WP4: WP4: Models to predict & test Models to predict & test recovery strategiesrecovery strategies

Cefas: Laurence Kell & John PinnegarCefas: Laurence Kell & John Pinnegar

Univ. Aberdeen: Tara Marshall & Bruce Univ. Aberdeen: Tara Marshall & Bruce McAdamMcAdam

ObjectivesObjectivesEvaluate alternative recovery strategies and identify the Evaluate alternative recovery strategies and identify the

relative value ofrelative value of– InformationInformation– ControlControl

Synthesise available models and data on key processes that Synthesise available models and data on key processes that may affect stock recovery in a common framework may affect stock recovery in a common framework

Use framework to evaluate alternative management strategies Use framework to evaluate alternative management strategies that are robust to uncertaintythat are robust to uncertainty

Quantify and compare the impacts of alternative management Quantify and compare the impacts of alternative management strategies in order to produce a suite of strategies to strategies in order to produce a suite of strategies to achieve stock rebuildingachieve stock rebuilding

1) Preparation of input data 1) Preparation of input data

2) Choice of performance criteria and 2) Choice of performance criteria and management objectivesmanagement objectives

3) Specify base-case scenario3) Specify base-case scenario

4) Perform evaluations4) Perform evaluations

TasksTasks

Starting state

of system

Performance Statistics used to evaluate performance of management procedures

against objectives

Operating Model represents the “true” dynamics of “ the biological system against which

performance will be measured

Observation Error Model generation of data on fishery and stock(s)

Management Procedure Assess status of stock and set

management options depending upon

perceived status of fishery stock(s)

Simulation

through time

Figure 1. Conceptual framework

From WP 5Alternative management strategies

Current Stock Status Future Stock Status

From WP 1,2,3Process modelsor alternative hypotheses

e.g. alternative assumptions about Natural mortalityMaturityRecruitmentDiscardsWeights at age

Model of data collection/samplingFeeds into WG Stock Assessment

Recovery? Yield of target/non-target stocks

FFramework for the ramework for the EEvaluation of valuation of MManagement anagement SStrategiestrategies

FEMSFEMS proposed and prototyped a generic framework known proposed and prototyped a generic framework known as as FLR FLR through a variety of contrasting case studiesthrough a variety of contrasting case studies

Why?Why?Despite constant efforts made to regulate fisheries fishing Despite constant efforts made to regulate fisheries fishing

capacity remains above that necessary to sustainable capacity remains above that necessary to sustainable exploit marine resources. exploit marine resources.

However, while the need to develop alternative management However, while the need to develop alternative management strategies is widely recognised it is almost impossible to strategies is widely recognised it is almost impossible to develop these by conducting large-scale experiments on develop these by conducting large-scale experiments on fish stocks. There has therefore been a trend towards the fish stocks. There has therefore been a trend towards the use of computer simulation to develop management use of computer simulation to develop management strategies that meet multiple, but often conflicting strategies that meet multiple, but often conflicting management objectives, and are robust to uncertainty management objectives, and are robust to uncertainty

FLRFLR is available from is available from http://www.flr-project.orghttp://www.flr-project.org

Process error:Process error: natural variability (in both time and space) in dynamic natural variability (in both time and space) in dynamic processes of the populations (e.g. recruitment, predation, growth and processes of the populations (e.g. recruitment, predation, growth and migration) and of the fisheriesmigration) and of the fisheries

Model error:Model error: related to the ability of model structure to capture the core of related to the ability of model structure to capture the core of the system dynamics, many models are assumption rich but data poorthe system dynamics, many models are assumption rich but data poor

Observation error:Observation error: related to collecting in-situ observations, such as total related to collecting in-situ observations, such as total catch, catch composition (e.g. length, age, sex), research survey indices, catch, catch composition (e.g. length, age, sex), research survey indices, efforteffort

Estimation error:Estimation error: related to estimating parameters of various models used related to estimating parameters of various models used in the assessment procedure, such as growth models, stock-recruitment in the assessment procedure, such as growth models, stock-recruitment models, virtual population analyses, statistical models models, virtual population analyses, statistical models

Implementation error:Implementation error: because management actions are never because management actions are never implemented perfectly and may result in realised total catch, catch implemented perfectly and may result in realised total catch, catch composition and effort that differ from those intended, e.g. misreporting.composition and effort that differ from those intended, e.g. misreporting.

UncertaintyUncertainty

Software Catalogue

Model Error?Model Error?

Relates to the ability of any one model structure to capture the core Relates to the ability of any one model structure to capture the core of the system dynamics, many models are assumption rich but data poor.of the system dynamics, many models are assumption rich but data poor.

FEMS was tasked by the European Commission with specifying FEMS was tasked by the European Commission with specifying

Cod and ClimateCod and ClimateHypotheses were that climate change acts Hypotheses were that climate change acts

throughthrough Growth, optimum temperature for growthGrowth, optimum temperature for growth Juvenile survivalJuvenile survival

oror Carrying capacityCarrying capacity

Therefore impacts onTherefore impacts onRecoveryRecoveryLong-term yieldsLong-term yieldsSustainable levelsSustainable levels

Management strategiesManagement strategies

Strategies investigated were either Strategies investigated were either those adopted by or under those adopted by or under consideration by the European consideration by the European CommissionCommission

Short-termShort-term– Recovery plans (30% increase in SSB)Recovery plans (30% increase in SSB)

Long-termLong-term– Harvest control rules (ensure F < FHarvest control rules (ensure F < FPA PA andand

SSB >SSB > BBPAPA))

Recovery PlansRecovery Plans

– This was because recovery in the This was because recovery in the short term depended upon conserving short term depended upon conserving fish that have already recruitedfish that have already recruited

Short-termShort-term– Despite contrasting climate Despite contrasting climate

change hypothesises, magnitude change hypothesises, magnitude of the change in temperature and of the change in temperature and the mechanism through which it the mechanism through which it acts (i.e. juvenile survival or acts (i.e. juvenile survival or carrying capacity), the predicted carrying capacity), the predicted recovery time was little affectedrecovery time was little affected

Recovery PlansRecovery Plans

– This was because recovery in the This was because recovery in the short term depended upon conserving short term depended upon conserving fish that have already recruitedfish that have already recruited

Short-termShort-term– Despite contrasting climate Despite contrasting climate

change hypothesises, magnitude change hypothesises, magnitude of the change in temperature and of the change in temperature and the mechanism through which it the mechanism through which it acts (i.e. juvenile survival or acts (i.e. juvenile survival or carrying capacity), the predicted carrying capacity), the predicted recovery time was little effectedrecovery time was little effected

– Recovery would be delayed however if bycatch Recovery would be delayed however if bycatch of cod in non-target fisheries was not controlledof cod in non-target fisheries was not controlled

Long-termLong-term

Scientific advice on safe biological limits to Scientific advice on safe biological limits to exploitation depends upon the correct exploitation depends upon the correct hypothesishypothesis

Reduced survival of recruits? Reduced survival of recruits?

Reduction in range?Reduction in range?

Since consequences areSince consequences are

↓↓FFlimlim if recruit survival reduced if recruit survival reduced

↓↓BBlimlim if range reduced if range reduced

However, the correct mechanism can only be However, the correct mechanism can only be detected through biological studies rather than detected through biological studies rather than through stock assessmentthrough stock assessment

North Sea FlatfishNorth Sea Flatfish100mm > 55100mm > 55°° 80mm < 5580mm < 55°°

Plaice in the NorthPlaice in the NorthSole in the SouthSole in the South

However, the distribution of However, the distribution of

plaice and sole varies wrt plaice and sole varies wrt

5555°°

North Sea FlatfishNorth Sea Flatfish100mm > 55100mm > 55°° 80mm < 5580mm < 55°°

Plaice in the NorthPlaice in the NorthSole in the SouthSole in the South

However, the distribution of However, the distribution of

plaice or sole may change plaice or sole may change

wrt 55wrt 55°°

0.2

0.3

0.4

0.5

1980 1985 1990 1995 2000 2005

Year

Wei

gh

t (K

g)

Plaice Age 4 Sole age 4

The productivity of plaice and The productivity of plaice and

sole has also changed sole has also changed

over timeover time

Cod and ClimateCod and ClimateHypotheses were that climate change acts Hypotheses were that climate change acts

throughthrough Growth, optimum temperature for growthGrowth, optimum temperature for growth Juvenile survivalJuvenile survival

oror Carrying capacityCarrying capacity

Therefore impacts onTherefore impacts onRecoveryRecoveryLong-term yieldsLong-term yieldsSustainable levelsSustainable levels

Management strategiesManagement strategies

Strategies investigated were either Strategies investigated were either those adopted by or under those adopted by or under consideration by the European consideration by the European CommissionCommission

Short-termShort-term– Recovery plans (30% increase in SSB)Recovery plans (30% increase in SSB)

Long-termLong-term– Harvest control rules (ensure F < FHarvest control rules (ensure F < FPA PA andand

SSB >SSB > BBPAPA))

Recovery PlansRecovery Plans

– This was because recovery in the This was because recovery in the short term depended upon conserving short term depended upon conserving fish that have already recruitedfish that have already recruited

Short-termShort-term– Despite contrasting climate Despite contrasting climate

change hypothesises, magnitude change hypothesises, magnitude of the change in temperature and of the change in temperature and the mechanism through which it the mechanism through which it acts (i.e. juvenile survival or acts (i.e. juvenile survival or carrying capacity), the predicted carrying capacity), the predicted recovery time was little affectedrecovery time was little affected

Recovery PlansRecovery Plans

– This was because recovery in the This was because recovery in the short term depended upon conserving short term depended upon conserving fish that have already recruitedfish that have already recruited

Short-termShort-term– Despite contrasting climate Despite contrasting climate

change hypothesises, magnitude change hypothesises, magnitude of the change in temperature and of the change in temperature and the mechanism through which it the mechanism through which it acts (i.e. juvenile survival or acts (i.e. juvenile survival or carrying capacity), the predicted carrying capacity), the predicted recovery time was little effectedrecovery time was little effected

– Recovery would be delayed however if bycatch Recovery would be delayed however if bycatch of cod in non-target fisheries was not controlledof cod in non-target fisheries was not controlled

Long-termLong-term

Scientific advice on safe biological limits to Scientific advice on safe biological limits to exploitation depends upon the correct exploitation depends upon the correct hypothesishypothesis

Reduced survival of recruits? Reduced survival of recruits?

Reduction in range?Reduction in range?

Since consequences areSince consequences are

↓↓FFlimlim if recruit survival reduced if recruit survival reduced

↓↓BBlimlim if range reduced if range reduced

However, the correct mechanism can only be However, the correct mechanism can only be detected through biological studies rather than detected through biological studies rather than through stock assessmentthrough stock assessment

North Sea FlatfishNorth Sea Flatfish100mm > 55100mm > 55°° 80mm < 5580mm < 55°°

Plaice in the NorthPlaice in the NorthSole in the SouthSole in the South

However, the distribution of However, the distribution of

plaice and sole varies wrt plaice and sole varies wrt

5555°°

North Sea FlatfishNorth Sea Flatfish100mm > 55100mm > 55°° 80mm < 5580mm < 55°°

Plaice in the NorthPlaice in the NorthSole in the SouthSole in the South

However, the distribution of However, the distribution of

plaice or sole may change plaice or sole may change

wrt 55wrt 55°°

0.2

0.3

0.4

0.5

1980 1985 1990 1995 2000 2005

Year

Wei

gh

t (K

g)

Plaice Age 4 Sole age 4

The productivity of plaice and The productivity of plaice and

sole has also changed sole has also changed

over timeover time