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Science Response 2011/001

Wild Salmon Populations in the Vicinity of a Proposed Finfish Aquaculture Development in St. Mary’s Bay, Nova Scotia


On December 6, 2010, Fisheries and Oceans Canada’s (DFO) Habitat Protection and Sustainable Development (HSPD) Division, Maritimes Region, requested that DFO Science, Maritimes Region, provide advice regarding wild salmon populations in the vicinity of a proposed finfish aquaculture development (two farm sites) in St. Mary’s Bay, Nova Scotia, as well as the likelihood of the proposed development project having negative impacts to the wild salmon populations and their habitat. The request for advice is in support of HPSD’s review of an environmental assessment (EA) of a proposed aquaculture development project pursuant to the Canadian Environmental Assessment Act. Specifically, DFO HPSD asked:

  1. What wild salmon populations (and their lifecycle stages) are present in the vicinity of the proposed finfish aquaculture sites in St. Mary’s Bay, Nova Scotia.
  2. How do the lifecycle stages of wild salmon populations make use of the habitat found in the vicinity of the proposed aquaculture sites?
  3. What is the likelihood/probability of any impacts on the survivability and recoverability of the wild salmon populations found in the vicinity of the proposed aquaculture sites?
  4. How can mitigation measures reduce any impacts on the wild salmon populations found in the vicinity of the proposed aquaculture sites? and
  5. How do the impacts to the wild salmon populations from the proposed aquaculture sites compare to the impacts from other anthropogenic sources?

The Science Special Response Process (SSRP) was based on existing data sources from the St. Mary’s Bay area, which are limited in resolution and scale relative to the location and size of the proposed aquaculture site. An SSRP was used due to the short deadline for advice of January 15, 2011.  

The conclusions of the SSRP are:

  1. A salmon aquaculture development at this site has the potential to impact on salmon populations in three designatable units (DUs): 1) the inner Bay of Fundy (iBoF), 2) the outer Bay of Fundy (oBoF) and 3) the Southern Upland (SU) DUs. IBoF is listed as Endangered pursuant to the Species at Risk Act.  The oBoF and SU DUs have been recommended for listing as Endangered by the Committee on the Status of Endangered Wildlife in Canada.
  2. The general area around the proposed site in St. Mary’s Bay is considered to be used as a salmon migratory corridor and feeding grounds in support of growth, maturation, and post-spawning reconditioning.
  3. IBoF salmon tend to migrate out along the New Brunswick side of the Bay of Fundy (the Bay) toward the outer Bay and Gulf of Maine, but are also detected on the Nova Scotia side of the outer Bay. Some portion of individuals may leave the Bay, over a period of approximately five months (June through October), but another portion may remain in the Bay during this same period. Post-smolts that remain in the Bay tend to move up into the Bay along the Nova Scotia side.
  4. Historically, adult salmon were captured in the vicinity of the proposed St. Mary’s Bay sites for extended periods during the spring, summer and fall. Based on tag returns for Saint John River salmon, adults returning to spawn are present in the Bay of Fundy from at least May until November. They are also known to be present near the coastline and to move in and out of estuaries during this time period. Returning adults from at least the iBoF, oBoF and SU DUs would be expected to pass nearby the proposed aquaculture sites, and potentially more than one time.
  5. Although a few salmon rivers in the SU region are located in or near the Bay of Fundy (the Annapolis and the Tusket Rivers are the largest), most are located on the Atlantic coast of Nova Scotia and salmon from the Atlantic populations (particularly the northerly rivers) are expected to be in the vicinity of the proposed sites infrequently. Effects on these populations would be expected to occur mainly via interactions with escaped aquaculture salmon.
  6. Salmon aquaculture sites can impact wild populations through: the transmission of parasites; pathogens and disease from cage-farmed salmon; potentially increased predation as a result of predator attraction to the cage sites; and through an additional range of pathways that arise from aquaculture escapees. Escapees can hybridize with wild salmon, which has the potential to reduce genetic fitness of wild populations. Salmon in the three DUs are at low abundance relative to past levels and are highly sensitive to increased stress and mortality.
  7. A number of mitigation measures have been identified to reduce impacts from aquaculture activities on wild salmon populations, although the likelihood of risk reduction if these measures were implemented is unknown.
  8. The relative severity of potential impacts from the proposed aquaculture sites relative to other anthropogenic sources can not be determined. However, these impacts have the potential to undermine the effectiveness of actions to improve the viability of salmon populations and to prevent their extirpation. All commercial and recreational fisheries have been closed in the oBoF, iBoF and SU. Live Gene Banking is currently being used to maintain the genetic diversity of iBoF salmon. Liming activities have been initiated in the SU DU. Fish passage improvements have been undertaken in all three regions. Activities that have the potential to jeopardize the survival of salmon in these regions need to be evaluated in the context of the activities that have been initiated to improve their survivability.

This Science Response report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Regional Science Special Response Process (SSRP) of December 1, 2010 on Potential Impacts to Wild Salmon Populations in the Vicinity of Two Proposed Finfish Aquaculture Sites in St. Mary's Bay, Nova Scotia.

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