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

Biology

General

There is limited information on the biology of the blackfin cisco in Canadian waters. Standard lengths for adults reported from the Great Lakes have ranged from 230‑370 mm (Clarke and Todd 1980). McAllister et al. (1985) reported a maximum length of 510 mm. Dymond (1926) gave a length of 388 mm for a specimen taken from Lake Nipigon. A small sample of blackfin cisco (n=4) taken from the Ogoki River in October 2004 had standard lengths of 431 and 465 mm for two males, and 485 and 499 mm for two females. Weights of these specimens were 660 and 1090 g for the males, and 1060 and 1110 g for the females (D. Stanley, pers. comm. 2005).


Reproduction

Little is known of the reproductive habits of blackfin cisco. Age of maturity, breeding frequency, fecundity, early life history, age/sex ratio and population structure are all unknown or poorly defined. Information originally reported by Koelz (1929) for the Great Lakes suggests that blackfin cisco spawned from October to January. Scott and Crossman (1973) suggest that spawning took place between November and January within the Great Lakes, possibly over a clay bottom.

Blackfin cisco in northwestern Ontario have been reported as co-occurring with C. artedi during a fall spawning run on the Little Jackfish River and on Crescent Lake (UMA 1987). The apparent similarity of spawning location and timing, at these locations, suggests a probable reason for encountering many intergrades between the two species.


Survival

No information related to survival, growth rates or population structure is available for this species. The growth potential of any remnant Great Lakes population (if existing), the Lake Nipigon population, and any other inland lake or river populations is unknown.

Scott and Crossman (1973) indicate that data on age of maturity, etc., for C. artedi could be used to give some idea of age of maturity, etc. for C. nigripinnis. This would suggest that males reach sexual maturity at age 4 or 5 and females at age 5, with a maximum age of 11 years. On this basis the generation time for the species would be 7.5 years.


Physiology

No information on the specific physiology of blackfin cisco was found during the preparation of this update status report.


Movements/Dispersal

Limited species-specific information has been reported for blackfin cisco regarding its movement/dispersal for the purposes of spawning or due to seasonal migration. Spawning areas have not been documented in the literature; however, ripe specimens collected from the lower Little Jackfish River in October (UMA 1987) suggest there may be movement of blackfin cisco from Lake Nipigon into this river to spawn.

Dymond (1926) suggested that the difference in depth distribution of blackfin cisco in Lake Nipigon may be the result of seasonal movement from deep to shallower waters during the summer months. No information is available regarding breeding or wintering ranges.


Nutrition and Interspecific Interactions

Koelz (1929) reported that blackfin cisco fed almost exclusively on opossum shrimp (Mysis relicta). Food in the stomachs of a limited number of individuals caught off the Michigan shore of Lake Huron and in Georgian Bay (1917 and 1919, respectively) contained primarily opossum shrimp with small amounts of plant fragments, insect remains and fish scales. All fish sampled were captured at depths of more than 110 m. Beyond this observation, little is known of the feeding habits of this species.

As a prey species, blackfin cisco, along with other cisco species, were believed to form the basic food of lake trout (Salvelinus namaycush) within the Great Lakes and Lake Nipigon until at least the 1950s (Scott and Crossman 1973). The blackfin cisco in the Great Lakes was also reported to have been preyed on by sea lamprey (Petromyzon marinus) (Moffett 1957).


Behaviour/Adaptability

No specific information was found during the preparation of this update status report regarding the behaviour of blackfin cisco, particularly as related to the ability of the species to cope with human disturbance. Such information is difficult to assess because human interference, where documented, has been of a dramatic nature. The intense exploitation of deepwater ciscoes, including blackfin cisco, by the commercial fisheries from the early 1900s to the 1950s contributed to the dramatic decline of populations in the Great Lakes (Smith 1964; Berst and Spangler 1972; Christie 1972; Lawrie and Rahrer 1972).

Similarly, information on the ability of blackfin cisco to adapt to environmental change or degradation (e.g., water temperature changes, water level fluctuation, and industrial discharges to water) is lacking.