La biologie du suceur cuivré (Moxostoma hubbsi) comparée à celle de quatre autres espèces de Moxostoma (M. anisurum, M. carinatum, M. macrolepidotum et M. valenciennesi)

Abstract

The copper redhorse, Moxostoma hubbsi (Legendre), which was discovered in 1942, is a threatened and endemic fish species of the lowlands around Montréal (Quebec). A survey of historical data, an investigation of the preserved specimens, and a comparison of selected biological characteristics of the five Quebec Moxostoma species living in sympatry in the Richelieu River show that this redhorse has a unique combination of life history characteristics. Compared with the other redhorses, it is among the most long-lived (more than 20 years), has the highest growth rate and fecundity, and is the latest spawner, its reproduction probably taking place at the end of June or at the beginning of July. The copper redhorse shows a high degree of specialization in the use of alimentary resources and feeds almost exclusively upon molluscs. The comparison of the stomach contents of the different species living in sympatry shows little diet overlap. This may be due to the specialization of their pharyngeal apparatus and to a certain degree of spatial segregation. Similar to its congeners, the copper redhorse shows a predilection for lowland rivers of medium size characterized by abrupt banks and uniformly deep channels (4–7 m) flowing over a solid clay, sand, or gravel bottom. The most populated sections of river have rather slow currents; they are interspersed by sections of rapids suitable for spawning. In the St. Lawrence system, the range of the copper redhorse is much more restricted than that of other redhorses, and this species appears much more vulnerable to habitat degradation.