howe and Coates 1975; Witherell and Burnett 1993), with Georges Bank fish growing and 

maturing the fastest. The stock area extends from Georges Bank westward to about midway 

along the Great South Channel. 

Data and Assessment: Similar to the 2008 assessment (NEFSC 2008), an ADAPT VPA model 

was run with catch-at-age data (ages 1-7+) for 1982-2010. Swept-area stock abundance from the 
52nd SAW B. Georges B 29 ank Winter Flounder 

NEFSC spring and fall surveys (1982-2010) and the Canadian spring surveys (1987-2010), for 

ages 1-7+, were used in the VPA calibration. For the U.S. surveys, length-based, stock-specific 

calibration coefficients were used to convert catches by the SRV H.B. Bigelow to SRV Albatross 

IV catches. Major model changes included: the addition of discards from the Canadian scallop 

dredge fleet, a new maturity schedule, a new assumption for the instantaneous natural mortality 

rate (M = 0.3 instead of 0.2), and new MSY-based biological reference points (BRPs). 

Biological Reference Points: FMSY, SSBMSY, and MSY were estimated from a stock-recruitment 

model using a range of fixed values (Table B1) for steepness (slope of the stock recruitment 

curve near the origin) which was consistent with the stock and recruitment data. Based on the 

assumption that steepness should be similar between the three winter flounder stocks, values of 

steepness were chosen which were constructed to be as similar as possible between stocks, but 

which also provided good fits to the stock-recruitment data for each stock. For the Georges Bank 

stock, steepness was set at 0.78 (further details in Appendix of the 2011 SAW-52 Stock 

Assessment Report). The new BRP estimates are direct MSY-based estimates. The 

recommended biological reference points are: FMSY = FTHRESHOLD = 0.42, SSBMSY = BTARGET = 

10,100 mt, 1/2 SSBMSY = BTHRESHOLD = 5,050 mt, and MSY = 3,700 mt. For comparison, F40%, 

computed using the same biological and fishery characteristics, is 0.32, SSB40% is 11,300 mt, and 

MSY40% is 3,200 mt. 

The existing biological reference points from the 2008 assessment (NEFSC 2008) are: F40%

(FTHRESHOLD) = 0.26, SSB40% (BTARGET) = 16,000 mt, 1/2 SSB40% (BTHRESHOLD) = 8,000 mt, 

MSY40% = 3,500 mt. However, given the new model assumptions in the current assessment 

(assumed M = 0.3 rather than 0.2), comparison of the 2010 estimates of SSB and F estimates 

with the existing reference points is not appropriate. 

Fishing Mortality: Fishing mortality (fully recruited F, ages 4-6) increased from 0.42 in 1982 

to a peak of 1.2 in 1984, and then ranged between 0.57 and 0.92 during 1985-1993 (Figure B4). 

Fishing mortality decreased to 0.26 in 1999, but then increased again to 0.85 in 2003. Following 

a decline to 0.20 in 2006, fishing mortality remained stable at low levels (0.21-0.23) during 

2007-2009, and then declined to a record low of 0.15 in 2010. A retrospective analysis for the 

2001-2009 terminal years indicated that the retrospective error in fishing mortality ranged from 

-48% in 2002 to +42% in 2009. 

Spawning Stock Biomass: SSB decreased from a peak of 17,400 mt in 1982 to a record low of 

3,400 mt in 1995, and then increased again to 13,800 mt in 2000. SSB varied between 5,300 and 

10,700 mt during 2001-2009, and was 9,703 mt in 2010 (Figure B5). Retrospective error in SSB 

ranged from -13% in 2008 to +43% in 2002. 

 

Recruitment: Recruitment at age 1 increased from 13.8 million fish in 1982 to a peak of 26.3 

million fish in 1988, but then declined to 5.2 million fish in 1993 (Figure B6). Recruitment has 

averaged 10.5 million during 2003-2010. Retrospective error in recruitment at age 1 (R) ranged 

from +78% in 2005 (2004 year class) to -11% in 2009 (2008 year class). 
52nd SAW B. Georges B 30 ank Winter Flounder 

Special Comments: 

Stock-recruitment data showed no significant relationship with temperature or other 

environmental factors examined, unlike the SNE/MA winter flounder stock. 

The stock-recruitment data for this stock are less informative than the SNE/MA data for 

predicting recruitment at low spawner levels making estimation of the spawner-recruit 

relationship difficult without external information (Table B1). 

The revised assessment model alters the historical perception of stock status. Four changes from 

the previous assessment are: 1) a change of M from 0.2 to 0.3 and 2) a new maturity schedule, 3) 

the addition of Canadian discards, and 4) a change to MSY-based BRPs rather than proxies. The 

assessment indicates that the stock has not been overfished since 1996. This contrasts with the 

2008 assessment which indicated the stock was overfished in 2007. 

References:

Collette, B. and G. Klein-MacPhee. 2002. Bigelow and Schroeder’s Fishes of the Gulf of Maine. 

3rd Ed. Smithsonian Institution Press. Washington, D.C., USA. 748 p. 

Howe, A.B. and P.G. Coates. 1975. Winter flounder movements, growth, and mortality off 

Massachusetts. Trans. Am. Fish. Soc. 104(1):13-29. 

Kendall, W.C. 1912. Notes on a new species of flatfish from off the coast of New England. 

Bull. U.S. Bureau Comm. Fish. 30: 391-394.

Lux, F.E. 1973. Age and growth of the winter flounder, Pseudopleuronectes americanus, on 

Georges Bank. Fish. Bull. 71(2): 505-512. 

Lux, F.E., A.E. Peterson, Jr., and R.F. Hutton. 1970. Geographical variation in fin ray number in 

winter flounder, Pseudopleuronectes americanus (Walbaum) off Massachusetts. Trans. 

Am. Fish. Soc. 99: 483-488.

NEFSC. 2008. Assessment of 19 Northeast groundfish stocks through 2007. Report of the 3rd

Groundfish Assessment Review Meeting (GARM III), Northeast Fisheries Science 

Center, Woods Hole, Massachusetts. August 4-8, 2008. NEFSC Ref Doc. 08-15. 884 p.

Perlmutter, A. 1947. The blackback flounder and its fishery in New England and New 

York.Bull. Bingham Oceanog. Collection, Yale University 11(2), 92 p. 

Wigley, S.E., P.J. Rago, K.A. Sosebee, and D.L. Palka. 2007. The analytic component to the 

Standardized Bycatch Reporting Methodology Omnibus Amendment: sampling design 

and estimation of precision and accuracy (2nd ed.). Northeast Fish. Sci Cent. Rec. Doc. 

07-09. 156 p.

Witherell DB, Burnett J. 1993. Growth and maturation of winter flounder, Pseudopleuronectes 

americanus, in Massachusetts. Fish. Bull. 91: 816-820. 
52nd SAW B. Georges B 31 ank Winter Flounder 

Table B1. AIC profile for unfished steepness (h) values from Beverton-Holt stockrecruitment models for the 1982-2009 year classes of Georges Bank winter flounder. 

 

Fixed 

AIC 

    

(h) FMSY SSBMSY MSY 

0.60 583.217 0.26 19,785 4,910

0.65 581.230 0.30 15,144 4,318

0.70 579.698 0.34 12,437 4,003

0.75 578.518 0.38 10,673 3,824

0.76 578.317 0.39 10,341 3,799

0.77 578.126 0.41 9,798 3,777

0.78 577.945 0.42 9,524 3,757

0.79 577.774 0.43 9,269 3,740

0.80 577.611 0.44 9,030 3,725

0.85 576.917 0.51 7,742 3,678

0.90 576.390 0.60 6,621 3,672

0.95 575.996 0.74 5,476 3,706

 
52nd SAW B. Georges B 32 ank Winter Flounder 

B1. Stock status for Georges Bank winter flounder, during 2010, based on FMSY and SSBMSY

reference points. 80% confidence intervals are shown for the 2010 SSB and F estimates.

 
52nd SAW B. Georges B 33 ank Winter Flounder 

B2. Landings of Georges Bank winter flounder, by country, during 1964-2010. 

B3. U.S. landings of Georges Bank winter flounder during 1937-1950 and total landings and 

catches during 1964-2010. 

 
52nd SAW B. Georges B 34 ank Winter Flounder 

B4. Trends in average fishing mortality rates (ages 4-6) for Georges Bank winter flounder during 

1982-2010. The MSY-based BRP is recommended for stock status determination. 

B5. Trends in spawning stock biomass (SSB, 000s mt) for Georges Bank winter flounder during 

1982-2010. The MSY-based BRP is recommended for stock status determination. 

 
52nd SAW B. Georges B 35 ank Winter Flounder 

B6. Trends in age 1 recruitment (Jan. 1 stock numbers in millions) for Georges Bank winter 

flounder during 1982-2011. 
52nd SAW C. Gulf of M 36 aine Winter Flounder 

C. GULF OF MAINE (GOM) WINTER FLOUNDER ASSESSMENT SUMMARY FOR 

2011 

State of Stock: 

The assessment of GOM winter flounder stock is based on an empirical swept-area model 

utilizing data from the 2010 NEFSC fall survey, the MADMF fall survey, and the Maine-New 

Hampshire fall inshore survey. Using a survey trawl efficiency value of 0.6 the estimated stock 

biomass in 2010 of fish greater than 30 cm was 6,341 mt (80% CI 4,230 - 8,800 mt). The 

overfished status remains unknown because a biomass reference point or proxy could not be 

determined and an analytical assessment model was not accepted. 

In 2010 overfishing was not occurring for the stock (Figure C1). A proxy BRP value of the 

overfishing threshold was derived from a length-based yield per recruit analysis that assumes all 

fish above 30 cm are fully recruited to the fishery and that natural mortality is 0.3. Using F40%

(0.31) as a proxy for FMSY, the corresponding threshold exploitation rate is 0.23. The overfishing 

status is based on the ratio of 2010 catch (195 mt) to survey based swept area estimate of 

biomass for winter flounder exceeding 30 cm in length (6,341 mt). Exploitation rate in 2010 was 

estimated at 0.03 (80% CI 0.02 - 0.05), which is less than the threshold exploitation rate (0.23). 

The conclusion that overfishing was not occurring in 2010 is robust to the range of uncertainty in 

the biomass estimate (Figures C7 and C8). 

The biomass estimate for 2010 is 16% lower than that for 2009 using the same survey methods 

but this difference is not statistically significant (Figures C3 and C5). 

The most recent biological reference points for this stock were FMSY=0.43 and BMSY=4,100 mt; 

these estimates came from the assessment at SARC 36 in 2003. It is not appropriate to compare 

the 2010 exploitation rate and stock size estimates to those earlier BRP values which should no 

longer be used. 

Projections: Projections were not possible. 

Catch: Commercial landings were near 1,000 mt from 1964 to the mid 1970s. Thereafter 

commercial landings increased to a peaked of 2,793 mt in 1982, and then steadily declined to 

350 metric tons (mt) in 1999 (Figure C2). Landings have been near 650 mt from 2000 to 2004 

and about 300 mt from 2005 to 2009. Landings have declined to a record low of 140 mt in 2010. 

Recreational landings reached a peak in 1981 with 2,554 mt but declined substantially thereafter. 

Recreational landings have generally been less than 100 mt since 1994, with exception of 2008 

where the landings were estimated at 103 mt. A discard mortality of 15% was assumed for 

recreational discards. Discards were estimated for the large mesh trawl (1982-2010), gillnet 

(1986-2010), and northern shrimp fishery (1982-2010). A discard mortality of 50% was 

assumed for commercial fishery. In general the total discards are a small percentage (time series 

average 11%) of the total catch (Figure C2). There has been a substantial decline in the total 

catch compared to the early 1980s (recent catch is roughly 5% of the 1980s catch). 
52nd SAW C. Gulf of M 37 aine Winter Flounder 

Catch Table (weights in 000s mt,): GOM Winter Flounder

Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Max1 Min1 Mean1

 

Commercial landings 0.7 0.7 0.8 0.6 0.3 0.2 0.3 0.3 0.3 0.1 2.8 0.1 0.9 

Commercial discards <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.4 <0.1 0.1 

Recreational landings <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.1 0.1 <0.1 3.0 <0.1 0.5 

Recreational discards <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 

Catch used in 

assessment 0.8 0.7 0.8 0.7 0.4 0.2 0.3 0.4 0.4 0.2 6.2 0.2 1.3 

 

1: Over the period 1982-2010 

Stock Distribution and Identification: Winter flounder (Pseudopleuronectes americanus) is a 

demersal flatfish species commonly found in North Atlantic estuaries and on the continental 

shelf. The species is distributed between the Gulf of St. Lawrence, Canada and North Carolina, 

U.S., although it is not abundant south of Delaware Bay. Gulf of Maine winter flounder undergo 

annual migrations from estuaries and near shore areas, where spawning occurs in the late winter 

and early spring, to offshore shelf areas of less than 60 fathoms (110 meters). The current Gulf 

of Maine stock extends from the coastal shelf east of Provincetown, MA northward to the Bay of 

Fundy, including NEFSC statistical areas 511-515. 

Data and Assessment: GOM winter flounder models developed in ADAPT VPA, SCALE, and 

ASAP (NFT 2011) were too unreliable for stock status determination. The population models 

have difficulty with the conflicting data trends within the assessment, specifically the large 

decrease in the catch over the time series with very little change in the indices or age structure in 

both the catch and surveys. A new value for natural mortality has been adopted, changing from 

M = 0.20 to M = 0.30 which was used in the estimation of the F40% reference point. A combined 

survey 30+ cm biomass area swept estimate using the NEFSC, MADMF and the Maine-New 

Hampshire surveys was used to estimate biomass. The fall surveys were selected over the spring 

surveys because some portion of the stock is located within estuaries, which are not surveyed 

during the spring. 

Uncertainty in the individual estimates of survey abundance and swept area trawl footprints were 

characterized empirically and used to construct an overall estimate of uncertainty in the 

aggregate biomass estimate. The efficiency value of 0.6 was supported by comparison of VPA 

estimates of efficiency for the Georges Bank winter flounder while making the assumption that 

the same fraction of each stock is available to the respective surveys. The NEFSC fall survey 

(expressed in Albatross equivalents) had an efficiency estimate of 0.3. Calibration experiments 

between the FSV Bigelow and the R/V Albatross revealed a biomass conversion coefficient of 

~2. Thus an efficiency estimate for the Bigelow survey estimate in 2010 of 0.6 was supported. 

An analysis of catch rates in overlapping areas by the NEFSC and MADMF surveys 

demonstrated similar catchabilities for winter flounder by the two surveys. Sensitivity analyses 

were conducted with efficiencies of 0.8 and 1.0. The sampling distributions of biomass and 

fishing mortality are approximated by integrating over the factors which constitute the primary 

sources of uncertainty. These factors include the sampling variability in the NEFSC, MADMF 

and the Maine-New Hampshire spring and fall bottom surveys for 2009 and 2010. The second 

major source of variability for the survey estimates is the variation in the size of the area swept 

by an average tow. 
52nd SAW C. Gulf of M 38 aine Winter Flounder 

Biological Reference Points (BRP): Biological reference points for stock biomass are 

unknown. 

A proxy value of the overfishing threshold was derived for the 2011 assessment from a lengthbased yield per recruit (NFT 2011) analysis that assumes all fish above 30 cm are fully recruited 

to the fishery and that natural mortality is 0.3 (Figure C4). Von Bertalanffy parameters were 

estimated from the spring and fall NEFSC survey age data (n = 2,035) from 2006 to 2010. 

Maturity at length information is estimated from the spring MDMF survey (L50=29cm). The 

reference points were converted to exploitation rates to be consistent with the swept area biomass 

approach. Using F40% (0.31) as a proxy for FMSY, the corresponding threshold exploitation rate is 

0.23. This serves as a proxy for the overfishing threshold (Figure C1). Current practice is to set 

catch advice based on 75% FMSY. 75% of the estimated F40% exploitation rate is 0.17. The 

previous estimates of FMSY (from SARC 36 in 2003) used an M of 0.2 and observed average 

weights at age. 

MSY could not be estimated. 

Fishing Mortality: Exploitation rate in 2010 was estimated at 0.03 (80% CI 0.02 - 0.05) using 

the 2010 ratio of catch (195 mt) to the 30+ area swept biomass (6,341 mt; 80% CI 4,230 - 8,800 

mt) from the fall surveys (Figure C6). An assumed efficiency of 60% was used to construct this 

estimate from the NEFSC fall survey, the MADMF fall survey, and the Maine-New Hampshire 

fall inshore survey. 

Recruitment: Recruitment is unknown. 

Spawning Stock Biomass: Spawning stock biomass is unknown. 

Special Comments: There is considerable uncertainty with the GOM winter flounder 

assessment. There was a major effort to develop an ASAP assessment model for GOM winter 

flounder; however, no version of the model was satisfactory. The attempted analytical models 

had difficulty estimating population scale due to the conflicting data trends within the 

assessment, specifically the large decrease in the catch over the time series with very little 

change in the indices or age structure in both the catch and surveys. The scaling of the 

population estimates was sensitive to the weighting imposed on the catch at age compositions. 

The ASAP model did allow errors in the fit to the catch at age and improved fit to the survey 

indices without the split in survey catchability (See GARM III). However this resulted in a lack 

of fit to the plus group in the catch at age composition. The stock assessment report will 

summarize the ASAP model application, but its results are not used for the determination of 

stock status. 

An analytic assessment was not accepted in GARM III (NEFSC 2008) resulting in the status of 

the stock being unknown in 2008. 
52nd SAW C. Gulf of M 39 aine Winter Flounder 

References:

NEFSC. 2008. Assessment of 19 Northeast groundfish stocks through 2007. Report of the 3rd

Groundfish Assessment Review Meeting (GARM III), Northeast Fisheries Science 

Center, Woods Hole, Massachusetts. Aug. 4-8, 2008. NEFSC Ref Doc. 08-15. 884 p. 

NOAA Fisheries Toolbox (NFT) 2011. [Internet address: http://nft.nefsc.noaa.gov/]. 
52nd SAW C. Gulf of M 40 aine Winter Flounder 

GOM Winter Flounder Overfishing status

30+ cm Exploitable Biomass (000s mt)

0123456789

Exploitation Rate

0.00

0.05

0.10

0.15

0.20

0.25

0.30

2010

Exploitation Rate Threshold = 0.23

C1. Stock status for GOM winter flounder in 2010 with respect to a proxy for FMSY. 80% 

confidence intervals are shown for biomass and exploitation rate. F40% = 0.31, which 

corresponds to an exploitation rate of 0.23. 

 
52nd SAW C. Gulf of M 41 aine Winter Flounder 

C2. GOM winter flounder composition of the catch by weight in metric tons from 1982 to 2010. 

 

Catch Weight

0

1,000

2,000

3,000

4,000

5,000

6,000

198219841986198819901992199419961998200020022004200620082010

metric tons

Shrimp Disc

LG Mesh Disc

Gillnet Disc

Rec Disc

Rec

Com
52nd SAW C. Gulf of M 42 aine Winter Flounder 

Area Swept 30+ cm Biomass Survey Components 

Spring 2009

Spring 2010

Fall 2009

Fall 2010

30+ cm Area Swept Biomass (mt)

0

2000

4000

6000

8000

MENH

NEFSC 

MDMF

C3. 30+ cm area swept biomass estimates for the spring and fall surveys from 2009 to 2010 

assuming efficiency is 0.6. The NEFSC survey used a TOGA tow criteria of 132x. 

 
52nd SAW C. Gulf of M 43 aine Winter Flounder 

C4. Length-based yield per recruit analysis using von Bertalanffy parameters estimated from the 

spring and fall 2006-2010 NEFSC surveys, maturity at length from the MDMF survey and 

assuming a natural mortality of 0.3. F40% was estimated at 0.31. The SSB/R line (red) decreases 

as F increases. 

 Yield per Recruit

Spawning Stock Biomass per Recruit
52nd SAW C. Gulf of M 44 aine Winter Flounder 

C5. Sensitivity of swept area 30+ cm biomass estimates for Gulf of Maine winter flounder for 

varying seasons and years under three alternative assumed values of trawl efficiency for all three 

surveys. 

 

B Estimates vs Assumed Efficiency

Fall2009

0.5 0.6 0.7 0.8 0.9 1.0

EFFIC

0

5000

10000

15000

20000

B oi mass m( t)

Fall2010

0.5 0.6 0.7 0.8 0.9 1.0

EFFIC

0

5000

10000

15000

20000

B oi mass m( t)

Spring2009

0.5 0.6 0.7 0.8 0.9 1.0

EFFIC

0

5000

10000

15000

20000

B oi mass m( t)

Spring2010

0.5 0.6 0.7 0.8 0.9 1.0

EFFIC

0

5000

10000

15000

20000

B oi mass m( t)
52nd SAW C. Gulf of M 45 aine Winter Flounder 

C6. Estimated exploitation rates for Gulf of Maine winter flounder for Fall 2010 based on three 

assumed gear efficiencies (0.6, 0.8, and 1.0) and 5 levels of catch (the 2010 catch of 195 mt, an 

assumed quota of 500 mt, assumed quota of 700 mt, 75% OFL of 1,078 mt and the OFL of 

1,458 mt based on F40%). Dashed lines represent length-based exploitation rate estimates of F40%

(0.23) and 75% of F40% (0.17). SSB per recruit is derived using GOM winter flounder growth 

and maturation relationships and an assumed knife edge selection curve at 30 cm. 

 

Exploitation Estimates: Fall 2010

0.6

0 500 1000 1500

QUOTA

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Exp ol i at t oi n Rate

0.8

0 500 1000 1500

QUOTA

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Exp ol i at t oi n Rate

1

0 500 1000 1500

QUOTA

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Exp ol i at t oi n Rate
52nd SAW C. Gulf of M 46 aine Winter Flounder 

C7. Estimated probability of exceeding FMSY proxy (F40%), expressed as an exploitation rate of 

0.23, and assuming efficiencies of 60%, 80% and 100% based of the fall 2010 survey across a 

range of quotas. 

 

Probability of Exceeding Fmsy Proxy=0.23

0 500 1000 1500

Quota (mt)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Pro

b

a

bility

F

>

F

m

s

y

Pro

x

y

60%

80%

100%

Efficiency
52nd SAW C. Gulf of M 47 aine Winter Flounder 

C8. Estimated probability of exceeding 75% of FMSY proxy (F40%), expressed as an exploitation 

rate of 0.17, and assuming efficiencies of 60%, 80% and 100% based of the fall 2010 survey 

across a range of quotas. 

 

Probability of Exceeding 75% Fmsy Proxy=0.17

0 500 1000 1500

Quota (mt)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Pro

b

a

bility

F

>

7

5

%

F

m

s

y

Pro

x

y

60%

80%

100%

Efficiency
52nd SAW Assessment Summary Report Appendix: Terms of Referen 48 ce 

Appendix: Assessment Terms of Reference 

TORs for SAW/SARC52 (June 6-10, 2011) 

(file vers.: 12/17/2010) 

A. Winter flounder (Southern New England Stock)

1. Estimate catch from all sources including landings and discards. Characterize the uncertainty in 

these sources of data. 

2. Present survey data being considered and/or used in the assessment (e.g., regional indices of 

abundance, recruitment, state and other surveys, age-length data, etc.). Characterize uncertainty in 

these sources of data. 

3. Estimate annual fishing mortality, recruitment and stock biomass (both total and spawning stock) 

for the time series (integrating results from TOR-5), and estimate their uncertainty. Include areaswept biomass estimates. Investigate if implied survey gear or catchability estimates are 

reasonable. Include a historical retrospective analysis to allow a comparison with previous 

assessment results. 

4. Perform a sensitivity analysis which examines the impact of allocation of catch to stock areas on 

model performance (in TOR-3). 

5. Examine the effects of incorporating environmental factors in models of population dynamics 

(e.g., spring water temperatures in an environmentally-explicit stock recruitment function).

6. State the existing stock status definitions for “overfished” and “overfishing”. Then update or 

redefine biological reference points (BRPs; point estimates or proxies for BMSY, BTHRESHOLD, and 

FMSY) and provide estimates of their uncertainty. If analytic model-based estimates are 

unavailable, consider recommending alternative measurable proxies for BRPs. Comment on the 

scientific adequacy of existing BRPs and the “new” (i.e., updated, redefined, or alternative) 

BRPs. 

7. Evaluate stock status (overfished and overfishing) with respect to the “new” BRPs (from TOR 6), 

and with respect to the existing BRPs (from a previous accepted peer review) whose values have 

been updated. 

8. Develop and apply analytical approaches and data that can be used for conducting single and 

multi-year stock projections and for computing candidate ABCs (Acceptable Biological Catch; 

see Appendix to the TORs) under a set of alternative harvest scenarios. If the stock needs to be 

rebuilt, take that into account in these projections. 

a. Provide numerical short-term projections (3-5 yrs, or through the end of the rebuilding 

period, as appropriate). Each projection should estimate and report annual probabilities of 

exceeding threshold BRPs for F, and probabilities of falling below threshold BRPs for 

biomass. In carrying out projections, consider a range of assumptions about the most 

important uncertainties in the assessment (e.g., terminal year abundance, variability in 

recruitment). 

b. Take into consideration uncertainties in the assessment and the species biology to 

describe this stock’s vulnerability (see “Appendix to the SAW TORs”) to becoming or 

remaining overfished, and how this could affect the choice of ABC. 

c. Develop plausible hypotheses (e.g., mixing among the three stocks) which might explain 

any conflicting trends in the data and undertake scenario analyses to evaluate the 

consequences of these alternate hypotheses on ABC determination. 
52nd SAW Assessment Summary Report Appendix: Terms of Referen 49 ce 

9. Review, evaluate and report on the status of the SARC and Working Group research 

recommendations listed in recent SARC reviewed assessments and review panel reports. Identify 

new research recommendations. 

B. Winter flounder (Georges Bank Stock) 

1. Estimate catch from all sources including landings and discards. Characterize the uncertainty in 

these sources of data. 

2. Present survey data being considered and/or used in the assessment (e.g., regional indices of 

abundance, recruitment, state and other surveys, age-length data, etc.). Characterize uncertainty in 

these sources of data. 

3. Estimate annual fishing mortality, recruitment and stock biomass (both total and spawning stock) 

for the time series (integrating results from TOR-5), and estimate their uncertainty. Include areaswept biomass estimates. Investigate if implied survey gear or catchability estimates are 

reasonable. Include a historical retrospective analysis to allow a comparison with previous 

assessment results. 

4. Perform a sensitivity analysis which examines the impact of allocation of catch to stock areas on 

model performance (in TOR-3). 

5. Examine the effects of incorporating environmental factors in models of population dynamics 

(e.g., spring water temperatures in an environmentally-explicit stock recruitment function).

6. State the existing stock status definitions for “overfished” and “overfishing”. Then update or 

redefine biological reference points (BRPs; point estimates or proxies for BMSY, BTHRESHOLD, and 

FMSY) and provide estimates of their uncertainty. If analytic model-based estimates are 

unavailable, consider recommending alternative measurable proxies for BRPs. Comment on the 

scientific adequacy of existing BRPs and the “new” (i.e., updated, redefined, or alternative) 

BRPs. 

7. Evaluate stock status (overfished and overfishing) with respect to the “new” BRPs (from TOR 6), 

and with respect to the existing BRPs (from a previous accepted peer review) whose values have 

been updated. 

8. Develop and apply analytical approaches and data that can be used for conducting single and 

multi-year stock projections and for computing candidate ABCs (Acceptable Biological Catch; 

see Appendix to the TORs) under a set of alternative harvest scenarios. If the stock needs to be 

rebuilt, take that into account in these projections. 

a. Provide numerical short-term projections (3-5 yrs, or through the end of the rebuilding 

period, as appropriate). Each projection should estimate and report annual probabilities of 

exceeding threshold BRPs for F, and probabilities of falling below threshold BRPs for 

biomass. In carrying out projections, consider a range of assumptions about the most 

important uncertainties in the assessment (e.g., terminal year abundance, variability in 

recruitment). 

b. Take into consideration uncertainties in the assessment and the species biology to 

describe this stock’s vulnerability (see “Appendix to the SAW TORs”) to becoming or 

remaining overfished, and how this could affect the choice of ABC. 
52nd SAW Assessment Summary Report Appendix: Terms of Referen 50 ce 

c. Develop plausible hypotheses (e.g., mixing among the three stocks) which might explain 

any conflicting trends in the data and undertake scenario analyses to evaluate the 

consequences of these alternate hypotheses on ABC determination. 

9. Review, evaluate and report on the status of the SARC and Working Group research 

recommendations listed in recent SARC reviewed assessments and review panel reports. Identify 

new research recommendations. 

C. Winter flounder (Gulf of Maine Stock) 

1. Estimate catch from all sources including landings and discards. Characterize the uncertainty in 

these sources of data. 

2. Present survey data being considered and/or used in the assessment (e.g., regional indices of 

abundance, recruitment, state and other surveys, age-length data, etc.). Characterize uncertainty in 

these sources of data. 

3. Estimate annual fishing mortality, recruitment and stock biomass (both total and spawning stock) 

for the time series (integrating results from TOR-5), and estimate their uncertainty. Include areaswept biomass estimates. Investigate if implied survey gear or catchability estimates are 

reasonable. Include a historical retrospective analysis to allow a comparison with previous 

assessment results. 

4. Perform a sensitivity analysis which examines the impact of allocation of catch to stock areas on 

model performance (in TOR-3). 

5. Examine the effects of incorporating environmental factors in models of population dynamics 

(e.g., spring water temperatures in an environmentally-explicit stock recruitment function).

6. State the existing stock status definitions for “overfished” and “overfishing”. Then update or 

redefine biological reference points (BRPs; point estimates or proxies for BMSY, BTHRESHOLD, and 

FMSY) and provide estimates of their uncertainty. If analytic model-based estimates are 

unavailable, consider recommending alternative measurable proxies for BRPs. Comment on the 

scientific adequacy of existing BRPs and the “new” (i.e., updated, redefined, or alternative) 

BRPs. 

7. Evaluate stock status (overfished and overfishing) with respect to the “new” BRPs (from TOR 6), 

and with respect to the existing BRPs (from a previous accepted peer review) whose values have 

been updated. 

8. Develop and apply analytical approaches and data that can be used for conducting single and 

multi-year stock projections and for computing candidate ABCs (Acceptable Biological Catch; 

see Appendix to the TORs) under a set of alternative harvest scenarios. If the stock needs to be 

rebuilt, take that into account in these projections. 

a. Provide numerical short-term projections (3-5 yrs, or through the end of the 

rebuilding period, as appropriate). Each projection should estimate and report 

annual probabilities of exceeding threshold BRPs for F, and probabilities of 

falling below threshold BRPs for biomass. In carrying out projections, consider a 
52nd SAW Assessment Summary Report Appendix: Terms of Referen 51 ce 

range of assumptions about the most important uncertainties in the assessment 

(e.g., terminal year abundance, variability in recruitment). 

b. Take into consideration uncertainties in the assessment and the species biology to 

describe this stock’s vulnerability (see “Appendix to the SAW TORs”) to 

becoming or remaining overfished, and how this could affect the choice of ABC. 

c. Develop plausible hypotheses (e.g., mixing among the three stocks) which might 

explain any conflicting trends in the data and undertake scenario analyses to 

evaluate the consequences of these alternate hypotheses on ABC determination. 

9. Review, evaluate and report on the status of the SARC and Working Group research 

recommendations listed in recent SARC reviewed assessments and review panel reports. Identify 

new research recommendations. 

 

Appendix to the SAW TORs: 

Clarification of Terms 

used in the SAW/SARC Terms of Reference 

(The text below is from DOC National Standard Guidelines, Federal Register, vol. 74, no. 11, January 16, 2009) 

On “Acceptable Biological Catch”: 

Acceptable biological catch (ABC) is a level of a stock or stock complex’s annual catch that accounts for the 

scientific uncertainty in the estimate of [overfishing limit] OFL and any other scientific uncertainty...” (p. 3208) [In 

other words, OFL ≥ ABC.]

ABC for overfished stocks. For overfished stocks and stock complexes, a rebuilding ABC must be set to reflect the 

annual catch that is consistent with the schedule of fishing mortality rates in the rebuilding plan. (p. 3209)

NMFS expects that in most cases ABC will be reduced from OFL to reduce the probability that overfishing might 

occur in a year. (p. 3180) 

ABC refers to a level of ‘‘catch’’ that is ‘‘acceptable’’ given the ‘‘biological’’ characteristics of the stock or stock 

complex. As such, [optimal yield] OY does not equate with ABC. The specification of OY is required to consider a 

variety of factors, including social and economic factors, and the protection of marine ecosystems, which are not 

part of the ABC concept. (p. 3189) 

On “Vulnerability”: 

“Vulnerability. A stock’s vulnerability is a combination of its productivity, which depends upon its life history 

characteristics, and its susceptibility to the fishery. Productivity refers to the capacity of the stock to produce MSY 

and to recover if the population is depleted, and susceptibility is the potential for the stock to be impacted by the 

fishery, which includes direct captures, as well as indirect impacts to the fishery (e.g., loss of habitat quality).” (p. 

3205) 
Procedures for Issuing Manuscripts

in the

Northeast Fisheries Science Center Reference Document (CRD) Series

Clearance

All manuscripts submitted for issuance as CRDs 

must have cleared the NEFSC’s manuscript/abstract/

webpage review process. If any author is not a federal 

employee, he/she will be required to sign an “NEFSC 

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includes material from another work which has been 

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to use that material by securing release signatures on 

the “NEFSC Use-of-Copyrighted-Work Permission 

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For more information, NEFSC authors should see 

the NEFSC’s online publication policy manual, “Manuscript/abstract/webpage preparation, review, and dissemination: NEFSC author’s guide to policy, process, 

and procedure,” located in the Publications/Manuscript 

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style manual is silent on many aspects of scientific 

manuscripts. The CRD series relies more on the CSE 

Style Manual. Manuscripts should be prepared to 

conform with these style manuals. 

The CRD series uses the American Fisheries Society’s guides to names of fishes, mollusks, and decapod 

crustaceans, the Society for Marine Mammalogy’s 

guide to names of marine mammals, the Biosciences 

Information Service’s guide to serial title abbreviations, 

and the ISO’s (International Standardization Organization) guide to statistical terms. 

For in-text citation, use the name-date system. A 

special effort should be made to ensure that all necessary bibliographic information is included in the list 

of cited works. Personal communications must include 

date, full name, and full mailing address of the contact.

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Once your document has cleared the review process, the Editorial Office will contact you with publication needs – for example, revised text (if necessary) and 

separate digital figures and tables if they are embedded 

in the document. Materials may be submitted to the 

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attachments, or intranet downloads. Text files should 

be in Microsoft Word, tables may be in Word or Excel, 

and graphics files may be in a variety of formats (JPG, 

GIF, Excel, PowerPoint, etc.).

Production and Distribution

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Editorial Office will develop the inside and outside 

front covers, the inside and outside back covers, and 

the title and bibliographic control pages of the document.

Once both the PDF (print) and Web versions of 

the CRD are ready, the Editorial Office will contact 

you to review both versions and submit corrections or 

changes before the document is posted online.

A number of organizations and individuals in the 

Northeast Region will be notified by e-mail of the 

availability of the document online. 
Research Communications Branch

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Publications and Reports

of the

Northeast Fisheries Science Center

The mission of NOAA’s National Marine Fisheries Service (NMFS) is “stewardship of living marine resources 

for the benefit of the nation through their science-based conservation and management and promotion of the 

health of their environment.” As the research arm of the NMFS’s Northeast Region, the Northeast Fisheries 

Science Center (NEFSC) supports the NMFS mission by “conducting ecosystem-based research and assessments of living marine resources, with a focus on the Northeast Shelf, to promote the recovery and long-term 

sustainability of these resources and to generate social and economic opportunities and benefits from their use.” 

Results of NEFSC research are largely reported in primary scientific media (e.g., anonymously-peer-reviewed 

scientific journals). However, to assist itself in providing data, information, and advice to its constituents, the 

NEFSC occasionally releases its results in its own media. Currently, there are three such media:

NOAA Technical Memorandum NMFS-NE -- This series is issued irregularly. The series typically includes: data reports of 

long-term field or lab studies of important species or habitats; synthesis reports for important species or habitats; annual reports 

of overall assessment or monitoring programs; manuals describing program-wide surveying or experimental techniques; literature 

surveys of important species or habitat topics; proceedings and collected papers of scientific meetings; and indexed and/or annotated 

bibliographies. All issues receive internal scientific review and most issues receive technical and copy editing.

Northeast Fisheries Science Center Reference Document -- This series is issued irregularly. The series typically includes: data 

reports on field and lab studies; progress reports on experiments, monitoring, and assessments; background papers for, collected 

abstracts of, and/or summary reports of scientific meetings; and simple bibliographies. Issues receive internal scientific review and 

most issues receive copy editing.

Resource Survey Report (formerly Fishermen’s Report) -- This information report is a regularly-issued, quick-turnaround report on 

the distribution and relative abundance of selected living marine resources as derived from each of the NEFSC’s periodic research vessel surveys of the Northeast’s continental shelf. This report undergoes internal review, but receives no technical or copy editing.

TO OBTAIN A COPY of a NOAA Technical Memorandum NMFS-NE or a Northeast Fisheries Science Center Reference Document, 

either contact the NEFSC Editorial Office (166 Water St., Woods Hole, MA 02543-1026; 508-495-2350) or consult the NEFSC webpage 

on “Reports and Publications” (http://www.nefsc.noaa.gov/nefsc/publications/). To access Resource Survey Report, consult the Ecosystem 

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