# 4.14. Migration mortality¶

The mortality.out.rate.sp# parameter is the annual mortality rate for species that move out of the simulated area, $$M_{out}$$. When a school moves out, none of the usual processes apply (predation, growth, fishing, natural mortality, growth, starvation).

The $$M_{out}$$ mortality rate comprises all sources of mortality outside the simulated area. It applies as long as the school is located out of the simulated area (see the parameter ‘movement.map0.file’ for detailled explanations on how to set up migration periods for a given school). The $$M_{out}$$ parameters is such that, at a given time step:

$N_{dead_{out}}(t) = N(t) \times \left(1 - e^{\frac{-M_{out}}{NDtPerYear}}\right)$