Pip 1992

Pip E. 1992. The ecology of subarctic molluscs in the lower Nelson river system, Manitoba, Canada. Journal of Molluscan Studies 58: 121-126.

This author studied the gastropods found at 18 sites along the Nelson river and its tributaries. Total diversity was 13 species, with maximum species richness at a site 10 species and the mean close to four. The single most common species was an apparent hybrid between Gyraulus parvus and G. circumstriatus, based on shell morphology. An earlier work based on incidental collections also found high abundance of this putative hybrid (Clarke, 1973).

Gastropods were collected by scooping macrophytes into plastic bags. Several species showed significant correlations (positive or negative) with some species of macrophytes. Most species appear to overwinter as subadults, and show a semelparous life history, common among freshwater pulmonates (Hunter, 1975; Calow, 1978). Oviposition and gonad development are influenced by minimum temperature in some species (e.g. Van der Schalie and Berry, 1973), though it is not known if local adaptation of this trait has occurred (i.e. lower minimum temperatures in northern Manitoba than southern Canada). This author does not state how species of either gastropods or macrophytes were identified.

In general, the large hydroelectric dams on the Nelson river had a strong negative effect on the structure of ecosystems. Other studies by this author and coworkers examine the water chemistry and macrophyte assemblages of this river.