What is it?
Conger eel is quite firm and meaty and there are lots and lots of bones, but it's pretty good just sliced into steaks (skin on, bones in) and cooked over charcoal, then eaten with fingers (the bones aren't a problem if you're prepared to get your hands messy)
Preparation Options
You can have conger is steaks or fillets, the fillets are still going to contain pin bones. The top of the eel contains less bones, the closer you get to the tail the more bones you get.
Is it sustainable?
Conger eels spawn once in their lifetime they die immediately after. They are not targeted by fishermen so any caught are a result of bycatch. The MCS regard this as a fish to avoid.