Abalone spatial- and age-structured assessment model results for Zones A, B, C and D in 2005

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University of Cape Town

A summary is presented of the results obtained from the 2005 Reference-case model that was fit to Zones A, B, CNP, CP and D in combination (hereafter referred to as the “combined ABCD model”). The full details of the spatial- and age-structured production model (ASPM) are provided in Appendix 1. Model results estimate a pristine spawning biomass, Bsp 0 (in tonnes), of 11930, 6190, 6890 and 7900 for Zones A, B, C and D respectively. The current spawning biomasses of abalone in Zones A, B and D are estimated at ca. 38 %, 40 % and 28 % respectively of their preexploitation levels. The “nonpoached” CNP and “poached” CP areas of Zone C are estimated at ca. 23 % and 10 % respectively with the inshore region particularly depleted: the model predicts zero remaining abalone in the inshore CP area. Natural mortality is reasonably estimated and in Zones C and D, the additional mortality estimated for 0-yr old abalone (due to the ecosystem-change effect) corresponds to near zero current annual survival rates. Poaching is severely impacting the resource, with Zone A particularly impacted in recent years. The combined Zones A-D model-predicted 2005 poaching estimate of 1150 MT (corresponding to the assumption that, on average, 19% of all poached abalone are confiscated) is more than six times the legal 2005 commercial TAC for these zones.