Thread:Project:Support desk/Wiki spam

Hello, I am one of the administrators of this wiki (http://www.ichscotlandwiki.org/index.php?title=Intangible_Cultural_Heritage_in_Scotland) that I will use for my PhD research. It has been affecting by massive spam for several months. We upgraded the software, we installed both Nuke and Block and Nuke (by putting in the white lists only the administrators) extensions, we regularly change the question for the registration (using Google reCAPTCHA), which also requires the confirmation through email link, and added a black list provided by MediaWiki. However, this wasn't enough to either stop the spam or even slow it down. Can anyone suggest further actions to be undertaken? Any advice welcome.