Fascinating Fish Species in the Credit River Watershed

If you’re familiar with fish species found in the Credit River, then you’ve likely heard of brook trout, chinook salmon and redside dace. However, the Credit River Watershed is home to plenty of other species of fish, many of which are common but seldom seen.

Three of our Favourite, Lesser Known Fish in the Credit River

Rainbow Darter

• Where it lives: The rainbow darter prefers shallow riffle sections of streams. Through fish community monitoring, we often capture them in large numbers in the Credit River near Terra Cotta.
• What it eats: The rainbow darter feeds from the bottom, mostly on insect larva, small crustaceans and molluscs.
• Spawning behavior: During the spring, the rainbow darter releases and fertilizes eggs in river riffles, a shallow place in a river where water flows quickly past rocks. The male aggressively guards a territory and chases away competing males. The female partially buries herself in the gravel and deposits the eggs, while the male fertilizes them from above the gravel’s surface. Both the male and female spawn with other partners over several weeks before abandoning the nest.

Common Shiner

• Where it lives: The common shiner is found in cool to warm streams and rivers. It prefers gravelly and rocky areas free of vegetation. While we find common shiner throughout the watershed, we often find larger individuals, some reaching over 11 centimetres, in the main Credit River.
• What it eats: The common shiner is an omnivore. It will eat anything that will fit in its mouth, including aquatic insects, plants and algae.
• Spawning behavior: In spring, the male clears gravel on the stream bed to create a nest and defends it from other fish, including other male common shiners. Females spawn when the water temperature is between 14 and 28 degrees Celsius. Though the male defends his nest and territory aggressively, other similar species such as river chub will spawn in the same nest location and sometimes at the same time as the common shiner.

Brook Stickleback

• Where it lives: the brook stickleback is found in a variety of habitats wherever there is plenty of vegetation, including small streams, rivers, lakes, ponds and wetlands. We find brook stickleback all over the watershed from slow-moving sections of Rogers Creek near Terra Cotta to the slow, weedy margins of the Credit River near Cheltenham. 
• What it eats: A brook stickleback’s diet consists of small insect larvae, crustaceans and occasionally small fish eggs.
• Spawning behavior: The brook stickleback has one of the most elaborate spawning behaviors. The male arrives at the spawning location first, where he creates a tube-shaped nest from leaves, twigs and a string he secretes. The male entices the female into the nest and once spawning is complete, he chases her out of the nest. He guards the nest and the young by performing aggressive displays, erecting his spines and quivering.

Fish Community Sampling Across the Credit River Watershed

Each year, staff from our Integrated Watershed Monitoring Program (IWMP) encounter these species and many more through fish community sampling. Last year we captured 44 species. For the past 25 years, we have collected data from stream monitoring stations across the Credit River Watershed, including small headwater tributaries near Orangeville down to the main Credit River in Mississauga. Our monitoring covers a diverse array of habitats, giving us a complete view of the fish communities of the watershed. This long-term monitoring provides important data for us and our partners, to use in planning, restoration prioritization and graduate student research.

View fish community data from across the watershed.

Learn about how conditions are changing in ecosystems across the watershed.

By: Kurtis Plourde-Rideout, Technician, Watershed Monitoring

Feature image credit: Jon Clayton, Aquatic Ecologist, Natural Heritage Management