## Initial Depletion

As noted in the previous section, the operating model initializes the population in an unfished dynamic state.

It is possible specify depletion in the first historical year by using OM@cpars$initD. When this feature is used, the population is initialized in a dynamic state with spawning biomass equal to$\text{initD} * SB_0$; that is, initial spawning biomass in Year 1 is relative to the unfished spawning biomass in Year 1. Analysts need to be aware that if there are large time-varying trends in life-history parameters, the$SB_0$in Year 1, which is no longer the first year that the fishery commenced, may be different to the$SB_0\$ from the (not modeled) period before fishing.