This all has to be defined in policy for habitat banks.
An ecological unit, as you know, is different; for example, the wild salmon policy defines an ecological unit as a conservation unit. That has been defined as an area where a subpopulation uses that area to continue its life processes.
The term “conservation unit” has been used a lot in conservation planning. A wide range of terminology has been used for watershed units, but essentially it has to be defined in policy based on the fish populations in question, and the geographical constraints of an area.