What Ontario is Doing
To prevent this unwanted invader from coming into the province, Ontario has regulated Common Yabby as prohibited under the Invasive Species Act. For more information on the Invasive Species Act and Regulations visit www.ontario.ca/invasionON.
Common Yabby is a freshwater species of crayfish. It is a bottom dweller that is found in a wide variety of aquatic habitats including lakes, rivers, streams, ponds, billabongs and reservoirs Common Yabby is an exceptional invader, characterized by having broad environmental tolerances, maturing at early ages, reproducing several times a year, and being able to migrate over many types of landscape through its ability to breathe air. It is highly adaptable to changing habitat conditions, and can survive long periods of drought conditions by burrowing into the substrate and entering a state of dormancy. Yabbies are opportunistic omnivores that feed on algae, plants, decaying matter, invertebrates, and fish and animal remains.
The native range of the Common Yabby is Southern Australia. Living in swamps, streams, reservoirs, and rivers, it can also survive for long periods in areas where a body of water has dried up by lying dormant in burrows in the mud. In their native range, Common Yabby is used as bait and is farmed for food, being considered a delicacy. Common Yabby are also a popular aquarium species. Outside of its native range, Common Yabby has been introduced to Tasmania, Spain, Italy, China, The Netherlands, South Africa, Zambia and Switzerland. This species has not been documented in the wild in North America, either in the United States or in Canada.
Impacts of Common Yabby
Being opportunistic omnivores, this species of crayfish will eat just about anything; from algae and plants, to zooplankton, to frog eggs, to decomposing matter like fish or animal remains. It is a strong competitor, and has displaced other native crayfish species in Western Australia once it was introduced to the area. They are aggressive making it easier for them to push out native species for food and habitat, reducing biodiversity and changing the species composition of ecosystems. They are also vectors for diseases to which native species may be vulnerable.
Yabbies mature at a young age, about a year for females, and even sooner for males. Once mature nearly all female Yabbies spawn, producing an average of 300 eggs each spawning event. Once the young have left their mother in the early spring, she will breed again, producing another 300 eggs on average, increasing their population size at staggering rates. Because Common Yabby is so aggressive and is a prolific breeder, it can easily take over an area and have ecological impacts. Its burrowing activity could also have impacts on nearby agriculture or cause infrastructure damage due to the destabilization of riverbanks.
How to Identify
Common Yabbies are large crayfish that have a hard covering called a carapace. Physical characteristics include:
- Typically about 10-20 cm in length (approximately 4-8 inches),
- There are four ridges that run from behind the eyes on top of the head to the back of the head segment
- The rostrum (the area between the eyes) is smooth
- Colours of Yabbies can vary widely depending on water conditions, season, and location, but could include green-beige to almost black or blue-grey with a dirty-white to grey belly. Common Yabby bred for the aquarium trade are often bright blue.
What You Can Do
- Learn how to identify Common Yabby and how to prevent the introduction or spread of this unwanted species.
- Never buy or keep Common Yabby for bait or as a pet. It is against the law to have Common Yabby in your possession.
- Don’t release any unwanted aquarium pets or bait into Ontario lakes or rivers. Dispose of them in the garbage or at least 30 meters away from any water body.
- If you have any information about the illegal importing, distribution or sale of Common Yabby, report it immediately to the MNRF TIPS line at 1-877-TIPS-MNR (847-7667) toll-free anytime. You can also call Crime Stoppers anonymously at 1-800-222-TIPS (8477).
- If you’ve seen a Common Yabby or other invasive species in the wild, please contact the toll free Invading Species Hotline at 1-800-563-7711, or visit EDDMapS Ontario to report a sighting.
OFAH/OMNRF Invading Species Awareness Program. (2016). Common Yabby. Retrieved from: www.invadingspecies.com.
This factsheet may be reproduced for non-commercial purposes.
Header photo from Wikipedia Commons