Forum Moderators: open
Not sure how often Slurp updates robots.txt, but you can try putting this in that file:
User-agent: *
Disallow: /catalog/
If you have other disallowed directories/files, just add them to this. Might as well keep all bots out of there until you turn off the SIDs. Let me know if he stops with that. If not, what kind of server is your site on -- Apache or something else?