"He" is a saltwater crayfish, a 10lb bull (male).
They were very common 40 years ago but, are pretty rare & accordingly expensive.
A big bull would weigh about 12-14lb.
I buy a couple every year for special occasions however they are not often available so the special occasion might have to be pretty impromptu!
They sell for £12.50 a lb but, a big one would make a dish for 10 people so affordable for an occasional treat if every one dips in :?
The flesh is lobster like, of course they don't have big claws like lobsters, they do have a club & spike arrangement for doing battle with other males.