Stock assessment, fishery management systems, and the FMSP Tools
-- Summary --
FMSP Stock Assessment Tools
Training Workshop
Bangladesh
19th - 25th September 2005
The management context
The legal regime• Domestic laws• International agreements
Management approach to uncertainty
• Precautionary or adaptive management? Or both?
Management scope• Single or multi-species?• Ecosystem approach?
Property rights• Use rights?• Control rights?
Stakeholder roles in management
• State or community control?• Co-management?
Fishery scale• Industrial or artisanal?• Economically important?
Management capacity• Technical skills, staff, funds?
Sections 1.1 and 2.1 – 2.4
Fishery Policy
Define management intentions• Policy goals and operational objectives (biological,
ecological, economic, social, other sectors)Section 2.5.1
Stock assessment process
Data/Inputs
Intermediate parameters
Indicators Reference points
Management advice in terms of risk,
allowing for uncertainty
Chapters 3 and 4 and Parts 2 and 3
Management process
Fishery Management Plan
Define management standardsFor each operational objective:• Conceptual reference points
(target, limit, precautionary)• Indicators • Technical reference points
Set management measures• Decision control rules defined by
reference points and harvesting strategy• Management strategy, comprising
one or more control measures (inputs; outputs; technical, ecological etc)
Monitoring Control and Surveillance
Sections 2.5.2 – 2.5.5
Figure 1.1
A framework for fishery management (FTP 487)
The new international legal regime
1992 Convention on Biological Diversity
Chapter 17 of UNCED’s Agenda 21
1995 UN ‘Fish Stocks Agreement’
1995 FAO Code of Conduct for Responsible Fisheries
2002 Johannesburg World Summit on Sustainable Development (WSSD)
Section 1.1
Examples of goals and op. objectives (3/3)
Section 2.3.1
Goals Operational Objectives
Biological To maintain the target species at or above the levels necessary to ensure their continued productivity
To maintain the stock at all times above 50% of its mean unexploited level
Ecological To minimise the impacts of fishing on the physical environment and on non-target (bycatch), associated and dependent species
To maintain all non-target, associated and dependent species above 50% of their mean biomass levels in the absence of fishing activities
Economic To maximise the net incomes of the participating fishers
To stabilise net income per fisher at a level above the national minimum desired income
Social To maximise employment opportunities for those dependent on the fishery for their livelihoods
To include as many of the existing participants in the fishery as is possible given the biological, ecological and economic objectives listed above
Indicators and reference points
Set indicators and reference points for each operational objective
An indicator is a specific state, or variable, which can be monitored in a system such as a fishery to give a measure of the state of the system at any given time (Cochrane, 2002)
A reference point is an estimated value derived from an agreed scientific procedure and/or an agreed model which corresponds to a state of the resource and/or of the fishery and can be used as a guide for fisheries management
Indicators and ‘RP’s should be used in combination to express the operational objectives in ways that can be measured in quantitative fisheries assessments.
Section 2.5.2
Catch
Fishing effort Stock size (biomass)
Catch
Fishing effort
Catch per unit effort (CPUE)
or
Stock size (biomass)
Long term (equilibrium) relationships
between Catch, Effort and Stock size Indicators
(not directly related!)
Risk of alternative reference points
Size ofCatch
Amount of Fishing
Maximum Catch - FMSY
Fcrash riskier
Point at which species
becomes extinct
Target or limit reference points?(defining the objectives and control rules)
Target RP - aim here, slightly above or below both OK
Indicator X
Limit RP - avoid danger zone below here
Indicator X
E.g. Catch rateE.g. Catch rate E.g. spawning stock size E.g. spawning stock size
BMSY Stock size this year
FMSY
If Bnow < BMSY, no fishing allowed next year (danger zone)
Fishing mortality rate to be allowed next year
If Bnow > BMSY, fishing allowed at rate of FMSY next year
Decision control rules – a simple example
Section 2.3.3
Precautionary reference points
Such points were adopted in response to the UN Fish Stocks Agreement (see point 5 of Annex II), to help make sure that the LRPs are avoided.
Define the point at which managers should take action, to avoid the LRPs being reached.
The distance by which the precautionary point is removed from the LRP is usually set according to:• the uncertainty in the data • and the risk tolerance of the manager.
Section 2.3.4
And ‘precautionary’ reference points...
Limit
RP
Indicator X
Take action at the Precautionary RP to avoid the risk of getting to the Limit RP
Precautionary
RP
Setting reference points allowing for uncertainty and risk
Blim
(BMSY)
Bpa
(%ileBMSY)
Low risk Bpa at ~90th percentile of Blim distribution
Blim
(BMSY)
Bpa
(%ileBMSY)
Higher risk Bpa at ~75th percentile of Blim distribution
Setting reference points allowing for uncertainty and risk
Management measures
1. Input controls (fishing effort restrictions)2. Output controls (catch limits)3. Technical measures (size limits, closed seasons, closed
areas etc) 4. Ecological and integrated management
Input and output controls often vary between years, depending on harvesting strategy and state of stock
Technical measures usually fixed, or updated every few years based on long-term assessments
Sections 2.3.5 and 5.4
Phase I
Where are you now?
Phase II
Where do you want to be?
Phase III
How are you going to get there?
Time
Phase IV
How will you know you are there?
Plan
Do
ReviewNew plan
Do
ReviewNew plan
etc
Process for developing a management plan
See new guidebooks from FMSP project R8468
Summary of the management plan
Purpose Goals Objectives Management Standards
Management Measures
Indicator Reference Point
Management Measures
Decision Control Rules
Biological
Ecological
Social
Economic
How to quantify the goals and objectives
How to achieve the goals and objectives
Phase II
Where do you want to be?
Phase III
How are you going to get there?
Part 2 - The stock assessment process
Collecting fishery data
( Estimating intermediate parameters )
Estimating the current status of the fishery (performance indicators)
Estimating technical reference points
Providing management advice
Monitoring and feedback
Chapter 3
Stock assessment – collecting fishery data
1. Catch, effort and abundance (CPUE or survey-based or fishing experiments)
2. Catch compositions (length and/or age frequencies to estimate indicator F)
3. Other biological data (maturity, fecundity etc)
Section 3.2
Estimating intermediate parameters
Individual growth rates of fish (e.g. by LFDA)
Population growth rate and carrying capacity (e.g. CEDA)
Natural mortality rate (e.g. by Pauly equation)
Exploitation pattern / gear selectivity (from LF data)
Catchability (e.g. by CEDA)
Maturity and reproduction (from biological samples)
Stock and recruitment (usually from VPA)
• Not of direct value, but used as inputs to fishery assessments
• Not constants, may vary over time (e.g. q, K etc)
• Values will usually be uncertain, so use sensitivity tests
Section 3.3
Biomass dynamic or analytical?
Biomass dynamic models like Schaefer surplus production model used in CEDA and ParFish• relate fishery outputs (catch) directly to inputs (effort)• Useful where fish are hard to age – used to set quotas and effort
Analytical models used in ‘Yield’ and other ‘per recruit’ and dynamic pool approaches• include intermediary processes, both biological and fishery (e.g.
from LFDA)• may be length-based or age-based• Needed for management advice on size limits, seasons etc
Neither approach is more right or wrong than the other – they are just based on different models and assumptions
Section 3.1.3
The analytical
stock assessment
approach using LFDA
and Yield
LFDA
Intermediate parameters
L∞, K, t0 (growth)
Z ( - M ) Fnow(Eq)
Biological data, management controls (size limits, closed seasons etc)
Compare to make management advice on F
e.g. if Fnow > FMSY, reduce F by management controls
if Fnow < FMSY, OK
Yield
Per recruit
Fmax F0.1 F%SPR
With SRR
FMSY Ftransient
Data / inputs
Assessment tools
Indicators
Reference points
Management advice
Length frequency data
Figure 4.1
The CEDA stock
assessment approach
(DRP / biomass dynamic
model)
Figure 4.5 Section 4.5
CEDA
Intermediate parameters
r, K, q
Bnow
Current catch / effort data
Compare to make management advice on effort or catches
Data / inputs
Assessment tools
Indicators
Reference points
Management advice
Catch / effort time series
BMSY fMSY MSY
fnow Cnow
The ParFish stock
assessment approach
Figure 4.10 Section 4.6
ParFish
Intermediate parameters
r, K, q
Current catch / effort data
Data / inputs
Assessment tools
Indicators
Reference points
Catch / effort time series
fnow Cnow
Stock assess’t interview data or other priors
Preference interview data
ParFish
flim Clim
Management advice on effort or catch controls, in terms of limit and target levels. Targets (fopt,Copt) incorporate the preferences of resource users. Limits are based on the risk that B will be reduced below a specified % of K.
fopt Copt
Management advice
Bnow
What do the different FMSP stock assessment tools estimate? (Table 5 of new guide)
Parameters estimated Available FMSP tools Type Parameters
LF
DA
Yie
ld
CE
DA
Pa
rFis
h
Em
pir
ica
l m
eth
od
s
Be
ve
rto
n
an
d H
olt
in
va
ria
nts
r, K, q (production model) x x K, Linf, t0 (von Bertalanffy growth) x M (natural mortality rate 1) x x
Intermediate
Z (total mortality rate) x YPR / BPR (yield / biomass per recruit) x Yield / biomass (absolute, equilibrium 3) x Bt (biomass in year t) x 2 x x Nt (numbers in year t) x 2 x Feq (fishing mortality rate, Z-M) x
Indicators
CPUA (catch per unit area) x MSY, fMSY, BMSY, FMSY x x x Fmax, F0.1, F0.x, F%SPR (per recruit) FMSY, F%SSB, Fcrash (absolute 3) Ftransient (risk-based)
x x x
flim, Clim (risk-based, biological limits) fopt, Copt (adjusted for ‘preferences’)
x x
Reference points
Fmax (max yield per recruit) FMSY (max absolute yield 3)
x x
Which tools can be used to provide advice for different management measures
(Table 6 of new guide)
Management measures
Bio
log
ical
st
ud
ies
Yie
ld
CE
DA
Par
Fis
h
Em
pir
ical
m
eth
od
s
Bev
ert
on
an
d H
olt
in
vari
ants
Fishing effort (‘input’) controls, e.g. limited vessel licensing x1 x x x2 x1 Catch (‘output’) controls, e.g. quotas or ‘TACs’ x3 x x x2 x3 Closed seasons x x x Changing size at first capture (e.g. with minimum legal mesh size or fish size regulations)
x x x
Closed areas x x x 1 In combination with LFDA or some other method of estimating current fishing mortality rate. 2 Per unit area. 3 If biomass also known.
See also Section 2.5.5 in FTP 487
Data collection training
Why collect data?
Useful references on data collection
------------------------------------------------------------------------------------
Data commonly used in stock assessments (e.g. using FMSP tools)
Data needs of the different SA approaches and FMSP tools
------------------------------------------------------------------------------------
Data collection methods (C/E, LF, biological, ParFish)
System design
Sampling design
Data forms
Database systems
Data needs of the different approaches / tools
Analytical approach (LFDA / Yield) (See FTP 487, Tables 4.1 & 4.3)
• Catch composition data (either from length frequency data – LF, or ageing studies)
• Biological data (e.g. size at maturity)
• Management advice can be produced from just one seasons’ sampling (e.g. from a short time-series sample of LF and biological data)
• But note some reference points also need long-term Stock-Recruit relationship
Biomass dynamic approach and depletion modelling (CEDA)• Multi-year time series of catch and effort data, or catch data with a
secondary index of abundance (e.g. from a survey)
• Short-term time series of C & E for depletion modelling of N0 and q
ParFish approach• Uses C/E and/or abundance data as with the other biomass dynamic
models
• Due to Bayesian formulation, can also add other sources of information to improve the analysis, e.g. where few or no C/E data are available, and to ‘tune’ the outputs to local users preferences
Data collection - Discussion questions
• What data do you have already that could be used for stock assessment? In FRSS or in local management units?
• How are catch and effort estimated? How reliable are the data?• What effort measures are used for different gear types? Would they
provide useful, unbiased indicators of abundance?• Do you have any routine survey data that could provide abundance
estimates (time series)• Do you collect length frequency or age frequency data? How often?
For what species, what sample sizes?• Do you have biological data needed for analytical methods?• How could national (e.g. FRSS) and local management data
collection systems be integrated, especially in inland fisheries? Are any data collected in both?
• What other data should be collected, besides C/E, LF, biological?
The management context
The legal regime• Domestic laws• International agreements
Management approach to uncertainty
• Precautionary or adaptive management? Or both?
Management scope• Single or multi-species?• Ecosystem approach?
Property rights• Use rights?• Control rights?
Stakeholder roles in management
• State or community control?• Co-management?
Fishery scale• Industrial or artisanal?• Economically important?
Management capacity• Technical skills, staff, funds?
Sections 1.1 and 2.1 – 2.4
Fishery Policy
Define management intentions• Policy goals and operational objectives (biological,
ecological, economic, social, other sectors)Section 2.5.1
Stock assessment process
Data/Inputs
Intermediate parameters
Indicators Reference points
Management advice in terms of risk,
allowing for uncertainty
Chapters 3 and 4 and Parts 2 and 3
Management process
Fishery Management Plan
Define management standardsFor each operational objective:• Conceptual reference points
(target, limit, precautionary)• Indicators • Technical reference points
Set management measures• Decision control rules defined by
reference points and harvesting strategy• Management strategy, comprising
one or more control measures (inputs; outputs; technical, ecological etc)
Monitoring Control and Surveillance
Sections 2.5.2 – 2.5.5
Figure 1.1
A framework for fishery management (FTP 487)
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