Cisco (Coregonus spp)

There are a number of similar species under the Coregonus genus, which is classified as a member of the Salmonidae family and generally acknowledged as a subfamily of whitefish. Whitefish and cisco inhabit many of the same waters and may be confused, although cisco are generally smaller.

One of the most common of these is Coregonus artedii, simply referred to as cisco. This species is often portrayed as the only cisco because the differences between species are only minor variations in body or snout shape, depth preference, or number of eggs. However, there are, or were, perhaps as many as 11 species of cisco, some of which were primarily very deep-dwelling fish.

In the Great Lakes, cisco have evidently suffered from competition with more aggressive plankton feeders (like alewives and smelt) and from predation by salmon and sea lampreys, all of which were nonnative species. The bloater (C. hoyi) has suffered the least of the Great Lakes species. Bloaters do not support any sportfishing effort, as they dwell far from shore and have mouths too small for ordinary lures. They are efficient feeders, however, and grow more on less food than do alewives.


Bloaters, as well as other Great Lakes cisco, are commonly called “chub.” The bloater, in fact, is also known as a bloater chub. These small, soft-fleshed, and oily fish are tasty table fare and are popular for commercial smoking, usually bearing the name “smoked chub.”

Cisco provide some sportfishing opportunity, especially for ice fishing, and are important forage fish for other species, particularly northern pike, walleye, perch, and rainbow trout. They are especially significant to lake trout.

Identification

Characterized by an adipose dorsal fin and a forked tail, the cisco has a terminal mouth (a lower jaw projecting slightly beyond the upper jaw). The body is elongate and slender, with less than 100 scales in the lateral line. The pelvic axillary process, or daggerlike progression, is well developed. Its coloring is dusky gray to bluish on the back, silvery on the sides, and white on the underside. All fins are relatively clear, although the anal and the pelvic fins may be milky on adults.

As a group, cisco (and whitefish) are quickly differentiated from other species by the presence of an adipose fin. Cisco can be differentiated from lake whitefish (Coregonus clupeaformis), which inhabit the same deeper waters, by their pointed snouts, terminal mouths, and lack of teeth; the cisco’s mouth is at the end of the head, whereas the whitefish’s mouth is behind and under the snout. Cisco are differentiated from lake trout (Salvelinus namaycush), by having larger scales, bigger mouths, and lack of teeth.

Size

Cisco can vary in length from 6 to 25 inches, the average size being between 10 and 14 inches and 0.5 pound; the all-tackle world record is a Manitoba fish (C. artedii) that weighed 7 pounds, 6 ounces. The average life span is 8 years. In some lakes, the cisco population may be stunted, and most fish are small.

Life history/Behavior

Cisco are schooling fish that spawn in large congregations in the late fall after moving into shallow water roughly 3 to 10 feet deep, often on reefs, and when the water temperature is about 39° to 41°F. Females can lay up to 30,000 eggs on the lake bottom, usually over gravel or stones.

The eggs are given no parental care and hatch within 4 months. Nearly all cisco reach maturity by their fourth season. Some, such as the least cisco (C. sardinella), are anadromous but do not stray far from river mouths during migration.

Food and feeding habits

Plankton is the main food source of cisco. During the early spring, which is their most active (and shallow) feeding season, they may also consume minnows, crustaceans, and mayflies.

Other Names

gray back, tullibee, lake herring, whitefish.

Distribution

Cisco are primarily inhabitants of Canada, where they range from roughly east of the Mackenzie River through Ontario and north throughout the Northwest Territories, as well as throughout much of Quebec.

They inhabit the Great Lakes and its tributaries (including the St. Lawrence River). They are found in some lakes of states bordering the Great Lakes, including the Finger Lakes in New York, and in upper Mississippi River drainages.

Habitat

Coldwater lakes are the favored dwelling places of cisco. They may be near the surface when the water is cold or at depths of several hundred feet, but they generally remain below the thermocline in lakes where this stratification occurs.

They tend to school in midwater and move into shallower areas when the water cools in the fall. Water temperatures ranging above 60°F are lethal to cisco, and as the surface waters warm, these fish move deeper. Many swim close to the surface during the winter, providing opportunities for ice fishing.

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