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COSEWIC assessment and status report on the Atlantic Salmon (Inner Bay of Fundy populations) in Canada

Executive Summary

Atlantic Salmon

Salmo Salar

Inner Bayof Fundy Populations


Species information

The anadromous form of the Atlantic salmon (Salmo salar) grows to maturity in the ocean but returns to fresh water to reproduce.  The species is naturally structured into genetically differentiated populations due to homing to natal rivers, juvenile rearing within the rivers, and the spatial isolation of river systems. This differentiation is generally hierarchical, with regional groups of populations having more genetic similarity than that found across groups.  Groups also tend to share adaptations that allow individuals to be successful in their specific local environment.  Six regional groups of Atlantic salmon have been proposed for Canada, and one of these consists of the populations that are contained within the inner Bay of Fundy (iBoF).


Designatable Unit: Inner Bay of Fundy Populations 

The cumulative evidence from genetics, phylogeography, local selection, life history, behaviour and demography, as well as consideration of stocking impacts, supports the hypothesis that the iBoF Atlantic salmon are differentiated from other regional groups of salmon in Canada (and elsewhere).  While there is evidence of some gene flow from the neighbouring outer Bay of Fundy (oBoF), the biological characteristics of iBoF salmon populations support their assessment as a COSEWIC Designatable Unit. 



Wild anadromous Atlantic salmon were once distributed along the east coast of North America, from the Hudson River, New York north to Ungava Bay, Quebec (plus one population in eastern Hudson Bay), and along the west coast of Europe, from Portugal to Russia.  However, many wild populations are now extinct and this distribution has therefore declined.

The entire iBoF salmon DU exists in Canada.  It includes all salmon rivers (32 to 40 or more) that drain into the Bay of Fundy, starting with the Black River (New Brunswick) and extending around the interior region of the bay to the Cornwallis River (Nova Scotia).  Adults occupy these rivers during breeding in the fall.  Juveniles migrate to the ocean after 2-3 years in fresh water, where they grow to adulthood.  While most North American salmon populations migrate to waters off Labrador and western Greenland, it has been hypothesized that iBoF salmon remain in the Bay of Fundy, Northern Gulf of Maine, and other local marine habitat. 



Freshwater habitat requirements for Atlantic salmon are well known, and there is no evidence of freshwater habitat loss that would explain the recent declines of the iBoF Atlantic salmon.  Currently there appears to be an abundance of quality freshwater habitat within the iBoF.  Ocean habitat requirements are less well known, but a decline in marine survival from the juvenile (smolt) to the adult life stage apparently underlies the collapse of iBoF populations.  If so, a significant decline in marine habitat quality or abundance may be occurring.



Adult iBoF salmon spawn in their natal rivers in October and November.  Young develop until May or June in gravel nest pits, emerge as fry, and grow as parr feeding on invertebrate drift.  Parr smoltify after two or three years in fresh water, then enter the ocean where they grow rapidly to maturity.  Most return after one sea-winter to spawn as grilse in their natal river.  Survival after reproduction is relatively high, and adults will return from the ocean to spawn in subsequent years. 

The iBoF salmon are thought to have several unique characteristics, including the high proportion of individuals that mature as grilse after one sea-winter, the high proportion of females among the grilse, the hypothesized local marine migration, and the high post-reproductive survival.  There is also limited evidence of demographic uncoupling with other regional groupings.

The generation time for iBoF salmon is estimated to be 3.7 years, based on an average 2.6 freshwater years (to smolt migration) and 1.1 marine years (to first adult maturity).  Thus, the three-generation timeframe used for demographic assessment is 11 years (3 x 3.7 = 11.1).


Population sizes and trends

The iBoF populations have collapsed and many rivers no longer contain any salmon at all.  The historical population size across all rivers likely exceeded 40,000 adults.  By contrast, the 2003 fall spawning estimate was less than 100 adults.  An extensive survey in 2002 of 34 natural rivers (without Live Gene Bank stocking) revealed no parr in 65% of the rivers, and no fry in 97% of the rivers (indicating little if any spawning in fall 2001).

Reconstruction of population sizes in the two main index rivers, the Big Salmon and the Stewiacke, give the following estimates of decline (90% level of confidence):

   Big Salmon: >94.1% over 3 generations (11 years); >96.7% over 30 years 

   Stewiacke: >99.0% over 3 generations (11 years); >99.6% over 30 years 

There is no opportunity for a ‘rescue effect’; the two nearest Canadian regional groups of Atlantic salmon -- the river populations of the outer Bay of Fundy and of the Scotian Coast -- have also collapsed.  The next nearest regional group is in Maine, and it too has collapsed and is listed as Endangered (US ESA).


Limiting factors and threats

The causes of the marked decline of Atlantic salmon throughout much of their range since the 1980s, and the complete collapse in some locations (such as the iBoF), are not well understood.  Most hypotheses are related to changes in marine conditions that have decreased the smolt-to-adult survival rate below levels necessary for population viability.  However, the cause(s) of the decline in marine survival is not known, and dozens of hypotheses exist, including: changes in marine primary production; changes in ocean temperatures; and diseases, parasites and predators associated with fish farms.  The development of the Atlantic salmon fish farming industry coincided with the collapse in iBoF salmon and likely poses genetic, ecological and pathological threats that are already documented for other populations.  Humans have also impacted both the quantity and the quality of freshwater habitat, especially through the construction of dams and other obstacles, and probably the marine habitat in ways that are not yet understood.  Commercial fisheries on Atlantic salmon have largely been closed (the iBoF commercial fishery existed for over 100 years but was closed in 1985).  Recreational and First Nation fisheries within the iBoF have also been closed since 1990.


Special significance of the species

The iBoF Atlantic salmon represent a unique Canadian lineage, distinct from all other Atlantic salmon worldwide.  They represent one of only a few Atlantic salmon lineages in Canada.  They contribute to both freshwater and marine ecology, moving energy and nutrients both within and between ecosystems.  They are also the principle host for at least one species of freshwater mussel.  Local people have used them for food, income, ceremony, and pleasure.  As the ‘king of fish’, their existence has special meaning to many Canadians.


Existing protection

Canadian Atlantic salmon are protected under the Fisheries Act administered by the Department of Fisheries and Oceans (DFO); all commercial, recreational and First Nations Atlantic salmon fisheries in the iBoF have been closed since 1990.  The iBoF DU was designated Endangered by COSEWIC in May 2001.  The federal government listed the iBoF DU as Endangered in June 2003 under the Species at Risk Act (SARA).

The National Recovery Team for the iBoF salmon has taken steps to protect and recover the DU. They are actively gathering data and monitoring the population.  Among their noteworthy projects is a Live Gene Bank program, which cultures the salmon in hatcheries but also employs natural selection to reduce deterioration in genetic quality.  


The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.  On June 5th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.



The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.



COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species. 




Wildlife Species: A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X): A wildlife species that no longer exists.

Extirpated (XT): A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E): A wildlife species facing imminent extirpation or extinction.

Threatened (T): A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*: A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**: A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***: A category that applies when the available information is insufficient (a) to resolve a species' eligibility for assessment or (b) to permit an assessment of the species' risk of extinction.

*       Formerly described as "Vulnerable" from 1990 to 1999, or "Rare" prior to 1990.
**     Formerly described as "Not In Any Category", or "No Designation Required."
***   Formerly described as "Indeterminate" from 1994 to 1999 or "ISIBD" (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

Environment                          Environnement
Canada                                 Canada

Canadian Wildlife                  Service canadien
Service                                 de la faune

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.