Stock Assessment

1
Stock Assessment Setting of Annual Catch Limits
inNew England

• Bob OBoyle, Steve Cadrin, Jake Kritzer
• SSC, NEFMC
• Steve Correia and Tom Nies
• PDT, NEFMC

2
Stock Assessment Peer Review

• Stock Assessment Review Committee (SAW/SARC)
• Transboundary Resources Assessment Committee
  (TRAC)
• Groundfish Assessment Review Meeting (GARM)
• Process
• NE Regional Coordination Committee (all NE
  clients NEFMC, MAFMC, ASMFC, NERO, NEFSC)
  determines schedule of assessments terms of
  reference
• NEFSC/Canada DFO/State Agency/University teams
  produce assessments to address TORs
• External review (CIE) with SSC chair
• Plan Development Team post processing (e.g.,
  projections for management alternatives that meet
  objectives of FltFmsy, rebuilding)
• SSC review of status determination catch advice

3
What is GARM III?

• Groundfish Assessment Review Meetings
• November 2007 August 2008
• 19 groundfish stocks managed under US Northeast
  Multispecies Fishery Management Plan
• GARM I - October 2002
• GARM II - August 2005
• GARM III most comprehensive to date

Benchmarks
4
GARM III Stocks

• Cod
• GB GOM
• Haddock
• GB GOM
• Yellowtail
• GB, GOM, SNE
• Witch Flounder
• American Plaice
• Winter Flounder
• GB, GOM, SNE

• Windowpane
• GB SNE
• Pollock
• White Hake
• Redfish
• Ocean Pout
• Atlantic Halibut

5
Four Meetings

• Data Inputs - 29 Oct 2 Nov 2007
• Assessment Models - 25 29 Feb 2008
• Biological Reference Points - 28 April 2 May
  2008
• Assessments - 4 8 August 2008

6
Data Inputs Terms of Reference

• Commercial survey data
• Statistical methods
• Tagging programs for cod yellowtail flounder
• Industry-Based Surveys
• Estimates of precision bias of data derived
  quantities
• Measures of uncertainty implications for use in
  assessment models

7
Models Terms of Reference

• Index methods, Production Models Age- or
  Length-based Models
• SCAA vs VPA with respect to
• Retrospective patterns
• Alternative parameterizations
• Incorporation of external information e.g.
  tagging environmental data
• Incorporation of prior, external information
• Potential factors responsible for retrospective
  patterns
• Assessment model to determine stock status
  productivity until next benchmark

8
BRP Terms of Reference

• Influence of retrospective patterns (F, SSB,
  recruitment) on BRPs forecasting
• Trends in life history parameters assess
  importance for BRPs rebuilding scenarios
• Aggregate ecosystem yield of groundfish fishery
  compare to aggregate single stock yield
  projections
• BRPs for use in stock status determination
• Models for forecasting for evaluating
  rebuilding scenarios

9
Assessors Reviewers

• NEFSC Woods Hole (approx 25)
• Data inputs
• Crecco, Van-Eeckhaute, Kahn, Needle, Rothschild,
  Smith, Helge-Vølstad
• Models
• De Oliveira, Gavaris, Ianelli, Jiao, Jones,
  Medley
• Biological Reference Points
• Bell, Gavaris, Haist, Reeves, Thompson
• Assessments
• Cieri, Mohn, Rosenberg, Sinclair
• Industry Experts
• Butterworth, Rademeyer
• Managers industry

10
GARM III Stock Status
11
Data Inputs

• Reliability of total Catch
• New trip/landings hierarchical algorithm
• VMS verification
• Sampling adequacy
• Estimation of uncertainty in CAA
• Design (bootstrap) vs model based provided
  similar results
• Importance of sampling rates at port level
  distribution of sampling effort amongst trips
• Discard estimation (Observer data)
• Ratio of Sums method (sum discard wt / sum kept
  wt) preferred over Avg (Discard wt / Kept wt) per
  trip
• More reliable data on total landings rather than
  total trips

12
Models

• Range of Models
• Relative Trends
• Trends in relative abundance fishing mortality
• Production
• By1By Yrep -Cy
• Yrep constant (Yrep a), linear (Yrep a bBy) or
  quadratic (Yrep rBy 1-By /K
• Age based
• VPA Statistical Catch at Age (SCAA)
• Length-and-age-based
• Age data limited
• Tendency for model software to become
  confounded
• Focus on model first
• Then choose software

13
Models
14
Retrospective Pattern

• Significant part of GARM review
• Primary potential causes
• Unrecorded catch
• Change in natural mortality
• Change in abundance index catchability (q)
• Change in fishery selectivity
• Not possible to identify cause through model
  diagnostics
• Adjusting model assumptions (e.g. altering survey
  q, catches or M) to remove pattern does not
  guarantee problem resolved
• Model may continue to be mis-specified
• Need testable hypotheses on cause(s)

15
Georges Bank Cod SSB Retrospective
16
GARM Practice on Retrospectiveif acceptable
adjustment cannot be made

• Default
• Terminal estimates in error whilst historical
  estimates correct
• Check age-specific retrospective patterns to
  determine age where magnitude consequential
• Adjust population numbers for terminal year of
  VPA (initial year of projection) to account for
  retrospective pattern
• Conduct projections using adjusted population
  numbers

17
Adjustment for Retrospective
Rho adjusted Base Split Survey generally
produced similar current status
18
Partial Recruitment

• PR on older age groups recurring issue
• Dome PRs may resolve retrospective but generated
  cryptic biomass
• Model biomass that has not been observed in
  either fishery or surveys
• Burden of proof (default)
• Demonstrate that fish exist when not observed in
  fishery surveys, even if model fit with
  dome-shaped PR is better
• Need external data to resolve
• Gulf of Maine Cod White Hake

Patterson (ICES 2002) In highly parameterized
models fishing mortality tended towards
zero population numbers tended towards infinity
19
Gulf of Maine Cod

• Butterworth Rademeyer used SCAA dome PR
• Requires supporting evidence
• Extend age range in Catch at Age
• April 2008 7 group
• August 2008 11 group
• Tagging
• If F declines due to dome PR, expect fraction cod
  recovered will decline as age of tagging
  increases
• 100,000 tagged cod released during 2003 2005
  (6000 recoveries to date)

Small Dome fit Raised issues in VPA computation
20
Gulf of Maine Cod Tagging
Predicted Recovery at age assuming Dome
More Flat than Domed PR
Predicted Recovery at age assuming Flat Top
Observed Recovery
21
Survey Qs based on Swept Area

• Allowed Examination of survey catchability
  patterns
• Stock by stock
• Season by season
• Species by species
• Patterns by age versus expectation
• Survey catchability expected to asymptote or
  decline at some age
• Patterns similar across stocks?

22
Biological Reference Points

• Limit BRPs
• Flim Fmsy or proxy
• Blim ½ Bmsy or proxy
• Relies on Stock Recruitment Relationship
• Default
• If recruitment SSB derived from assessments
  informative, compute FMSY BMSY using parametric
  projections
• If S / R not informative, use F40MSP as proxy
  BMSY proxy computed using non-parametric
  projections
• Non-parametric projections
• Conduct hindcast model
• Conduct projections using bootstrapped residuals
• Sample from empirical S/R using Breakpoint if
  necessary

23
Hierarchy of Limit RPs
No Target RPs as yet
24
Estimation of BRPs
Most stocks used non-parametric approach to BRPs
25
Changes relative to BRPs
Number of biomass RPs declined Reduced
Productivity
26
Average Weight (kg) at Age Georges Bank Haddock
27
Single species vs Aggregate MSY

• Surplus Production Model fit to Aggregate
  Demersal Catch NMFS Spring Fall Surveys
• MSY
• 139 kt versus 145 kt from GARM
• Bmsy
• 1066 kt vs 950 ky from GARM
• System wide Fmsy 0.15

28
Ecosystem Considerations
GARM 4.3 of 14.6 t /km2 Target biomass for all
NE demersal fish species Just below avg
productivity of many ecosystems
29
Ecosystem Conclusions

• 2nd Tier quota could be considered during
  recovery for long-term maintenance
• System recovery predicated on low fishing
  mortality (FMSY 0.15)
• Several stocks constrain recovery of complex
  (i.e. halibut, GB cod, GB Yt, white hake, SNE Yt)
• Unless stocks can be targeted independently, much
  lower fishing effort required

Could estimate M if model nodes stocks not
guilds
30
Where is NEFMC in ACL Implementation?

• July
• Groundfish Plan Development Team (PDT) developed
  approach
• SSC consideration of approach
• August - October
• GARM assessments of 19 Groundfish stocks
• Comments on draft National Standards 1 guidelines
• November
• Further development to consider guidance from
  this workshop

Approach not to be detailed in FMP Amendment
16 Changes through experience without formal
management action
31
NS 1 Guidelines ProposalSetting ACLs Process
Rationale for ABC ACL Difference?
32
NE Multispecies FMP Definitions
ACT optional for Councils who wish to use them
33
NEFMC Groundfish ACL Process

• ACLs element of existing adjustment process
• SAFE every year management revisions every two
  years
• ACL recommendations for 3 years
• NMFS Science
• August peer review of assessments
• PDT
• Drafts recommended ABCs for SSC
• Interacts with SSC on ABC recommendations prior
  to September
• ACL Recommendations to Council by September
• SSC
• ABCs to Council by September
• Council
• Decision on PDT recommendations prior to December
• ACLs to NMFS prior to mid December

34
NEFMC Stock Assessment / Advisory Process
NMFS
US / Canada Under Development
ACL
ACL
ACL
NMFS Science
TRAC
TMGC
Council
PDT
ABC
ACL check for consistency with ABC
ABC
SSC
Comment on Biological Uncertainty
35
Role of NEFMC SSC

• Interface between science Council
• add value to process
• Interpret peer reviewed science for Council
  process
• Define peer review as needed
• Avoid unnecessary duplication of accepted peer
  review
• Complement tactical decisions from PDTs with
  strategic thinking
• Strategically placed to undertake MSEs

36
Implementation Schedule

• Groundfish ACLs rarely based on data more recent
  than two years old
• Some ACLs based on data five years old
• SSC
• Consider Control Rules informed by data available
  on more frequent basis (e.g. trawl surveys)
• Process used on South African Hake
• Validated by MSE

37
ACL Setting Framework

• Informed by Rosenberg et al (2007)
• Framework applicable to data poor data rich
  stocks
• Determine vulnerability (risk to impact) of stock
• Productivity / Susceptibility Analysis (PSA)
• Relate risk to uncertainty to determine buffer
  sizes
• Biological buffer OFL gt ABC
• Management buffer ABC gt ACL
• Design ABC ACL Control Rules
• Default buffer size for given level of risk

38
Risk impact x P (impact)
Susceptibility
Productivity
HIGH RISK
Impact
LOW RISK
P (Impact)
39
Attributes of Vulnerability

• Productivity
• Maximum age
• Age at maturity
• Size at maturity
• Annual fecundity
• Maximum size
• Reproductive strategy
• Trophic level

• Susceptibility
• Availability
• Overlap with fishery
• Global distribution
• Encounterability
• Water column position
• Depth range overlap
• Adult Habitat
• Selectivity
• Size at Maturity
• Total records (/-) (TEP, DI, TA/BP)
• Post-capture mortality
• Fate on discarding

If data missing, assume high risk
40
Productivity ScoringIllustrative from Rosenberg
Average Rank 1.43
41
Susceptibility ScoringIllustrative from Rosenberg
Average Rank 1.75
42
Vulnerability ScoreIllustrative from Rosenberg
43
Determination of ACL

• As risk to overfishing increases, buffer should
  increase
• Higher risk larger buffer

44
Determination of ACL

• Aspects of vulnerability already incorporated
  into BRPs
• Risk to resource of not conforming to BRPs varies
  with vulnerability
• Risk function of biological management
  uncertainty

45
Sources of Uncertainty

• Biological
• Model
• Process
• Observation
• Management
• Implementation

Assessment Related
Management Related
46
Buffer Estimation

• Rosenberg et al (2007) envisioned two tables
• biological management uncertainty

RISK
Initially choose default buffer size by
cell Adjustment of buffer size in each cell
informed by analyses of data rich stocks
47
Setting ABC Biological Uncertainty (OFL ABC)

• Risk f (Productivity but not susceptibility)
  being revisited
• ABC Control Rule f (Biological Uncertainty)
• ACL Control Rule f (Management Uncertainty)

48
Productivity (draft)
High Risk
Low Risk
Equivalent to PSA chart
49
Biological Uncertainty (draft)
High Risk
Low Risk
50
ABC Control Rule
Low Risk
ABC set at x ile of stock projections (AGEPRO)
Productivity Factor (low to High)
High Risk
Biological Uncertainty Factor (More to Less)
51
Setting ACLManagement Uncertainty (ABC ACL)

• Similar approach for setting ABC
• Productivity Factor table
• Management uncertainty table
• ACL Control Rule still needs to be developed

52
(No Transcript)
53
ACL Sub-Components
Xs to be determined
Important to have ACLs for all subcomponents due
to link to AMs
54
Further Developments

• Relationship between buffer size uncertainty
  (biological management) requires exploration
• Apply approach to past data to explore
  relationship performance using different rules
• Data rich situations can inform buffer sizes in
  data poor situations
• Management Strategy Evaluations (MSE) to explore
  buffer sizes

55
Management Strategy Evaluation

• Evaluate impacts of uncertainty on achievement of
  objectives (biological, economical, social)
• Assessment
• Benchmarks annual fishery survey indices
• Strategies
• Rebuilding schedules implications for stock
  fishery
• Implementation
• Seasons, closed areas, gear regulations

56
Management Strategy Evaluation

• Managers industry set goals propose
  strategies
• Scientists assist in modeling
• Economists assist in evaluation of costs
  benefits of options (e.g. GOM cod)
• cost of 50 to 25 prob of exceeding overfishing
• 27 reduction in landings
• Negligible difference in achieving rebuilding by
  2014

Valuation of Risk Analysis
57
Concerns with NS 1 Guidelines

• ABC ACL should be sufficient
• ACT not stipulated by MSA
• Keep optional rather than essential
• Overfishing definition
• Redefining in terms of catch inconsistent with
  MSA
• Keep as fishing mortality
• AMs in-season adjustment
• Adjustment of ACLs implementation of AMs should
  be based on fishery performance data
• In-season adjustment unrealistic

58
http//www.nefsc.noaa.gov/nefsc/saw/
59
Summary

• NEFMC SSC, PDT Council working on ACL setting
  framework
• Groundfish initial focus of work to date
• PSA framework given broad applicability
• Need to define OFL ABC ABC ACL buffer sizes
  based upon further work

60
THANK YOU!
61
Issues

• PSA part II of three step ERA process
• Triage to determine where in depth quantitative
  analysis required
• Rosenberg et al (2007) recognized need to learn
  from data rich situations
• Guide to ACL setting not intended to replace
  assessments
• Need to ensure that risk is not double
  counted
• Assessments present current status based upon
  adjustment for retrospective patterns
• Biological reference points incorporate
  information on productivity susceptibility

How best to incorporate risk into control rules