What Are Coregonines?

Image Credit: Paul Vecsei

A cisco captured in the Spanish River (a tributary to northern Lake Huron), captured just below the dam, in fall 2022. Credit: Cory Brant.

The eleven species of coregonines recognized in the Great Lakes includes three “whitefishes” (Lake Whitefish, Round Whitefish, Pygmy Whitefish) and eight “ciscoes” (Longjaw Cisco, Deepwater Cisco, Blackfin Cisco, Shortnose Cisco, Shortjaw Cisco, Cisco, Bloater, Kiyi). Yes, we know it is confusing that “ciscoes” are a catch-all name to refer to eight species, while “Cisco” is the common name for the species Coregonus artedi. One way to distinguish the meaning is to pay attention to the capitalization!

Whitefishes and ciscoes can be distinguished by their mouth orientation and gill rakers. Whitefishes have mouths more oriented towards the bottom that are adapted for benthic feeding and tend to have fewer and shorter gill rakers, whereas ciscoes have more terminally oriented mouths that are adapted for more pelagic feeding and tend to have more numerous and longer gill rakers.

Although the Coregonine Restoration Framework was developed to be inclusive of all Great Lakes coregonine species, the current focus and application is to restore or conserve the diversity of the ciscoes. In fact, the losses in diversity have mostly occurred with ciscoes.

Although the status of each species has not been fully assessed in both Canada (by the Species at Risk Act) and the United States (by the Endangered Species Act), at least one agency has determined Deepwater Cisco, Blackfin Cisco, and Longjaw Cisco to be classified as extinct. In Canada, Shortnose Cisco has been classified as endangered and Shortjaw Cisco as threatened. Some other species such as Kiyi have been extirpated in some of the lakes, but still are abundant in Lake Superior.

The eight ciscoes can be difficult to distinguish without a lot of practice and experience. Key diagnostic characters include the head and body shape, the length of the paired fins, and the number and shape of the gill rakers. Genetic tests can now help us confirm species identity of all species. Ecologically, the ciscoes tended to occupy different depths of the large and deep Great Lakes. They have remained different species by reproducing at different times of the year (fall, winter, and spring) and at different depths.

A shortjaw cisco (C. zenithicus, top) and a kiyi (C. kiyi, bottom) from the Thunder Bay region of Lake Superior. Credit: Andrew Muir.

Coregonine Species of the Great Lakes

Cisco (Coregonus artedi)

Lake Michigan, illustrated by Cory Brant

Cisco was widely distributed, occurring in the shallow waters (from embayments to rivers to the offshore) of all five Great Lakes. Cisco also can display different “forms” or sub-species in some lakes. As an adult, it can reach sizes 12 inches and greater. It typically consumes zooplankton, supplemented occasionally with small minnow-sized fishes. Present-day, it is most abundant in Lake Superior. It also occurs in lakes Michigan, Huron, and Ontario, but with smaller population sizes and with more limited distributions than historically. It has been extirpated from Lake Erie since the 1950s. There is currently an effort to restore them in Saginaw Bay, Lake Huron.

Bloater (Coregonus hoyi)

Lake Superior, illustrated by Paul Vecsei

Bloater is a deepwater cisco (i.e., occupies bottom waters during the day and moves up into midwater depths at night) that once occurred in four of the five Great Lakes (all but Lake Erie). Compared to other deepwater ciscoes, it was the among the smallest in size and occurred in shallower, offshore waters. Recent diet studies in the Great Lakes reveal diverse diets of zooplankton (e.g., calanoid copepods) and other invertebrates (e.g., mysids, Diporeia spp.) that live in the deep, cold waters of the lakes. Present-day, it occurs in lakes Superior, Michigan, and Huron, although in Lake Huron some of its physical characteristics differ from what was previously described. It has been extirpated from Lake Ontario for several decades, although a reintroduction program (using bloater from Lake Michigan) has been underway since 2012.

Kiyi (Coregonus kiyi)

Lake Superior, illustrated by Paul Vecsei

Kiyi is a deepwater cisco (i.e., occupies bottom waters during the day and moves up into midwater depths at night) that once occurred in four of the five Great Lakes (all but Lake Erie). Compared to other deepwater ciscoes, it is among the smaller species and occurs in the deepest, offshore waters. Recent diet studies in Lake Superior have revealed domination by mysids. Present-day, it occurs only in Lake Superior and was extirpated from the other three lakes by at least the 1960s. Scientists are researching the feasibility of collecting gametes in Lake Superior during the winter months when Kiyi spawn and determine whether they can be reared in artificial conditions.

Shortnose cisco (Coregonus reighardi)

Lake Huron, illustrated by Cory Brant

Shortnose Cisco is a deepwater cisco (i.e., occupies bottom waters during the day and moves up into midwater depths at night) that once occurred in four of the five Great Lakes (all but Lake Erie). Compared to other deepwater ciscoes, it was intermediate among species in terms of size and occupied relatively shallow offshore bottom depths. Its diet was only rarely described in the Great Lakes, but from this limited information mysids and Diporeia were the primary prey, with smaller numbers of zooplankton, small mussels, and aquatic insect larvae. Shortnose Cisco have a relatively low number of gill rakers compared to other ciscoes, suggesting it most efficiently consumes larger invertebrates rather than smaller zooplankton. Present-day, it has been extirpated from lakes Michigan, Huron, and Ontario, and its status in Lake Superior is currently under scientific examination.

Shortjaw cisco (Coregonus zenithicus)

Lake Superior, illustrated by Paul Vecsei

Shortjaw Cisco is a deepwater cisco (i.e., occupies bottom waters during the day and moves up into midwater depths at night) that once occurred in Lakes Superior, Michigan, and Huron. Compared to other deepwater cisco species, it was intermediate in terms of size and bottom depth occupied. Its diet in the Great Lakes has rarely been described, but from this limited information Diporeia, mysids, and zooplankton are important. Present-day, it has been extirpated from lakes Michigan and Huron, and its status in Lake Superior is currently under scientific examination.

Blackfin cisco (Coregonus nigripinnis)

Lake Superior, illustrated by Paul Vecsei

Blackfin Cisco is a deepwater cisco (i.e., occupies bottom waters during the day and moves up into midwater depths at night) that once occurred in Lakes Superior, Michigan, and Huron. Compared to other deepwater cisco species, it was among the largest species in terms of size and deepest in terms of bottom depth occupied. Its diet has rarely been described in the Great Lakes, but with the limited information mysids were important. Blackfin cisco had a relatively high number of gill rakers compared to other ciscoes, suggested it could also consume pelagic zooplankton with efficiency. Present-day, it has been extirpated from lakes Michigan and Huron, and its status in Lake Superior is currently under scientific examination.

Longjaw cisco (Coregonus alpenae)

Lake Michigan, illustrated by Paul Vecsei

Longjaw Cisco was a deepwater cisco (i.e., occupied bottom waters during the day and likely moved up into midwater depths at night) that once occurred in Lakes Michigan, Huron, and Erie. It was the only deepwater cisco in Lake Erie. Sadly, this species has been assessed as ‘extinct’ in the United States. In the early 1980s, scientists also questioned whether it was its own species or was instead just a variant of the Shortjaw Cisco. Compared to other deepwater ciscoes in lakes Michigan and Huron, it was intermediate among species in terms of size and bottom depth occupied. Its diet was only rarely described in the Great Lakes, but from this limited information it appears to have been dominated by mysids, small mussels, and aquatic insect larvae.

Deepwater cisco (Coregonus johannae)

Lake Huron, illustrated by Paul Vecsei

Deepwater Cisco was one of seven described deepwater cisco species (i.e., occupied bottom waters during the day and likely moved up into midwater depths at night) that once occurred in Lakes Michigan and Huron. Sadly, it has been assessed as ‘extinct’ by both Canada and the United States. Compared to other deepwater cisco species, it was intermediate in terms of size and occupied relatively deep bottom depths. Its diet was only rarely described in the Great Lakes, but from this limited information it appears to have been dominated by mysids with smaller numbers of small mussels and Diporeia spp. It had the lowest number of gill rakers compared to other ciscoes, further suggestion that eating smaller zooplankton would be rare.

Lake whitefish (Coregonus clupeaformis)

Lake Michigan, illustrated by Cory Brant

Lake Whitefish is the most broadly distributed of the three whitefish species in the Great Lakes and is still present in all five Great Lakes. It can grow to relatively large sizes (i.e., >20 inches), compared to the other coregonines in the Great Lakes. Its populations are relatively large in Lakes Superior, Michigan, and Huron and support large commercial fisheries and even regional recreational fisheries (e.g., Green Bay). In fact, it is one of the most popular fishes to eat in the Great Lakes region. In Lakes Michigan and Huron, however, recruitment has been declining over the past 10-15 years and has led to large declines in commercial catches. Lake Whitefish abundance in Lakes Erie and Ontario is only a fraction of historical levels. Lake Whitefish tend to occupy the bottom of the lakes, but generally shallower depths than the deepwater ciscoes. They also have fewer gill rakers than most of the deepwater cisco species. Their diets are dominated by benthic invertebrates (including invasive dreissenid mussels) and small fishes. Relative to round whitefish, their bodies are more laterally compressed.

Round whitefish (Prosopium cylindraceum)

Round Whitefish can be distinguished from the more commonly known Lake Whitefish primarily by its more cylindrical body shape, smaller maximum size (12-18 inches), and even shorter and fewer gill rakers. It occurs in all of the Great Lakes, except Lake Erie, although its population is currently extremely low in Lake Ontario and it is considered endangered in New York waters. Round Whitefish tend to occupy the bottom of the lakes, but at shallower depths than the deepwater ciscoes. Their diets are dominated by benthic invertebrates and insect larvae. They are also known as “Menominee” and “Pilot” in some areas.

Pygmy whitefish (Prosopium coulterii)

Bluefish Lake, illustrated by Paul Vecsei

Pygmy Whitefish is the smallest of the whitefishes (and all of the coregonines) in the Great Lakes and only occurs in Lake Superior. It is generally smaller than 6 inches and has around 12 spots along its midline and sometimes additional larger, rounder marks along its lateral line. It was not discovered until the 1950s, and it remains unclear why it doesn’t occur in at least Lakes Michigan and Huron. In Lake Superior, it lives on the bottom in water depths of 100-300 feet. Primary diet items include Diporeia, ostracods, zooplankton, and fish eggs.