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Recovery Strategy for the Pacific Water Shrew (Sorex bendirii) in Canada - 2014 [Proposed]
Part 1: Federal Addition to the Recovery Strategy for the Pacific Water Shrew (Sorex bendirii) in British Columbia, prepared by Environment Canada
The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996) agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of recovery strategies for listed Extirpated, Endangered, and Threatened species and are required to report on progress within five years.
The federal Minister of the Environment is the competent minister for the recovery of the Pacific Water Shrew and has prepared the federal component of this recovery strategy (Part 1), as per section 37 of SARA. It has been prepared in cooperation with the Province of British Columbia. SARA section 44 allows the Minister to adopt all or part of an existing plan for the species if it meets the requirements under SARA for content (sub-sections 41(1) or (2)). The Province of British Columbia provided the attached recovery strategy for the Pacific Water Shrew (Part 2) as science advice to the jurisdictions responsible for managing the species in British Columbia. It was prepared in cooperation with Environment Canada.
Success in the recovery of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy. Recovery of the Pacific Water Shrew will not be achieved by Environment Canada, or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this strategy for the benefit of the Pacific Water Shrew and Canadian society as a whole.
This recovery strategy will be followed by one or more action plans that will provide information on recovery measures to be taken by Environment Canada and other jurisdictions and/or organizations involved in the conservation of the species. Implementation of this strategy is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.
Additions and Modifications to the Adopted Document
The following sections have been included to address specific requirements of SARA that are either not addressed, or which need more detailed comment, in the Recovery Strategy for the Pacific Water Shrew (Sorex bendirii) in British Columbia (Part 2 of this document, referred to henceforth as “the provincial recovery strategy”). In some cases, these sections may also include updated information or modifications to the provincial recovery strategy for adoption by Environment Canada.
1. Species Status Information
Legal Status: SARA Schedule 1 (2007).
Table 1. Conservation status of the Pacific Water Shrew (from NatureServe 2010 and B.C. Conservation Framework 2010).
- Global (G) Rank
- G4a (apparently secure)
- National (N) Rank
- N1 (critically imperiled)
- Sub-national (S) Rank
- British Columbia (S1) (critically imperiled), Washington (S4), Oregon (S4), California (S3S4)
- COSEWIC Status
- Endangered (2006)
- B.C. List
- B.C. Conservation Framework
- Highest priority : 1, under Goal 3b
a Rank 1 - Critically Imperiled; 2 - Imperiled; 3 - Vulnerable; 4 - Apparently Secure; 5 - Secure; H – possibly extirpated; SNR – Status Not Ranked; SNA – Not Applicable
b The three goals of the B.C. Conservation Framework are: 1. Contribute to global efforts for species and ecosystem conservation; 2. Prevent species and ecosystmes from becoming at risk; 3. Maintain the diversity of native species and ecosystems.
It is estimated that the Canadian range of this species comprises approximately 5% of its global range (COSEWIC 2006).
2. Socio-economic Considerations
The provincial recovery strategy contains a short statement on socio-economic considerations. As socio-economic factors are not a consideration in any aspect of the preparation of SARA recovery strategies (see section 41(1) of SARA), the Socio-economic Considerations section of the provincial recovery strategy is not considered part of the federal Minister of the Environment's recovery strategy for this species. Furthermore, socio-economic factors were excluded from the preparation of all other sections of this federal addition, including Population and Distribution Objectives, and Critical Habitat.
3. Recovery Feasibility
This section replaces the “Recovery Feasibility” section in the provincial recovery strategy.
The feasibility of recovery of Pacific Water Shrew (Sorex bendirii) is addressed below, based on the four criteria outlined in the draft SARA Policies (Government of Canada 2009). There is uncertainty regarding whether there is sufficient suitable habitat to recover the species. However, in keeping with the precautionary principle, a recovery strategy has been prepared as per section 41(1) of SARA as would occur when recovery is determined to be feasible. The schedule of studies (Section 5.2) proposed in this recovery strategy outlines studies aimed at assessing the habitat required to recover this species.
- 1. Individuals of the wildlife species that are capable of reproduction are available now or in the foreseeable future to sustain the population or improve its abundance.
- Yes. Captures of adult and juvenile Pacific Water Shrews over time indicate that reproductive individuals are available.
- 2. Sufficient suitable habitat is available to support the species or could be made available through habitat management or restoration.
- Unknown. Currently there is limited information on habitat associations of Pacific Water Shrew. Additional research is required to determine whether sufficient suitable habitat currently exists or if it can be restored and/or created to sustain the population in the long-term.
- 3. The primary threats to the species or its habitat (including threats outside Canada) can be avoided or mitigated.
- Yes. The primary threats of habitat loss, habitat degradation, and habitat fragmentation can be mitigated through habitat protection, implementation of best management practices, and rehabilitation in many, but perhaps not all, areas.
- 4. Recovery techniques exist to achieve the population and distribution objectives or can be expected to be developed within a reasonable timeframe.
- Yes. The population and distribution objective can be achieved through ongoing threat mitigation techniques such as habitat protection, implementation of best management practices, and rehabilitation.
4. Population and Distribution Objectives
This section replaces the “Recovery Goal and Rationale for the Recovery Goal” sections in the provincial recovery strategy.
Environment Canada has identified the following Population and Distribution Objectives for the Pacific Water Shrew:
To maintain the known extant populations and supporting habitat of this species in Canada, and to increase the known number of populations and the distribution of those populations within the species’ natural range where suitable and/or connecting habitat still exists, or can be restored.
The Pacific Water Shrew is a rare and elusive species. There are few records of the species and the little information available on population abundance or trends is insufficient to support a population viability analysis. Additional research is required to determine the current population size, and to identify the amount and quality of habitat required to promote recovery.
In Canada, the Pacific Water Shrew has likely always been primarily restricted to riparian areas of the Lower Mainland of British Columbia (COSEWIC 2006). This habitat type is declining in availability and suitability within the range of the species (COSEWIC 2006). The Pacific Water Shrew was assessed as Endangered in 2006 based on its small extant range in severely fragmented habitat, and continuing declines in quality and quantity of suitable habitat (COSEWIC 2006).
There have been 157 captures or recoveries of Pacific Water Shrew recorded in Canada since 1888; the majority of these records are from shrews captured/recovered >30 years ago and do not have accurate location data (K. Welstead and V. Craig, pers. comm.). Twenty three Pacific Water Shrew populations in suitable habitat have been identified (Figure A.1). A Pacific Water Shrew population was defined based on the distance between records. Records >1 km apart with unsuitable but not impassable connecting habitat (i.e., dry upland habitat), or >5 km apart with suitable connecting habitat (i.e., aquatic/riparian habitat), were considered separate populations (NatureServe 2010). These populations are based on 48 Pacific Water Shrew captures or recoveries since 1991 and two from 1981 (K. Welstead and V. Craig pers. comm.). One of these recent records (Thunderbird Creek – Figure A.2) expanded the range of the Pacific Water Shrew beyond the range described in the COSEWIC status report (COSEWIC 2006). An extant population is assumed to still occur at the location of the two 1981 captures based on the continued presence of suitable habitat and the limited amount of habitat modification in the surrounding area. To ensure the survival of the species in Canada, and to meet the population and distribution objectives for the species, it is necessary to maintain the populations associated with these 23 areas of suitable habitat.
Based on the known records of this species in Canada, the continued capture of this species in new areas during surveys, and the continued presence of suitable habitat within its range (Craig 2010, D. Knopp pers. comm.), it is likely that additional populations exist. Maintaining and/or increasing the number of Pacific Water Shrew populations and the supporting habitat in these additional areas will be required to recover the species. A schedule of studies has been included in this federal addition for the purpose of completing the identification of critical habitat through the location of additional populations and associated suitable habitat. If additional populations are discovered they should be maintained, and the habitat around the location should be considered to be critical habitat.
5. Critical Habitat
5.1 Identification of the Species’ Critical Habitat
This section replaces the “Critical Habitat” section in the provincial recovery strategy.
Section 41(1)(c) of SARA requires that recovery strategies include an identification of the species’ critical habitat, to the extent possible, as well as examples of activities that are likely to result in its destruction. Information is available to identify critical habitat for all 23 populations of Pacific Water Shrew in the Lower Mainland of British Columbia (Figures A.1-22). Additional critical habitat may be added in the future, if research supports the inclusion of areas beyond what is currently identified. Future work may also include mapping the boundaries of the critical habitat areas more precisely. The primary consideration in the identification of critical habitat is the amount, quality, and locations of habitat needed to achieve the population and distribution objectives.
Pacific Water Shrews require habitat that possesses the following biophysical attributes:
- coniferous or deciduous forest or dense marsh/wetland vegetation to provide cover and maintain a moist microenvironment (B.C. Ministry of Environment, unpublished data);
- an area of water (natural stream, wetland, or channelized watercourse, whether permanent, ephemeral, or intermittent) to support foraging and provide a moist microenvironment (Gomez 1992, B.C. Ministry of Environment, unpublished data); and
- downed wood to provide cover and nesting and foraging substrate (Pacific Water Shrew Recovery Team 2009).
Based on observations from the closely related American Water Shrew Sorex palustris (Thomas 1979), the length of watercourse required to support a Pacific Water Shrew population is believed to be approximately 1.5 km. Forest/dense vegetation should be intact 100 m from each side of the watercourse to maintain nesting and dispersal habitat and the moist microenvironment required by Pacific Water Shrew. The 100 m width is based on the fact that the majority of Pacific Water Shrew records have been within 50 m of water (Anthony et al. 1987, Gomez 1992, McComb et al. 1993, Galindo-Leal and Runciman 1994, Stinson et al. 1997, Gomez and Anthony 1998, and all records in B.C.), and studies of edge effects (reviewed in Kremsater and Bunnell 1999) suggest that the majority of microclimatic edge effects in forested habitat occur within 50 m (meaning that 100 m of riparian habitat should be present to ensure that a suitable microclimate will be maintained 50 m from the watercourse edge).
Critical habitat for Pacific Water Shrew is identified at locations where the species has been captured or a carcass recovered, the capture/recovery coordinates are known with a high degree of certainty and/or suitable habitat (possessing the critical biophysical attributes listed above) exists at the point of capture/recovery or in close proximity. Critical habitat is identified at a minimum as the area surrounding the occurrence including at least 1.5 km of linear watercourse length extending out from the capture location along all connecting watercourses and 100 m of riparian habitat on each side of the watercourse(s). Critical habitat was extended beyond this initial area when information was available to support such an extension and/or maintenance of connectivity between subpopulations. Connecting habitat was included between sub-populationsPart 1 Footnote 1 where they occurred within 1 km and the intermediate habitat was unsuitable but not impassable (i.e., dry upland habitat) or where they occurred within 5 km and the intermediate habitat was suitable (i.e., aquatic/riparian; NatureServe 2010). Connecting habitat was also included between the critical habitat identified around the occurrence and existing protected areas that contain additional suitable habitat when the two areas were within 1 or 5 km of each other (based on the criteria above). Extension areas were identified by a species expert (using either satellite imagery or ground- truthing).
The 23 areas containing critical habitat are shown in Appendix 1 (Figures A.1-22). Areas within these mapped squares that do not possess the biophysical attributes are not considered critical habitat (e.g., roads and buildings). A complete identification of critical habitat will be made upon completion of the Schedule of Studies (Section 5.2).
5.2 Schedule of Studies to Identify Additional Critical Habitat
This section replaces the “Recommended schedule of studies to identify critical habitat” section in the provincial recovery strategy.
The following schedule of studies (Table 2) outlines the research required to identify additional critical habitat needed to meet the population and distribution objectives.
|Description of activity||Rationale||Timeline|
|Refine sampling method for Pacific Water Shrew. Options include: adding no-kill minnow traps to survey, adding live-traps, using bait tubes||The current method of assessing presence/absence is labour intensive and limits widespread surveys for the species, which will be required to support the population and distribution objective, to increase the number of known populations within the species’ range.||2014-2017|
Identify quantity, size, and extent of additional suitable habitat for Pacific Water Shrew needed to support population and distribution objectives:
|It is believed that additional populations exist beyond those that have been identified in this strategy. In order to support the population and distribution objective of increasing the number of known populations (and then maintaining them once they are discovered) targeted surveys must be conducted (throughout the species’ range) and then critical habitat identified to protect those populations where supporting habitat still exists.||2014-2017|
5.3 Examples of Activities Likely to Result in Destruction of Critical Habitat
Understanding what constitutes destruction of critical habitat is necessary for the protection and management of critical habitat. Destruction, or the potential for destruction, is determined on a case by case basis. Destruction would result if part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from single or multiple activities at one point in time, or from the cumulative effects of one or more activities over time.
Activities described in Table 3 include those likely to cause destruction of critical habitat for Pacific Water Shrew; destructive activities are not limited to those listed. Where a situation does not clearly fit in with the activities identified in Table 3, but has a potential impact on riparian habitat within identified critical habitat and/or water quality associated with waterways or wetlands that have a direct influence on identified critical habitat, the proponent should contact Environment Canada – Canadian Wildlife Service, Pacific and Yukon Region, for guidance on the activity.
|Activity||Description of how activity would destroy critical habitat|
|Partial or total riparian vegetation removal (e.g., forest harvesting, urban or agricultural conversion, linear developments, livestock grazing/trampling).|
|Removal of woody debris in riparian understorey.|
|Alteration of water courses/wetted areas (e.g., ditching/channeling, culverting, ditch cleaning)|
|Release of pollutants into or adjacent to water courses (e.g., herbicide/pesticide application, road and agricultural run-off)|
|Installation of impassable barriers (e.g., multi-lane roads with no culverts)|
6. Statement on Action Plans
One or more federal action plans will be posted on the Species at Risk Public Registry by 2018.
7. Effects on the Environment and Other Species
A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision-making.
Recovery planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that strategies may also inadvertently lead to environmental effects beyond the intended benefits. The planning process, based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts upon non-target species or habitats. The results of the SEA are incorporated directly into the strategy itself.
The provincial recovery strategy notes that recovery actions for Pacific Water Shrew are unlikely to have any negative effects on non-target species or communities within its range, and may benefit other species at risk. Habitat requirements of Pacific Water Shrew overlap those of the Salish Sucker (Catostomus catostomus ssp), Nooksack Dace (Rhinichthys cataractae ssp.), and the Oregon Spotted Frog (Rana pretiosa), which are all listed as Endangered under SARA, and the Pacific Pond Turtle (Actinemys marmorata), which is listed as Extirpated. The threats to these species are similar to those of Pacific Water Shrew, and include habitat degradation, habitat loss, and habitat fragmentation. Recovery actions for Pacific Water Shrew such as protection or rehabilitation of habitat will improve the habitat for these other species at risk, where they co-occur. Likewise, the Pacific Water Shrew is likely to benefit from habitat-focused recovery actions for these other species at risk.
The proposed actions emphasize habitat protection, restoration, and connection with natural communities and processes, and restoring the proper functioning of riparian ecosystems, all of which will benefit other native species including several commercial fish species.
Anthony, R.G., E.D. Forsman, G.A. Green, G. Witmer, and S.K. Nelson. 1987. Small mammal populations in riparian zones of different-aged coniferous forests. The Murrelet 68:94-102.
B.C. Conservation Framework. 2010. Conservation Framework Summary: Pterygoneurum kozlovii. B.C. Minist. of Environment. (December 8, 2010)
COSEWIC. 2006. COSEWIC assessment and update status report on the Pacific Water Shrew Sorex bendirii in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 28 pp.
Craig, V. J. 2010. Predictive mapping landscape model for Pacific water shrew (Sorex bendirii). Prepared for the B.C. Ministry of Environment, Surrey. 32 pp.
Galindo-Leal, C. and J. B. Runciman. 1994. Status report on the Pacific water shrew (Sorex bendirii) in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, ON.
Gomez, D. M. 1992. Small mammal and herpetofauna abundance in riparian and upslope areas of five forest conditions. M.Sc. Dissertation. Oregon State University, 118 pp.
Gomez, D. M., and R. G. Anthony. 1998. Small mammal abundance in riparian and upland areas of five seral stages in western Oregon. Northwest Science 72:293-302.
Government of Canada. 2009. Species at Risk Act Policies, Overarching Policy Framework [Draft]. Species at Risk Act Policy and Guidelines Series. Environment Canada. Ottawa. 38 pp.
Kremsater, L. L. and F.L. Bunnell. 1999. Edges: Theory, evidence, and implications to management of western forests. Pp. 117-153 in J. A. Rochelle, L. A. Lehmann and J. Wisniewski (editors.) Forest Fragmentation: Wildlife and Management Implications. Brill, Leiden, Netherlands.
McComb, W.C., K. McGarigal, and R.G. Anthony. 1993. Small mammal and amphibian abundance in streamside and upslope habitats of mature Douglas-fir stands, western Oregon. Northwest Science 67:7-15.
NatureServe. 2010. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. (Accessed: December 8, 2010 and May 2, 2011).
Pacific Water Shrew Recovery Team. 2009. Recovery Strategy for the Pacific Water Shrew (Sorex bendirii) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 27 pp.
Stinson, D.W., D.E. Runde, and K. A. Austin. 1997. A small mammal community in managed forest of southwestern Washington. Draft Technical Report, Western Timberlands Research, Weyerhaeuser, Tacoma, WA. 19 pp.
Thomas, J. W. (editor). 1979. Wildlife habitats in managed forests. USDA Forest Service Agricultural Handbook No. 533, Washington, DC.
Craig, V. Environmental Consultant and Pacific Water Shrew Expert. EcoLogic Research. Galiano Island, B.C.
Knopp. D. Environmental Consultant and Pacific Water Shrew Expert. B.C.’s Wild Heritage. Sardis, B.C.
Welstead, K. Species at Risk Biologist and Pacific Water Shrew Recovery Team Chair. B.C. Ministry of Forests, Lands, and Natural Resource Operations. Surrey, B.C.
Appendix 1. Maps of critical habitat for Pacific Water Shrew in Canada
Critical habitat is represented by the shaded yellow polygon where the criteria set out in Section 5.1 are met. The 1 km x 1 km UTM grid overlay shown on this figure is a standardized national grid system that highlights the general geographic area containing the critical habitat.
Part 1 Footnotes
- Footnote 1
Sub-populations of Pacific Water Shrew represent records of individuals, or patches of individuals, that are within 5 km of each other in areas with suitable connecting habitat, or within 1 km of each other in areas with unsuitable connecting habitat (NatureServe 2010).
- Date Modified: