Proposed changes to the conservation unit for Nanaimo River watershed spring chinook

Abstract

Several years ago the Committee on the Status of Wildlife in Canada (COSEWIC) served notice to Fisheries and Oceans Canada (DFO) that they wanted to review the status of Chinook Salmon (Oncorhynchus tshawytscha) in southern British Columbia (BC). Subsequently, DFO initiated a committee whose task was to prepare the information required and to review the Conservation Units (CU) which are used to subdivide the species on the basis of genetics and life history. This information was presented as Canadian Science Advisory Secretariat (CSAS) Science Response and Research Documents (DFO 2013, Brown et al. 2019, Brown et al. in prep.1). In their assessment of Chinook (CK) stocks with low or no artificial releases in the last 12 years, COSEWIC assessed the East Vancouver Island Stream, Spring Chinook Designated Unit (DU 19) as ENDANGERED (COSEWIC 2018). This DU is comprised of the Conservation Unit CK-23 East Vancouver Island-Nanaimo_SP. The assessment triggered a response from DFO to prepare a Recovery Potential Assessment (RPA) report to inform a listing decision for the population under the Species at Risk Act (SARA). During the process of assembling the information and data for the RPA, similarities were noted between the CK-23 East Vancouver Island-Nanaimo_SP CU and the CK-83 East Vancouver Island-Georgia Strait_SU_0.3 CU. The latter CU was designated by COSEWIC as East Vancouver Island Summer (DU 20), and assessed as ENDANGERED (COSEWIC 2020), also triggering the need for a Recovery Potential Assessment. The objective of this Science Response is to examine the available biological characteristics of the early Chinook populations in the Nanaimo River in support of a review on the associated Conservation Units that will inform DFO Science and the Species at Risk Program. The alignment of Chinook populations within these CUs will need to be clarified prior to the completion of an RPA report. The CSAS Research Document Wade et al. (2019) provides a framework for reviewing and approving changes to Wild Salmon Policy (WSP) CUs. Extant CUs can be changed to: Extirpated: There are no known sites with fish spawning successfully in the wild and there are no known hatchery sites. Deprecated: An extant CU was merged with another CU or CUs. The CU should no longer be used. A deprecated CU is neither deleted nor extirpated because at least one of its populations persists or is believed to, and has been assigned to another CU. This category is used to manage changes to CUs, and is not a CU. Deleted: The CU was deleted after confirmation that no persistent populations were ever present within recorded history within the area of the CU. This category is used to manage changes to CUs, and is not a CU. This Science Response results from the Regional Science Response Process of November 9, 2021 on the Proposed Changes to the Conservation Unit for Nanaimo River Watershed Spring Chinook.