The shortjaw cisco is a member of the same family as salmon and trout.  Like all salmonids, it has a small second back fin near its tail called an adipose fin.  Shortjaw ciscoes have green backs, silvery sides with purple specks, and white bellies.  They are a medium-sized fish with an average length of 28 cm. Illustration:  Canadian Wildlife Service / Reproduced with permission of the Minister of Public Works and Government Services Canada, 2000.

Distribution

Shortjaw ciscoes are found only in North America.  Historically, they were found in all of the Great Lakes except Lake Erie.  The last confirmed catch of a shortjaw cisco in either Lake Michigan or Lake Huron was in 1975 and 1982 respectively.  Shortjaw ciscoes are no longer considered to be present in either of these lakes. They are found in Lake Winnipeg in Manitoba; Reindeer and Barrow Lakes in Saskatchewan; Lake Athabasca in Alberta; and, Great Slave Lake in the NWT.

NOTE: Click on map for full view. Distributions are approximate and not intended for legal use. (JPG = 1995 KB)

Population Size and Trends

Shortjaw ciscoes were common in the Great Lakes until the 1930s.  Over-fishing and competition from imported species have caused their numbers to decline. They have vanished from Lakes Michigan and Huron, and are severely depleted in Lake Superior.  In the 1920s, shortjaw ciscoes made up 90 per cent of the commercial fish catch in Lake Superior.  Today, they make up less than five per cent of the catch.  Only in Lake Nipigon are they still considered common.  Very little is known about shortjaw cisco populations in other areas but they are not considered to be abundant in the NWT.

Shortjaw ciscoes are deepwater fish.  Some have been caught as deep as 183 metres .   They are usually found in waters between 55 m and 144 m deep, depending on the season.  They are found in water between 110-144 m in spring, 55-71m in summer and 73-91m in winter.

Shortjaw ciscoes usually reach sexual maturity at age five or six.  They were originally thought to spawn in the fall but recent observations of spring spawning in Lake Superior make this uncertain.  They spawn in half the depth of water they are normally found in.  They usually deposit their eggs on a clay bottom and abandon them.  Little is known about development of the young.  Males and females grow at the same rate but females live longer and can grow larger than males.  The number of eggs laid depends on the size of the female. A 30 cm female may lay more than 20,000 eggs.  Shortjaw ciscoes eat freshwater shrimp and insect larva.  They are prey for lake trout.

The two main limiting factors for shortjaw ciscoes in the Great Lakes are commercial over-fishing and competition from introduced species.  As larger ciscoes were over-fished in the Great Lakes, fishing pressure increased on the shortjaw cisco.  Once their numbers declined, they were unable to recover due to competition with imported species such as rainbow smelt (Osmerus mordax), alewife (Alosa pseudharengus) and the sea lamprey (Petromyzon marinus). Pollution of the Great Lakes may also have had a serious impact on the health of the shortjaw cisco population.

The shortjaw cisco receives no special protection in Canada.  In 1987, COSEWIC designated the shortjaw cisco as Threatened based on the reduced population and level of habitat exploitation. 

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       Site last updated Tuesday, February 19, 2008