If a tribe needs to take more than 50% of harvestable surplus of one stock (Stock A) in order to get 50% of harvestable surplus of another stock (Stock B), I'd say there is a pretty good argument they better find out a way to get their share of Stock B without taking more than they are entitled to out of Stock A.

Now, it may be that ESA-allowed impacts and harvestable surplus don't line up perfectly, but it seems like they shouldn't be too far apart.