Mapleleaf mussel (Quadrula quadrula) COSEWIC assessment and status report: chapter 13
Technical Summary: Great Lakes-Western St. Lawrence
Quadrula quadrula
Mapleleaf Mussel - Great Lakes-Western St. Lawrence population – Mulette feuille d’érable
Range of Occurrence in Canada:
Ontario
Extent and Area Information: Great Lakes-Western St. Lawrence
Extent of occurrence (EO) (km²)
13,000 km² (calculated using ARCview on GIS maps)
Specify trend in EO
Decline, about 50%, due mostly to losses of Lake Erie, Lake St. Clair and Detroit River populations
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
see text for details
- 0.29 km² in Ausable River
- 0.16 km² in North Sydenham River
- 1.2 km² in East Sydenham River
- 8.8 km² in Thames River
- 24.75 km² in Grand River
- Total = ~ 35.2 km²
Specify trend in AO
Decline due mostly to losses of Lake Erie, Lake St. Clair and Detroit River populations; Ausable River unknown; stable to perhaps increasing in rest
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations
5 rivers
Specify trend in #
Decline due mostly to losses of Lake Erie, Lake St. Clair and Detroit River populations; Ausable River unknown; stable to perhaps increasing in rest
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:
Decline due mostly to losses of Lake Erie, Lake St. Clair and Detroit River populations; Ausable River unknown; stable to perhaps increasing in rest
% 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, populations from different rivers don’t mix
Specify trend in number of populations
Decline
Are there extreme fluctuations in number of populations?
No
List populations with number of mature individuals in each:
Unknown, total population estimated to be 5.5 million individuals
Threats (actual or imminent threats to populations or habitats)
- Zebra mussels (invasive species)
- Habitat loss and degradation resulting from municipal and industrial pollution, urbanization and agricultural activity (resulting nutrient loading, loss of riparian vegetation and siltation).
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA: Status apparently secure within most of US distribution. In same watersheds as Canadian populations (Lake Erie) it is either not ranked or is S2 or is in the same state of decline as Canadian populations.
Is immigration known or possible?
Not possible
Would immigrants be adapted to survive in Canada?
Likely but needs to be confirmed by testing
Is there sufficient habitat for immigrants in Canada?
No, currently occupied by existing populations
Is rescue from outside populations likely?
No
Quantitative Analysis
Not available
Current Status
COSEWIC: Threatened (2006)
Status and Reasons for Designation
Status: Threatened
Alpha-numeric code: Met criteria for Endangered, B2ab(i,ii,iii,iv), but designated Threatened because populations are stable or perhaps increasing in most existing locations. Criteria met for Threatened: B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv).
Reasons for Designation: This heavy-shelled mussel that is shaped like a maple leaf has a very small area of occupancy in watersheds dominated by agriculture, with past and continuing declines due to habitat loss and degradation. Although the mussel has been lost from the Great Lakes and connecting channels due to zebra mussels, the numbers of mature individuals appear to be very large in two of the watersheds and three of five watersheds have recovery teams in place for aquatic species at risk. Zebra mussels continue to be a potential threat in watersheds that have numerous impoundments.
Applicability of Criteria
- Criterion A (Declining Total Population): Not Applicable.
- Criterion B (Small Distribution, and Decline or Fluctuation): B2ab(i,ii,iii,iv); B1ab(i,ii,iii,iv) applies to threatened only.
- Criterion C (Small Total Population Size and Decline): Not Applicable.
- Criterion D (Very Small Population or Restricted Distribution): AO threshold exceeded for Threatened.
- Criterion E (Quantitative Analysis): Not available.
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