COSEWIC Status Appraisal Summary on the Round Pigtoe Pleurobema sintoxia in Canada - 2014

Endangered
2014

Table of Contents

List of Figures

List of Tables


Document Information

COSEWIC
Committee on the Status
of Endangered Wildlife
in Canada

COSEWIC logo

COSEPAC
Comité sur la situation
des espèces en péril
au Cananda

COSEWIC status appraisal summaries are working documents used in assigning the status of wildlife species suspected of being at risk in Canada. This document may be cited as follows:

COSEWIC. 2014. COSEWIC status appraisal summary on the Round Pigtoe Pleurobema sintoxia in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xxii pp. (Species at Risk Public Registry website).

Production note:

COSEWIC acknowledges Daelyn Woolnough for writing the status appraisal summary on the Round Pigtoe, Pleurobema sintoxia in Canada, prepared under contract with Environment Canada. This status appraisal summary was overseen and edited by Gerry Mackie, Co-chair of the COSEWIC Molluscs Specialist Subcommittee.

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment Canada
Ottawa, ON
K1A 0H3

Tel.: 819-938-4125
Fax: 819-938-3984
E-mail: COSEWIC E-mail
Website: COSEWIC

Également disponible en français sous le titre Sommaire du statut de l’espèce du COSEPAC sur le Pleurobème écarlate (Pleurobema sintoxia) au Canada.


COSEWIC Assessment Summary

Assessment Summary - May 2014

Common name
Round Pigtoe
Scientific name
Pleurobema sintoxia
Status
Endangered
Reason for designation
This mussel species occupies a small area in the Lake St. Clair watershed and three other watersheds in southern Ontario, where its habitat has been declining in extent and quality. Urban development, agricultural runoff, and impacts from the Zebra Mussel and the Round Goby are threatening the survival of the species in Canada.
Occurrence
Ontario
Status history
Designated Endangered in May 2004. Status re-examined and confirmed in May 2014.

COSEWIC Status Appraisal Summary

Wildlife species:

Change in eligibility, taxonomy or designatable units:
No

Explanation:

The Canadian population of Pleurobema sintoxia remains as one designatable unit and there has been no change in the formal taxonomy. The authority for classification for aquatic molluscs in Canada is Turgeon et al. (1998). Although there has been significant information published on the unionid tribe Pleurobemini since 2004 (COSEWIC 2004), this tribe is poorly understood phylogenetically (Campbell et al. 2005, 2008). Campbell and Lydeard (2012) suggest that based on molecular data a new genus, Sintoxia, be erected that would encompass Pleurobema sintoxia and related species, including P. cordatum, P. riddellii and P. rubrum. The change to the genus Sintoxia has yet to be formally established.

Range

Change in extent of occurrence (EO):
Yes
Change in index of area of occupancy (IAO) :
Yes
Change in number of known or inferred current locations:
Yes
Significant new survey information
Yes

Explanation:

Extent of Occurrence (EO)

COSEWIC (2004) calculated EO at 12,360 km2. With the data used from COSEWIC (2004) a recalculation within Canada’s extent of jurisdiction EO was 10,224 km2; with Canada and US jurisdiction EO would be 10,309 km2 (Figure 1). The current calculated EO for 2003-2012 data is 3,018 km2 (Figure 2). The apparent 70.5% decline since last report is, in part, inferred from presumed extirpations at a number of sites that lack recent survey information, including the Niagara River (see Number of Locations), Pelee Island, and Holiday Beach Conservation area (Lake Erie), and Long Point. The Niagara River unionid communities have been impacted by the Zebra Mussels (Dreissena polymorpha), and 2011 surveys on the US side of the river (two sites) showed no evidence of live or weathered shells of P. sintoxia (Zanatta pers. comm. 2014). These two US sites were within 5 km of the two most southern historic Niagara River sites (both upstream of Niagara Falls (Zanatta pers. comm. 2014)). While the historical EO (pre-2002, which includes pre-1994 data) was 26,592 km2 (COSEWIC 2004) and the current EO is 3,018 km2 the percent decline over 3 generations (one generation >10 yrs) is unknown but likely >70.5% for the last 20 yrs. Part of the 20-year decline is due in part to increased search effort over time (not always recorded) but some subpopulations have also been lost, so 70.5% decline is based on best available information.

Severely Fragmented

The populations are not severely fragmented according to IUCN criteria.

 

Index of Area of Occupancy (IAO)

IAO was not calculated in the 2004 status report but AO was estimated at ~15 km2. This included 8 km2 in Lake St. Clair delta, a 0.5 km reach of Bear Creek/North Sydenham River (~0.01 km2), a 75 km reach of East Sydenham River (~2 km2), a 0.5 km reach of Middle Thames River (~0.02 km2), and a 45 km reach of lower Grand River (~5 km2). The newly calculated (2 km x 2 km grid) historical IAO (pre-2002) is 300 km2 (75 unique sites) (Figure 3), and the current IAO is 140 km2 for 2003-2012 (35 unique sites) (Figure 4), which represents a 53.3% decline. However, the Niagara River and Lake Erie sites were not included in the 2004 status report so percent historical decline is unknown.

Number of Locations

COSEWIC (2004) described five locations (Lake St. Clair Delta, Bear Creek [North Sydenham River], East Sydenham River, Middle Thames River, Lower Grand River).

The Niagara River, although not surveyed in the past 10 years (on the Canadian side), has significant Zebra Mussel populations and therefore habitat is considered not conducive for successful recruitment or survival of P. sintoxia (COSEWIC 2004) and is not considered a location.

The Lake St. Clair Delta and the Sydenham River sites occur in very different physical habitat (i.e., lotic versus lentic) and have different threats. Both of these populations appear to be reproducing and because the threats differ between the two, these sites are considered separate locations (#1 and #2 in Figure 2). Round Pigtoe in the North Sydenham River, site 5, showed no signs of reproduction (Figure 2). The Grand River sites (#4 in Figure 2) and the Thames River sites (#3 in Figure 2; are represented by only 3 animals) and likely have non-reproducing, senescent individuals but could be counted as another two locations. Round Pigtoe was found in McGregor Creek for the first time in 2010 and corresponds to site 6 in Figure 2, but the specimens showed no signs of reproduction. Based on the most severe threats, agricultural runoff and invasive species, the maximum number of locations for P. sintoxia could be considered to be six, but two appear to be not viable (#5 and #6), leaving four locations (Lake St. Clair Delta, Sydenham River, Thames River, and Grand River); of these, two may also be non-reproducing (Thames and Grand rivers) (Figure 2) so minimum number of locations is two. The Lake Erie sites are represented only by weathered shells in the past 10 years (Table 2); therefore this was not counted in the number of locations.

New Survey Information
Quadrat Surveys

Since the COSEWIC 2004 status report there have been significant surveys performed from 2003-2012 in which 11 quadrat (quantitative excavation; much more extensive than traditional timed surveys) surveys found live P. sintoxia in the Sydenham River (n = 8), Thames River (n = 2), and Grand River (n = 1) (Table 1). In a pre-2002 quadrat survey in the Sydenham River (see COSEWIC 2004), P. sintoxia was found at eight quadrat survey sites. Of those sites, the species was recorded again from seven of the eight in the more recent 2003-2012 surveys. One additional site (SR-07, 0.8km west of Shetland, ON) has since been surveyed and one live individual was found. The Bear Creek site (tributary to the North Sydenham River), which had P. sintoxia previously, was re-surveyed by quadrat survey in 2012 and one live P. sintoxia was found. Two quadrat surveys were performed in the Thames River watershed where P. sintoxia had not been reported in the 2004 status report and at both sites live P. sintoxia were found. McGregor Creek, a tributary to the Thames River, was one of the Thames River watershed sites that had been surveyed in 1996 by Dr. Todd Morris (DFO; site TR-47) and no P. sintoxia were found. But, at the same site during a 2010 quadrat survey, two live P. sintoxia were found. The second Thames River site was in the Middle Thames River south of Thamesford and 25 live P. sintoxia were found during a 2004 quadrat survey. Also, six live individuals were found during a 2010 quadrat survey of site GR-21, 1.5 km downstream of York near Mount Healey in the Grand River, where live P. sintoxia had also been previously reported.

Timed Surveys

During 2003-2012 there were 49 separate sampling events where P. sintoxia were found (live or shells, Table 2). Nearly half of these sampling events (n = 24) occurred in Lake St. Clair, which were snorkeling surveys. The Lake St. Clair surveys were all in the delta and were at 11 individual sites. In and around Bass Bay appears to be a stronghold for P. sintoxia, even with the presence of dreissenids, because during this period 251 live P. sintoxia were found. Sampling of Lake St. Clair did not expand the range of P. sintoxia beyond the general localities of the 2004 status report. Fifteen sampling events in the Sydenham River found evidence of P. sintoxia at seven sites during 2003-2012. All these sites were previously reported to have evidence of P. sintoxia in the 2004 status report. Seven of these sampling events in the Sydenham River found more than one and less than five live individuals; the other eight sampling events found only one live P. sintoxia. The Thames River watershed had five separate sampling events where P. sintoxia were found alive at four sites. One site was sampled twice in one year (2004) and 36 live individuals were found (South of Thamesford, TR-31); each of two sites had one live P. sintoxia; one was found in the Middle Thames River, one was found in the South Thames River, and one site (3.35 km downstream of Muncey bridge at a First Nations site) had only two weathered valves of P. sintoxia. Surveys during 2003-2012 of the Grand River had three sampling events, all during 2011, each showing evidence of P. sintoxia, which were all within the historical reach of the species. One site (GR-06, 4.5 km north of Cayuga) was sampled twice that year with the initial survey of 4.5 person-hours (ph) finding one weathered valve and the second survey (5.75 ph) finding six live individuals. At the second Grand River site (GR-05, upstream of York ~2.5 km), surveyors found two live P. sintoxia in 6 ph. Lake Erie was surveyed at two sites; one was a snorkel survey and two weathered valves of P. sintoxia were found; one was strictly a beach survey where two weathered P. sintoxia shells had washed up.

Aboriginal Traditional Knowledge (ATK) was requested for P. sintoxia but no ATK information was available, nor was it referred to in the COSEWIC (2004) status report.

Population Information:

Change in number of mature individuals:
Unknown
Change in population trend:
Yes
Change in severity of population fragmentation:
No
Change in trend in area and/or quality of habitat:
Yes
Significant new survey information
Yes

Explanation:

While there appear to be changes in the number of individuals at specific sites, the overall changes in numbers of mature individuals of P. sintoxia since the last report are unknown. With comparable search effort (~4.5 ph) during timed searches, there is a change in the number of live P. sintoxia at sites where live individuals were found previously. There was increased search effort from quadrat surveys (Figure 6; Table 1) since the COSEWIC 2004 status report. In general, the numbers of live individuals found were lower in the Lake St. Clair, Sydenham and Middle Thames river sites, with the exception of new sites for which comparisons cannot be made. However, new sites in the Grand River have larger numbers of live individuals than many other sites surveyed in the past, but these individuals are all larger/old animals; this increase in abundance relative to other previously surveyed sites is likely due, in part, to increased search effort using quadrat surveys performed in 2010. Surveys since the last status report in areas between the sites with living P. sintoxia showed no evidence of live individuals. No new dams, crossings or construction appear to have negatively affected the P. sintoxia populations.

Extent, area and quality of habitat for P. sintoxia are declining in Lake St. Clair, Lake Erie and Niagara River (if any live individuals exist), and the Sydenham, Thames, and Grand rivers (see Threats).

For new survey information see Range.

Threats:

Change in nature and/or severity of threats:
No

Explanation:

Although the threats calculator was not used in the P. sintoxia 2004 status report (COSEWIC 2004), the report highlighted the following four threat categories to P. sintoxia: Zebra Mussels; anthropogenic stressors (i.e., nutrient loading, toxins, and sedimentation); potential for commercial harvest; change in host community.

According to the threats calculator, the future survival of P. sintoxia is likely to be influenced by 12 potential threats (Appendix A). An additional threat, that of dams’ effects on host movement (e.g., potential limitations of movement of P. sintoxia during early life stages) is unknown and could not be assessed, but is documented in Appendix A. These 12 specific threats are categorized into 7 main threats. Climate change and severe weather is a predicted threat in peer review literature but is beyond the timeframe considered in this SAS. Two ‘High’ impacts are from the threats of invasive species, namely Round Gobies (Neogobius melanostomus), Zebra and Quagga Mussels (Dreissena rostriformis bugensis), and pollution, including that from oil drilling and pipeline crossings in southwestern Ontario, as emphasized by the nearby Kalamazoo River oil spill in Michigan. Three million litres of bitumen oil were spilled and covered ~48 river km. There is still evidence of oil in the benthic zone after two years (Woolnough and Parker 2013). The same pipeline that caused the Kalamazoo River oil spill crosses into Canada in southwestern Ontario and is within the Sydenham and Thames Rivers (Canadian Association of Petroleum Producers 2014). Agricultural inputs occur in all watersheds in which P. sintoxia occurs (see COSEWIC 2004), but especially the riverine sites. For more detail on these high-impact threats see Appendix A. Details of the low and negligible impact threats are outlined in Appendix A.

The threats calculator summary highlights the watershed where these threats to P. sintoxia are probable in the future. If watershed(s) are not mentioned explicitly then all sites are affected by that threat. References beyond those cited in COSEWIC 2004 (e.g., climate change) that relate directly to P. sintoxia or unionids in general are included within the comments section of the threats calculator (Appendix A).

Past and ongoing threats have had negative effects on the populations of P. sintoxia and sympatric unionid communities. These ongoing threats include impoundments in the Grand River, which are likely influencing host movement and therefore dispersal of P. sintoxia in the past. Also, invasive species (i.e., Zebra Mussels and Quagga Mussels) influence on the Lake St. Clair delta population has occurred in the past and is ongoing; however, the P. sintoxia sites appear to have reproducing individuals, as evidenced by small animals. Invasive species are a larger ongoing threat to the Lake St. Clair populations, whereas agriculture is the dominant threat in the riverine sites.

Protection:

Change in effective protection:
Yes

Explanation:

Pleurobema sintoxia is listed under Schedule 1 (Subsections 2(1), 42(2) and 68(2)) ofCanada’s Species at Risk Act (SARA),which affords measures that protect and recover this species; critical habitat of P. sintoxia has yet to be protected under SARA. In 2007 the Ontario Ministry of Natural Resources enacted the Ontario Endangered Species Act (ESA). Pleurobema sintoxia is now listed as Endangered under the ESA with individuals more broadly protected than with previous Ontario legislation and general habitat protection came into effect June 30, 2013 (Sections 9 and 10). In June 2012, Bill-C38 passed and made changes to the federal Fisheries Act that will change the effective protection of P. sintoxia. The Fisheries Act now only covers fish (including shellfish) that are “commercial, recreational or Aboriginal fishery” [subsection 35(1)] and therefore P. sintoxia would no longer be protected under the Fisheries Act.

As stated in COSEWIC (2004), the Round Pigtoe population in Lake St. Clair is located entirely within the territory of the Walpole Island First Nation (WIFN). Special user permits are required to access First Nation territory and waters, which limits human disturbance in the area. Ecosystem recovery strategies have been developed for mussel species at risk, including P. sintoxia, in the Sydenham River (Dextrase et al. 2003) and Thames River (Thames River Recovery Team 2003, see Cudmore et al. 2004). A Recovery Action Plan (2003) for the Sydenham River has been established (Sydenham River Recovery Action Group 2003). A five-species federal recovery strategy (Morris and Burridge 2010), as well as one for the Ontario Ministry of Natural Resources (Morris and Burridge 2010), includes P. sintoxia and highlights the biological and technical feasibility of recovery. The Fisheries Management Plan for the Grand River focuses on fish species but likely the actions provide some protection for P. sintoxia as well as their hosts (Ontario Ministry of Natural Resources 2004).

Rescue Effect:

Change in evidence of rescue effect:
No

Explanation:

Pleurobema sintoxia still occurs in 19 US states in addition to the Ontario populations. It is afforded some protection in states where it is listed as endangered (Iowa, Pennsylvania), threatened (Minnesota), and special concern (Michigan, Wisconsin). Although this species has protection in these states, it has not changed throughout the US where many of the occurrences have viable populations (NatureServe 2013). Recent surveys of the Niagara River on the US side (< 5 km from the historic Canadian sampling sites) have not shown any live individuals that could aid in natural rescue (Zanatta pers. comm. 2014). The populations in Kentucky appear the largest and are showing evidence of recruitment (Cicerello and Schuster 2003). However, natural rescue is likely low and there is no current evidence of any rescue due to invasive species prohibiting reproduction and therefore immigration to the Canadian populations (see Additional Considerations for potential augmentation rescue).

Quantitative Analysis:

Change in estimated probability of extirpation:
No

Explanation:

Although P. sintoxia has not been modelled explicitly there have been advances in estimating probabilities of extirpation of native freshwater mussels. Ricciardi and Rasmussen (1999) estimate recent extinction rates for freshwater mussels as 1.2% loss per decade using data from this century, and 6.4% loss per decade as a future extinction rate (next century). Also, Spooner et al. (2011) estimate that upwards of 60% of the Great Lakes Drainage unionid fauna and on average 35% of the unionid community could be extirpated due to cumulative effects of changes in flow regime (i.e., change in water quantity due to climate change) and loss of host fish. Also, Berg et al. (2008) have outlined a model to link demographic and population genetics of freshwater mussels to create population viability analyses (PVA). Information that is readily available for P. sintoxia could contribute to the potential PVA for P. sintoxia, especially for linking the genetics (see Wildlife Species) and demographics (COSEWIC 2004) of P. sintoxia.

Summary and Additional Considerations: 

Pleurobema sintoxia occurs in 19 states and the province of Ontario. Range-wide trends for this speciesare relatively stable and even increasing in Minnesota (Sietman 2003; NatureServe 2013). Pleurobema sintoxia could be extirpated from the Niagara River and Lake Erie; 2011 surveys at two sites on the US side of the Niagara River found no P. sintoxia or weathered valves (three other live species, of similar size, were found), which supports the potential extirpation of P. sintoxia from the Niagara River; however, more surveys are needed on the Canadian side of the Niagara River for confirmation. The populations in Lake St. Clair and Sydenham, Thames and Grand Rivers appear to be variable in size (Figure 6) likely due to the variability in threats and various search effort; however, no quantitative data are available to support these general observations.

The Center for Mollusk Conservation in Kentucky has been successful in producing metamorphosed P. sintoxia juveniles in captivity (Owen pers. comm. 2013). The University of Guelph and Central Michigan University are two facilities that specialize in host fish testing and propagation of Great Lakes species, and therefore there is the potential for producing laboratory-raised juveniles for eventual release to augment current P. sintoxia populations once habitat and genetic testing are performed. Hoftyzer et al. (2008) outline precautions and implications of reintroducing laboratory-raised juveniles into natural habitats.


Authorities Contacted:

Contacted for updated information for SAS:

iDenotes that information was provided by authority contacted.

Benoit, Dan. December 2012. COSEWIC ATK Subcommittee

iMackie, Gerald, December 2012, January and February 2013. Professor Emeritus, Department of Integrative Biology, University of Guelph, or Water Systems Analysts, 23 Avra Court Guelph, ON N1H 7B2, gerry.mackie@sympatico.ca

iMcNichols-O’Rourke, Kelly. December 2012, January 2013. Aquatic Science Technician, Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences, Burlington, Ontario Department of Fisheries and Oceans, Burlington, Ontario, Kelly.McNichols-O'Rourke@dfo-mpo.gc.ca

iMorris, Todd. December 2012. Research Scientist, Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences, Burlington, Ontario, Morrist@dfo-mpo.gc.ca

iOwen, Christopher. June 21, 2012. Kentucky Department of Fish and Wildlife Resources, Frankfort, Kentucky, christopher.owen@ky.gov

iZanatta, David. December 2012, January 2013. Assistant Professor, Institute for Great Lakes Research, Biology 83 Department, Central Michigan University, 156 Brooks Hall, Mount Pleasant, MI 48859, zanat1d@cmich.edu


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Campbell, D.C., J.M. Serb, J.E. Buhay, K.J. Robe, R.L. Minton, and C. Lydeard. 2005. Phylogeny of North American amblemines (Bivalvia, Unionoida): Prodigious polyphyly proves pervasive across genera. Invertebrate Biology 124:131-164.

Canadian Association of Petroleum Producers. 2014. Map of Canadian and U.S. pipelines and refineries.. [accessed February 2014].

Cicerello, R.R., and G.A. Schuster. 2003. A Guide to the Freshwater Mussels of Kentucky. Kentucky State Nature Preserves Commission. Louisville. 62 pp.

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Owen, C., pers. comm.. 2013. Email correspondence to D. Woolnough. May 2012. Malacologist, Center for Mollusk Conservation, Kentucky Department of Fish & Wildlife Resources. Frankfort, Kentucky, USA.

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Professor, Malacologist, Biology Department, Central Michigan Univesity, Mt. Pleasant, MI, USA.

Table 1. Quadrat surveys that found Pleurobema sintoxia present in Canada from 2003-2012. Quadrat surveys consist of excavation surveys of ~20% of 400 m2. Shells were either not recorded or not found during these surveys. Live column is the total # of live P. sintoxia found at that site for all surveys of the unique locality. Sample sites are numbered based on date of earliest sampling rather than specific locality (e.g., latitude and longitude); specific locality information is housed in the Department of Fisheries and Oceans database. Site numbers are not related to those in Figure 2; see text for explanation.
WaterbodySite NumberNumber of Surveys (2003-2012)Live
Grand RiverSite 116
Sydenham RiverSite 113
Sydenham RiverSite 222
Sydenham RiverSite 312
Sydenham RiverSite 4129
Sydenham RiverSite 511
Bear CreekSite 6 (Bear Creek)11
Sydenham RiverSite 716
Middle Thames RiverSite 1110
Thames River – McGregor CreekSite 212
Table 2. Surveys that found Pleurobema sintoxia present in Canada from 2003-2012. Live column is the total # of live P. sintoxia found at that site for all surveys at the unique locality. Sample sites are numbered based on date of earliest sampling rather than on specific locality (e.g., latitude and longitude); specific site information is housed in the Department of Fisheries and Oceans database. Not all methods or efforts were recorded but the best available data are in the Method/Effort column. ? indicates unknown or not recorded for the total person-hours surveyed. Site numbers do not correspond to sites in the Figure 2; see text for details.
WaterbodySite NumberNumber of Surveys (2003-2012)LiveFresh Shells (Whole)Weathered Shells (Whole)Weathered Shells (valve)Method/Effort (person-hours)
Grand RiverSite 126010Timed/10.25
Grand RiverSite 21 000Timed/6
Lake ErieSite 110002Snorkel/1.5
Lake ErieSite 210002Visual beach search/?
Lake St. ClairSite 111000Snorkel/3.5
Lake St. ClairSite 2387000Stake & rope (x2)/? + half hectare/?
Lake St. ClairSite 3315000Stake & rope (x2)/? + 3 100m transects/?
Lake St. ClairSite 4145000Snorkel/4
Lake St. ClairSite 5379000Stake & rope/? + untimed species relocation + unknown survey
Lake St. ClairSite 6574000Stake & rope (x2)/? + half hectare/?
Lake St. ClairSite 7467000(x2)/? + quantitative/2 + half hectare (x2)/2+stake & rope/?
Lake St. ClairSite 824000Stake & rope (x2)/?
Lake St. ClairSite 913000Snorkel/3
Lake St. ClairSite 10310000Timed/(3x30 min) + Stake & rope (x2)/?
Lake St. ClairSite 1110100Stake & rope /?
Lake St. ClairSite 1210100Stake & rope /?
Lake St. ClairSite 1311000Stake & rope /?
Middle Thames RiverSite 1236000Timed/4.5 + quantitative/?
Middle Thames RiverSite 111000Incidental observation/?
South Thames RiverSite 111000Timed/4.5
Sydenham RiverSite 1613000Timed/26.25 + unknown methods (x2)/?
Sydenham RiverSite 212000Timed/5.1
Sydenham RiverSite 333000Timed/12.75 + unknown search methods(x2)/?
Sydenham RiverSite 412000Unknown/?
Sydenham RiverSite 511000Unknown/?
Sydenham RiverSite 611000Unknown/?
Sydenham RiverSite 722000Unknown/?
Thames RiverSite 110000Timed/4.5
Figure 1. Historical extent of occurrence for Pleurobema sintoxia, which shows all records (live, fresh, and weathered shells) from 1885 to 2012 and is based on minimum convex polygon within Canada’s extent of jurisdiction. COSEWIC (2004) states EO = 12,360 km2, recalculation with US EO = 10,309 km2, within Canada’s extent of jurisdiction EO = 10,224 km2.
Map of occurrence for Pleurobema sintoxia 1 (see long description below)
Long description for Figure 1

Map showing the historical occurrence (1885 to 2012) of Pleurobema sintoxia, which is based on observations of live shells, fresh shells and old shells in Canada. Symbols indicate the localities where the species was observed, and the occurrence is shown by a minimum convex polygon.

Figure 2. Current extent of occurrence for Pleurobema sintoxia, which shows sites of live and fresh shells (whole) from 2003 to present. EO = 3,018 km2. Red circles indicate viable and reproducing locations. Locations 1 and 2 have large numbers of reproducing individuals. Purple circles indicate locations with large/old individuals with no signs of reproduction and/or low numbers. Location 3 represents only large/old individuals which are potentially not reproducing. Location 4 is only 2 sites with 8 large/old individuals. Location 5, Bear Creek of North Sydenham River represents only 2 individuals that appeared not viable. Location 6, McGregor Creek of Thames River, represents two live animals that appeared likely not viable.
Map of occurrence for Pleurobema sintoxia 2 (see long description below)
Long description for Figure 2

Map showing the current extent of occurrence of Pleurobema sintoxia in Canada, which is based on observations of live shells and fresh shells (whole) from 2003 until now. Symbols indicate the localities where the species was observed, and the occurrence is shown by a minimum convex polygon. The circles that encompass two groups of sites (numbers 1 and 2) indicate that these sites have viable breeding individuals. The circles that encompass two groups of sites (numbers 3 and 4) indicate that the sites have large individuals or older who show no sign of reproductive or whose numbers are low.

Figure 3. Historical index of area of occupancy for Pleurobema sintoxia (pre-2002). 2 km x 2 km grid IAO calculation based on above; replicates of exact sites were combined to one site.
Map of occurrence for Pleurobema sintoxia 3 (see long description below)
Long description for Figure 3

Map showing the AO index (IAO) history of Pleurobema sintoxia in Canada before 2002. The symbols indicate the sites where live or fresh shells were found, and IAO is shown through a gate 2 square kilometers across.

Figure 4. 2002- 2012 index of area of occupancy for Pleurobema sintoxia. 2 km x 2 km grid AO calculation based on above; replicates of exact sites were combined to one site.
Map of occurrence for Pleurobema sintoxia 4 (see long description below)
Long description for Figure 4

Map showing the AO index (IAO) of Pleurobema sintoxia in Canada from 2002 to 2012. The symbols indicate the sites where live or fresh shells were found, and IAO is shown by a grid squares 2 km aside.

Figure 5. 2002- 2012 index of area of occupancy (dissolved) for Pleurobema sintoxia. 2 km x 2 km grid IAO calculation based on above; replicates of exact sites were combined to one site being part of one location and overlapping grid cells were hence dissolved (see insert for example).
Map of occurrence for Pleurobema sintoxia 5 (see long description below)
Long description for Figure 5

Carte indiquant l’indice de zone d’occupation (regroupé) du Pleurobema sintoxia au Canada, de 2002 à 2012. Les symboles indiquent les sites où des coquilles vivantes ou fraîches ont été trouvées, et l’IZO est montré au moyen d’une grille à carrés de 2 kilomètres de côté sans recoupement. Une carte en médaillon montre comment les aires de recoupement de la grille ont été comptées une seule fois pour le lac Sainte Claire. Pour obtenir des renseignements supplémentaires au sujet de la méthode, voir la légende de la figure 5.

Figure 6. Live Pleurobema sintoxia from individual site surveys (timed and quadrat) pre-2003 (red) and 2003-2012 (green).
Map of occurrence for Pleurobema sintoxia 6 (see long description below)
Long description for Figure 6

Carte montrant les localités (indiquées par des symboles) où des individus vivants du Pleurobema sintoxia ont été trouvés durant des relevés minutés et par quadrat menés à chacun des sites avant 2003 et entre 2003 et 2012. La taille du symbole indique le nombre d’individus vivants.

Appendix A: Threats Calculator
Threat No.Threat descriptionThreat impact codeThreat impactScopeSeverityTimingComments
1.1Housing & urban areasCMediumRestricted (11-30%)Serious (31-70%)High (Continuing)Grand River Watershed see Pollution 9.1
1.3Tourism & recreation areas-----See 5.4 and 6.1
2Agriculture & aquacultureDLowSmall (1-10%)Extreme (71-100%)High (Continuing)-
2.3Livestock farming & ranchingDLowSmall (1-10%)Extreme (71-100%)High (Continuing)Throughout Sydenham and Thames Watersheds (Lake St. Clair Drainage), trampling in the river on animals (likely around the low end of 1-10%)
4Transportation & service corridors-NegligibleNegligible (<1%)Moderate (11-30%)High - Moderate-
4.1Roads & railroads-NegligibleNegligible (<1%)Moderate (11-30%)High (Continuing)New road and bridge crossings and culverts throughout range.
5Biological resource use-NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)-
5.4Fishing & harvesting aquatic resources-NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)Host fish and bait fish capture and translocations, impact on juveniles is very high (no survivorship if host dies because encysted on host) but effect on adults is negligible
6Human intrusions & disturbanceDLowSmall (1-10%)Serious - Moderate (11-70%)High (Continuing)-
6.1Recreational activitiesDLowSmall (1-10%)Serious - Moderate (11-70%)High (Continuing)ATV in shallow riffles in Sydenham and possible other riffle sites (e.g., Thames), minimal effects of canoe and kayaking traffic in Grand R.
7Natural system modifications-UnknownUnknownUnknownUnknown-
7.2Dams & water management/use-UnknownUnknownUnknownUnknownImpoundments in Grand River Watershed (n=32) and Thames River--limitations to host fish movement (see Singer and Gangloff 2011).
8Invasive & other problematic species & genesBHighLarge (31-70%)Serious 31-70%)High (Continuing)-
8.1Invasive non-native/alien speciesBHighLarge (31-70%)Serious (31-70%)High (Continuing)Dreissenids, round goby, potential for Asian carp, Hemimysis, etc. (Poos et al. 2010, Ricciardi and Rasmussen 1999, Ricciardi et al. 2012).
9PollutionBHighPervasive (71-100%)Serious (31-70%)High (Continuing)-
9.1Household sewage & urban waste waterBHighPervasive (71-100%)Serious (31-70%)High (Continuing)All watersheds (e.g., Grand watershed serves >700,000 people with sewage treatment). Lake St. Clair receives effluent from Thames and Sydenham R. sediment, salts (Gillis 2011), PAHs.
9.2Industrial & military effluentsBHighLarge (31-70%)Serious (31-70%)Moderate (Possibly in the short term, < 10 yrs/3 gen)Oil drilling and pipeline crossings in SW Ontario. Aging pipelines (e.g., Kalamazoo Oil Spill 2010, Michigan, USA; Woolnough and Parker 2013).
9.3Agricultural & forestry effluentsBHighPervasive (71-100%)Serious (31-70%)High (Continuing)Tiles throughout Sydenham and Thames watersheds (which flow into Lake St. Clair). Nutrient input from tiles, direct from agricultural land use. Sediment, bacteria, FPOM, CPOM.
11Climate change & severe weather-Not Calculated (outside assessment timeframe)Pervasive (71-100%)Serious (31-70%)Low (Possibly in the long term, >10 yrs/3 gen)-
11.1Habitat shifting & alteration-Not Calculated (outside assessment timeframe)Pervasive (71-100%)Serious (31-70%)Low (Possibly in the long term, >10 yrs/3 gen)Unstable habitat shifts during events moving adult mussels downstream to potentially sub-optimal habitat. Potential shift in host fish community. Estimated losses of freshwater mussels due to climate change in North America up to 70% and in the Great Lakes Region >40 % (Spooner et al. 2008). This is a 60-year prediction.
11.2Droughts-Not Calculated (outside assessment timeframe)Pervasive (71-100%)Serious (31-70%)Low (Possibly in the long term, >10 yrs/3 gen)Water quantity declining in Great Lakes inland rivers; desiccation, inability to reproduce (suitable host availability due to declining populations and habitat loss). Spooner et al. 2008. This is a 60-year prediction.
11.3Temperature extremes-Not Calculated (outside assessment timeframe)Pervasive (71-100%)Serious (31-70%)Low (Possibly in the long term, >10 yrs/3 gen)Temperature increases due to increases in CO2- increase in water temperatures and unknown changes in reproduction, survival, perhaps to lethal levels (esp. glochidia and juveniles). This is a 60-year prediction.
11.4Storms & flooding-Not Calculated (outside assessment timeframe)Pervasive (71-100%)Serious (31-70%)Low (Possibly in the long term, >10 yrs/3 gen)See Spooner et al. 2008. This is a 60-year prediction.

Technical Summary

Scientific Name:
Pleurobema sintoxia
English Name:
Round Pigtoe
French Name:
Pleurobème écarlate
Range of occurrence in Canada:
Ontario

Demographic Information

Demographic Information of the species
Summary ItemsInformation
Generation time (usually average age of parents in the population; indicate if another method of estimating generation time indicated in the IUCN guidelines(2008) is being used). Average maximum average age for Pleurobemini is 32 (Haag and Rypel 2011) and although average age or reproductive age of these populations are unknown it can be assumed that generation time likely exceeds 10 years.>10 yrs
Is there a continuing decline in number of mature individuals? Assumed from decline in IAOWill decline
Estimated percent of continuing decline in total number of mature individuals within 2 generations. Unsure of the maturity of the individuals.Unknown
Inferred percent reduction in total number of mature individuals over the last 3 generations. Unsure of the maturity of the individuals.Unknown
Projected percent reduction in total number of mature individuals over the next 3 generations. Unsure of the maturity of the individuals.Unknown
Observed percent reduction in total number of mature individuals over any 3 generation period, over a time period including both the past and the future. Unsure of the maturity of the individuals.Unknown
Are the causes of the decline clearly reversible and understood and ceased?Probability of reversing causes low to not possible. Causes understood.
Are there extreme fluctuations in number of mature individuals? Not noted during recent surveysUnlikely

Extent and Occupancy Information

Extent and Occupancy Information of the species
Summary ItemsInformation
Estimated extent of occurrence3,018 km2
Index of area of occupancy (IAO) (Always report 2x2 grid value).140 km2
Is the population severely fragmented?No

Number of locations
(Note: See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)

  1. Lake St. Clair Delta
  2. Sydenham River
  3. Thames River (Upper reach)- possibly not viable
  4. Grand River- possibly not viable
2-4 (Locations with signs of reproduction = 2)
Is there an observed continuing decline in extent of occurrence? 10,224 km2 to 3,018 km2 is a 70.5 % decline, but may be due to lack of surveys for some sites.Yes
Is there an observed continuing decline in index of area of occupancy? 300 km2 to 140 km2 a 53.3% decline, but may be due to lack of surveys for some sites.Yes
Is there an observed continuing decline in number of populations? Lake Erie site only represented by weathered shells and Niagara river sites likely extirpated. Thames River population not reproducing, most upstream sites all adults and no signs of reproduction. Grand River population mostly large individuals showing no signs of reproduction. Oil Springs location (North Sydenham) as well as the South Thames has no signs of reproduction and low number(s) of animals.Yes
Is there an observed continuing decline in number of locations?
(Note: See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)
Using current definition for locations the five locations in the 2004 Status Report are now considered as four (or two) locations so there is a decline in overall number of locations with a projection that it is declining into the future (2004 there were five location and currently there are four to two locations).
Yes
Is there an observed continuing decline in area, extent and/or quality of habitat? Invasive species increasing in Lake St. Clair drainage (e.g., Round Goby), agriculture and pollution effects especially from roads increasing in both watersheds.Yes (area, extent and quality)
Are there extreme fluctuations in number of populations?No
Are there extreme fluctuations in number of locations?
(Note: See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)
See above comment
No
Are there extreme fluctuations in extent of occurrence? Niagara River and Lake Erie sites could be extirpated but further surveys are needed on the Canadian side of the river.No
Are there extreme fluctuations in index of area of occupancy? 33 versus 75 unique sampling sites where P. sintoxia was found however these numbers are due to sampling effort with no evidence showing extreme fluctuations in the index of area of occupancy.No

Number of Mature Individuals (in each population)

Number of Mature Individuals of the species
PopulationN Clones (index of Mature Individuals)
1) Grand River> 100
2) Lake St. Clair drainagethousands
Totalthousands

Quantitative Analysis

Quantitative Analysis of the species
Summary ItemsInformation
Probability of extinction in the wild Not enough data to calculateUnknown

Threats (actual or imminent, to populations or habitats)

There are twelve potential threats that are known to effect P. sintoxia. The potential of dams limiting P. sintoxia host movement (e.g., therefore potential limitations of movement of P. sintoxia during early life stage while attached to the host) is unknown and could not be assessed. These 12 specific threats are categorized into seven main threats. One main threat, climate change and severe weather, is predicted in peer review literature but is beyond the timeframe considered in the SAS. Two threats that have ‘High’ impacts on P. sintoxia are invasive species and pollution. Agricultural inputs occur in all of the watersheds that P. sintoxia occur but especially the riverine sites; invasive species are the largest ongoing threat to the Lake St. Clair sites.

Rescue Effect (immigration from outside Canada)

Rescue Effect of the species
Summary ItemsInformation
Status of outside population(s)? Alabama (S1), Arkansas (S3), Illinois (SNR), Indiana (S3), Iowa (S1), Kansas (S2), Kentucky (S4S5), Michigan (S2S3), Minnesota (S2), Missouri (S4), Nebraska (SNR), New York (S1), Ohio (S3), Oklahoma (S4), Pennsylvania (S2), South Dakota (S1), Tennessee (S4), West Virginia (S2), Wisconsin (S3). US: N4N5 (2007) Global Status: G4G5 (2009)-
Is immigration known or possible? Immigration may be possible from the Michigan populations to the Lake St. Clair locations. Also, Ohio populations (from inland rivers and Lake Erie coast) could immigrate to the Canadian Lake Erie locations. It is possible that US Niagara River populations (if viable) could immigrate to the historical Niagara river locations.Unknown but possible
Would immigrants be adapted to survive in Canada? Unlikely given invasive species and pollution they would need to adapt to.Unknown
Is there sufficient habitat for immigrants in Canada? Probably not because habitat availability is restricted due to invasive species use of habitat.Probably not
Is rescue from outside populations likely? No. Natural rescue is highly unlikely.No, not natural rescue.

Data-Sensitive Species

Data-Sensitive information of the species
Summary ItemsInformation
Is this a data sensitive species?Yes

Status History

Designated Endangered in May 2004. Status re-examined and confirmed in May 2014

Status and Reasons for Designation:

Status:
Endangered
Alpha-numeric code:
B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)
Reasons for designation:
This mussel species occupies a small area in the Lake St. Clair watershed and three other watersheds in southern Ontario, where its habitat has been declining in extent and quality. Urban development, agricultural runoff, and impacts from the Zebra Mussel and the Round Goby are threatening the survival of the species in Canada.

Applicability of Criteria

Criterion A (Decline in Total Number of Mature Individuals):
Not applicable because Zebra Mussels are no longer considered a threat in the Delta St. Clair region. The south Thames River loss may result in a reduction of EO but not necessarily a reduction of greater than 30% of mature individuals.
Criterion B (Small Distribution Range and Decline or Fluctuation):
Meets EN B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) since the EO is less than 5,000km², the IAO is less than 500km², is known to exist at less than five locations and there are continuing declines in the IAO, in the area, extent and quality of habitat, in the number of locations, and in the number of mature individuals.
Criterion C (Small and Declining Number of Mature Individuals):
Not applicable. Number of mature individuals is unknown.
Criterion D (Very Small or Restricted Population):
Not applicable. Total number of mature individuals is possibly more than 1000.
Criterion E(Quantitative Analysis):
Not applicable.

COSEWIC logo

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2015)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.
Extinct (X)
A wildlife species that no longer exists.
Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered (E)
A wildlife species facing imminent extirpation or extinction.
Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.
Special Concern (SC)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.
Not at Risk (NAR)
(Note: Formerly described as “Not In Any Category”, or “No Designation Required.”)
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.
Data Deficient (DD)
(Note: Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.