The monsters will move to a different habitat if the lake is purified—

Indirect, I'd prefer to contend. Beechwood forests are the chief habitat of roe deer, you see, in turn a staple of the basilisk diet.

Before coming here, I dispatched requests to several local hunters. They located the habitats of the species of interest to me and marked out their ranges on the map.

That's more or less what it amounts to, yes. Except, you will first have to track down the creatures I wish to capture. I know only the very approximate locations of their habitats.