[Feature]: Apply the depletion survey (option 34) with an initial year that is not unfished

Describe the solution you would like.

I think the current implementation of the depletion survey option assumes the first year entered is at unfished. It would be great to have a flexible definition of what the first year is relative to unfished.

For instance, in a model that does not have a full time series of catch, but the user has a guess of depletion in the initial year of available catches, it would be great to be able to specify the survey with that depletion in the first year of the model.

As an example, say catches start in 1975 forward, but there were removals before that time. The user may want to presume the stock is at, say 75% of unfished in 1975, thus the model can move forward with that depletion assumption, instead of it being assumed unfished in 1975.

Describe alternatives you have considered

The tricky part of this I see is assuming what the age/length structure is in that initial year if it is not unfished.
Current ways of doing this is to use the equilibrium catch approach to calibrate a model's population structure and achieve a certain depletion value in a specified year.

If this can be automated in the model, it could be much easier for users to apply.

Statistical validity, if applicable

No response

Describe if this is needed for a management application

No response

Additional context

No response