Retrospective analysis of the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity, including stochastic projections

• Main Authors: Brandao, Anabela, Butterworth, Doug
• Format: Report
• Language: unknown
• Published: University of Cape Town 2021
• Subjects: 10401 Applied Statistics; FOS Mathematics; 10202 Biological Mathematics; 10402 Biostatistics; Tac; Prince Edward Islands
• Online Access: https://dx.doi.org/10.25375/uct.15000615; https://zivahub.uct.ac.za/articles/report/Retrospective_analysis_of_the_toothfish_Dissostichus_eleginoides_resource_in_the_Prince_Edward_Islands_vicinity_including_stochastic_projections/15000615

For stochastic future recruitment and for annual catch levels of 375 tonnes to 775 tonnes, in increments of 100 tonnes, the median of the spawning biomass estimates for the Base case model drops initially, but returns to its current level within a decade, while the exploitable biomass continues to increase. However the retrospective analysis gives rise to a concern: the 2013 assessment suggested a continuing increase in spawning biomass under a 575 tonne TAC, whereas the update of this assessment to 2016 shows an initial decline that returns to its present level only some 10 years later. Hence it is suggested that until either improved values of standardised trotline CPUE become evident, or an OMP is introduced, the TAC should not be increased above its present value of 575 tonnes. Lowering the tag-reporting rate results in a slightly more pessimistic view of resource status.