Hugh Cai¹, Kerry Hobden², Peter Addison², Lowia Al-Hussinee¹, Pat Bell-Rogers¹, Nathan Bennoit¹, Tanya Brock¹, Calvin Kellendonk¹, Lisa Ledger¹, Fernando Munevar¹, Pauline Nelson-Smikle¹, Heindrich Snyman¹, Qiumei Yu¹, and Maria Spinato¹

¹Animal Health Laboratory, University of Guelph, Canada / ²Ontario Ministry of Natural Resources, Canada

AHL Newsletter 2025;29(4):22.

Supporting Ontario’s Fisheries and Biodiversity

Ontario’s fish culture and stocking program is a cornerstone of the province’s recreational fishing and biodiversity restoration efforts. Each year, 9 fish culture stations (3 of which also have separate sub-stations) raise and release more than 6.5million fish into over 1,200 lakes and rivers, sustaining a vibrant recreational fishery enjoyed by 1.2 million anglers and contributing $1.7 billion annually to the provincial economy.

To ensure the health of these stocked fish—and to protect wild populations—the Ontario Ministry of Natural Resources (MNR) partnered with the University of Guelph’s Animal Health Laboratory (AHL) to conduct a comprehensive fish health monitoring program from 2022 to 2025.

Comprehensive Testing and Strong Results

Over the three-year monitoring period, 6,930 fish from multiple species - including Atlantic salmon, brook trout, brown trout, chinook salmon, lake trout, rainbow trout, splake, lake whitefish, and walleye - were sampled across MNR facilities.

In total, 16,162 tests were conducted, including:

• 9,512 PCR tests,
• 4,923 bacterial cultures,
• numerous necropsy and histopathology assessments.

Results revealed very low pathogen detection rates, with only 0.9% of PCR tests returning positive results. Importantly, no detections were made for key notifiable viral pathogens such as IHNV, ISAV, IPNV, VHSV, or the parasite Myxobolus cerebralis (whirling disease agent).

Bacterial culture results were also encouraging; 87% of fish samples showed no bacterial growth or only growth of non-pathogenic species.

Effective Biosecurity and Ongoing Vigilance

These findings highlight the effectiveness of MNR’s biosecurity, surveillance, and health management programs in maintaining healthy hatchery populations. The low rate of pathogen detection and absence of major reportable diseases demonstrate that current fish health safeguards are working as intended.

Ongoing monitoring remains vital to:

• safeguard fish health,
• prevent potential disease outbreaks,
• support biodiversity restoration and sustainable recreational fishing across Ontario.

Acknowledgements

The project team extends sincere thanks to the MNR hatchery staff and field biologists for their commitment and expertise, and to the AHL Specimen Reception staff for their assistance.