Management plan evaluation of western horse mackerel
Management Plan Evaluation of
western horse mackerel
José A. A. De Oliveira, Beatriz A. Roel
HCR and MSE
– to find an HCR that would meet ICES criteria
for sustainability and precaution.
– modelled 100 populations w/ different stock-
recruit relationships to tease apart what is
causing the long recovery times and high risk
MSE and BB
• “simple” implementation of an MSE using
– speed up run time
– Simplify adjusting parameters
• Operating Model
Conditioned on WGWIDE 2014 assessment
Uncertainty based on variance-covariance matrix
o Three forms (Bev-Holt, Ricker, Hockeystick)
o Resampled residuals
o Serial correlation included
o Recruitment spikes included
• Reference points (WKMSYREF3)
Long-term simulations (>100 years)
Model-free (Eggs) and model-based (SSB)
Medium-term simulations (50 years)
Include protection rule
Management Plan Evaluation
• Given assessment uncertainty and the
status of the population at the start of
projections, a suitable HCR could not be
• Based on the existing information on western horse mackerel, catches above
100 000 t cannot be sustained without occasional high recruitment events (spikes).
• Even under no fishing, risk 1 ≤ 5% is achieved only during the final years of a 50-year
projection, and therefore, under current conditions and assuming the already-set
2014-2016 TAC/advice levels are fully adhered to, there is no HCR that will meet
this risk criterion in the short- to medium-term.
• Given the precautionary criterion of risk 1 ≤ 5%, the current HCR cannot be
considered precautionary in the short- medium- or long-term.
• The current HCR associated with a protection rule activated at low stock size is
precautionary only in the long term.
• Egg HCRs perform best in terms of minimising risk 1 and maximising average catch
by setting the egg threshold to around 1 000×1015 eggs and applying a rapid
reduction below this threshold (𝑔 ≥ 2).
• For the options tested, Egg HCRs outperform SSB HCRs in terms of risk 1 and
average catch in the long term (final years of a 50-year projection).
• Without a mechanism for stabilising catch, SSB HCRs currently lead to more variable
catches than Egg HCRs, with values of 𝛼 beyond 0.1 leading to markedly poorer
performance in terms of risk 1 and average catch.