Stream trout — rainbows, browns, and brookies — probably prefer open water over their heads at all times, but many are stocked in ponds, lakes and reservoirs throughout the frozen north. Being coldwater fish, however, they don't stop biting aggressively just because the ceiling freezes.
Finding stream ice trout in lakes and reservoirs can be easy. The overall principles of location include the reversal strategy, and, as always, the forage factor. The reversal strategy refers to the trout's need for cold water, a trait which forces them deep during the hot months, limiting their world to a temperate buffer zone around the thermocline in many lakes. Winter opens their world up even as it appears to close them in.
The shallows become approachable again during late fall and shallow flats produce the most food. By freeze up, trout in many lakes settle into a diurnal feeding pattern. They invade shallow flats during low-light periods of morning and evening, typically feeding on burrowing mayfly nymphs, caddis pupae, small minnows and anything else they can find. This pattern is defined by inflow. Flats created by streams or springs feeding the lake tend to see the most activity.
The other major pattern involves trout suspending over deeper water near those flats. Trout cruise a lot, so suspending trout can be found almost anywhere in a trout lake. Concentration points tend to be near the shallow flats they use early and late in the day, but also near main-lake structures like reefs, islands with bluff-like drop-offs, and hard-bottom humps. If mainlake currents sweep these spots, all the better. Depending on how much food is available on the shallow flats, suspending trout may or may not be active. The largest trout tend to remain suspended, feeding on schools of minnows, most of the time.
Even large trout (topping 10 pounds) can be caught on tiny things in winter. On shallow flats, few livebaits outproduce mayfly nymphs, also called wigglers. These are available commercially in Michigan. (Elsewhere you have to wade ice-cold streams and seine your own out of the sand.) But a tiny jig (1/100-ounce) or bare hook loaded with squirming maggots is a close second. Among artificials, the new FoodSource grubs, Berkley Gulp! Mini Earthworms and other biodegradable baits are among the most productive because, as any trout fisherman will tell you, trout pick up scent like bloodhounds.
Tactically, since trout begin moving even before light levels increase, it's necessary to have holes drilled in the shallows an hour or so before it gets light in the morning. Drilling over active trout in 4 to 8 feet of water is a bad idea. Trout often follow trenches, creek channels, slots, glacial grooves or any other "streets" leading to the shallows. Have several holes drilled in those areas where the deepest water comes closest to the flat, and several more holes that follow any slightly deeper grooves or trenches extending up into shallow water.
Pick a hole and stay with it. Moving around on the ice 4 feet or so over a trout's head is another bad idea. Unlike lake trout (Salvelinus namaycush), brooks, browns, and rainbows often spook from auger activity and the sounds of buckets or cleats scraping the roof over their heads. Sit down, plant your feet, drop a line and stay put. Use a shelter, too, to reduce light streaming down the hole. Otherwise, get the bait down and cover the opening with snow. Most of the time I use a small hook (size #16 up to size #8) dressed with a bait or an artificial like a Berkley Micro Power Worm.
I prefer 26- to 32-inch panfish rods, like the Thorne Brothers Panfish Sweethearts, which allow you to sit back away from the hole. They also provide plenty of shock absorption, which is needed because the best lines for trout are thin, low-vis varieties, including 1- and 2-pound fluorocarbons. A smooth drag on a good reel, like the Shimano Symetre 750, is important. Better equipment helps when a hefty 6-pounder takes off on a 75-foot run.
With lines this light, some fluorocarbons won't bring many large fish back to the hole. I tie 10-foot leaders of 2-pound Maxima, Gamma, Raven or Ashimi fluorocarbon, tied with back-to-back uni knots to the mainline. The knot becomes an indicator, letting you know the fish is approaching. With lots of big trout around, upgrade to 4-pound mainline and fluorocarbon leaders. It's still necessary to go light, even with large trout, because the things they bite best tend to be diminutive, fragile, or both — which calls for tiny hooks and jigs. A mayfly nymph, for instance, matches best with a size #10 hook, which could straighten out on 8-pound line.
Trout get big in lakes with lots of pelagic minnows. They may not spend as much time foraging shallow, preferring to ghost along behind schools of cisco, smelt, alewives or shad in semi-open water. In many of these lakes around North America, livebait is banned. Which is fine, because artificials like spoons, blade baits and tube jigs account for many a suspended minnow-eating trout each winter.
In lakes where minnows are allowed, one minnow on a jig may not be enough to draw a trout from any appreciable distance, but a school of minnows always brings them in. A handful of crappie minnows dropped in the hole stay in a relatively tight ball while slowly descending all the way to bottom. Put a hook through the skin along the dorsal of one minnow and slowly feed line while watching the ball of bait descend on your sonar unit.
Look for suspending trout around structure. Sharp breaks along mid-lake islands, main-basin reefs adjoining deep water, humps and bluff banks are good places to look. Trout seldom hold tight to structure, but it pays to have a few holes drilled right over any major breaks from shallow to deep water. The best hole, of course, is one where you can't find bottom because of all the suspended baitfish. That's the hole you want to find before the sun comes up.