Science Response 2022/023
Fallowing as a Tool for Disease Mitigation in Marine Finfish Facilities in British Columbia
Context
Fisheries and Oceans Canada’s (DFO) Aquaculture Management Division (AMD) is the lead regulatory body for managing aquaculture in British Columbia (BC). The aquaculture management regime in BC is robust and complex, with oversight from provincial and other federal regulatory agencies. Licences are the primary tool used to manage this fishery, and are issued under the authority of the Pacific Aquaculture Regulations and the Fisheries Act. AMD licences marine finfish, marine shellfish, and land-based hatchery and production facilities, including approximately 111 marine finfish farms which are the focus of this review.
Currently, AMD requires farms to fallow prior to re-stocking a farm when benthic impacts are beyond acceptable levels to ensure seabed recovery. There is also an interest in determining if a fallow period based on the presence of pathogens or disease would be beneficial to reduce the risk of transmission between production cycles, in addition to other health management tools. This fallow period could be required by all farms as a precautionary approach, or could be performance based and only occur if active disease was present. To support AMD decision-making, a science-based understanding is needed to determine the factors that contribute to the benefits of fallowing in a BC context.
The use of farm-and area-level fallowing has been used in other countries as a strategy to reduce transmission of infectious pathogens between production cycles (Bron et al. 1993, Kilburn et al. 2012, McVicar 1987, Murray 2006; Rae 2002; Werkman et al. 2011, Wheatley et al. 1995). For example, Price et al. (2017) found that a 3-month farm-level fallowing was effective at significantly reducing the risk of Salmonid Rickettsial Septicaemia (SRS) between production cycles at farm sites in Chile. However, the effect of farm- and area-level fallowing has not been assessed for most pathogens that are endemic to BC waters. While fallowing is practiced voluntarily in BC, it is not regulated.
AMD has requested that the DFO Science Branch assess what is currently known about infectious pathogens found at BC Atlantic and Chinook salmon farms, in order to determine if fallowing can successfully minimize the transmission of pathogens between production cycles. Decreasing pathogens and disease on farms may also reduce the risk of transmission to wild salmon.
The assessment and advice arising from this Canadian Science Advisory Secretariat (CSAS) Science Response (SR) process will be used to inform AMD on the use of fallowing as an effective management tool to minimize the transmission of pathogens at finfish aquaculture farms in BC. The advice may be reflected in the conditions of license scheduled to be updated in 2022, and could inform area based management.
This Science Response results from the Regional Science Response Process of June 15, 2021 on Fallowing as a tool for disease mitigation in marine finfish facilities.
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