Alternative Assessment for the Indian Ocean Yellowfin Tuna Stock; with Generic Goodness of Fit Diagnostics

The objective of this work is to assist the IOTC Scientific Committee in providing robust
management advice for yellowfin tuna by evaluating alternative assessment methods and
scenarios that reflect uncertainty about the assumptions and datasets used in the assessment.
• Specific tasks are to agree datasets (CPUE series and catch series) based on alternative
assumptions about mis-reporting, run biomass dynamic based stock assessments. and
compare the results to the base case SS3 assessment using a common set of diagnostics.
• The report summarises the analysis and provides a set of diagnostics that can be used for
comparison across different modelling platforms
• All scenarios other than 2 (high productivity and the reference case fitted to the estimate of
biomass from stock synthesis) indicate that the stock is overfished and experiencing
overfishing.
• The work is based on data available on July 8th, 2019.