Research Document - 2008/059

Assessment of the Recovery Potential for the Atlantic Salmon Designatable Unit Inner Bay of Fundy: Threats

By Peter. G. Amiro¹, John C. Brazner¹, and Jennifer L. Giorno²

Abstract

The purpose of this Research Document is to provide background information on the key threats affecting the recovery of the inner Bay of Fundy (iBoF) population of Atlantic salmon. It covers issues related to activities that threaten habitat quality or quantity, activities that are direct sources of mortality for iBoF Atlantic salmon, and the extent and consequences of all the threats. It also includes a rough estimate of the magnitude of the major sources of mortality identified in the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) status report and by other Department of Fisheries and Oceans (DFO) reports, and it describes options for minimizing, mitigating, or finding alternatives to threats when possible. The leading marine threats identified were (importance not implied by order): interactions with farmed and hatchery salmon, ecological community shifts, depressed population phenomena, environmental shifts, and fisheries. The leading threats identified in freshwater habitats were (importance not implied by order): depressed population phenomena, changes in environmental conditions, contaminants, and barriers to passage. To date, there is no evidence of a single overriding factor that could account for the extensive decline in abundance of Atlantic salmon from iBoF rivers. A review of studies suggested that efforts focused on potential threats in the marine environment and on the synergistic or cumulative effects of several threats are crucial to recovery. Options for minimizing, mitigating, or finding alternatives to threats/sources of mortality were reviewed and include: improved containment and incorporation of risk assessment for decisions related to hatcheries and salmon farms, documentation of predator distributions and impact assessment, documentation of ecological community structure to assess possibilities for ecosystem management, further assessment of the impact of fisheries, barrier removal, fish passage improvement, limiting habitat degradation, and reducing contaminant inputs. Mechanisms that could restrict recovery due to reduced survival in either the marine or freshwater environments and that are independent of those causing the original decline include the consequences of very low population abundance, such as inbreeding depression, behavioural shifts, and inability to find mates.

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