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Terms of Reference

Recovery Potential Assessment – Southern BC Chinook Salmon – Four Designatable Units

Regional Peer Review Meeting – Pacific Region

February 22-24, 2022
Virtual Meeting

Chairperson: Ben Davis


After the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses an aquatic species as Threatened, Endangered or Extirpated, Fisheries and Oceans Canada (DFO) undertakes a number of actions required to support implementation of the Species at Risk Act (SARA). Many of these actions require scientific information on the current status of the wildlife species, threats to its survival and recovery, and the feasibility of recovery. Formulation of this scientific advice has typically been developed through a Recovery Potential Assessment (RPA) that is conducted shortly after the COSEWIC assessment. This timing allows for consideration of peer-reviewed scientific analyses into SARA processes including recovery planning.

The following four populations of Southern BC Chinook Salmon (Oncorhynchus tshawytscha) were designated as Endangered or Threatened by COSEWIC in 2020 based on population declines (COSEWIC 2020, In press).

  1. DU 1, Boundary Bay Ocean Fall population (Threatened): Hatchery releases, which are ongoing and have included fish from other populations, have allowed the total population size to increase while threatening the genetic integrity of the remaining wild fish. This fall run of Chinook spawning in Boundary Bay drainages occurs in highly altered marine and freshwater habitats. Low marine survival, bycatch, and fish culture effects are continuing threats to this population.
  2. DU 6, Lower Fraser Ocean Summer population (Endangered): This summer run of Chinook spawning at a single site (Maria Slough) has declined.
  3. DU 13, South Thompson Stream Summer population (Endangered): This summer run of Chinook has declined and is projected to continue declining.
  4. DU 15, Lower Thompson Stream Spring population (Endangered): From 2013-2018, the number of mature individuals steeply declined and marine survival has been low since 2000.

DFO Science has been asked to undertake a Recovery Potential Assessment (RPA), for these four populations based upon the national RPA Guidance. This will be the first RPA completed for these DUs, as no previous RPA or critical habitat assessment has been done for any of these DUs. Data limitations will prevent advanced population dynamic modelling for these DUs. As such, no forward projections will be produced, but advice will be provided in the form of qualitative assessments of population trajectories. The advice in the RPA may be used to inform both scientific and socio-economic aspects of the listing decision, development of a recovery strategy and action plan, and to support decision making with regards to the issuance of permits or agreements, and the formulation of exemptions and related conditions, as per sections 73, 74, 75, 77, 78 and 83(4) of the Species at Risk Act (SARA 2002). The advice in the RPA may also be used to prepare for the reporting requirements of SARA section 55. The advice generated via this process will update and/or consolidate any existing advice regarding these populations of Southern BC Chinook Salmon.


To provide up-to-date information, and associated uncertainties, to address the following elements:

Biology, Abundance, Distribution and Life History Parameters

Element 1: Summarize the biology of these four DUs of Chinook salmon.

Element 2: Evaluate the recent species trajectory for abundance, distribution and number of populations.

Element 3: Estimate the current or recent life-history parameters for these four DUs of Chinook salmon.

Habitat and Residence Requirements

Element 4: Describe the habitat properties that these four DUs of Chinook salmon need for successful completion of all life-history stages. Describe the function(s), feature(s), and attribute(s) of the habitat, and quantify by how much the biological function(s) that specific habitat feature(s) provides varies with the state or amount of habitat, including carrying capacity limits, if any.

Element 5: Provide information on the spatial extent of the areas in these four DUs of Chinook salmon’s distributions that are likely to have these habitat properties.

Element 6: Quantify the presence and extent of spatial configuration constraints, if any, such as connectivity, barriers to access, etc.

Element 7: Evaluate to what extent the concept of residence applies to the species, and if so, describe the species’ residence.

Threats and Limiting Factors to the Survival and Recovery of these four DUs of Chinook salmon.

Element 8: Assess and prioritize the threats to the survival and recovery of these four DUs of Chinook salmon.

Element 9: Identify the activities most likely to threaten (i.e., damage or destroy) the habitat properties identified in elements 4-5 and provide information on the extent and consequences of these activities.

Element 10: Assess any natural factors that will limit the survival and recovery of these four DUs of Chinook salmon.

Element 11: Discuss the potential ecological impacts of the threats identified in element 8 to the target species and other co-occurring species. List the possible benefits and disadvantages to the target species and other co-occurring species that may occur if the threats are abated. Identify existing monitoring efforts for the target species and other co-occurring species associated with each of the threats, and identify any knowledge gaps.

Recovery Targets

Element 12: Propose candidate abundance and distribution target(s) for recovery.

Element 13: Project expected population trajectories over a scientifically reasonable time frame (minimum of 10 years), and trajectories over time to the potential recovery target(s), given current population dynamics parameters for these four DUs of Chinook salmon.

Element 14: Provide advice on the degree to which supply of suitable habitat meets the demands of the species both at present and when the species reaches the potential recovery target(s) identified in element 12.

Element 15: Assess the probability that the potential recovery target(s) can be achieved under current rates of population dynamics parameters, and how that probability would vary with different mortality (especially lower) and productivity (especially higher) parameters.

Scenarios for Mitigation of Threats and Alternatives to Activities

Element 16: Develop an inventory of feasible mitigation measures and reasonable alternatives to the activities that are threats to the species and its habitat (as identified in elements 8 and 10).

Element 17: Develop an inventory of activities that could increase the productivity or survivorship parameters (as identified in elements 3 and 15).

Element 18: If current habitat supply may be insufficient to achieve recovery targets (see element 14), provide advice on the feasibility of restoring the habitat to higher values. Advice must be provided in the context of all available options for achieving abundance and distribution targets.

Element 19: Estimate the reduction in mortality rate expected by each of the mitigation measures or alternatives in element 16 and the increase in productivity or survivorship associated with each measure in element 17.

Element 20: Project expected population trajectory (and uncertainties) over a scientifically reasonable time frame and to the time of reaching recovery targets, given mortality rates and productivities associated with the specific measures identified for exploration in element 19. Include those that provide as high a probability of survivorship and recovery as possible for biologically realistic parameter values.

Element 21: Recommend parameter values for population productivity and starting mortality rates and, where necessary, specialized features of population models that would be required to allow exploration of additional scenarios as part of the assessment of economic, social, and cultural impacts in support of the listing process.

Allowable Harm Assessment

Element 22: Evaluate maximum human-induced mortality and habitat destruction that the species can sustain without jeopardizing its survival or recovery.

Expected Publications

Expected Participation



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