Shortjaw Cisco (Coregonus zenithicus)

Description
  • Shortjaw cisco are trout-like fish that are shiny and silver in color.
  • Shortjaw cisco are almost identical to the common cisco, or lake herring, species (see Similar species below), but can be distinguished by a smaller number of gillrakers - long, thin bony projections that filter out harmful particles as water enters a fish’s gills.
  • Studies of Alberta’s Barrow Lake shortjaw cisco population noted that shortjaw cisco generally had a larger size, shallower head, smaller eye, and longer dorsal fin than the local common cisco population.
Distribution
  • Most shortjaw cisco are found in the Great Lakes Basin.
  • Outside this basin, the distribution stretches across a band extending from the Great Lakes to Great Slave Lake in the Northwest Territories. However, the populations outside the Great Lakes Basin are thought to be small and widely scattered.
  • Exact distribution in the north is unknown because much of this area is remote and relatively few lakes have been sampled.
  • In Alberta, the known distribution of shortjaw cisco is small and limited to Barrow Lake in the Canadian Shield Region of northeastern Alberta.
  • Other possible Alberta locations for this species may be Lake Athabasca, Cold Lake, or Gregoire Lake. More research and sampling are needed before this can be conclusively determined.
Natural History

Habitat

  • Shortjaw cisco are generally found in the depths of deep, cold and large lakes. However, the species appears to be adaptable and can be found in shallower lakes (e.g., Barrow Lake in Alberta).

Food

  • Shortjaw cisco are filter feeders and their diet includes plankton and crustaceans, especially opossum shrimp
Reproduction and Growth

Breeding Behaviour

  • Shortjaw cisco are broadcast spawners, meaning they deposit their eggs over the bottom of a spawning site without building a nest or providing any parental care.
  • Eggs develop over the winter and hatching occurs in the spring.

Growth Process

  • The age at which the shortjaw cisco becomes reproductively mature varies among habitat sites.
  • In Barrow Lake in Alberta, data on when shortjaw cisco mature is not certain, but estimates suggest that female shortjaw cisco may begin spawning at age two, while males may spawn at age three.
Conservation and Management

Status

Shortjaw cisco are classified as At Risk in the current General Status of Alberta Wild Species report. See:

This species is also classified as Threatened under Alberta’s Wildlife Act. Protective regulations under the act have yet to be placed outside of current Alberta sportfishing regulations. See:

Issues

  • In Alberta, the population appears stable and is not under any immediate threat of extinction. However, the distribution of shortjaw cisco is naturally limited, isolated to one lake in the province, making the Alberta population especially vulnerable to any threats.
  • Current threats to the Alberta population include potential competition and interbreeding with the closely related and abundant lake herring.

Current management

  • Other ongoing research by the Royal Alberta Museum and Fisheries and Oceans Canada is focused on identifying whether other populations of shortjaw cisco exist in lakes other than Barrow Lake in Alberta.

Fishing

  • Alberta's sportfishing regulations have been modified to reflect the recommendations made in the recovery plan for this species. A zero bag limit is enforced on cisco and whitefish in Barrow’s Lake, and no domestic fishing licences are issued for the lake.
Similar Species

Common cisco (lake herring)

Shortjaw cisco and common cisco are very difficult to tell apart. The most widely accepted way to tell these species apart is by counting gillrakers. The shortjaw cisco generally has fewer gillrakers.

 

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Updated: May 11, 2010