. The Canadian field-naturalist. 5CM Figure 1. Bloater, Coregonus hoyi (from Todd 1980, by permission). (1980) had considered the species probably extirpated in Lake Ontario, but the 1982 record indicates the population may still be present. Coregonus hoyi populations increased dramati- cally in Lake Michigan during the 1940s and 1950s following a decline in predators and larger deepwater cisco competitors (Moffet 1957; Smith 1964). Subsequent overexploitation and recruit- ment failure resulting from a highly unbalanced sex ratio (female-biased), led to a dramatic decline in abundance by 1976,
. The Canadian field-naturalist. 5CM Figure 1. Bloater, Coregonus hoyi (from Todd 1980, by permission). (1980) had considered the species probably extirpated in Lake Ontario, but the 1982 record indicates the population may still be present. Coregonus hoyi populations increased dramati- cally in Lake Michigan during the 1940s and 1950s following a decline in predators and larger deepwater cisco competitors (Moffet 1957; Smith 1964). Subsequent overexploitation and recruit- ment failure resulting from a highly unbalanced sex ratio (female-biased), led to a dramatic decline in abundance by 1976, when the fishery for deepwater cisco was closed (Brown 1970; Wells and McLain 1973; Holey 1983). Populations have since rebounded and limited quota fisheries have been reopened in Wisconsin (Holey 1983), Michigan (A. Wright, personal communication), and Illinois (R. Hess, Illinois Department of Conservation, Zion, Illinois, personal communica- tion) waters of Lake Michigan. Coregonus hoyi now constitutes from 90 to 99% of the commercial catches of deepwater ciscoes in these FlCURl 2. Distribution of the Bloater, Coregonus hoyi: (1) Probably extirpated (Clarke and I odd 14X0); (2) Rare (Clarke and Todd 1980). In hatehed area it is common to abundant (Todd 1978, 1980). In Lake Superior, Bloater stocks increased during the 1950s and 1960s from historic levels of abundance in response to decreased predation by Lake Trout (Salvelinus namaycush) and reduced competition from larger deepwater ciscos (Lawrie and Rahrer 1972; Peck 1975; Pratt 1980). Populations in waters appear to have been decreasing since 1970 (Peck 1975, 1977; Pratt 1980). R. Cullis (OMNR, Thunder Bay, Ontario, personal communication) indicates that chubs are common in some areas of Lake Superior and are commercially harvested. No size or trend information is available for the Bloater population in Lake Nipigon. This species was reported as common in the lake by Koelz (1929), but was not taken by
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