Considering Uncertainties

In the Indian Ocean case study that is used here for illustration, nine sources of uncertainties were considered. The choice of uncertainties is informed by the stakeholders’ beliefs as to what is important. So while we should not overinterpret MSE results as comprehensive, they are informative about relative performance of management strategies.

Explore uncertainties pertinent to Indian Ocean swordfish MSE using the image below. Currently, only those listed in bold are taken into consideration within the model.

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Image showing uncertainty pertinent to Indian Ocean swordfish management strategy evaluation
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Image showing uncertainty pertinent to Indian Ocean swordfish management strategy evaluation

Catch

  1. Catch mis- and under-reporting
  2. Discard mortality
  3. Unreported discards
  4. CPUE standardisation / conflicts
  5. Bycatch
  6. Selectivity; gear selectivity / catchability changes by fleet (e.g. gear/equipment changes)
  7. Changes in effort distribution: seasonal dynamics (stock/fleet)

Environmental

  1. Climate change and / or increased variability's potential to change population dynamics
  2. Environmental forcing; environmental considerations and behaviour

Life History Traits

  1. Growth and maturity
  2. Natural mortality (M)
  3. Sex dependent migration: spatial sexual segregation of the stock (real or observed)
  4. Fecundity
  5. Stock structure and mixing; group dynamics, skipped-spawning, density dependence

Model

  1. Model complexity
  2. Steepness
  3. Alternative data weights (length comp); length compositions effective sample size
  4. Scaling

Socio-Economic

  1. Economic uncertainty; market and other economic data to be used in assessing the risks
  2. Uncertainty over objectives; management objectives
  3. Uncertainty over reference points; lack of information on virgin stock levels
  4. Risk attitudes of managers
  5. Catchability increase
  6. Effect of regulations on effort; minimum size recommendation; implementation options
  7. Social impacts on local communities; impacts / effect on small local communities
  8. Illegal fishing; regulations that change the balance of effort between legal and illegal fisheries
  9. Effect of regulations on species; impacts and effect on global distribution of the species.

Population Structure

  1. Oxygen minimum zone, i.e. vertical displacement of individuals
  2. Cyclic movement of adult swordfish
  3. Changes in migration; environmental factors that influence migration patterns
  4. Spatio-temporal dynamics of sub-populations
  5. Existence of genetically distinct and vulnerable sub-stocks
  6. Sex ratio
  7. Interactions with other species
  8. Recruitment Variability Recruitment failure of success (cyclic trends / regime shift)

Reference Points

  1. Dynamics of reference points; stationarity, cohort year effects, density dependence

Learn more about

MSE Operating Models Management Procedures

We have put together an MSE Handout; download the free PDF here.

MSE Handout