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What Do Trout Eat? Facts Every Angler Should Know

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Trout eat an amazing variety of insects, minnows, worms, crustaceans, amphibians, reptiles, and even rodents!

Fishing for trout would be super easy if they ate a decent imitation of these foods, but they don’t.

How do Some Anglers Land so Many Trout?

One of the most important things to know about fishing is this: An amazing day of trout fishing isn’t really about luck at all. Successful trout fishing is about successful observation. The stories of fishermen and fish go hand in hand.

But if they were honest, they would tell you that accurate imitation of natural trout food is the most important factor in catching significant numbers of big and mature trout. Presenting those imitations with a fly rod is by far the most effective method.

For some fly pattern suggestions on where to start, take a look at our picks for the best flies for trout. The appearance of the foods that trout eat will vary from one water to the next, and even from one day to the next.

What do Trout Eat in the Wild?

1. Mayflies

Mayflies have been the focus of fly fishing since its beginnings. The mayfly’s four life stages undergo extraordinary changes as they transition from egg to nymph to dun to spinner.

Egg to Nymph

Adult female mayflies deposit eggs on the surface of the water, sometimes below the surface. The eggs sink and stick to the various structures on the stream bed or lake bottom. Hatching times vary between a few days and a few weeks.

The eggs then hatch into tiny nymphs that crawl or swim to their preferred environments for feeding and growth. These areas are where mayflies spend the majority of their life cycle, feeding on plants and going through metamorphic skin changes as they grow.

Trout consume mayfly nymphs when they become vulnerable, either by swimming around or by becoming dislodged and drifting in the current.

Nymph to Dun

When the nymph is fully mature, it will float or swim to the surface to transform into the adult dun mayfly. Some mayflies make practice runs to the surface leading up to their emergence.

During this time, nymphs are particularly vulnerable to trout. Trout eat mayflies with relative ease as they leave the bottom and move through the water column to the surface.

When emergence occurs, the nymph moves to the surface and splits its skin to emerge through a back split. The remaining skin floats in the surface film and serves as a launching platform for the newly emerged dun to stretch its wings and begin its life in the air.

Dun to Spinner

When emergence occurs, air exposure quickly hardens the wings and skin, and shortly after, the dun flies to nearby trees and bushes to await its next transformation.

The dun will again shed its skin after a half- to full-day wait, whenever the weather is optimal. After once again shedding its skin, the dun transitions into the final stage, known as the spinner.

Spinner to Egg

Swarms of male adult spinner mayflies form over waters that are optimal for hatching mature nymphs. Males catch female mayflies in the air and mate before depositing their eggs.

Spinner swarms usually form 18–24 hours after the adult duns emerge and only last a few short hours. The female mayflies then deposit their eggs on or below the surface of the water, skipping on the surface or even occasionally diving.

Both males and females are quickly exhausted from the mating swarm and die on or near the water soon after. The cycle begins again as the eggs hatch and mature.

2. Caddisflies

People often mistake caddisflies for tiny moths. However, unlike moths, caddisflies have a distinct ten-like formation to their wings while at rest.

Getting a favorable look at a resting caddisfly can be a challenge due to the erratic behavior of most caddisflies. Caddisflies outnumber the mayfly in numbers of species and at least inhabit an equal number of aquatic environments.

Accordingly, trout eat caddisflies in large numbers. Thankfully, the erratic behavior of caddisflies is quite easy for fly anglers to imitate. The life cycle of caddisflies passes from egg to larva, pupa to adult.

Egg to Larva

Adult female caddisflies drop their eggs or directly stick them to bottom structures using a process known as ovipositing. After about two weeks, the eggs will hatch into tiny larvae that settle in adjacent environments.

Caddis larvae ambitiously feed on plants and animals, including tiny minnows and large dead fish. Many caddisfly larvae build cases from sand or woody debris that protect them from injury and conceal them from predators. Regardless of their casing, trout consume caddis that build cases.

The caddis enlarge their cases as they grow to accommodate their size. Those caddis that don’t build cases conceal themselves on, under, and inside various bottom structures. Of course, trout eat these free-living caddisflies, and these larval caddisflies also offer anglers the best opportunity for imitation.

Larva to Pupa

When the larva has reached its full size, it will build a case, if it does not already have one. Like many butterflies and moths, the caddisfly lies dormant for a period of time as it pupates.

The caddisfly first anchors the case to bottom structures, and then constructs a door to close the case. During pupation, the caddis develops its wings and legs, as well as the necessary anatomy to breathe air and reproduce.

The pupa then waits until specific water conditions are met before emerging as an adult.

Pupa to Adult

When light and water temperatures are optimal, the pupa emerges from its case and either crawls or swims to the surface. This is a vulnerable time for caddisflies and hungry trout to eat the pupae whenever possible.

Adult caddis pupae, on the other hand, are often quick swimmers and can emerge from the water quite quickly. At the time of emergence, the pupa’s outer skin inflates and separates from it.

The air-filled shuck adds to their natural buoyancy and helps the caddisfly ascend to the surface. Trout eat these emerging pupae during their ascent, or on the surface if they can catch them. However, during intense caddis hatches, the fast emergence often results in numerous splashy rises.

Adult to Egg

The adult caddisflies congregate among the nearby vegetation and begin mating flights that last a few weeks. Caddisflies tend to favor the most enjoyable times of day to make these mating flights and deposit their eggs.

Adult caddisflies are still remarkably capable on or in the water. Female egg-laying caddis will often crawl or swim under the water to oviposit their eggs in ideal locations.

Because the mating flights last a number of weeks, trout eat them almost all summer. For this reason, a wide variety of adult caddisfly imitations are an excellent tool for anglers to query unfamiliar waters.

3. Stoneflies

The stonefly is an important insect for anglers to understand. They require relatively clear and clean water that contains high levels of dissolved oxygen.

Stoneflies cannot breathe with the same level of efficiency as other aquatic insects and often depend on flowing water to pass oxygen through their gills. With that in mind, slow-flowing streams and lakes do not often harbor large numbers of stoneflies.

Stoneflies’ need for high-quality water can also be a good indicator of a suitable trout habitat. Stoneflies have three major life stages: the egg, the nymph, and the adult. But the stonefly life cycle is long, with generations ranging from two to four years.

Egg to Nymph

The adult female stonefly deposits egg clusters just below or on the water’s surface. The egg clusters break up, sink, and hatch over a very long time span.

Some species hatch in a few days or a few weeks, while others can almost take a year. Regardless, the eggs and the very tiny nymphs that emerge have no real significance to anglers. But as they grow, the stonefly nymph becomes a significant food source.

The small stonefly nymphs settle in the best locations for the sake of feeding and their need for highly oxygenated water. Some species eat only plant life, while others are highly predacious.

Stoneflies compete for food and territory, consuming other aquatic insects and newly hatched fish. Stonefly nymphs shed their tough outer skin multiple times to facilitate their growth. Due to their unique characteristics, it is fairly simple to avoid confusing them with other aquatic nymphs.

Nymph to Adult

Mature stoneflies pass directly from nymph to adult. When the time is right, the water temperature and sunlight cue the larger species to crawl to shore.

The emergence typically occurs at night and may continue into the early morning hours. The mature stoneflies pull themselves onto exposed banks, logs, and rocks, where they split and shed their nymph skin.

The newly emerged adults require a period of drying before their wings and skin harden. Smaller adult stoneflies will often emerge right on the surface in a similar fashion as mayflies and caddisflies.

The small stoneflies shed their nymph skin and stood on the surface film to dry their wings. These mid-stream emerging stoneflies can easily go unnoticed due to their flat profile. Mayflies and caddisflies that emerge simultaneously can also mask them.

Adult to Egg

Most often, the adult stonefly hides in the bushes and trees along the stream, rarely flinging its wings. The adults mate far away from the hungry trout. But once the females have mated, they begin egg-laying flights back and forth to the water.

Stoneflies, however, are not graceful pilots. The egg-laying females often appear to crash land and skitter across the water, causing quite the obvious attraction to trout. With wild excitement, the waiting trout eat the clumsy adults and ambitiously gorge themselves on the sizeable bugs.

Over a period of one to two weeks, the adults deposit their eggs and eventually exhaust themselves, unable to fly from the water’s surface. Hungry trout gobble up the fatigued and drowned insects, and the stonefly life cycle begins again with the newly deposited eggs.

4. Midges

Midges are more widespread and important to trout than most anglers know. Their mosquito-like appearance often adds to the mistaken identity of these tiny insects.

In fact, the order of Diptera includes mosquitoes, craneflies, gnats, and midges. Midges hatch continuously from early spring to late fall and inhabit a range of water conditions that are well beyond what trout can tolerate.

It is very likely that trout eat more midges than any other aquatic insect. Midges can be frustrating for anglers to attempt to imitate due to their small size, which is often 18 or smaller. Midges have life stages similar to those of the caddisfly, in that midges go from egg, larva, pupa, and adult.

Egg to Larva

Once midge eggs hatch, the larvae take up residence in the surrounding structures of the lake, river, or stream. Larva are very thin and appear much like a tiny worm.

Midge larvae eat plant life and quickly grow to a size that interests hungry trout. When swimming, the larvae make whip-like movements that are very attractive to nearby trout.

The midge larvae often sport brightly colored reds, bright greens, gold, olive, yellow, and black.

Larva to Pupa

Once the larva reaches full maturity, it will initiate the pupation process. Like caddisflies, midge species that live in flowing water will make a pupal case and attach themselves to the stream bottom.

In still waters, the midge pupa will remain free to swim. Within a few days, the midge pupae quickly develop legs and wings, and their abdomen and thorax become enlarged.

Like the larval midge, the pupa will rise to the surface when they are prepared to emerge. In calm waters, trout frequently cruise just beneath the surface, often exposing their dorsal fins as they feast.

Pupa to Adult

When mature midge pupa rise to the surface, they hang in the surface film with a very different posture than caddisflies and mayflies. Instead, the midge pupa hangs vertically.

The pupa then splits its skin, emerges, and extends its wings to dry and harden. The emerging midges transition from vertical to a more horizontal orientation in or on the surface film.

The adults often clump together in small groups as they sit on the water’s surface. It is an observable phenomenon that trout eat groups rather than individual insects.

Adult to Egg

Adults form mating swarms within one day after leaving the water. The females return to the water and lay their eggs on the surface or slightly below it.

Both males and females die shortly after mating but rarely fall to the water like other aquatic insects. As a result, the spent midges are not a significant food source for trout.

The life cycle begins again as the eggs sink to the bottom and establish a new generation.

5. Dragon And Damselflies

Dragonflies and damselflies are an incredible food source for trout. Anglers often overlook this valuable food source. In lakes and ponds, dragonflies and damselflies can reach nearly two inches in length.

These large insects not only provide a big meal, but they also live much longer in their aquatic and terrestrial forms than the previous four insect orders we’ve discussed.

Both dragonflies and damselflies life cycles pass from egg to nymph to adult. While dragonflies have a life cycle of two to four years, damselflies have a life cycle of one or two years.

Egg to Nymph

After about two weeks, the tiny nymphs emerge from the egg. Dragonfly and damselfly nymphs are active predators that vigorously pursue, kill, and eat any smaller aquatic insect or small fish.

The nymphs are very capable swimmers that prefer to crawl around structures like plants and roots to hunt their prey. The nymphs are truly fierce predators, to the point that they will even kill each other when possible.

This is why you rarely find them in concentrated numbers. But because of their large size and tendency to fearlessly expose themselves, they present a captivating opportunity for big trout.

Nymph to Adult

In the spring or early summer, the mature nymph crawls out of the water onto nearby structures in order to dry and split its skin. This emergence can require hours of effort and strain.

Once emerged, the adult slowly extended its wings to allow them to dry and harden. The abdominal structure also undergoes significant changes and elongation. Within a twenty-four-hour period, the transformation is complete.

The newly emerged adults are very vulnerable, as they are somewhat clumsy fliers and can end up back in the water, struggling to escape. Those who successfully take off will likely be completely out of reach of the trout until they return to lay eggs.

Some aquatic insects stop eating entirely once they emerge from the water, which only shortens their terrestrial lives. Dragonflies and damselflies, on the other hand, continue to hunt and prey on other small insects and live very long terrestrial lives.

Adult to Egg

Adult dragonflies and damselflies form pairs to mate. While dragonflies have wide ranges that often stray far over land, damselflies remain very near water as adults.

Egg-laying dragonflies return to the water, skimming the surface to deposit their eggs. Damselflies land on weed beds and sometimes even crawl down plant life to deposit their eggs deep beneath the water’s surface.

The cycle begins again as the eggs hatch. Because of their long life cycles, dragonflies and damselflies will have multiple generations of aquatic nymphs living in one body of water.

Wrap-Up

Their size, color, shape, and movement can be very different depending on the location and which phase of their life cycle happens to be occurring.

Before you can imitate a particular trout food, you need to develop the ability to recognize it for what it is.

We hoped we helped you understand it, and next time you go on a fishing trip, you come back with a dozen trout.