FWCP Arctic Grayling Synthesis Report Limiting Factors, Enhancement Potential, Conservation Status, and Critical Habitats for Arctic Grayling in the Williston Reservoir Watershed, and Information Gaps Limiting Potential Conservation and Enhancement Actions Mike Stamford,1 John Hagen,2 and Susanne Williamson3 April, 2017 Prepared for: Fish and Wildlife Compensation Program – Peace Region 9228 – 100th Avenue, Fort St. John, BC, V1J 1X7 Prepared with financial support of the Fish and Wildlife Compensation Program on behalf of its program partners BC Hydro, the Province of BC, Fisheries and Oceans Canada, First Nations and public stakeholders. ________________________________________________________________ 1 Stamford Environmental, 877 West Bay Rd, Gambier Island, BC, V0N 1V0; [email protected] 2 John Hagen and Associates, 330 Alward St., Prince George, BC, V2M 2E3; [email protected] 3 Ministry of Environment, 2000 South Ospika Blvd., Prince George; V2N 4W5; [email protected] EXECUTIVE SUMMARY FWCP strategic objectives. The FWCP Streams Action Plan (FWCP 2014) identifies two over-arching strategic objectives for the conservation and enhancement of Arctic Grayling and other priority fish species in the upper Peace Basin: 1. Maintain or improve the conservation status of Arctic Grayling populations. 2. Maintain or improve the integrity and productivity of Arctic Grayling habitats. This study was initiated by FWCP to evaluate the existing knowledge base relative to these strategic objectives, and fulfill objective 1b-1 of the Streams Action Plan: Review existing information (including provincial management plan), summarize status and trends of Arctic Graying and its habitats, undertake actions that are within the FWCP scope and lead directly to the development of conservation and enhancement actions, and develop a cost- effective monitoring program to assess status and trends. The study has two components to provide guidance to grant seekers wishing to submit Arctic Grayling monitoring projects through the FWCP’s annual intake of grant applications. This report is the first of these components, and presents extensive background information from past studies of Arctic Grayling in the Williston Reservoir watershed, and from the scientific and management literature. The aim of the report is to identify and prioritize knowledge gaps on a watershed-by-watershed basis, to facilitate a quicker transition to on-the-ground conservation and enhancement actions for Arctic Grayling populations. The second component of this study is a more concise companion document, FWCP Arctic Grayling Monitoring Framework for the Williston Reservoir Watershed (Hagen and Stamford 2017), which provides a condensed list of recommended monitoring needs for implementation in the near term. Priority information categories. Information gathering was prioritized according to those types of data most relevant to the FWCP strategic objectives, which include: 1) information indicating potential limiting factors for Arctic Grayling populations (e.g. habitat degradation, ecological changes, exploitation), 2) information about the effectiveness of enhancements for Arctic Grayling populations, 3) quantitative population data required to assess conservation status and risk (population structure, distribution, abundance, trend, threats), and 4) geographic information delineating critical habitats (providing habitats for key life history stages and where limiting factors may operate). In this report, information about conservation status and critical habitats is organized according to conservation units, termed ‘core areas,’ which correspond to the putative i metapopulation structure. Information about limiting factors and enhancements specific for any particular core area in most cases could not be discriminated and are therefore discussed generally for the upper Peace Basin as a whole. During this assessment of existing information, it was evident that a substantial amount of information exists already that can be applied to Williston Reservoir Arctic Grayling. It was also clear that serious information gaps remain, which probably preclude major FWCP investments in conservation and enhancement actions at this point in time. Data gaps considered of highest immediacy were those likely to be significant obstacles to the initiation of on-the-ground conservation and enhancement actions. These can potentially provide a guide to action in the short-to-medium term, and are summarized below with respect to priority information categories #1-4 listed above. 1) Limiting factors. Relative to pre-impoundment conditions, the most significant factors limiting potential Arctic Grayling productivity in the upper Peace Basin have probably been physical habitat and ecological changes, along with interrupted connectivity among populations, resulting from the flooding of critical habitats. These changes are poorly understood, but probably include flooding of key juvenile rearing and overwintering habitats in low gradient, lower reaches of grayling streams, and high lacustrine predator abundance (e.g. protected Bull Trout populations) in these areas. Studies to address these data gaps are of high immediacy because they may indicate which factors must be addressed and monitored during potential recolonization experiments, and include: 1) inventory studies (e.g. traditional sampling techniques targeting adult and juvenile life stages; environmental DNA) to identify remnant populations that have adapted to the reservoir environment, and physical habitat characteristic of streams or shorelines they inhabit, 2) recolonization experiments, and 3) coordinated Arctic Grayling and Bull Trout monitoring studies in select tributaries, in combination with MFLNRO-led experiments to regulate predator abundance. 2) Enhancements. The most obvious, desirable enhancement would be to facilitate the Arctic Grayling’s recolonization of its former range in small-to-medium sized tributaries of Williston Reservoir. A review of Arctic Grayling recolonization efforts in Montana, where a similar loss of populations following dam construction has occurred, provided the most relevant background information. It appears that recolonization experiments may not succeed if transplanted Arctic Grayling are required to shift their native migratory behaviour (e.g. from adfluvial to fluvial life history), and successful techniques include those providing opportunities for imprinting during key periods of ontogeny. With respect to the potential for recolonization, two key data gaps of high immediacy are: ii 1) poor understanding of limiting factors that drove extirpation in small-to-medium sized tributaries of Williston Reservoir, and 2) the serious lack of knowledge about spawning areas within the ranges of existing populations and potential sources of gametes. 3) Conservation status and risk. Eight core areas have been delineated for the upper Peace Basin upstream of the W.A.C. Bennet Dam: Parsnip, Nation, Omineca, Ingenika, Williston, Upper Peace, Lower Finlay, and Upper Finlay/Toodoggone. Assessed levels of risk ranged from Potential Risk in the relatively pristine Upper Finlay core area, to High Risk for the Ingenika, Williston, and Upper Peace core areas. The latter two core areas comprise small-to-medium sized watersheds that are direct tributaries to the reservoir, where Arctic Grayling populations may be largely extirpated or exist only as remnants. The remaining four core areas (Parsnip, Nation, Omineca, Lower Finlay) are considered to be At Risk, largely as a result of major habitat loss, diminished connectivity, and population declines over the scale of decades (i.e. the effects of impoundment were included in the analysis). While these assessments corroborate prior levels of conservation concern expressed for upper Peace Basin Arctic Grayling, they were severely limited by a lack of population data with which to estimate adult abundance and trend, which are key conservation status indicators (Arctic Grayling abundance monitoring has not occurred anywhere in the Williston watershed since 2007). A coordinated Arctic Grayling monitoring plan for the Williston Reservoir watershed is urgently needed to address this data gap. 4) Critical habitats. A total of 80 stream segments providing critical habitats for at least one Arctic Grayling life stage (subadult/adult, juvenile, fry) were identified. Among these, information adequacy was estimated to be relatively high in 39 cases, and fair or poor in the remainder. In the analysis of critical habitats, a total of 47 information gaps were identified that potentially limit the ability to initiate conservation and enhancement actions. From these, four categories of high immediacy, recurring data gaps (affecting all core areas) could be discerned: 1) Unknown total distribution of grayling within core areas, and the relative importance of streams within core areas. Potential study techniques include: electrofishing and seining studies targeting fry and juvenile Arctic Grayling, otolith microchemistry, summer habitat use studies targeting adults (e.g. snorkeling surveys, angling), radio telemetry studies, and the promising new technique of environmental DNA. The distribution data gaps of highest immediacy were those for the Williston and Upper Peace core areas, where it is uncertain whether self-sustaining Arctic Grayling populations still exist. 2) Poor understanding of adult migratory behaviour and locations of natal areas. This data gap limits both habitat