The smelt is anadromous, meaning that it migrates from its North American saltwater habitat to spawn in fresh water. It's a small (average 4 to 7 inches long) fish with a translucent silver-green back shading into shimmering silver sides and belly. Its delicate flesh is rich, oily and mild-flavored. There are many varieties of this fish, the most widely distributed being the rainbow smelt, found along the Atlantic coast. Two popular Pacific Coast varieties are whitebait and on. The latter is also called candlefish, a nickname that came about because Indians would dry these high-fat fish, run a wick through the flesh and use them for candles. Fresh smelts are best from September through May. Because they're very perishable, many are now flash-frozen immediately after being caught. They are also available canned. Smelts are marketed whole and are usually eaten that way -- head, viscera and bones. Though they can be cooked in a variety of ways, they're generally simply coated with flour and fried.