Lake Winnipeg Physa
Scientific Name: Physa sp.
Other/Previous Names: Lake Winnipeg Physa Snail
Taxonomy Group: Molluscs
Last COSEWIC Assessment: November 2012
Last COSEWIC Designation: Data Deficient
SARA Status: No schedule, No Status
Image of Lake Winnipeg Physa
Scientists believe that the Lake Winnipeg Physa Snail is a new species - one that is at risk of disappearing before it has even been given a full scientific name. It belongs to the family Physidae, and is clearly distinct from the three other snails in the same family that also occur in Lake Winnipeg.
The shell of the Lake Winnipeg Physa Snail is usually less than 11 mm long, globe-shaped, and fragile. The spire (whorls of a spiral shell, excluding the last) is flattened, making the snail appear relatively wide, and the surface of the shell is dull and often pitted. Fresh shells are bluish-grey, and the skin of living snails is light grey and sparsely peppered with black spots.
Distribution and Population
The Lake Winnipeg Physa Snail has not been formally described yet, so it is not surprising that there is no information published on its distribution. However, it appears to be found only in Lake Winnipeg. Extensive surveys of almost 1000 sites in Manitoba, Ontario, Saskatchewan, North Dakota, and Minnesota, including the adjacent lakes and tributaries of Lake Winnipeg, did not detect the snail anywhere except in Lake Winnipeg. The distribution of the Lake Winnipeg Physa Snail in Lake Winnipeg is quite patchy. It was found at only 5 of 90 stations surveyed in 2001. The disappearance of the snail from two previously known sites suggests a population decline.
The Lake Winnipeg Physa Snail can be found on algae-coated rocks that are submerged just below the surface in open, wave-swept areas close to the shore of the lake. The lake bottom is usually a mixture of sand, gravel, and rocks, or occasionally limestone shingle. The Lake Winnipeg Physa Snail tends to occur only in sites with a higher number of other snail species. The average site where the Lake Winnipeg Physa Snail was found had 6.2 species of snails, while the overall average for sites with snails was 3.9 species. The Lake Winnipeg Physa Snail also is always found with at least one other species of Physa snail. The snail appears to be sensitive to metal contamination - the water at the sites where it was found had significantly lower levels of cadmium, copper, and lead than the sites where it was absent.
The Lake Winnipeg Physa Snail feeds on algae. Other species of Physa snail that occur in Lake Winnipeg spend the winter as adults and then reproduce in June and July of the following year. The shells of these snails are fragile and individuals typically do not survive for more than one year in Lake Winnipeg.
The main threats to the Lake Winnipeg Physa Snail are degradation of the shoreline habitat due to cottage development and recreational use, and pollution of the water from agricultural, municipal, logging, and pulp mill activities near the rivers that drain into Lake Winnipeg. Increased shoreline erosion resulting from water level regulation is an additional concern.
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
11 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- COSEWIC Assessments (1 record(s) found.)
- Response Statements (1 record(s) found.)
- Orders (4 record(s) found.)
- COSEWIC Annual Reports (2 record(s) found.)
- Consultation Documents (2 record(s) found.)
COSEWIC Status Reports
COSEWIC Annual Reports
COSEWIC Annual Report - 2003 (2003)May 2003 Annual Report to the Canadian Endangered Species Conservation Council by the Committee on the Status of Endangered Wildlife in Canada.
Consultation Workbook on the Addition of Four Aquatic Species to the List of Wildlife Species at Risk- Lake Winnipeg Physa snail, Channel darter, Shortjaw cisco, Atlantic Cod (Arctic population) (2004)Your opinion is being sought to assist the government of Canada in making an informed decision on whether to add the Lake Winnipeg Physa Snail, Channel Darter, Shortjaw Cisco, and Atlantic Cod (Arctic population) to the Schedule 1 (the List of Wildlife Species at Risk) of the Species at Risk Act (SARA). Your input on the impacts of adding these species to the List is important. This workbook has been developed to give you an opportunity to provide Fisheries and Oceans Canada with your feedback, advice, and other comments regarding adding these species to Schedule 1 of SARA (Schedule 1 identifies which species are legally protected under SARA).
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