Big trout get that way by focusing as soon as they can on large protein sources. This does not mean they'll quit sipping minuscule insects--particularly when an intense hatch is on. Give them the chance, though, and trout that delicately rise to pinhead-size bugs are quick to display another side to their feeding behavior.

It's about as subtle as a blue tick hound wolfing dinner after an all-night hunt. Big trout eat big bugs, a potpourri of minnow life, crustaceans, amphibians like frogs and salamanders, assorted small mammals, reptiles, and the nuggets of junk food from marshmallows to bits of bologna tossed to them by fishermen with bizarre experimental whims.

Don't let a trout's seemingly ravenous feeding habits fool you, though. Just because the fish will eat a large morsel doesn't mean you can toss it to him any old way or any time of day or season. Like all living creatures, trout learn when and where regularly occurring food items appear in their environment. Those patterns affect where the fish locate seasonally in rivers, flowages, and lakes, and also where they set up relative to specific ambush points. They dictate areas a trout will regularly patrol in search of food. Though there will always be some fish that will eat a bait presented unnaturally or at the wrong time, you'll do far better imitating nature with your presentations.

COMPARED TO BROWNS, rainbow trout are not as well known for their evening or nighttime feeding, but that was when you could really get to them in some small lakes I used to fish near the ocean in Massachusetts. These lakes were inhabited by great crayfish populations. The trout keyed on the crustaceans which would become very active during low-light conditions in the evenings, early night, and also very early in the mornings. The crayfish used the banks and shallows of the lakes and that was where the trout came to find them, even in mid-summer. It was a lot easier fishing than in mid-day when you had to work the deep water. Besides using the natural bait, you could catch these fat rainbows on crayfish-suggestive flies or jigs--if the retrieve was an erratic bottom hopping motion that imitated the real forage.

Some trout lakes are known for terrific dragonfly and damselfly populations. The big swimming nymphs of these species are greedily devoured by trout, but new anglers often strike out trying to fish imitations of the bugs. Usually a simple change in presentation will solve the problem. The nymphs of these species head from deeper water toward shore, timber, or other objects on which they can climb and metamorphose into adults. The presentation and retrieve must match the precise direction of nymph migrations to be successful. The actual retrieve cannot be too fast or slow either. Typically, a sharp four-inch stripping retrieve, with occasional pauses, brings strikes while a slightly shorter or longer strip can draw a blank.

The towards-shore or parallel-to-shore retrieve is often best for brown trout after dark, and the key is a steady retrieve so the fish can home in on an offering that's difficult to see.

My oddest experience along these lines occurred on Tasmania's Lake Pedder where the drill was to try dragonfly-imitating hair bugs in the evening, but switch to bass poppers when it turned black. You wanted always to work the bugs toward or along shore and not step too far into the water where the drop to great depths occurred a couple of feet from the bank. I was left with a supply of bugs and a warning not to worry about the leech infestation as I put on chest-high waders. The big browns sloshed like pigs at a trough in the blackness, and I caught some, too, but kept worrying about the legions of unseen leeches I was convinced were working up my legs.

Horrific flashbacks to African Queen aside, leech imitations are one of the more consistent "beef" baits for larger trout. In some cases what the trout are actually eating may be small eels. It doesn't matter, the profile is the same.

LEECH LURES WORK IN RIVERS, lakes, and ponds. I've used them as small as an inch long and know others who've struck late-season success far north on giant rainbows using big five-inch leeches that you'd normally toss to largemouth bass. Leech lures are best worked in the shallows in still waters, and always slowly.

For fly anglers, a slow strip retrieve is best. For spin anglers, an ultra-slow crank with occasional rod lift is right. There is no lack of leech-imitating flies around, from the fur bunny flies to variations on the Woolly Bugger, but spin anglers can get into the game, too. The right lures are micro-size crappie jigs with marabou tails. I trim them with small strips cut from a plastic worm, party balloon, or assorted latex products colored black with a felt-tip marker. Slightly larger panfish jigs already dressed with plastic-action tails work, too. Alternately, spin anglers can use leech flies with split shot about 10 inches up the line.

One leech fly variation, the Egg-Suckin' Leech, (or Red-Head Flash-a-Bugger, if you prefer ) is explosively effective when various salmonids are spawning--which can be over a wide period of the year if you do any traveling. Somehow I don't think leeches run around carrying a trout or salmon egg in their mouths, which is what this lure suggests. A little eel could, though. More likely it's the combined stimuli of an egg and a leech/eel that triggers a kind of "eureka--two-for-one!" response from the fish. But there is this to consider and it's important.

Eels are very likely to be working over organic matter (including stray eggs) near spawning activity. This behavior is defined with cookie cutter sharpness in Alaska, which holds a variety of other lessons for all of us who live in the lower 48.

RAINBOW TROUT IN ALASKA are totally in tune with Pacific salmon migrations, spawning activity, and eventual death. Take the well-exploited egg-eating behavior, for example. Anglers use egg-imitating flies and lures almost exclusively when salmon are spawning and rainbows are hanging slightly downcurrent chomping on washed-out spawn. Sure, the trout are eating what eggs they can, but there are also eels about--and perhaps more important, sculpin.

One of the great places to experiment with things of this nature is the wild Alagnak River within Katmai National Reserve. Populations of large fish are holding strong due to strict kill regulations, enabling Tony Sarp to make thorough study of their behavior in the river. No longer does he believe it is the eggs that are the main attraction for rainbows.

"In shallow water I've watched the real egg eaters," Sarp told me. "They are sculpin. Sculpin are the key forage for larger trout at other periods of the year when salmon aren't in the river. How do you think they act when they find a concentrated gang of them eating eggs? I've seen trout nail egg-eating sculpins near spawning salmon over and over."

In the West and lately the East, egg flies and egg-imitating lures are extremely popular early-season trout takers. Many of the rivers where they're popular also have good sculpin populations. Maybe if we'd try imitations of that forage during so-called egg season, we'd have surprising results. Before more enlightened regulations on such rivers as the Yellowstone, natural sculpin baits accounted for far too many large spawning trout taken and killed. The fish will not ignore a well-presented sculpin imitation.

In fall, which is brown trout and brook trout spawning time, I've rarely fished egg imitations for some reason. Maybe it's because seasons have traditionally closed just about the time of concentrated spawning. Today with no season closures in many areas, anglers who try them should be successful. What has worked for me during prespawn, however, are giant, weighted sculpin patterns, not only at undercut river bends, but farther upstream near gravel areas where trout are coming to build their redds. In northern Quebec and Labrador, giant brook trout respond similarly, and scaled-down sculpin imitations work beautifully on our smaller brookies close to home.

ANOTHER ALASKAN EXAMPLE of "beef"-eating trout holds a lesson for close-to-home fishing. At many of the northern camps, the spot where remains of cleaned salmon go into the water is a favorite after-dinner fishing area for anglers. Not that trout are primarily cannibals, chomping on carcass remains (though some certainly consume bits of drifting flesh). It's the concentrations of other minnow life, from sculpins to a variety of minnows and even salmon fry, that concentrate near the cleaning stations that are the main attraction for trout. You can watch the small fish attack a carcass. When one flees with an extra large morsel in its mouth waving like a pennant, he is followed by school mates trying to take their share. The minnow or fry with a piece of flesh in its mouth stands out from the others, and I'm sure it is noticeable to trout as well. What works here are little white marabou jigs and small weighted marabou flies. Do the trout take the lures as small forage fish alone or perhaps a minnow carrying a flesh strip? Either is possible.

When the Pacific salmon die naturally after fall spawning, their carcasses are peppered by the same forage fish. Salmon carcasses are still available in rivers in early spring. Some trout no doubt work at them, too, but the forage fish provide the main attraction. Bigger flashy streamers, spinners, spoons, or jigs--as well as more subdued sculpin patterns with a bit of flash--are best. In the lower 48 where brown trout in reservoirs run upriver to spawn, there is a certain amount of adult mortality. Sculpins plus a variety of other river species including fry, avail themselves of the carcasses. The concentrations of smaller fish naturally attract healthy trout. Depending on how fast winter shuts things down, these carcasses may be finished in fall or still available early in spring before snow runoff or rain flushes them away.

Years ago when large brook trout were common in the Northeast, fishermen used bits of their first-taken fish as bait. Popular was one of the fins of a fall-brightened brookie (probably an effort at not wasting any more preferable parts). Trout ate the fins of their brothers and sisters so readily, an orange-white-black fly (called the trout fin) was designed. Today, it can still produce brook trout as well as lakers that come shallow in autumn.

NO MATTER HOW APPEALING, a potential flesh or egg imitation will not be devoured unless presented in the right place. Learn the prespawn and spawning areas. During periods when forage fish are not concentrated, they are still available to larger trout. You've got to study a lake or river to see how and where they'll become available to a trout in its lie or holding station. The forage might hold in a small eddy, cut, or slough edge and become available only when foolishly venturing into a run, or when swept out by weather or debris. Trout learn how turbines affect forage location in tailwaters. They learn how minnows will come to them, just as they learn how to station themselves to pick off shoreward migrating dragonfly nymphs. They also learn about other mainly land- bound creatures coming from the banks. Even the smaller brook and brown trout in mountain streams will pounce on salamanders or newts dropping from the banks.

Though big brown trout have been known to eat such things as bats, and at least slash at small ducklings, a more feasible forage staple is lemmings or mice. Tradition has stymied the development of trout mousing technique in the East and Midwest, though lately anglers are picking up on this method following trips to Alaska where it is highly developed.

In its most exciting form, mousing is done in lower-water conditions on bright days with little wind. It is sometimes visual sport, the hair mice presented to individual fish spotted in clear waters. The trick is to drop a mouse fly or lookalike spinning lure (one of those soft rubber bass mice would work) tight to a grassy bank where the real thing sometimes drops in or tries to ford the river. Trout become conditioned to expect them there just as they do large grasshoppers during hopper season. To see one of those great Alaskan rainbows going on point, finning rapidly, then exploding on a phony mouse, is not for the faint of heart.

MOUSING IS POSSIBLE IN OTHER FORMS during other conditions. You can fish them subsurface, for instance. I once was having some luck with a sculpin in the Alagnak fishing shoulder to shoulder with Tony Sarp. We were fishing downstream from a little underwater sand point. I fished the outside main current, while Tony worked his mouse down the inside slower water. Fishing blind to the bank of the backwater, bringing the mouse out in quick little strips brought strikes for Tony. A fish that suddenly broke closer by, accidentally showed him what else would work. Tony began stripping the fly in fast to pick up for a cast at the nearby splashy trout when a rainbow he hadn't seen slammed the mouse and turned cartwheels in the air. So quartering downstream casts followed by fast stripping became a successful technique.

Back home I learned that large brown trout would certainly not pass up a mouse. The key is finding a likely lie near roots, blowdowns, other timber snags, boulders, or any lie favored by a big fish. I've seen mouse-intrigued browns come from the ruins of old mills, concrete bridge abutments, and the remains of small hydro dams.

A friend of mine returned wide-eyed from a trip to Quebec with a story about one of the large brookies he caught. At 3 1/2 pounds, it was big by current U.S. standards, not a trophy in that country. Its stomach was bulging, disproportionate to the rest of its body. The reason for the fish's unnatural girth was that it had recently consumed a small rodent my friend was sure was a lemming. Still, it had taken a fly, a dressed Muddler skittered across the surface. How it expected to get another thing past its gullet is mystifying.

It's vital to be aware of changing lake, pond, and river environments that effect the availability of large forage. Timbering practices can change bottom makeup, causing silt buildup, eliminating minnow species dependent on gravel and irregular rocks--sculpins, for example. Farming changes can destroy grasshopper availability near riverbanks. Immediate lack of usual forage makes trout susceptible to lures or flies that suggest the old feed. Given enough time, the trout may learn new behavior if the environment is not destroyed and there is enough of an alternate forage.

Wyoming's New Fork is a good example of this evolution. Big browns over 18 inches usually fed on red-bellied dace there. The habitat has changed and now produces less of the traditional forage. Like the unfortunate souls during Ireland's historic potato famine, the trout have not evolved to adapt to other things. Some no doubt will begin focusing on the ample small suckers in the river, plus tiny whitefish which are also available. Right now, if you were to toss something like a light spruce streamer with a touch of red in the dressing into the river, the dace lookalike would shortly be pounced upon.

Even the smaller trout streams near you may hold a good-size trout that would welcome the opportunity to dine on something other than minutiae. Sometimes it may take slightly scaled-down versions of larger naturals--a mini-mouse rather than one you'd toss at fish of the far north or a one- or two-inch leech rather than one of those five-inch eel specials. At the very least it's worth the experiment. Or maybe you could try a little hamburger.