Bill wrote:
Is there anything more which can be done?

Have you tried strong detergent? I'm guessing the fish smell is
probably oil-based, and good strong dish soap (maybe straight dawn?) or
some kind of citrus degreaser might help. If household-grade stuff
doesn't work, see if your janitor at work has anything stronger.
Just guessing here - believe it or not, I've never tried to get a fish
smell out of concrete.
Good luck,
Andy