u may set max density for some time to se how that affect taxes for you. But CND is mining place. After 200K peds finds there i must say all mobs in all domes were just anoying for me.
So my vote went for Extermination. Hunters already have some pro atrax lands on amethera, so few peds more from taxes from ocasionaly kiled by miner atrax is realy nothing compared to that they may not visit that dome at all if atraxes will be there. Ocasional mob on the way is just wasting of time for miner, aditiona unecesary decay and costs...and like in my case all mobs cause me to change my mining route or kep timing wchich effect in less bombs spent in such dome.
I'm posting as someone who only ever goes to CND to mine but I would say increase the density of Atrax in dome 9, although ensure they are low maturity. In the past I've been used to having to deal with many more of these than there are at present so it wouldn't be a worry to me.