Fly fishing for trout in Montana or anywhere in the world can be an exciting experience. Because trout live in dynamic and ever-changing aquatic environments, it is essential to understand how a trout survives and thrives. Whether a trout lives in a bio-rich river like the Missouri River or one of the Paradise Valley spring creeks or inhabits a wilderness freestone river or a high mountain lake, their daily needs do not change. Just like humans have habits--and most humans thrive when things are routine and consistent--so do trout. If you want to fish with more confidence and catch more fish, then use the needs of a trout to your favor and bring more fish to hand.
Trout Need to Breathe, Hide, and Eat
To survive, grow big, and proliferate their species, trout must have oxygen, shelter, and food. They must do this with cool water, plenty of cover, and a variety of available grub; in other words, something to breathe, somewhere to hide, something to eat. All trout require these for survival and big trout require these in abundance. In any trout stream in the world, a variety of habitat exists. Knowing what each habitat provides is crucial. Riffles and rapids are more oxygenated than slow moving pools, so trout tend to seek out the bumpy water when the air temperature is hot; but the faster moving water also requires more energy to hold in, so trout tend to seek out deep pools and glides in spring and late fall when air and water temperature have dropped. Because a trout’s lie often depends heavily on its current food source, we can simplify a trout’s holding spots into two categories: holding lies and feeding lies. With the advent of radio-telemetry tracking, the age-old idea of the Grandad trout that sits under a log for its whole life was put to bed. We know now that trout move great distances with great regularity, usually in search of food.
Trout Follow the Food
Take, for instance, salmonfly season on a freestone river such as the Yellowstone or Gallatin Rivers. During morning hours, trout will be congregated underneath the overhanging willows to catch the migration of huge stonefly nymphs, which make their way from mid-stream boulder to bank in order to climb ashore and emerge from their shucks. Come afternoon, though, when hatched bugs have begun their dive-bombing mating flights, big trout will often seek out long mid-river bubble-seams to gorge on egg-laying, hummingbird-sized chunks of protein. Toward the evening, these same fish will seek out eddies where the dead or crippled bugs are still swirling around, and have not yet been washed downstream. The old saying, “Fish where the fish are” should be modified: “Fish where the food is, and the fish will be there.”
River-Specific "Food or Hatch Events"
Much like a hatch of insects, trout are habituated to "food events." Food-induced trout migrations occur throughout the season in myriad ways on myriad rivers. The Mother's Day caddis hatch is an obvious example. Another not-so-obvious one is the Smith River earthworm gumbo feed, which happens each year during early season runoff on the Smith River, often in May--when the water is the color of a macchiato. This time of year the river runs big, and often flows over grass islands, displacing earthworms. Trout know that such food is extremely vulnerable as worms can wiggle but can’t swim like a minnow and are protein-rich, so they literally nose up into the grass, sometimes in six inches of water, and open their mouths to the surge of worms. It’s commonplace to catch a trout that literally vomits up a gob of worms once you get it into the net.
Find the Hiding Trout and Catch More Fish
Trout take cover to hide from direct sunlight, but mostly from predators, the list of which does not exclude trout. From the time they are fry, trout learn that danger—in the form of birds, crayfish, raccoons, other fish, even strange alien-like water beetles—abounds. Some times six-inch fish are eaten by fourteen-inch fish, and then fourteen-inch fish eaten by twenty-two-inch fish. We've seen a bull trout eat a 14-inch cutthroat—both fish died, of suffocation and trauma, respectively. This is all to say that the ratio of predator-size to prey-size can be surprisingly small. The angler pitching an 8” streamer of one of their favorite streamer patterns might catch a ten-inch trout or a coveted two-footer. Perhaps more threatening to trout than trout, though, are birds of prey, such as kingfisher, osprey, eagle, etc. It is because of these birds’ sharp beaks and claws that trout flee your noisy, botched cast so quickly, and it’s why guides in New Zealand won’t allow their clients to fish with bright fly lines—because trout are constantly attuned to shadows, flicks of light, anything out of ordinary that occurs from above.
Big Trout Hide in Special Places
In general, the biggest trout generally occupy the most ideal lies in the river, holding spots that put fish in the prime spot to get the most food with the least amount of effort. When fishing for big trout, it is almost important to understand there are a lot of variables. Overall, trout will take refuge hiding along or in undercut banks, near downed trees, in front of and behind boulders, under choppy water, alongside cliffs, in weeds, rip-rap constructed of old cars half a century ago, on color-changes, amongst other fish—ultimately, a trout will take cover anywhere it can. Landing a truly large wild trout is a special event that doesn't happen every day. If you are serious about chasing larger than average trout you need to stack the deck in your favor. Paying attention to where, when and how you fish can often make the difference between stumbling into a big one every few years and regularly netting trout over 20" every season.
Many trout fishing trips take you to some of the world's most beautiful places. Whether you are pursuing trout on an overnight fishing and camping trip or stalking fish in New Zealand or Patagonia, often times the catching of a fish is secondary to the experience. However, we'd all be fooling ourselves if we didn't admit that catching a fish definitely makes fishing more fun. By better understanding the essential needs of trout, from Chile to Craig, you are going to catch more fish.