Further results and sensitivity tests for the Reference-case abalone spatial- and age-structured assessment model for Zones A, B, C and D
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2009
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University of Cape Town
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Abstract
This paper reports on results for the Reference-case model (when the updated and extrapolated “old” CPUE series is used in the model fitting procedure) that were requested as well as results for two sensitivity tests. Details of the Reference-case model are provided in Brandão and Butterworth (2009). The Reference-case model using the stratified Zone B FIAS series estimates a pristine spawning biomass, sp B0 (in tonnes) of 10 069, 5 917, 7 465 and 10 567 for Zones A, B, C and D respectively. Under the revised policing efficiency, these values are 18 785, 6 008, 7 419 and 9 024. The 2010 (inshore+offshore) spawning biomasses of abalone in Zones A, B, C and D are estimated at ca. 29 %, 25 %, 6% and 11 % respectively of their pre-exploitation levels for the sensitivity test that uses the stratified Zone B FIAS series and at ca. 36%, 29%, 6% and 16% if the revised policing efficiency trends are used. In essence use of the stratified Zone B FIAS series has little effect on results; however for the revised policing efficiency the estimates for the current status of Zone A particularly, and also Zones B and D, are improved.
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Brandão, A., & Butterworth, D. S. (2009). Further results and sensitivity tests for the Reference-case abalone spatial- and age-structured assessment model for Zones A, B, C and D. MARAM: University of Cape Town.