Like Dr. Bill said, it's been a long time here in So Cal since we could take abalone. In the olden days, I would trim the foot to prepare steaks and throw away the trimmings. Bad idea!
A dive buddy, PK, suggested something that I will pass on to those of you who are free-diving for abs in Northern CA or in NZ. Remove the ab from the shell and scrub the foot with a stiff brush to remove all the black schmutz. Trim the foot as usual, but save all the trimmings, cover the trimmings with water, bring to a boil, reduce the heat, cover the pan and simmer for at least two hours. Reserving the liquid, chop the pieces and make abalone chowder using any clam recipe! It's delicious, the ab trimmings are tender and the flavor is magnificent.
I wish I had known about this many years ago.