Fish Die-off in the Thames River (media release, February 4, 2021)

London, ON – The Upper Thames River Conservation Authority (UTRCA) was recently alerted to a large die-off of fish in the Thames River in London. The fish are Gizzard Shad, a species that is prone to large wintertime die-offs.

“The most likely cause of the die-off is a combination of stressful winter conditions, high numbers of fish, and the presence of an infectious fish disease called Viral Hemorrhagic Septicemia (VHS) in the Gizzard Shad population,” explained Michelle Fletcher, the UTRCA Aquatic Biologist who visited the site earlier this week.

“To survive the winter, thousands of Gizzard Shad will gather around warm water outputs, such as the outlets from the wastewater treatment plants or underground storm sewer network,” said Fletcher. “However, while a die-off may occur near these sites, it does not mean that it is the result of something released from these sites, such as a spill or environmental pollution.”

The Ontario Ministry of the Environment, Conservation and Parks (MECP) is aware of this die-off and does not believe it is related to a spill or environmental pollution.

The Ontario Ministry of Natural Resources and Forestry (MNRF) is also aware of the die-off and will be recording additional die-offs, should they occur, throughout the winter.

• Report a large fish die-off (more than 100 fish) to the MNRF: 1-800-667-1940
• Report a spill to the MECP: 519-873-5199 (during business hours) or 1-866-663-8477 (outside of business hours)

More information:

• Photos of Gizzard Shad
• Video – Michelle Fletcher, UTRCA Aquatic Biologist explains why we have been seeing thousands of Gizzard Shad in the Thames River this winter in London
• Webpage about Gizzard Shad
• Viral Hemorrhagic Septicemia (VHS)

Contact: Michelle Fletcher, Aquatic Biologist, or Steve Sauder, Marketing Specialist