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COSEWIC Assessment and Update Status Report on the Blackfin Cisco in Canada

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COSEWIC
Executive Summary

Blackfin Cisco
Coregonus Nigripinnis

Species Information

The blackfin cisco is a freshwater fish characterized by its darkly pigmented fins and deep body. It is one of the largest of the 10 cisco species found in Canada, averaging 330 mm in length and 0.7 kg in weight although, it may reach lengths of up to 510 mm and weigh up to 1 kg or more.

 

Distribution

Historically, the blackfin cisco was reported as an endemic species to each of the Great Lakes, except Lake Erie and Lake Nipigon. However, the occurrence of blackfin cisco in lakes Superior and Ontario was never confirmed. Recent sampling suggests that the stocks from the Great Lakes are extirpated. Historical records of blackfin cisco for inland lakes in Ontario, Manitoba, Saskatchewan and Alberta are now considered to be invalid due to taxonomic uncertainty.

 

Habitat

The blackfin cisco was considered to have inhabited the deeper waters of the Great Lakes, occurring at depths of 90-183 m in lakes Huron and Michigan. In Lake Nipigon, the blackfin cisco has been captured at depths to 104 m. However, the species has been found at shallower depths in riverine situations, perhaps related to spawning.

 

Biology

Little is known of the biology of the blackfin cisco. Age of maturity, breeding frequency, fecundity, early life history, age/sex ratio and population structure are all unknown or poorly defined and no information related to survival, growth rates or population structure is available for this species. Limited species-specific information has been reported for blackfin cisco regarding its movement/dispersal for the purposes of spawning or seasonal migration. Information on food preferences indicate that blackfin cisco feed almost exclusively on opossum shrimp (Mysis relicta). The blackfin cisco was a likelyprey species of sea lamprey (Petromyzon marinus) and lake trout (Salvelinus namaycush) within the Great Lakes, and may still be an important prey item for lake trout and other larger, predacious species within Lake Nipigon and other inland water locations.

 

Population Sizes and Trends

Little or no information exists on population size or trends for this species. Currently, the species is felt to be extirpated within the Great Lakes. In Lake Nipigon, the species is considered to be extant and is reported as an incidental species in the lake whitefish (Coregonus clupeaformis) fishery at a rate of approximately 4500 kg/year. Other existing populations of blackfin cisco are reported in the Little Jackfish River, a tributary of Lake Nipigon.

 

Limiting Factors and Threats

Factors suspected to have caused the decline of blackfin cisco in the Great Lakes are over-exploitation by commercial fisheries, sea lamprey predation and competition from other invasive fish species such as alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax). Continued capture of blackfin cisco as an incidental catch species in commercial fish nets on Lake Nipigon may have a detrimental effect on species populations in that lake; however, present information is insufficient to quantify this effect.

 

Special Significance of the Species

Within the Great Lakes, blackfin cisco would have formed a part of the deepwater community where it was known to occur. Blackfin cisco would also have served as a traditional forage fish for lake trout populations in the Great Lakes. Its continued presence as part of the deepwater community of Lake Nipigon is of continued value to the ecological integrity of the lake. Similarly, its occurrence in other inland waters enhances the biodiversity of those waterbodies where it is found.

 

Existing Protection or Other Status

General protection is afforded to this species through the fish habitat sections of the federal Fisheries Act. Although listed under Schedule 2 of the federal Species at Risk Act as a species to be reassessed for consideration on Schedule 1, it receives no official protection as a species at risk.