. The Canadian field-naturalist. 1988 Houston: Status of Shortjaw Cisco 99. Figure 2. Canadian distribution of the Shortjaw Cisco. Former distribution: stippled. Present distribution: soUd. trawl catches and Coregonus nigripinnis and Coregonus johannae appeared to be extinct in Lake Michigan (Smith 1964). The bloater now dominates all areas of lakes Michigan, Superior and Huron, where the larger ciscoes once had healthy stocks (Todd 1985). Koelz (1929) reported that Coregonus zenithicus was the most common species in Lake Superior (up to 90%) in the 1920s. It now represents less than 5% of cat
. The Canadian field-naturalist. 1988 Houston: Status of Shortjaw Cisco 99. Figure 2. Canadian distribution of the Shortjaw Cisco. Former distribution: stippled. Present distribution: soUd. trawl catches and Coregonus nigripinnis and Coregonus johannae appeared to be extinct in Lake Michigan (Smith 1964). The bloater now dominates all areas of lakes Michigan, Superior and Huron, where the larger ciscoes once had healthy stocks (Todd 1985). Koelz (1929) reported that Coregonus zenithicus was the most common species in Lake Superior (up to 90%) in the 1920s. It now represents less than 5% of catches (Peck 1977). Shortjaw Cisco, it would appear, were abundant throughout their range until the early 1930s. At this time these fish were probably at their highest numbers with little competition and predation from larger fish. The intensive and selective fishery required to maintain catch levels subsequently seriously decreased their numbers by the mid 1950s. Coregonus zenithicus bowed to the pressure of the fishery, competition, and predation from exotic species. It is also possible that introgressive hybridization completed their demise in lakes Michigan and Huron. At present the Shortjaw Cisco should be considered to be threatened with extinction, at least in Lake Superior (T. Todd, personal communication) and common in Lake Nipigon, especially in Mclntyre Bay where they occur sympatically with Coregonus clupeaformis, the Lake Whitefish, and Catostomus Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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