Management Procedures

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Management Procedures

• Fish 558

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CURRENT MANAGEMENT CYCLE
Fishery Actual Catches
Data Collection
Management Decision
Assessment
 
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This system is unsatisfactoryfor the industry

• Stock status is uncertain, and can easily change
  with new interpretation of data or change of
  models
• There are no rules about how quotas will be set
  and thus no transparency and understanding of
  what will happen
• There are no rules about what model assumptions
  will be used and thus no transparency of
  understanding of what will happen

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This system is unsatisfactory for managers because

• With no rules about how quotas will be set, there
  is no way to determine the long term consequences
  of the quota set for any individual year
• The assessment process is not transparent to
  managers
• At best risk can be evaluated by calculating
  impacts of constant catch levels
• But we know that we wouldnt hold the catch
  constant if data changed dramatically
• Thus managers have no way of evaluating the
  probability of achieving objectives

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Management ProceduresA way forward
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Elements of a management procedure

• A list of data that will be collected
• Rules about how the data will be used to
  determine the quota for the next year
• The rules may be data based if CPUE is going up
  raise catches, if going down lower catches
• The rules may be model based but the details of
  the models will be specified and not subject to
  annual changes

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Example the New Zealand rock lobster decision
rule
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CPUE trends in Gisborne
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The Decision Rule

• Other areas, particularly CRA8 want to emulate
  the Gisborne success
• Adopted a rebuilding target of increasing CPUE
• The rule
• If CPUE is above target trajectory increase TAC
• If CPUE is below target trajectory lower TAC

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Testing possible management procedures

• Define a set of operating models that are
  alternative hypotheses about the stock status
• Stock productive and will increase under current
  catch
• Stock unproductive and will decrease under
  current catch
• Pretend the operating models are true, and test
  possible management procedures to find those that
  are robust to uncertainty in stock status
• Our goal is to find a management procedure that
  will do as well as possible with whatever the
  stock status and SBT biology happens to actually
  be true

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Evaluation Simulation Model
CONDITIONING COMPONENT
Operating Model
Current Stock Size Catches
Historic Data

• Population and Fishery Dynamics
• Stochastic in dynamics
• Alternative Hypotheses/Model Formulations
• to Capture Real Uncertainty e.g.
• stock/recruitment
• ? selectivity/? catchability
• mortality rates density dependent
• Consistent with Historic Data

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Evaluation Simulation Model
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Evaluation Operating Model

• A key issue ensuring that the operating model
  appropriately incorporates the full uncertainty
  about the real stock, its dynamics and the
  sampling processes.

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Limitations

• Robust only to what has been evaluated
• Generation of hypotheses for what we dont know?
• Low probability events do happen
• Tinkering pressure to modify to meet short term
  expediency
• Tinkering genuine desire to improve
• ( endless development cycle/
• highly complex assessment)

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Increasingly being used

• Examples
• International Whaling Commission RMP/AWMP
• South Africa small pelagic, lobster, etc
• Namibia small pelagic
• New Zealand rock lobster
• Australia gemfish, trawl fisheries, tuna
• CCSBT (under development) international large
  pelagic

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A simple CPUE based rule for SBT

• TAC next year
• TAC Last year carryover
• (1-carryover)TAC Last year (1slope of cpueK)

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