By Harold McGee
The innards of fish and shellfish offer their own special pleasures. Fish eggs are described below. Many fish livers are prized, including those of the goatfish (“red mullet”), monkfish, mackerel, ray, and cod, as is the comparable organ in crustaceans, the hepatopancreas. The “tongues” of cod and carp are actually throat muscles and associated connective tissue that softens with long cooking. Fish heads can be 20% fatty material and are stuffed and slow-cooked until the bones soften. And then there are “sounds,” or swim bladders, balloons of connective tissue that such fish as cod, carp, catfish, and sturgeon fill with air to adjust their buoyancy. In Asia, fish sounds are dried, fried until they puff up, and slowly cooked in a savory sauce.