Hi Laura.
What you are seeing is a new warning regarding an illogical situation
  that could arise when using a relatively new feature: mean recruitment
  in forecast.
The warning contains the essential instruction. In your control file,
  change the phase for forecast recruitment to be negative, so not estimated:
 -5 #_forecast_recruitment phase (incl. late recr) (0 value resets to
  maxphase+1)
  
Apology for fact that you invoke use of mean recruitment in the
  forecast file and that forces you to go to the control file to change
  the dev phase.  That happens when we gradually add model features
  while maintaining backward compatibility of file structure.