Round pigtoe (Pleurobema sintoxia) COSEWIC status report: chapter 14
Pleurobema sintoxia
Round Pigtoe
Pleurobème écarlate
Range of occurrence: Southwestern Ontario
Extent and Area Information
| Extent of occurrence (EO) (km2) By drawing polygons in Arcview, historical EO was 26 592 km2, the current EO is 12 360 km2 |
Lake St. Clair, Sydenham River, Middle Thames River, Lower Grand River ~12 400 km2 |
| Specify trend in EO | Decline (~54%) |
| Are there extreme fluctuations in EO? | No |
| Area of occupancy (AO) (km2) | 8 km2 in Lake St. Clair delta, 0.5 km reach of Bear Creek/North Sydenham River (~0.01 km2), 75 km of East Sydenham River (~2 km2), 0.5 km reach of Middle Thames River (~0.02 km2), 45 km reach of lower Grand River (~5 km2). Total = ~15 km2. |
| Specify trend in AO | Decline |
| Are there extreme fluctuations in AO? | No |
| Number of known of inferred locations | 5 |
| Specify trend in # | Decline |
| Are there extreme fluctuations in number of locations? | No |
| Specify trend in area, extent or quality of habitat | Decline |
Population Information
| Generation time (average age of parents in the population) | Unknown (estimate 10 years) |
| Number of mature individuals | Unknown |
| Total population trend | Declining |
| % decline over the last/next 10 years or 3 generations | Unknown |
| Are there extreme fluctuations in number of mature individuals? | No |
| Is the total population severely fragmented? | Yes, no mixing between populations in different watersheds |
| Specify trend in number of populations | Decline |
| Are there extreme fluctuations in number of populations? | No |
| List each population and the number of mature individuals in each: | Total population ~200 000 but # of mature individuals unknown |
Threats (actual or imminent threats to populations or habitats)
- Zebra Mussels (invasive species).
- Habitat loss and degradation due to agricultural impacts (siltation, nutrient loading, loss of riparian vegetation), urbanization, and municipal and industrial pollution.
- Habitat loss and degradation due to agricultural impacts (siltation, nutrient loading, loss of riparian vegetation), urbanization, and municipal and industrial pollution.
Rescue Effect (immigration from an outside source): None
| Status of the outside population(s)? | Largely stable |
| Is immigration known or possible? | No |
| Would immigrants be adapted to survive in Canada? | Likely (genetic testing required) |
| Is there sufficient habitat for immigrants here? | No |
| Is rescue from outside populations likely? | No |
Quantitative Analysis
Status and Reasons for Designation
| Status: Endangered |
Alpha-numeric code: A2ace; B2ab(i,ii,iii,iv) |
| Reason for designation: Species limited to a small area of occupancy in the Lake St.Clair and three watersheds in southern Ontario with continuing declines in habitat area, extent and quality. Threats include urban, industrial and agricultural development and irreversible impacts from zebra mussels in Lake St. Clair, with potential threats from introduction of zebra mussels in impoundments in the Sydenham River. |
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Applicability of Criteria
Criterion A (Declining Total Population):
population size reduction estimated from 54% decline in extent of occurrence (and probably area of occupancy), continuing declines in quality and extent of habitat, and effects of introduced taxa (Endangered, A2a,c,e).
population size reduction estimated from 54% decline in extent of occurrence (and probably area of occupancy), continuing declines in quality and extent of habitat, and effects of introduced taxa (Endangered, A2a,c,e).
Criterion B (Small Distribution, and Decline or Fluctuation):
qualifies for threatened under B1 (Extent of Occurrence < 20 000 km2) but Endangered for the following criteria: species has a small area of occupancy (<15 km2), population is severely fragmented and there are continuing declines in: Extent of Occurrence; Area of Occupancy; area, extent and quality of habitat; number of locations (Endangered B2a,b(i-iv)).
qualifies for threatened under B1 (Extent of Occurrence < 20 000 km2) but Endangered for the following criteria: species has a small area of occupancy (<15 km2), population is severely fragmented and there are continuing declines in: Extent of Occurrence; Area of Occupancy; area, extent and quality of habitat; number of locations (Endangered B2a,b(i-iv)).
Criterion C (Small Total Population Size and Decline):
number of mature individuals unknown.
number of mature individuals unknown.
Criterion D (Very Small Population or Restricted Distribution):
qualifies for Threatened under D2, small area of occupancy.
qualifies for Threatened under D2, small area of occupancy.
Criterion E (Quantitative Analysis):
unable to estimate probability of extinction.
unable to estimate probability of extinction.
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