Growth rates: depending on size can grow 0.1mm/day at 21o C under laboratory conditions (Richards et al. in prep.)
Size at sexual maturity: in western USA reaches sexual maturity at 3.0 mm. Larger NZMS produce more offspring (Richards et al. submitted).
Number of young and Brooding time: ranges from 20-120 embryos per female (Richards unpublished data, Winterbourn 1970). Young born every three months in NZ (Winterbourn 1970), can bear young at any time of year in spring habitats western USA (Richards unpublished data) but most often summer and autumn (Richards, Kerans, Gustafson, Shinn, pers. comm.).
Habitat preference: wide range of tolerances: rivers, reservoirs, lakes, and estuaries. Densities usually highest in systems with high primary productivity, constant temperatures, and constant flow.
Rivers: found
in all habitat substrates in Snake River; silt, sand, gravel, cobbles,
and vegetation (Richards et al. 2001).
Reservoirs:
occurs in all reservoirs in mid-Snake River (Shinn unpublished data)
Lakes: Population expanding in Lake Ontario, populations reached 800,000/m2 in Lake Zurich (Dorgelo1987), present in most lakes in New ZealandMovement: very fast snail. estimated substrate cruising speed is > 1 meter/hour (Richards personal observation). In five years went from an undetectable level to abundant in most sections of Snake River in Hells Canyon (Shinn personal communication). Conjectured to be transported by waterfowl in Danish estuaries (Lassen 1978). Most likely transported to new systems in western USA by passive dispersal via recreationalists and contaminated equipment.
Estuaries: found in Columbia River estuary, and most estuaries in Europe. Tolerates up to 17-24% salinity (Bondesen and Kaiser 1949).
Food preferences: Classified as a scraper/grazer. Prefers diatoms, plant and animal detritus, attached periphyton.
Predators and parasites: no known predators or parasites in western
USA. Snails found in mountain whitefish (Prosopium williamsoni)
(W.P.Dwyer, pers. comm.) and rainbow trout stomachs (Oncorhynchus mykiss)
(Cada, pers. comm.) in Montana but unknown if any nutritional value.
As many as 14 tremotode parasites in NZ and several native fish species
frequently eat them (Ryan 1982, Sagar and Glova 1995, Cadwallader 1975,
Lively 1996).