Managing transfers and fish health at British Columbia salmon farms

Fish health on British Columbia salmon farms is managed throughout the production cycle to maintain healthy fish populations and to identify and address disease occurrences as soon as they arise. Aquaculture licence conditions set out mandatory monitoring and reporting requirements to ensure any potential impacts are appropriately mitigated at salmon farms.

A central component of on-farm fish health management is a Fish Health Management Plan (FHMP). FHMPs are approved by Fisheries and Oceans Canada (DFO) and describe the fish health principles that the licensee must follow to maintain fish health and biosecurity at the farm.

Both DFO and aquaculture companies have veterinarians on staff (or available on contract, for some companies) to monitor fish health on farms. Company veterinarians oversee routine health screening and ensure appropriate husbandry in day-to-day operations and identify appropriate management measures if fish health concerns arise.

Licence holders must routinely submit a variety of fish health data to DFO. Routine reports include monthly sea lice abundance, antimicrobial use and information on mortality rates, including the suspected cause of mortality. Additional reports are submitted if there are elevated mortalities, a fish health event that requires the involvement of a veterinarian or sea lice abundance over the DFO determined threshold.

Through the Fish Health Audit and Surveillance Program, DFO oversees the health of cultured salmon to minimize fish health and disease risks to wild and farmed fish and publishes reports on regulation and monitoring of BC’s marine finfish aquaculture facilities. Sites are routinely inspected to ensure compliance with licence conditions and FHMPs, to verify the accuracy of industry reporting, and to collect samples for independent fish health and disease screening.

All salmon aquaculture transfers require authorization under section 56 of the Fishery (General) Regulations. Movements of fish to and from farms may be required to introduce new stock, facilitate growth at different life stages or optimize production. All transfer applications are accompanied by a signed veterinary attestation which details the health status of the fish to be transferred and attests to their health. DFO reviews these applications to determine whether the movement may adversely affect local aquatic species and habitats.

DFO veterinarians and biologists assess the information gathered by DFO audits and inspections, as well as that submitted by industry to gain a complete picture of the health status of the fish to be moved. Occasionally a fish health concern will be identified during the review conducted by DFO fish health staff. Most often, clarification with the industry’s fish health staff will be sufficient to address the concern; however occasionally additional mitigative measures are deemed necessary to address potential risks. Animal welfare and ensuring humane treatment of the fish are an important consideration when choosing the most appropriate mitigation option.

Common mitigation measures include:

• Pre-transfer grading to select the healthiest fish within the age class

• Humane culling to remove affected fish or “poor performers” that are most likely to harbour disease or unlikely to ingest medicated feed. Poor performers are fish that fail to thrive, stop or reduce feeding, and may be emaciated (long and skinny). There are various reasons a fish becomes a poor performer, including failure to adapt to salt water entry.

• Pre-transfer antibiotic treatment

• Post-transfer monitoring and reporting to ensure that any ongoing issues are addressed and reported quickly to DFO

• Freshwater bath treatment during transfer to kill off Paramoeba that may affect the gills of farmed Atlantic salmon.

• In some cases, a transfer itself is the appropriate mitigation measure. Reduction in the number/density of fish on the farm decreases the likelihood of pathogen transfer between fish and reduces stress on fish, promoting a healthy culture environment.

If the fish health risks can’t be mitigated to the satisfaction of DFO, then the transfer will be denied.