Science Response 2011/017

Fish Populations in the Vicinity of Three Proposed Finfish Aquaculture Sites in Shelburne County, Nova Scotia

Context

On May 31, 2011, Fisheries and Oceans Canada’s (DFO) Habitat Management Division, Maritimes Region, requested that DFO Science, Maritimes Region, provide advice regarding wild salmon and other fish populations in the vicinity of three proposed finfish aquaculture sites at Middle Head, Jordan Bay and Blue Island in Shelburne County, Nova Scotia. The impact of the proposed development project on wild salmon populations and the likelihood of negative effects on the wild salmon populations and their habitat are provided to enable DFO Aquaculture and Habitat managers to assess the risk of these proposals with respect to wild salmon. A list of the fishery resources to be considered in assessing the risk to other fish populations is also documented. The request for advice is in support of Habitat Management’s review of an environmental assessment (EA) of a proposed aquaculture development project pursuant to the Canadian Environmental Assessment Act. Specifically, Habitat Management asked:

Wild Salmon Populations

1. To determine the risk of genetic impacts or parasite or disease transmission to wild salmon populations (and their lifecycle stages) from the proposed aquaculture sites, Habitat Management is requesting Science advice regarding the salmon populations that are known to be or are potentially present in the vicinity of the proposed finfish aquaculture sites at Middle Head, Jordan Bay and Blue Island, Nova Scotia and their relative abundance.
2. To determine the extent and duration of the potential impacts to wild salmon populations, Habitat Management is requesting Science advice on the times of the year and the duration that wild salmon would be expected to be in the vicinity of the proposed aquaculture sites.
3. To determine the impacts of escaped fish on salmon reproduction, Habitat Management is requesting Science advice on which freshwater systems in the vicinity of the proposed sites currently have successful salmon spawning that could be impacted by the escaped fish and what those potential impacts might be.

Other Fish Populations

4. Within the general vicinity of the proposed aquaculture sites, are important fishery resource species missing from the attached table, and is there any critical or valuable habitat for these species in the area.

DFO’s Science Special Response Process was used to respond to this request due to the short deadline for advice of August 31, 2011. This Science Response report was developed and reviewed through email correspondence. No review meeting was held. The conclusions of this Science Response are:

1. The proposed aquaculture sites are in the Atlantic Salmon Southern Upland Designatable Unit (DU). This DU was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in November 2010.  The 2008 Conservation Status Report conclusion that there: “is no scope for additional harm in the southern most CUs (Conservation Units),” places Southern Uplands DU salmon in the Extreme Impact category (5) and is consistent with the statement: “Species, stock, or population is already threatened or endangered: further impact may lead to permanent loss” (Appendix 1).
2. Genetic effects have been clearly demonstrated to occur in the conditions existing in the Southern Upland DU.  Thus, likelihood in a plausible range of 2 – 4 is warranted, i.e., “has occurred infrequently before to others in similar circumstances,” to: “has occurred more than once, or is occurring to others in similar circumstances” (Appendix 2).
3. Redd disturbance and competition occurs among wild salmonids; the establishment by escaped farmed fish in wild rivers indicates that the likelihood of competition and disturbance effects is expected.   Therefore, the likelihood that these will occur is at least 2: “has occurred infrequently before to others in similar circumstances” (Appendix 2).  There is not enough known about these effects to describe a plausible range for the circumstances considered in this document.
4. The likelihoods that wild migrating salmon will encounter the sites and that if escapes occur they will encounter wild salmon have been identified as ranging from 2 – 4.  That is, likelihoods range from: “has occurred infrequently before to others in similar circumstances,” to: “has occurred more than once, or is occurring to others in similar circumstances” (Appendix 2). In the absence of a direct link, no advice can be offered on the likelihood of effects on disease transmission when these encounters occur.  The risk assessor must balance the likelihood that an encounter will occur with the circumstantial evidence associated with suspected cases of disease transmission and pathogen or parasite transfer.
5. The likelihood of wild/farmed salmon interaction effects will increase as the number of sites and total individuals among sites increases.

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