There is nothing uglier than a catfish. With its scaleless, eel-like body, flat, semicircular head, and cartilaginous whiskers, it looks almost entirely unlike a cat. The toothless, sluggish beasts can be found on the bottom of warm streams and lakes, living on scum and detritus. Such a diet is healthier than it sounds: divers in the Ohio River regularly report sighting catfish the size of small whales, and cats in the Mekong River in Southeast Asia often weigh nearly 700 pounds. Ugly or not, the catfish is good to eat. Deep-fried catfish is a Southern staple; more ambitious recipes add Parmesan cheese, bacon drippings and papri­ ka, or Amontillado. Catfish is also good for you. One pound of channel catfish provides nearly all the protein but only half the calories and fat of 1 pound of solid white albacore tuna. Catfish is a particularly good source of alpha­ tocopherol and B vitamins. Because they are both nutritious and tasty, cats are America's biggest aquaculture product.