search

Pacific-salmon-assess / samSim

3 stars 0 forks source link

Question about error around exploitation rate #23

Closed catarinawor closed 3 years ago

catarinawor commented 3 years ago

I noticed that when the exploitation rates for Canadian fisheries are generated there are two layers of beta distributed errors applied to them. The first layer uses the ER average from the input file and a common cv for all CUs. One ER value for all CUs is generated with this call and this function (?). The second layer uses the output ER from the first layer as average and has CU specific CVs. See call and function

@carrieholt or @krHolt could you help me explain the rationale for this structure? I am assuming that the first is the ER implementation error (representing fishery variability?) and he second is representing the ER variability arising from changes in availability for each CU?

carrieholt commented 3 years ago

Yes, the first error is SMU-level variability, due to, for example, interannual variability in harvest on the high seas common to all CUs in that SMU. The second is CU-specific deviations to that variability, due to, e.g., local fisheries. Does that make sense?

catarinawor commented 3 years ago

CW:So we should only use samsim to model one MU at a time? - as the first error only allows for one set of parameters? CH: Yes, we have only included 2 levels. samSim could be applied to one CU with component sites, OR one MU with component CUs, OR even one region with component MUs . We have not yet included 3 levels, which would be a great next step though adds significant complexity.