Blackfin cisco COSEWIC assessment and status report: chapter 9
Population Sizes and Trends
Although the deepwater cisco fishery (commonly known as the “chub fishery”) was very important in the Great Lakes, the catches were rarely identified to species (Lawrie and Rahrer 1972). Too few collections of blackfin cisco (recorded to species) have been documented over time in a standardized manner to evaluate population sizes and trends.
The blackfin cisco was formerly abundant in Lake Michigan (Koelz 1929). Smith (1964) reported that commercial fishery exploitation during the late 1800s to early 1900s, combined with sea lamprey predation, resulted in a drastic reduction in abundance by the 1930s. Blackfin cisco constituted less than 1% of the 1930-31 catch of deepwater ciscoes taken during experimental fishing in Lake Michigan (Smith 1964). The blackfin cisco was absent from areas of former abundance in experimental index surveys made during 1954-55 and 1960-61 (Smith 1964). Moffett (1957) reported the species was near extinction by 1956. The last record from Lake Michigan was in 1969 (Clarke and Todd 1980). Index fishing and sampling of the commercial catch from Lake Michigan in Illinois, Indiana, Wisconsin and Michigan conducted in the mid-1980s have not produced any further specimens (Parker 1988).
Specific information regarding population size and trends of blackfin cisco in Lake Huron is limited. Berst and Spangler (1972) stated that the larger species of the deepwater cisco complex (which could include blackfin cisco) were selectively removed from Lake Huron by the 1940s as a result of commercial harvesting and sea lamprey predation. Records from the Canadian Museum of Nature indicate that the most recent record for blackfin cisco from Lake Huron is for two specimens collected in the Canadian waters off Southampton, Ontario in 1960 (S. Laframboise, Assistant Collection Manager, Fish Collection, Canadian Museum of Nature, Ottawa, ON, personal communication 2003). An examination of 1943 ciscoes, collected at 46 deepwater locations in Lake Huron in 2002 and 2003, failed to find any blackfin cisco (N.E. Mandrak, unpubl. data).
The results of a fish community index netting program conducted by the OMNR in Lake Nipigon since 1998-99 indicates that blackfin cisco are seen with relative frequency, representing 2-6% of the index catch each year. Catch rates (CUE values) of blackfin cisco have been relatively consistent over the 1998-2006 sampling period, although many of the other cisco species (particularly C. artedi) are declining (R. Salmon, OMNR, pers. comm. 2007). Blackfin cisco is reported as an incidental species (along with other ciscoes) caught by the lake whitefish (Coregonus clupeaformis) fishery in Lake Nipigon at a rate of 1 blackfin cisco to 57 lake whitefish in commercial nets, which would represent an incidental harvest of < 1000 kg from lake Nipigon in 2006 (R. Salmon, OMNR, pers. comm. 2007).
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