KAH 1
An assessment was undertaken for KAH 1 in 2007. In the assessment for KAH 1 there was uncertainty
in some important model inputs (e.g., recreational catch history and abundance indices) and some
influential biological parameters could not be estimated within the model (e.g., natural mortality and
the spawner recruitment relationship).
The approach taken to represent uncertainty was to determine the four main factors for which
uncertainty was likely to have an impact on key model outputs (referred to as the ‘axes of
uncertainty’) and then to select a limited number of plausible options across each axis. Model runs
were then undertaken for all possible combinations of options across each axis – this set of options
was referred to as the ‘grid’. Overall, the grid comprised 36 model runs which in totality were thought
to be a realistic reflection of the extent of uncertainty in the KAH 1 assessment.
Based on the scenarios examined, it is likely that current spawning biomass is above B
MSY, but it isMSY it is unlikely that the stockMSY at current assumed catch levels, given the model recruitment assumptions.M=0.18 and including all abundance indices were undertaken in
uncertain how far above.
Current assumed removals are lower than almost all estimates of deterministic MSY. Combining this
with the result that most estimates of current biomass are well above B
will decline below B
The current TAC for KAH 1 is 3315 t with a TACC and allowances outlined in Table 1. The estimates
of deterministic MSY depend on model assumptions, in particular the assumed natural mortality and
time series of non-commercial catches. When non-commercial harvests are assumed to have been 800 t
per year, median MSY estimates from grid strata range from 2130 to 4007 t. When non-commercial
harvests are assumed to have been 1865 t per year, median MSY estimates from grid strata range from
3042 to 5564 t.
Within the range of non-commercial catches investigated, estimates of stock status are relatively
insensitive to the absolute level of the non-commercial catch, provided that these catches are assumed to
be constant over the model period.
Deterministic projections assuming
2008 based on the 2007 assessment and the current TACC and assumed non-commercial removals.
These indicated that biomass was predicted to increase over the next five years for both steepness and
non-commercial catch scenarios.
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