Fish nocturnal

Kiyi

Coregonus kiyi

A shimmering specter of the deep, the Kiyi is one of the Great Lakes' most elusive treasures. Known for its massive eyes and iridescent purple glow, this deep-water specialist is a marvel of freshwater evolution.

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Quick Identification

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Size

10-14 inches (25-35 cm) in length; typically weighs between 0.5-1 lb (0.2-0.45 kg)

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Colors

Brilliant silver sides with a distinctive pinkish or purple iridescence; dark olive to blue-black back and a white belly

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Key Features

Extraordinarily large eyes adapted for the dark
Lower jaw slightly overlaps the upper jaw
Long, delicate pectoral fins
Deep-bodied and laterally compressed compared to other ciscos

When You’ll See Them

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Activity pattern nocturnal

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Peak hours 10 PM - 3 AM

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Season Late Fall

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Diet Mainly feeds on deep-water invertebrates like Mysis (opossum shrimp) and the amphipod Diporeia

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Habitat Deep, cold freshwater; specifically the benthic and mid-water zones of Lake Superior

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Behavior

The Kiyi is a master of the Great Lakes' deep-water abyss, primarily found today in the cold, clear waters of Lake Superior. These fish are highly social and spend much of their lives in large schools, navigating the dark benthic zones where few other species can thrive. They are a critical link in the aquatic food web, serving as a primary food source for deep-dwelling predators like the Lake Trout.

One of the most fascinating aspects of Kiyi behavior is their daily vertical migration. During the daylight hours, they hug the lake floor at depths of up to 600 feet to avoid being seen by predators. As the sun sets, they swim hundreds of feet upward toward the surface to feed on plankton and small crustaceans that move with the light. This rhythmic movement makes them a dynamic part of the lake's ecosystem, though it also makes them quite elusive for the average observer.

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Camera Tips

Capturing a Kiyi on camera is an advanced project that requires specialized underwater equipment, as these fish rarely venture into the shallow waters where standard backyard cameras operate. If you live on the shores of Lake Superior, your best opportunity lies in using a high-pressure rated underwater trail camera or a tethered ROV (Remotely Operated Vehicle). Look for rocky drop-offs or deep-water piers where the bottom depth exceeds at least 50 feet, as this is the minimum range they might visit during their nightly upward migration.

Lighting is the biggest hurdle when filming Kiyi. Because they have evolved with massive eyes for life in the dark, they are extremely sensitive to white light. A standard bright LED will likely cause the school to scatter instantly. To get natural behavior, use infrared (IR) or deep-red light settings. Fish perceive red light poorly in deep water, allowing you to illuminate the scene without disturbing their natural foraging patterns. Position your lights at a 45-degree angle away from the lens to minimize backscatter from suspended particles in the water.

Since Kiyi are migratory within the water column, timing your deployment is everything. Set your camera to record during the vertical transit times—roughly an hour after sunset and an hour before sunrise. During these windows, Kiyi are moving between the deep bottom and the surface, increasing your chances of a close encounter. If you are using a stationary camera, try attaching a small mesh bait bag containing crushed shrimp or fish meal. The scent trail can lure a curious school into the frame, providing you with a spectacular view of their shimmering, iridescent scales.

Finally, ensure your camera is set to a high shutter speed or a high frame rate (at least 60 fps). Kiyi are incredibly agile and tend to dart in and out of view. A slow frame rate will result in a silver blur. By using a higher frame rate, you can capture the delicate movement of their long pectoral fins and the beautiful purplish sheen that reflects off their sides. If your camera has a low light mode that doesn't rely purely on digital gain, enable it to keep the image crisp despite the challenging Great Lakes depths.

Similar Species

Species that look similar or are commonly confused with Kiyi.

Cisco (Lake Herring)

The common Cisco has smaller eyes and a more slender body compared to the deep-bodied Kiyi.

Bloater

Bloaters have a smaller eye and a shorter, more rounded snout, whereas the Kiyi has a distinctively large eye and a projecting lower jaw.

Shortjaw Cisco

The Shortjaw Cisco has a lower jaw that is shorter than or equal to the upper jaw, the opposite of the Kiyi.

Frequently Asked Questions

Kiyi are most active during the night. They perform a vertical migration where they rise from depths of over 500 feet toward the surface under the cover of darkness to feed, returning to the bottom before dawn.

Attracting Kiyi to a standard backyard is difficult unless your property sits directly on the deep waters of Lake Superior. For those with deep-water access, using a submerged bait bag with crushed invertebrates can draw them toward an underwater camera rig at night.

Kiyi primarily eat small deep-water crustaceans, including Mysis (opossum shrimp) and Diporeia. They use their large, sensitive eyes to spot these tiny creatures in the low-light environment of the Great Lakes.

No, Kiyi are not found in suburban ponds or small lakes. They are endemic to the Great Lakes and are currently only found in significant numbers within the deep, cold waters of Lake Superior.

The Kiyi can be distinguished by its exceptionally large eyes (which take up about a quarter of its head) and its unique purplish-pink iridescence. It also has a lower jaw that usually projects slightly beyond the upper jaw.

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