Plants and Animals
Stagnicola contracta Deepwater pondsnail
Key Characteristics
The deepwater pondsnail is a large freshwater snail with a narrowly conic shell that is 2.5 cm in height and 1.1 cm wide with a long, pointed spire and dextral whorls (i.e., curving clockwise when the spire is pointed upwards). The aperture (main opening) is narrow and elongated.
Status and Rank
US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G1 - Critically imperiled
State Rank: SH - Possibly extirpated
Occurrences
| County | Number of Occurrences | Year Last Observed |
|---|---|---|
| Charlevoix | 2 | 1940 |
| Crawford | 1 | 1957 |
| Leelanau | 1 | 1949 |
| Roscommon | 2 | 1957 |
Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.
Habitat
This species is found in medium sized to large lakes in northern Michigan at depths of approximately 33 ft (10 m).
Natural Community Types
- Inland lake, littoral, benthic
- Inland lake, littoral, midwater
- Submergent marsh
For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.
Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.
Management Recommendations
Almost nothing is known about this species, but it is probable that it is sensitive to water pollution as well as pesticides and herbicides, especially those used to control invasive weeds such as eurasian water milfoil in large lakes. Alternatively, controlling invasive aquatic weeds may be beneficial by allowing native vegetation that might be associated with the snail to flourish. Snail-killing chemical molluscicides (copper sulfate or copper carbonate) that are used to treat lakes with swimmer's itch should be strictly avoided in lakes and streams occupied by rare snails. The introduction of fish species for recreational or commercial fishing is also strongly discouraged since many fish prey on aquatic snails and could greatly reduce populations or cause local, state, or global extirpation.
Active Period
Active from third week of May to second week of September
Survey Methods
This species can be surveyed using several techniques. One survey method consists of sweeping aquatic vegetation or scraping the substrate with a fine mesh aquatic sampling net or dip net (e.g., D-frame net). Another survey technique consists of vigorously shaking aquatic vegetation over a pail of water causing the various snails clinging to the plants to drop to the bottom of the pail. Visual surveys also can be conducted for this species by looking for snails attached to vegetation, rocks, woody debris and other cover. Glass bottomed buckets may be used to see snails clinging to vegetation or rocks underwater. Rocks, vegetation, and other cover also should be picked up, examined for snails, and returned to their original positions.
Shaking vegetation survey
Survey Period: From third week of May to second week of September
Time of Day: Daytime
Water Level: Low Water Levels
Water Turbidity: Low Turbidity
Sweep with dip net
Survey Period: From third week of May to second week of September
Time of Day: Daytime
Water Level: Low Water Levels
Water Turbidity: Low Turbidity
Visual surveys
Survey Period: From third week of May to second week of September
Time of Day: Daytime
Water Level: Low Water Levels
Water Turbidity: Low Turbidity
References
Survey References
- Berry, E.G. 1943. The Amnicolidae of Michigan: Distribution, Ecology, and Taxonomy. University of Michigan Press, Ann Arbor. 68pp.
- Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Science, National Museums of Canada, Ottawa. 446pp.
Technical References
- Burch, J.B. 1988. North American Freshwater Snails. Walkerana 2(6)
- Dillon, R.T. Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, UK. 509pp.
- Environmental Protection Agency. 1982. Freshwater Snails (Mollusca: Gastropoda) of North America. EPA Publication 600/3-82-026. Environmental Monitoring and Support Laboratory, Office of Research and Development, U.S. EPA, Cincinnati. 294pp.
- Evers, D.C. 1994. Endangered and Threatened Wildlife of Michigan. The University of Michigan Press, Ann Arbor. 412pp.
- Goodrich, C. 1932. The Mollusca of Michigan. The University of Michigan Press, Ann Arbor. 121pp.