The robots.txt file.

Search engines, when looking for sites to show in search results, will first
look for the file /robots.txt.  If this file is found and has lines that apply
to them they will do as instructed.  A very basic robots.txt follow as an
example:

# go away
User-agent: *
Disallow: /

This tells every search engine that cares (User-agent: *) to not index the site
(Disallow everything past /).

If you have installed Koha to /usr/local/koha3 then this file would be placed
in the directory /usr/local/koha3/opac/htdocs/.  This should prevent search
engines from browsing every biblio record, and every view of each record, on
your Koha install periodically.