. The Canadian field-naturalist. 190 The Canadian Field-Naturalist Vol. 103. Figure 4. General location of collection records for Nocomis micropogon in Ontario. Congregations of many species of fish can occur over River Chub nests and other minnow species have been observed spawning upon these gravel mounds (Reighard 1943; Tsai and Zeisel 1969; Scott and Crossman 1973). These include the Common Shiner, Notropis cornutus, and the Longnose Dace, Rhinichthyscataractae, (Raney 1940; Cooper 1980). Longnose Dace x River Chub hybrids were collected by Raney (1940). The author hypothesized that the hy
. The Canadian field-naturalist. 190 The Canadian Field-Naturalist Vol. 103. Figure 4. General location of collection records for Nocomis micropogon in Ontario. Congregations of many species of fish can occur over River Chub nests and other minnow species have been observed spawning upon these gravel mounds (Reighard 1943; Tsai and Zeisel 1969; Scott and Crossman 1973). These include the Common Shiner, Notropis cornutus, and the Longnose Dace, Rhinichthyscataractae, (Raney 1940; Cooper 1980). Longnose Dace x River Chub hybrids were collected by Raney (1940). The author hypothesized that the hybrids resulted from accidental cross- fertilization above a River Chub nest. The use of River Chub nests by other species has been attributed to scarcities of suitable breeding areas (Tsai and Zeisel 1969; Cooper 1980). On the other hand it may be a kind of nest parasitism where the parasite takes advantage of superior spawning sites prepared by the host without having to expend energy in nest construction. Each of the associated species observed by Reighard (1943) [Rosyface Shiner, Notropis rubellus, Common Shiner, and Central Stone- roller, Camposloma anomalum] spawned in species-specific areas over River Chub nests. In this case, all 6 interspecific hybridizations were possible, though out of 12 possible reciprocal crosses, Reighard (1943) logically determined that only 8 were probable and the other 4 were unlikely. Although Cooper (1980) did not observe simultaneous spawning of Longnose Dace and River Chub, eggs of both species which he collected from the same nests were close in development. This may indicate that the spawning events of each of the two species had occurred at close to the same time, perhaps because the Longnose Dace do not spawn until nest building activity has stopped. Of course, this is also when the River Chub spawn. These fish grow at a uniform rate throughout their life and are sexually mature at about 3 years of age (Lachner 1952). Their lifespan can
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