The monitoring season for Asian carps has been a busy one for our partners at the Department of Fisheries and Oceans (DFO) and staff with our Invading Species Awareness Program (ISAP), with three Grass Carp having been captured to date in 2023.


Grass Carp is one of four invasive Asian carps, along with Black Carp, Bighead Carp, and Silver Carp, and it can consume up to 40% of its body weight each day in aquatic vegetation. Grass Carp, if it becomes established, would have extreme consequences on our aquatic habitats and our native fish species.


On June 20th DFO captured one while they were conducting early detection surveillance in the Grand River, near Dunnville. Once analyzed, it was determined the fish was a sterile male that weighed 8.29kg (approx. 18lbs).

On July 3rd a commercial fisher caught, reported and transferred a Grass Carp to the Lake Ontario Ministry of Natural Resources and Forestry (MNRF) Unit. The fish was then given to DFO, and it was determined to be a fertile female. Upon learning the fish was fertile, MNRF and DFO crews searched the nearby waters for five days and found no additional Grass Carp.

The third capture occurred on August 16th and was captured by a fisherman, who then reported the fish to the ISAP via the Invading Species Hotline. The fish had been circling near the surface of the water and the angler, recognizing the fish as a Grass Carp, was able to net the fish before reporting it. ISAP then coordinated with DFO and the angler to ensure the fish ended up with DFO biologists the same day. Once analyzed, it was determined to be sterile.


“Despite capturing more Grass Carp than we would like in 2023, this year shows how collective work between government, commercial fishers, and recreational anglers can assist in the protection of our environment and our fisheries from unwanted invaders,” says ISAP coordinator, Alison Morris.

REPORT: If you suspect you’ve seen a Grass Carp, note your location, capture a photo, and report it to the Invading Species Hotline (1-800-563-7711) or report online at

I.D: For what to do with a Grass Carp if you capture one as well as how to tell the difference between a Grass Carp and native lookalike species, click here.