Warning This Web page has been archived on the Web.

Archived Content

Information identified as archived on the Web is for reference, research or recordkeeping purposes. It has not been altered or updated after the date of archiving. Web pages that are archived on the Web are not subject to the Government of Canada Web Standards, as per the Policy on Communications and Federal Identity.

Skip booklet index and go to page content

Recovery Strategy for the Round Hickorynut (Obovaria subrotunda, Rafinesque 1820) and Kidneyshell (Ptychobranchus fasciolaris, Rafinesque 1820) in Canada [Proposed]


II. Recovery

  1. Recovery Goal
  2. Recovery Objectives (5 Year)
  3. Approaches to Meeting Recovery Objectives
    1. Research and Monitoring Approaches
    2. Management Approaches
    3. Stewardship Approaches
    4. Awareness Approaches
  4. Potential Impacts of Recovery Strategy on Other Species/Ecological Processes
  5. Actions Already Completed or Underway
  6. Recovery Action Plans
  7. Evaluation

1. Recovery Goal

The long-term goals of this recovery strategy are:

  1. to prevent the extirpation of the Round Hickorynut and Kidneyshell in Canada;
  2. to return healthy self-sustaining populations of Round Hickorynut to the Sydenham River and Lake St. Clair delta and;
  3. to maintain healthy self-sustaining Kidneyshell populations in the Ausable and Sydenham rivers while returning the Lake St. Clair delta population to a self-sustaining level;
  4. to re-establish populations in historically occupied habitats.

These populations can only be considered recovered when they have returned to historically estimated ranges (see Figure 3 and 6) and/or population densities and are showing signs of reproduction and recruitment.

2. Recovery Objectives (5 year)

  1. Determine extent, abundance and population demographics of existing populations.
  2. Determine fish hosts and their distributions and abundances.
  3. Define key habitat requirements to identify critical habitat.
  4. Establish a long-term monitoring program for Round Hickorynut and Kidneyshell populations, their hosts and the habitat of both.
  5. Identify threats, evaluate their relative importance and implement remedial actions to minimize their impacts.
  6. Examine the feasibility of relocations, reintroductions and the establishment of managed refuge sites.
  7. Increase awareness about the distribution, threats and recovery of these species.

3. Approaches to Meeting Recovery Objectives

The approaches to recovery have been organized into four distinct groups – research and monitoring, management, stewardship and awareness. Successful recovery across the ranges of the Round Hickorynut and Kidneyshell will require consideration of approaches from all categories. A narrative has been included after each table where appropriate.

Recovery of these two species can not be achieved through the actions of any one party. Implementation of the recovery approaches outlined below will require a concerted effort of many groups including, but not limited to, federal, provincial and municipal governments, conservation authorities, academic institutions, First Nations communities, non-governmental organizations and local citizens.

a) Research and Monitoring Approaches

Table a) Research and Monitoring Approaches
PriorityNumberObjective AddressedBroad Approach/ StrategySpecific StepsAnticipated EffectThreat Addressed
Urgent1-1ii, vResearch – host fish.Confirm the host fish species for the Round Hickorynut.Will help determine if host abundance is limiting the Round Hickorynut.
Will assist with defining the larval residence site and in identifying critical habitat.
Host fish declines.
Urgent1-2ii, vSurveys – host fish.Determine the distribution and abundance of the host species.Will help determine if host abundance is limiting the Round Hickorynut or Kidneyshell.Host fish declines.
Urgent1-3iiiResearch – Critical Habitat.Determine the habitat requirements for all life stages.Will assist with further refining critical habitat for the Round Hickorynut and Kidneyshell. 
Urgent1-4iii, viSurveys – Critical Habitat.Prepare a distribution map of areas of suitable habitat.Will assist with defining critical habitat and potential areas of reintroduction. 
Urgent1-5viResearch – managed refuge sites.Investigate the feasibility of establishing actively managed refuge sites in the St. Clair delta.Will determine if Round Hickorynuts in the St. Clair delta can be insulated from the effects of dreissenid mussels.Dreissenid mussels.
Necessary1-6i, ivMonitoring – mussel and fish host populations.Establish a network of permanent monitoring stations throughout the distribution of the Round Hickorynut.Will permit tracking of populations, analysis of trend patterns, and permit the evaluation of recovery actions.Host fish declines.
Necessary1-7iv, vMonitoring – habitat.Establish permanent monitoring sites for tracking changes in habitat.Provides trend data for key habitat and will help evaluate the relative threat of habitat loss.All threats.
Necessary1-8vResearch – threats.Identify and evaluate threats to all life stages.Will assist with determining reasons for declines and developing remedial actions.All threats.
Necessary1-9viResearch – conservation genetics.Compare the within and among population genetic variability of Canadian populations and determine if populations show genetic structure by comparing variability between populations in Canadian and U.S.waterways.Will assist with determining if population translocation or augmentation is appropriate. 
  • 1-1 & 1-2: The necessity for a period of encystment represents a potential bottleneck in the lifecycle of the mussel. Research and recovery actions focusing on the pre or post encystment period may prove unproductive if the presence of a host fish is the limiting step. In order to determine if these species are host limited it is necessary to first identify the host species and then to confirm that the distributions of the mussel and its host overlap in time and space in a manner that will permit successful encystment. The identification of high host specificity in some mussel species requires that hosts be identified for local populations whenever possible. McNichols and Mackie (2004) have identified three host species for Canadian populations of the Kidneyshell but no Canadian host for the Round Hickorynut has yet been identified. Efforts should be directed towards confirming that species identified as hosts for American populations also function as hosts in Canada.

    Once the Canadian hosts have been confirmed for both of these species it is necessary to verify that host species distributions overlap with the Round Hickorynut and Kidneyshell distributions. Since adult mussels are essentially sessile this can be accomplished by confirming that members of the hosts species occur in reaches with mature female mussels at times when the female mussels possess mature glochidia.

  • 1-3 & 1-4: Determination of critical habitat is an essential component in the recovery of these species. Although adult mussels are relatively passively distributed, distinct habitat types can be associated with adult distributions suggesting that survival is linked to local habitat conditions. Habitat conditions may be equally important during the juvenile stage and attention must also be paid to the habitat preferences of the hosts. Identification of critical habitat will be a multi-stage incremental process.

  • 1-5: The best remaining population of Round Hickorynuts along with a small population of Kidneyshells can be found in the delta area of Lake St. Clair despite the presence of dreissenid mussels. Metcalfe-Smith et al. (2004) reported zebra mussel infestation rates ranging from 0 to 36 zebra mussels/unionid in this area during 2003. While this rate of infestation is below the lethal limits reported elsewhere (Ricciardi et al. 1995) it may be resulting in long term chronic effects that are causing prolonged declines. Comparisons of collections made in 2001 with those in 2003 showed that abundance of all unionids had declined by about 14% while declines were much higher for some species (i.e., 80% decline of Round Hickorynut) (Metcalfe-Smith et al. 2004). Although the overall trend was toward declining unionid densities some sites showed stable overall abundances. These sites were associated with low zebra mussel infestation rates and high unionid diversity and may represent potential refuge sites. Since these sites are still affected by zebra mussels it is likely that unionids will need to be actively managed with regular zebra mussel removal and the active relocation of Round Hickorynuts, Kidneyshells and other mussel SAR to these locations from the more heavily infested sites. The feasibility of actively managing refuge sites in the St. Clair delta must be determined quickly as this will likely represent the only chance of saving the Round Hickorynut.

  • 1-6 & 1-7: A network of detailed, permanent monitoring stations should be established throughout the present and historic ranges of the Round Hickorynut and Kidneyshell. Monitoring sites should be established in a manner so as to permit:
    • Quantitative tracking of changes in mussel abundance or demographics (size distribution, age structure etc.) or that of their hosts.
    • Detailed analyses of habitat use and the ability to track changes in use or availability.
    • The ability to detect the presence of exotic species (i.e. dreissenid mussels). Reservoirs represent the likely seed locations for dreissenid mussels in the Sydenham and Ausable rivers. Monitoring sites should be established within or close to these reservoirs to permit the early detection of dreissenid mussels in the event that they invade these systems. Monitoring of exotics in the Lake St. Clair delta will likely be conducted in close association with the managed refuge sites.

b) Management Approaches

Table b) Management Approaches
PriorityNumberObjective AddressedBroad Approach/ StrategySpecific StepsAnticipated EffectThreat Addressed
Urgent2-1i-viCapacity BuildingPromote and enhance expertise in freshwater mussel identification/biology and provide for the transfer of knowledge.Will ensure correct identification of mussel species at risk. 
Urgent2-2v, viCooperation – ecosystem recovery strategiesWork with existing ecosystem recovery teams to implement recovery actions.Encourage a seamless implementation of all recovery actions. 
Necessary2-3vMunicipal PlanningEncourage municipal planning authorities to consider Recovery Goals in official plans.Will provide further protection for the Round Hickorynut and Kidneyshell and promote future development that does not degrade important habitat.Urbanization, water quality, water quantity, impoundments.
Necessary2-4vDrainageWork with drainage supervisors, engineers and contractors to limit the effects of drainage activities on mussel habitat.Will reduce the harmful effects of drainage activities.Water quality, siltation, water quantity.
Necessary2-5ii, iii, vFish Management PlansEncourage the development of management plans for non SAR fish species within watersheds inhabited by the Round Hickorynut and KidneyshellWill provide protection for potential host species.Host fish declines.
Necessary2-6vBaitfishWork with the baitfish industry to reduce the impacts of commercial baitfishing on host species.Will provide protection for potential host species.Host fish declines.
Necessary2-7vWastewater treatment plants and stormwater management facilitiesVerify that wastewater treatment plants are functioning up to specifications and encourage upgrading where appropriate. Review stormwater management facilities for quantity and quality control in new developments, and retro-fit existing development where possible.Will improve water quality by reducing nutrient and suspended solid inputs from urban centres.Water quality, water quantity, impoundments.
  • 2-1: The current capacity within southwestern Ontario to perform the necessary survey and monitoring work is insufficient. Knowledge of freshwater mussel identification, distribution, life history and genetics is limited to a small number of individuals from a limited number of government and academic institutions. Furthermore, the retirement of several key researchers is expected prior to the 5-year re-evaluation period for this strategy. A concerted effort must be made to increase this capacity by:
    • Training personnel in the identification of all mussel species with emphasis on the rare species.
    •  Producing a field guide to the mussels of Ontario.
    • Encourage graduate and post-graduate research aimed at fulfilling the needs identified under Research and Monitoring.


  • 2-2: Many of the threats to the Round Hickorynut and Kidneyshell can be classified as widespread and chronic (Table 1) and represent general ecosystem threats affecting numerous other aquatic species. Efforts to remediate these threats will benefit many species in addition to these two mussel species and should be attempted in close connection with the aquatic ecosystem recovery teams for the Ausable and Sydenham rivers (see section II.5, Activities already completed or underway) to eliminate duplication of efforts and ensure that undertaken activities are not detrimental to other species.

  • 2-5: The host fishes for these two mussel species must be afforded some degree of protection if the Round Hickorynut and Kidneyshell are to recover. The greenside darter, which functions as the probable host for the Round Hickorynut, is listed as a species of special concern by COSEWIC. This species is given consideration in the aquatic ecosystem recovery strategies for both the Sydenham River (Dextrase et al. 2003) and Ausable River (ARRT 2003) and will therefore be actively monitored and managed within these systems. The three host species for the Kidneyshell (blackside darter, johnny darter and fantail darter) are not listed by COSEWIC and therefore not explicitly considered in any recovery plans. It may be necessary to develop formal management plans for these species to make certain that their populations remain healthy and do not hinder the recovery of the Kidneyshell.

  • 2-6: While the host species of the Round Hickorynut and Kidneyshell are not typically targeted as baitfish they are potentially collected as bycatch during legal bait harvesting activities. Effort should be made to minimize potential bycatch of these species and to verify that gear selection and operation do not contribute to habitat degradation which may adversely affect host populations. In watersheds supporting Round Hickorynut and Kidneyshell, live bait storage ponds should be isolated from the watercourse in order to prevent accidental escapement of round gobies. Mechanisms to confirm that bait bucket releases do not further spread the round goby and detrimentally impact host populations should be employed.

c) Stewardship Approaches

Table c) Stewardship Approaches
PriorityNumberObjective AddressedBroad Approach/ StrategySpecific StepsAnticipated EffectThreat Addressed
Urgent3-1vRiparian buffersEstablish riparian buffer zones in areas of high erosion potential by encouraging naturalization or planting of native species.Will improve water quality by reducing bank erosion, sedimentation and overland run-off.Water quality, siltation, water quantity.
Urgent3-2vTile drainageWork with landowners to mitigate the effects of tile drainage.Will reduce nutrient and sediment inputs.Water quality, siltation, water quantity.
Urgent3-3vHerd managementEncourage the active exclusion of animals from the watercourse.Will reduce bank erosion, sediment and nutrient inputs.Water quality, siltation.
Urgent3-4vLivestock waste managementAssist with establishing adequate manure collection and storage systems to avoid accidental spills, and winter-spreading of manure.Will improve water quality by reducing nutrients.Water quality.
Urgent3-5vFarm planningEncourage the development and implementation of Environmental Farm Plans and Nutrient Management Plans.Will assist with minimizing inputs of nutrients and sediments.Water quality.
Urgent3-6vSewage treatmentWork with landowners to improve faulty septic systems.Will improve water quality by reducing nutrient inputs.Water quality.
Beneficial3-7vSoil testingEncourage soil testing to determine fertilizer application rates.Will reduce nutrient inputs to the river.Water quality.

The stewardship activities outlined here can be described as "best management practices" and represent a non-exhaustive selection of activities that can be encouraged within these predominantly agricultural watersheds to help reduce the impacts of terrestrial practices on aquatic ecosystems. Encouragement can be achieved through increasing awareness of these activities as well as through the provision of financial assistance to local landowners.

d) Awareness Approaches

Table d) Awareness Approaches
PriorityNumberObjective AddressedBroad Approach/ StrategySpecific StepsAnticipated EffectThreat Addressed
Urgent4-1viiAwareness – stewardship actionsIncrease public knowledge of stewardship options and financial assistance available to participate in activities.Increased public participation in recovery actions and a reduction in threats to the Round Hickorynut and Kidneyshell.Water quality, siltation, water quantity.
Urgent4-2viiExotic speciesIncrease public awareness of the potential impacts of transporting/releasing exotic species.Will reduce the risk of dreissenid mussels or gobies becoming established.Exotic species
Beneficial4-3viiOutreachEncourage public support and participation by developing awareness materials and programs.Will increase public awareness of the importance of species at risk.All threats.

Public participation in the recovery process for these species is essential as the primary threats to populations in the Ausable and Sydenham rivers result from diffuse non-point source inputs relating to the general agricultural activities within these watersheds. Recovery can not occur without the full participation of local citizens and landowners. The need for an effective public awareness program is crucial to the recovery of these two species.

4. Potential Impacts of Recovery Strategy on Other Species/Ecological Processes

The Round Hickorynut and Kidneyshell are sensitive species, particularly to issues of water quantity and quality. For this reason, we expect that efforts made to improve conditions for these mussels will benefit most other aquatic species. A few opportunistic species that can readily adapt to degraded conditions (e.g., giant floater (Pyganodon grandis) or fathead minnow (Pimephales promelas)) may see a decline in numbers/range as a result of rehabilitative efforts. These changes should not be viewed in a negative light but rather as a restoration of the aquatic community to pre-disturbance conditions.

5. Actions Already Completed or Underway

Sydenham River Aquatic Ecosystem Recovery Strategy

The Sydenham River Recovery Team became the first group in Canada to adopt an ecosystem approach to recovering aquatic species when they completed the Sydenham River Aquatic Ecosystem Recovery Strategy (SRAERS) in 2003 (Dextrase et al. 2003). The recovery strategy focuses on the 14 aquatic species (5 mussels, 8 fishes, 1 turtle) within the basin that are listed as endangered, threatened or of special concern by the COSEWIC. Both the Round Hickorynut and the Kidneyshell were listed after the SRAERS was completed and so these species are not directly considered within the strategy. Despite their exclusion from the strategy many of the actions proposed by Dextrase et al. (2003) to benefit the 5 included mussel species will be beneficial for recovery of these two species.

Thames River Recovery Ecosystem Strategy

The Thames River Recovery Team (TRRT) has set out to develop an ecosystem based recovery strategy for the Thames River watershed. The stated goal is to develop "a recovery plan that improves the status of all aquatic species at risk in the Thames River through an ecosystem approach that sustains and enhances all native aquatic communities" (Thames River Recovery Team 2003). This recovery strategy addresses 25 COSEWIC listed species including 7 mussels, 12 fishes and 6 reptiles. Both the Round Hickorynut and the Kidneyshell are being considered in the development of this strategy as both species historically occurred within this watershed. Although neither species is still known to occur in the Thames River, recovery actions proposed by the TRRT will increase the likelihood that Recovery Habitat for these species in the Thames River will prove suitable for possible future repatriations.

Ausable River Ecosystem Recovery Strategy

The Ausable River Recovery Team is developing an ecosystem Recovery Strategy for the 14 COSEWIC listed aquatic species in the Ausable River basin. This plan covers 4 endangered mussel species including the Kidneyshell. The overall goal of the strategy is to "sustain a healthy native aquatic community in the Ausable River through an ecosystem approach that focuses on species at risk" (Ausable River Recovery Team 2004). The Ausable River Recovery Team (2004) has also established a species-specific recovery goal for all mussels of "maintain(ing) existing populations of species at risk and restor(ing) self-sustaining populations of each species to areas of the river where they formerly occurred".

Grand River Fish Species at Risk Recovery Strategy

The Grand River Recovery Team has developed a draft recovery strategy for fish species at risk in the Grand River. The goal of this strategy is "to conserve and enhance the native fish community using sound science, community involvement and habitat improvement measures" (Portt et al. 2003). Although the strategy does not directly address any mussels species, their "habitat preferences and requirements will be taken into account when assessing management actions targeting fish species at risk. In most cases, it is anticipated that recovery actions benefiting fishes at risk will also benefit these other rare species" (Portt et al. 2003).

Walpole Island Ecosystem Recovery Strategy

The Walpole Island Ecosystem Recovery Strategy Team was established in 2001 to develop an ecosystem based recovery strategy for the area containing the St. Clair delta with the goal of outlining steps to maintain or rehabilitate the ecosystem and species at risk (Walpole Island Heritage Centre 2002). Although the strategy is initially focusing on terrestrial ecosystems there are future plans to include aquatic components of the ecosystem.

Fish Host Identification

A research group led by Dr. J. Ackerman and Dr. G. L. Mackie has been established at the University of Guelph to investigate aspects of the reproductive cycle of freshwater mussels (host fish determination, glochidial development, juvenile growth and survival). The group conducts its research at the Hagen Aqua Lab on the grounds of the university in Guelph, Ontario, Canada. This facility has been used to investigate potential hosts for four species of endangered mussels including the Kidneyshell (McNichols and Mackie 2003). In 2003 they identified three host species for the Kidneyshell (blackside darter, Johnny darter, fantail darter) but have yet to attempt to identify or confirm the host for the Round Hickorynut (McNichols and Mackie 2004).

Stewardship Activities

Stewardship programs have been available in the St. Clair Region Conservation Authority in 2000 for projects involving tree planting; stream stabilization; wetland creation; buffer strips; grassed waterways; sediment traps; repair or replacement of faulty septic systems; manure storage facilities; clean water diversions; runoff collection systems; fencing livestock from watercourses; plugging and repairing wells and nutrient management plans. Implementation of these projects improves and protects rural water quality, and the habitat for aquatic species at risk.

Currently, the Ausable-Bayfield Conservation Authority is able to provide funding for stewardship activities such as: tree planting, windbreaks, buffer strips, Nutrient Management Plans, well-decommissioning, wellhead protection, livestock washwater, manure spreading equipment modifications, conservation tillage modifications, clean water diversion, livestock restriction, fertilizer, fuel and chemical storage and handling, erosion control, conservation tillage equipment modifications and septic system upgrades. Implementation of these projects improves water quality and habitat for aquatic species at risk.

Mussel Monitoring Network

Fifteen permanent monitoring stations for mussels have been established on the Sydenham River and a further 6 on the Thames River. Additional stations will be located on the Ausable River during 2006. These sites will be part of an ongoing monitoring system as part of the Sydenham, Ausable and Thames ecosystem recovery strategies and will provide quantitative trend through time data to evaluate recovery actions as well as the overall status of mussel communities.

Nutrient Management Act

Implementation of this provincial legislation, which came into force September 30 2003, will regulate the storage and use of nutrients including manure, farmyard run-off and farm washwater. This should reduce nutrient inputs to the watercourses, which will benefit the aquatic habitats of the mussels.

Source Protection Planning

A White Paper on Watershed-based Source Protection Planning was released in February 2004. Source Protection Planning will identify potential sources of contamination to the surface water and groundwater, determine how much water is readily available, evaluate where that water is vulnerable to contamination and implement programs to minimize risk of contamination to water quality as well as minimizing threats to water quantity.

6. Recovery Action Plans

One or more action plans relating to this recovery strategy will be produced within 5 years of the strategy being completed. Wherever possible recovery action plans should be linked to existing watershed recovery teams. Recovery resources in southwestern Ontario (both fiscal and personnel) are limited. Partnership with these other recovery teams will ensure that efforts are not duplicated and will help to prevent the implementation of recovery efforts for differing species that may conflict.

7. Evaluation

The routine monitoring programs will provide the primary means of evaluating the success of the listed recovery approaches. The monitoring programs will provide trend through time data allowing the tracking of Round Hickorynut and Kidneyshell populations and habitat and will form the basis of an adaptive management program. Recovery Implementation Groups will develop specific targets in the Recovery Action Plans to provide a further basis for evaluating success. The entire Recovery Strategy will be reviewed in 5 years at which time all goals, objectives and approaches will be re-evaluated.