When is a steamed fish ready?

I cooked a sea bass using the excellent Chinese method of steaming. This involved placing the entire fish on a plate on a trivet in a covered wok. Part of the appeal here is visual (you bring the plate to the table with the fish intact). The thing is, I couldn’t tell whether the fish was cooked through and I didn’t want to probe too deep to find out. Short of taking a chunk out to see if it is done by the bone, is there any secret to knowing when a fish is cooked without being over-cooked?