Watch this video of shimmering ‘rainbow fish’ in Lake Simcoe

yellow perch Photo by Keith Publicover/Shutterstock

You don’t have to book a scuba diving trip to the Great Barrier Reef to see brightly-coloured, sparkly fish. A videographer from Kempenfelt Bay, Lake Simcoe captured a group of yellow perch shining as bright as a disco ball. These real-life ‘rainbow fish’ are just one example of the amazing diversity of beautiful fish that can be found within the lakes and rivers of Ontario.

The yellow perch video was captured by Kevin Biskaborn, a professional digital media producer and designer. “Looking from above the water, you’d never see or appreciate the spectrum of colours on display underwater,” says Biskaborn. “Luckily with the camera submerged, I was able to capture the magic of the sun bouncing off the scales of these fish.”

Robin Gaspardy, an aquatic science technician with Fisheries and Oceans Canada, says the shine on display in the video is an iridescent effect created by layers of tiny crystal structures in the fish’s scales that reflect and refract light in different directions. She compares the phenomena to hanging up a decorative glass prism to scatter rays of sunlight into rainbows.

For these shiny yellow perch, there’s safety in numbers. The dazzling effect produced by a shifting mass of iridescent fish, “can be really confusing to predators,” says Gaspardy. The iridescence protects yellow perch from ending up on the lunch menu for Lake Simcoe’s top predatory fish like muskie, largemouth bass and smallmouth bass.

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Colourful and flashy lures work well for anglers in Lake Simcoe, adds Gaspardy, because large predatory fish interpret the flashes from the lures as the iridescent shine of small prey fish.

“We have a lot of these really beautiful, colourful, and interesting fish here in Ontario and across Canada,” says Gaspardy. Iridescent scales and colourful pigmentation are used by fish to communicate with one another and to camouflage from predators.

Rainbow darter
Photo courtesy of Fisheries and Oceans Canada

A standout for colourful Ontario fish is the Rainbow darter. This small fish only grows to about 3 inches in length but boasts intense blue and orange colours on its fins.

Some fish change colour based on the time of year. Gaspardy points to the bowfin as an example. The males develop, “almost unnatural, highlighter green” fins and a big spot on the tail during spawning seasons.

Photo courtesy of Fisheries and Oceans Canada

Gaspardy stresses that individual fish from the same species can exhibit a huge range in colouration depending on where they live. Fish that live in murky water tend not to have bright colours, she says, because they can’t see each other very well.

This gigantic school of fish in Lake Simcoe is a rare find

Because of the colour variation, anglers that collect and fish with live minnows must be able to identify species of fish without relying on colour, says Gaspardy. Some Canadian minnows, like the eastern sand darter, are species at risk and illegal to use as baitfish.

Instead of identifying fish based on colour and iridescence, anglers should use other characteristics, like fin placement, and eye and mouth size, to determine baitfish species. Gaspardy recommends that anglers download and use the Baitfish Primer, a free smartphone app developed by Fisheries and Oceans Canada, to guide both novices and experts through the process of identifying Ontario’s baitfish.

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