COSEWIC Assessment and Update Status Report on the Bering Cisco in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status
- Technical Summary
- Acknowledgements and Information Sources
- Biographical Summary of Report Writer and Authorities Contacted and Personal Communications
COSEWIC Status Report
Coregonus laurettae Bean 1882
Bering cisco. Lauretta, herring, lake herring, tulibee, sharp nose
Bickham et al. (1997) assessed the degree of differentiation between the Bering cisco and Arctic cisco (C. autumnalis) using mitochondrial DNA haplotypes of samples from the Colville River delta and concluded the forms are valid species. Reist et al. (1998) examined sequence variation in a portion of the d-loop of mitochondrial DNA in several coregonine fishes including Arctic cisco, Bering cisco and lake cisco (Coregonus artedi) to confirm the separate, but closely related status of these species.
The Bering cisco (Figure 1) is a coregonid, distinguished from other cisco species by the pale, almost colourless pelvic and pectoral fins and a lower number of gill rakers (18-25) on the lower portion of the first gill arch (Morrow 1980). Anadromous forms occurring in Arctic drainages and the lower mainstem of the Yukon River have a spotted back and dorsal fin (Mecklenburg et al. 2002). The body is more elongate and less laterally compressed than other species of cisco, with the greatest body depth in front of the dorsal fin. The dorsal fin is considered rather high and falcate, with 11 to 13 rays (Morrow 1980). Pelvic fins are characterized with a distinct axillary process similar to other ciscos. Coloration of adult fish can vary from brownish to green on back, with silvery sides and belly (Scott and Crossman 1973). Caudal and dorsal fins are dusky (Morrow 1980). Very little information is available to identify early life history stages. The average size of migrating Bering cisco sampled in the Yukon River near Fort Yukon in 1998, 1999, and 2001 was 37 cm in fork length and approximately 600 gm in weight (Brown, R., U.S. Fish and Wildlife Service, Fairbanks, Alaska; personal communication 2003).
In the Yukon Territory, Bering cisco are easily confused with other coregonines. Catch data from a rotary screw trap in the Yukon River near Dawson City, Yukon Territory, produced a significant cisco juvenile catch. However, until recently, technicians were unable to differentiate to species (J. Duncan, Yukon Salmon Committee, Dawson City, Yukon, personal communication 2003). In coastal regions they overlap in distribution with Arctic cisco, the species they most closely resemble (Edge 1991). Species differentiation may be difficult for the novice due to similar morphological characteristics based on a probable common ancestry. They can, however, be differentiated on the basis of gill-raker counts; 18-25 for C. laurettae and 25-31 for autumnalis (McPhail 1966; Alt 1973). In the Yukon River, confusion with riverine populations of least cisco (C. sardinella) is probable (Milligan, P., Department of Fisheries and Oceans, Whitehorse, Yukon, personal communication 2003).
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