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Creature Feature: Protecting the Brilliant Brook Trout

Displaying a dazzling array of colors on their shimmering scales, the brook trout (Salvelinus fontinalis) is one of the most beautiful fishes native to Illinois. They can easily be identified by their olive green bodies speckled with a pattern of yellow and red spots, with some spots sporting a beautiful blue halo. Mature males also have a distinguishable reddish-orange belly.

These gorgeous fish are more than their good looks — they are the Great Lakes’ only native stream-dwelling trout. They serve an important role in their freshwater ecosystems, are a prized catch by anglers and deserve our care and protection.

A brook trout swims among others in a dimly lit habitat.

All About Brook Trout

Brook trout are related to other species of char, trout and salmon and can be found in creeks, rivers and lakes in their native range from Eastern Canada to the Midwest. Like any Chicago native, these fish are made for the cold. Brook trout thrive in water temperatures colder than 55 degrees Fahrenheit.

As temperatures begin to cool in the fall, female brook trout dig a small hole in the gravel-covered riverbed with their tails called a redd and can lay thousands of eggs. Young brook trout feed on the egg yolk, microscopic animals and plankton, and will mature within a year or two.

Because they are sensitive to temperature changes and pollution, brook trout are considered an indicator species. Indicator species are the first to decline when their habitat degrades, like the proverbial “canary in the coal mine.”

A brook trout's head.
A brook trout swims facing the viewer.

These fish not only provide color and diversity to our lakes and rivers, they also help control our insect population, including mosquito larvae. Brook trout are not picky eaters so they will eat whatever is in abundance. This can range from beetles and mayflies to an array of other aquatic insects.

If brook trout populations were to begin to decrease, animals like river otters, snapping turtles and herons that prey on brook trout would lose a source of food. Without brook trout, insect populations would flourish. These fish are vital to maintaining the natural balance of freshwater ecosystems and the Great Lakes at large.

A brook trout swims in a dimly lit habitat.

What Can you Do to Help Brook Trout?

So, how do we keep brook trout safe? Everyone can make changes in their daily life to protect vital brook trout populations.

  1. Help stop water pollution: Properly dispose of waste, especially plastics and fertilizers. You can learn more about how to dispose of household and hazardous waste through resources like Illinois’ Household Waste Disposal Guide.
  2. Volunteer: Want to lend a hand maintaining freshwater ecosystems through beach clean-ups, woodland habitat restoration or river planting? Join a Shedd Aquarium Action Day.
  3. Donate: A donation to Shedd will help bolster our conservation work on the Great Lakes.
  4. Educate others: It’s easy to forget that every animal in our waterways plays a pivotal part in its ecosystem. Spread the word about the importance of brook trout and freshwater fishes like it.
  5. Be mindful when fishing: Overfishing can contribute to population decline in brook trout. Practice catch and release or avoid fishing in areas where brook trout are plentiful.

When we all take seemingly small steps individually to protect freshwater ecosystems, together we make a big impact to help brook trout thrive! On your next visit here at Shedd, spot the brook trout in At Home on the Great Lakes gallery.

Steve, Lena and Claudia, Fall 2022 ACCA Freshwater Ecology Students