Bring a snow shovel, waterproof boots and a box of large frozen minnows to Hebgen Lake just outside Yellowstone National Park's west entrance. Dig your way down to the ice for a good shot at catching rainbow and brown trout that often reach three or four pounds.The key to success on this impoundment is big bait. Hebgen is one of the few Montana fisheries populated by Utah chubs, and they're so prolific that the resident trout are husky. But the abundant natural food also makes them hard to catch. That's why the larger minnows are required bait.The snow can pile pretty deep on the ice (up to five feet), and all that natural insulation makes the ice spotty. You'll often drill through a layer of ice, then encounter a few inches of water, then another layer of ice before you punch through to the reservoir itself.Use a drop-shot rig to suspend your minnow above the weight at the desired depth. Generally trout are within 15 or 20 feet of the surface. You can either leave your bait motionless or you can gently jig. A number of anglers bait larger jigheads with the frozen minnows to add a color component to their presentations. Expect mostly rainbows, but if you catch a Hebgen brown, it's likely a Goliath. Best spots are along the northern shoreline, the point between the Rainbow Arm and the Grayling Arm and a few hundred yards behind the dam. Pull well off Highway 287 or risk getting ticketed and towed; plow crews take their job seriously. Contact: Blue Ribbon Flies, West Yellowstone (406-646-9365); Kirkwood Resort and Marina (406-646-7200).