Captivating Crayfish

Hand wearing a glove and holding a crayfish.

How Well Do You Know Crayfish?

Crayfish are a fascinating group of animals with incredible adaptations that make them perfectly suited to their environment. Here are six amazing facts you might not know about crayfish.

1. Five different species live in the Credit River Watershed

There are five native species of crayfish in the watershed. While non-native species like the rusty crayfish dominate some streams in the Greater Toronto Area, non-native crayfish aren’t in the Credit River. Remember, never move species and always clean watercrafts and fishing gear when moving between bodies of water. Read the Anglers Invasive Species Action Plan to learn important practices to prevent introduction of invasive species.

Crayfish face many of the same pressures as other freshwater animals, like invasive species, urbanization and climate change. Aquatic invertebrates, like crayfish, insects and other crustaceans, tell us a lot about the health of streams and how streams are responding to these pressures. Through our Integrated Watershed Monitoring Program (IWMP), we use aquatic invertebrates as indicators of stream health. A diverse group of invertebrates is a sign of a healthy stream.

Crayfish in water
Virile crayfish is common species in streams across in the watershed.

2. They have ten “feet

Crayfish are invertebrates which mean they don’t have a backbone and are part of a group called decapods, which literally means “ten-footed” (or ten-legged). The first pairs of legs are modified into multi-purpose claws, called chelae. Other decapods include lobsters, crabs and shrimp.

3. They breathe through gills

Like other crustaceans that live in water, crayfish use gills to breathe. Crayfish gills can even draw oxygen from the air, allowing them to survive out of the water as long their gills stay moist.

4. They’re not picky eaters

Crayfish are an important part of the food web. As omnivores, they feed on just about anything: plants, invertebrates, small fish and decaying plants or animals. Crayfish themselves are preyed upon by fish, birds, mammals and even other invertebrates.

5. They stick with their moms, literally, when first born

Female crayfish release a sticky substance that allows fertilized eggs to attach to the underside of their abdomen. Once the eggs hatch, the tiny crayfish stay attached for several more days until they grow big enough to survive on their own.

Crayfish upside down, carrying eggs on its tail.
Egg-carrying female crayfish are described as: in berry.

6. Some are underground excavators

While we usually think of streams, ponds, lakes and wetlands as crayfish habitat, some species live away from open water. Burrowing crayfish dig tunnels deep into the ground where the water table is high or where the soil is moist. Some of these species build chimneys at the top of their burrows, made from mud bulls.

Crayfish may be small but they play a big role in helping us understand the health of the Credit River. Learn more about conditions and trends in streams and other ecosystems across the watershed through our interactive IWMP StoryMap Collection.

Have crayfish photos of your own? Share them with us on Facebook, Twitter and Instagram.

By Adrienne Ockenden, Watershed Monitoring Specialist

Comments (5)

  1. I have an owl box on my property near the Credit River. It has only been occupied once for a couple of days by an Eastern Screech Owl. Sometime after it left, I cleaned out the owl box, and in it was a small owl pellet. Something orange coloured in the pellet caught my attention, and when I broke it apart, the orange object turned out to be a tiny crayfish claw. I didn’t know Screech Owls ate crayfish!

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