Salamander Mussel Evaluation

Committee on the Status of Species at Risk in Ontario (COSSARO)
Assessed by COSSARO as Endangered
June 2011

Part 1

1.1 Current status and distribution

Current designations:

GRANK – G3 (Assessed March 2007; NatureServe, accessed 18 May 2011).

NRANK Canada – N1 (Assessed July 2006; NatureServe, accessed 18 May 2011).

COSEWIC – Endangered (COSEWIC 2011).

SARA – Endangered (Schedule 1). (Environment Canada 2011).

ESA 2007 – Endangered. (Ministry of Natural Resources 2011).

SRANK – S1 (NHIC/NatureServe, Accessed May 2011).

Distribution in Ontario:

The Salamander Mussel, formerly known as the Mudpuppy Mussel, presently occurs with certainty in only a single river system in Ontario, the Sydenham River, which drains into Lake St. Clair. Four sites along a 50 km stretch of this river supported live specimens of this mussel in 2007. Despite the discovery of a single fresh, dead specimen at one location in the Thames River, in London, in the late 1990s, the most recent survey failed to find any evidence of its continuing presence there. In the past (until at least 1983), it also occurred in the Detroit River.

Distribution and status outside Ontario:

The distribution of the Salamander Mussel is limited by the range of its glochidial host species, the mudpuppy (Necturus maculosus). The mussel is known from the Lake Huron, Lake St. Clair, and Lake Erie drainage basins, and from the Ohio, Cumberland, and upper Mississippi River systems, south as far as Arkansas and, formerly, Tennessee (Roe 2003). Throughout its range, it occurs under large rocks and prefers silty or sandy substrates in clear, fresh water in river stretches where there is a swift current (NatureServe Explorer; website visited 20 May 2011; Watson et al. 2000).

Part 2 - Eligibility for Ontario status assessment

2.1 Application of eligibility criteria

Taxonomic distinctness

Yes. The taxonomic status of the Salamander Mussel is not in dispute. It is the only North American unionid to use a non-fish glochidial host.

Designatable units

There is a single designatable unit in Ontario.

Native status

Yes. There has never been any suggestion that this species is not native in Ontario. Also, there is no evidence, circumstantial or otherwise, that it has arrived recently or had been introduced.

Presence/absence

Present. Inventories of the Sydenham River confirm that the Salamander Mussel is still present in Ontario (COSEWIC 2011).

2.2 Eligibility results

1. The putative taxon or DU is valid. Yes
2. The taxon or DU is native to Ontario. Yes
3. The taxon or DU is present in Ontario, extirpated from Ontario or extinct? Present

Part 3 - Ontario status based on COSSARO evaluation criteria

3.1 Application of primary criteria (rarity and declines)

1. Global rank

Threatened. G3

2. Global decline

Threatened. One source (Watson et al. 2000) has suggested that this species was thought to be absent from at least 60% of formerly occupied rivers and streams in the U.S.A. However, a more recent compilation/summary by NatureServe suggests that the long-term range-wide decline in this species is in the range of 25-50%, with a continuing short-term decline trend of 10-30%. These declines are non-cyclical. The difference in these trend assessments may be based on focused sampling in streams where the species previously was known to occur. It is considered to be extirpated in Iowa, and is known only from historical records in New York, suggesting that it may be extirpated there as well (Nature Serve Explorer; website checked 20 May 2011).

3. Northeastern North America ranks

Endangered. This species is ranked as S1, S2, SH, or SX in 11 of 12 northeastern North American jurisdictions in which it occurs (92%).

4. Northeastern North America decline

Threatened. Since the bulk of the global range of this species is within northeastern North American jurisdictions (only Missouri, Arkansas, and Tennessee are not among these jurisdictions, and the species is ranked as S1 in each of these three states), the discussion of global decline applies here, as well.

5. Ontario occurrences

Endangered. Although there are 10 element occurrences noted in the NHIC database, one of which is considered to be extirpated, recent surveys have confirmed only 4 sites of occurrence along the Sydenham River, and none elsewhere.

6. Ontario decline

Threatened. One new site was located within the 50 km stretch of the Sydenham River within which the 3 previously documented sites had been found. Targeted searches of the Thames River failed to find any animals, suggesting that this species may no longer occur along that river system (COSEWIC 2011, Morris and Edwards 2007). At the site level (number of occurrences), there has been one gain and one loss since the last status evaluation (10-year period), and therefore, no overall change has occurred at that scale. Overall, given the 10 previously known element occurrences, plus the new one reported during the most recent status evaluation by COSEWIC (2011), there have been 11 occurrences known, of which 4 are extant (64% decline). Furthermore, the loss of a population along the Thames River constitutes the loss of an entire drainage system. Thus, at that drainage or watershed scale, the decline since the last evaluation is 50% (lost in 1 of 2 watersheds).

7. Ontario’s conservation responsibility

Not in any category. Ontario’s portion of the range of this species constitutes considerably less than 10%. However, it is worth noting that this species is considered to be rare, threatened, or endangered in every jurisdiction in which it occurs (see Appendix 1).

3.2 Application of secondary criteria (threats and vulnerability)

8. Population sustainability

Insufficient information. The lack of repeated, standardized population sampling, as well as the small numbers of specimens detected during previous surveys (a total of 59 individuals, 34 of these from a single site; due, at least in part, to difficulty of detection of this species; COSEWIC 2011), precludes population trend analysis. No population viability analysis has been conducted.

9. Lack of regulatory protection for exploited wild populations

Not in any category. The federal Fisheries Act and Species at Risk Act provide protection for this species, as does the provincial Endangered Species Act.

10. Direct threats

Endangered. Threats that affect the glochidial host also affect the Salamander Mussel, since the life cycle cannot be completed without the host. The stretch of the Sydenham River in which the host and the mussel occur is surrounded by lands undergoing intensive agriculture, and as such, is subjected to inputs of agricultural pesticides, fertilizers, and silt. These inputs are known to be detrimental to the Mudpuppy. Furthermore, the Mudpuppy is susceptible to certain lampricides used to control the Sea Lamprey (Petromyzon marinus) and to toxins such as PCBs (summarized by Watson et al. 2000, Zammit and Sutherland 2001). However, there have been no systematic surveys of the Mudpuppy in the Sydenham River system, so the impacts of these factors cannot be determined directly at this time. Nevertheless, any catastrophic event upstream of the populations of the mussel or its host could severely reduce or eliminate this species from the river. Although the Zebra Mussel (Dreissena polymorpha) is a significant threat to many other unionid mussels in Ontario’s rivers and lakes, it does not appear to be a threat to the Salamander Mussel, at least at present (Watson et al. 2000). Thus, the potential is very high for various threats to impact upon populations in the Sydenham River watershed; a few of these threats have been demonstrated elsewhere in the species' range, particularly upon its glochidial host.

11. Specialized life history or habitat-use characteristics

Endangered. The Salamander Mussel has a specialized life history relative to all other North American unionids, in that it is the only freshwater mussel on the continent that utilizes a non-fish host, the mudpuppy (Necturus maculosus). Furthermore, it appears to be somewhat colonial, unlike most other Ontario unionids, and inhabits the undersurfaces of large, flat rocks in rivers which serve as refugia for Mudpuppies.

3.3 COSSARO evaluation results

1. Criteria satisfied in each status category

Endangered – [2/2]
Threatened – [4/0]
Special concern – [0/0]

Ontario-specific criteria met (primary criteria 5, 6 and 7):
Endangered – [1]
Threatened – [1]
Special concern – [0]

2. Data deficiency

No. Specific inventories have targeted this species, particularly in the Sydenham River. Although it is possible that it may occur in additional sites, and may persist somewhere in the Thames River, the likelihood of this is small.

3. Recommended status

The application of COSSARO evaluation criteria suggests that the Salamander Mussel is Endangered in Ontario.

Part 4 - Ontario status based on cosewic evaluation criteria

4.1 Application of COSEWIC criteria

Regional (Ontario) COSEWIC criteria assessment

Criterion A – Decline in total number of mature individuals

Insufficient information. No systematic population monitoring data are available, and numbers of individuals have been too small to enable any trend analysis.

Criterion B – Small distribution range and decline or fluctuation

Endangered (B1abiii, 2abiii). Population Extent of Occurrence has been estimated at 93 – 357 km² and Index of Area of Occupancy has been estimated at 136 km² (COSEWIC 2011). Number of locations is 4; evidence of continuing decline is based on continuing detrimental impacts from inputs into river from adjacent lands, thus continuing to reduce habitat quality for the mussel and its host.

Criterion C – Small and declining number of mature individuals

Not in any category. Although population estimates are not reliable for this species in Ontario, an estimate of 45,000 individuals has been produced, based on extremely small sample sizes and many other assumptions (see COSEWIC 2011). Using this estimate, thresholds for this criterion are not met. Otherwise, Insufficient information would be appropriate.

Criterion D – Very small or restricted total population

Not in any category. See Criterion C above. Although the population estimate is of low veracity, it is too high to meet the thresholds for this criterion. However, the number of locations, and the fact that they are all in one river system, does mean that the entire population could be subject to stochastic events that could eliminate or seriously endanger it, and the criterion would then be met at the Threatened level.

Criterion E – Quantitative analysis

Insufficient information. No quantitative analysis of population viability is possible at the present time.

Rescue effect

No. Highly unlikely, due to lack of connectivity between American populations and Sydenham River, and highly precarious status of the species in all American jurisdictions.

4.2 COSEWIC evaluation results

1. Criteria satisfied in each status category

Indicate whether or not a criterion is satisfied in each of the status categories.

Endangered – Yes
Threatened – No
Special concern – No

2. Data deficiency

No. Specific inventories have targeted this species, particularly in the Sydenham River. Although it is possible that it may occur in additional sites, and may persist somewhere in the Thames River, the likelihood of this is small.

3. Status based on cosewic evaluation criteria

The application of COSEWIC evaluation criteria suggests that Salamander Mussel is Endangered in Ontario.

Part 5 - Ontario status determination

5.1 Application of COSSARO and COSEWIC criteria

COSSARO and COSEWIC criteria give the same result. Yes

5.2 Summary of status evaluation

Salamander Mussel is classified as Endangered in Ontario.

The Salamander Mussel is a highly specialized unionid mussel that utilizes the Mudpuppy as its glochidial host, unlike all other North American unionids, which use various fish species as hosts. It is found in silty or sandy substrates of freshwater rivers, usually under large rocks, where there is a swift current. It occurs in the Midwestern U.S.A. from the Lakes Huron, St. Clair, and Erie south in the Ohio, Cumberland, and Mississippi River systems to Arkansas, and formerly, Tennessee. In Ontario, it now occurs only in a few locations along a 50 km stretch of the Sydenham River. Populations in previously known locations, for example, in the Thames and Detroit Rivers, appear to have become extirpated. The primary threats to this species include threats to the glochidial host, and are primarily related to inputs to the river from agricultural uses (fertilizers, pesticides, silt). Given the decline in the numbers of locations of this species, as well as the threats to its habitat and glochidial host along this river, the Salamander Mussel is considered to be Endangered in Ontario.

Information sources

1. Literature Cited

Morris, T. J. and A. Edwards. 2007. Freshwater mussel communities of the Thames River, Ontario: 2004-2005. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2810. v + 30 pp.

Roe, K. J. 2003. Conservation assessment for the Salamander Mussel (Simpsonaias ambigua) Say, 1825. USDA Forest Service, Eastern Region. 11 pp.

Watson, E. T., J. L. Metcalfe-Smith, and J. Di Maio. 2000. Status of the Mudpuppy Mussel, Simpsonaias ambigua, in Canada. Draft, prepared for the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 46 pp.

Zammit, A. E. and D. A. Sutherland. 2001. COSSARO candidate V, T, E species evaluation form for Mudpuppy Mussel (Simpsonaias ambigua). COSSARO, Ontario Ministry of Natural Resources, Peterborough. 12 pp.

2. Community and Aboriginal Traditional Knowledge Sources

None.

Appendix 1 - Northeastern North America rank, status and decline

Occurs as a native species in 12 of 29 northeastern jurisdictions
S-rank or equivalent information available for 12 of 12 jurisdictions = (100%)
S1, S2, SH, or SX in 11 of 12 = (92%)