What Do Brook Trout Eat?

Brook trout are a common freshwater fish species that live in lakes and rivers. As juveniles, they eat plankton and when they grow to adulthood, their diet varies. 

Adult brook trout have been known to eat insects, worms, crustaceans, leeches, amphibians, small fish, small mammals, and even plants.

In this article, we’ll provide you with the nutritional benefits of brook trout’s favorite snacks to better understand the diet of this popular fish. 

Juvenile Brook Trout Diet

After hatching from their eggs in the winter, juvenile brook trout only grow to about three or four inches by the end of their first summer.

Being so small, the choices for food are limited but they need plenty of nutrients in order to grow to adult size. As such, juvenile brook trout generally eat lots of plankton – microscopic organisms which float in the water.

Plankton is a great source of micronutrients including vitamins, carotenoids, sterols, amino acids, trace elements, enzymes, fatty acids, and other organic materials that help juvenile brook trout grow into healthy adult fish.

As they continue to grow, juvenile brook trout may also start to consume insect larvae from species such as caddisflies and mayflies as these are usually in abundance during the spring and early summer months. These give an added boost of protein for a juvenile brook trout’s diet. 

Adult Brook Trout Diet

By the end of their second year, sometimes even as early as their first, brook trout are fully mature adults and their diet expands beyond the minuscule meals of plankton and insect larvae.

They become opportunistic feeders and eat a wide variety of prey including worms, leeches, insects, crustaceans, amphibians, small fish, small mammals, and, on occasion, plants. 

Nutritional Benefits of Worms and Leeches

Worms and leeches provide a great source of protein and iron for adult brook trout and can be found in abundance in the lakes and rivers brook trout inhabit.

They provide a well-rounded meal and are also easy for brook trout to detect through the disturbances the worms’ wriggling motions make in the water. 

Insects: The Most Abundant Prey

what do brook trout eat

It is well known that insects comprise the most numerous of groups in the animal kingdom and this makes them the most abundant food source for adult brook trout.

Aquatic insects are a particular favorite of adult brook trout, most likely due to the ease of locating and catching them as they are in vast abundance within the habitat of these fish.

Caddisflies, mayflies, stoneflies, and midges are among the most common aquatic insects that adult brook trout will consume.

However, brook trout are not exclusive feeders on aquatic insects and willingly devour terrestrial insects as well, most commonly ants and beetles that unwittingly fall into the waters of the lakes and streams brook trout call home.

Insects are an important part of a brook trout’s diet, not only due to their availability, but also because of their high amino acid content which is essential for a healthy growing adult brook trout.  

Crunchy Crustaceans

Crayfish are a type of freshwater crustacean that is abundant in the summertime in a lot of the lake and stream habitats also occupied by brook trout. Adult brook trout will happily snack on these swimming crustaceans and receive a lot of nutritional benefits in return. 

Crayfish contains a suite of important nutrients to maintain the health and wellness of brook trout including vitamins A, B, D, E, and K, calcium, zinc, phosphorus, and iron. Not to mention these little critters are also high in copper and selenium, a great source of protein, and low in fat.

Edible Amphibians 

Believe it or not, adult brook trout are not shy about hunting for frogs to eat for a dose of variety in their diet. While most of the time, the fish will consume frog eggs or tadpoles, small adult frogs are not off the menu. 

It isn’t very advantageous for brook trout that live in moving waters, such as streams and rivers to prey on amphibians as the energy expenditure by going against the current is not worth the meal in the end.

However, brook trout that live in still waters, such as lakes and ponds, have no qualms about making an opportunistic meal out of an unsuspecting small frog.

Like crayfish, frogs are high in protein but low in fat and can provide adult brook trout with many other essential vitamins and minerals such as vitamin B, zinc, iron, and omega-3 fatty acids.

Look Out Little Fishies

Although adult brook trout do not grow to a particularly large size – on average about 10 inches in length – they are voracious predators to other fish species smaller than them.

Brook trout will feed on minnows and smaller bottom-dwelling fish that are easy to catch and a suitable size to swallow. 

The prey fish of adult brook trout provide a source of food high in protein and omega-3 fatty acids – essential to maintain a healthy growing adult brook trout that is able to spawn for the coming season. 

Mammals for Meals

Adult brook trout have quite the appetite and although it isn’t common, they have been known to snack on the occasional small mammal, usually of the rodent variety, that may happen to fall into their aquatic domain.

As long as the little furry land dweller is small enough for the adult brook trout to eat, they will not hesitate to gulp it up attesting to their opportunistic feeding nature.

Small mammals can be a great source of protein but are not relied upon for an adult brook trout’s diet because of the unlikelihood of encountering an unfortunately clumsy rodent.

Prime Opportunistic Feeders

Brook trout are a prime example of what it means to be an opportunistic feeder with a taste for anything available from the smallest plankton and insect to a mouthful of mammal or frog.

No matter what they eat, having such a varied palate helps ensure a well-balanced diet and high availability for a meal.