Rusty crayfish facts for kids

Quick facts for kids Rusty crayfish
Rusty crayfish (Faxonius rusticus) in Guelph, Ontario, Canada
Rusty spots on sides of carapace
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Crustacea
Class:	Malacostraca
Order:	Decapoda
Family:	Cambaridae
Genus:	Faxonius
Species:	F. rusticus
Binomial name
Faxonius rusticus (Girard, 1852)
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Synonyms
Cambarus rusticus Girard, 1852 Orconectes rusticus (Girard, 1852)

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The rusty crayfish (Faxonius rusticus) is a large and tough type of crayfish that lives in fresh water. It originally comes from the Ohio River area in the United States, including parts of Ohio, Kentucky, and Indiana. These crayfish are now spreading quickly across eastern North America. They are taking over places where native crayfish used to live.

The rusty crayfish was first found in Illinois in 1973. By 2005, it had even reached the John Day River in Oregon, west of the Continental Divide.

What They Look Like

Measuring a rusty crayfish

So, how can you tell a rusty crayfish apart from other crayfish? They have some special features!

• Size: Adult rusty crayfish can grow to be about 10 centimeters (that's about 4 inches) long. That's roughly the length of a standard crayon! They become grown-ups when they are about 4.4 centimeters (1.7 inches) long.
• Color: Their bodies can be different shades, from a greenish-grey to a reddish-brown.
• The "Rusty" Spots: This is their most famous feature and how they got their name! If you look closely at the sides of their back shell, you might see two reddish-colored spots that look a bit like rust. These spots can be a little different on each crayfish, but they are a great clue to identify them.
• Big Claws: Rusty crayfish have large front claws, which they use for many things, like finding food, defending themselves, and even digging. These claws often have cool black bands around their tips, like little gloves!

• 

  Male rusty crayfish in Illinois

How They Behave

Two adult male rusty crayfish fighting

Many animals, including some vertebrates (animals with backbones) and even some invertebrates (animals without backbones), create a "pecking order" or dominance hierarchy. This helps them set up who is in charge in their group. For crayfish, this order is very important to how they live.

Crayfish often form these groups with others in their area. The biggest male usually shows the most power by being the most aggressive. He might pick fights with smaller crayfish. The crayfish that wins the most fights becomes the leader. Other crayfish usually rank below him based on their size and whether they are male or female.

Invasive Species

While rusty crayfish are fascinating, their ability to travel and be tough has also made them a bit of a problem in many places. When they move into a new body of water where they don't naturally belong, they are called an "invasive species." This means they are like a super-traveler that takes over new homes.

Here's why they can be a problem:

• Tough Fighters: Native fish in these new areas aren't used to crayfish that fight back. Most native crayfish would try to run away from a predator, but the rusty crayfish is different. When a fish comes near, the rusty crayfish will often stand its ground, raising its big claws above its head in an "attack stance." This can scare away many fish that are used to an easy meal.
• Too Big to Eat: Adult rusty crayfish can grow quite large, sometimes too big for many fish to eat. This means fewer predators can keep their numbers in check.
• Taking Over Homes: Because they are so good at avoiding predators and are very aggressive, rusty crayfish populations can grow incredibly fast in new places. Within just twenty years, their numbers can explode! This has happened in the Northern United States and parts of Canada.
• Pushing Out Neighbors: When rusty crayfish move in, they often take over the homes and food sources of the native crayfish species. They are like a very pushy neighbor! This has caused many native crayfish populations to shrink drastically over the past fifty years, and the rusty crayfish has become the dominant species in much of the Midwestern United States.

Controlling Their Spread

Once rusty crayfish have moved into a new lake or river, it can be very, very difficult to get rid of them completely.

So, the best way to help is to stop them from spreading even further. Here are some important things we can all do:

• 'Learn to Identify Them: Knowing what a rusty crayfish looks like (remember those "rusty" spots and black-tipped claws?) is the first step!
• Don't Move Them: If you're fishing or exploring, never use rusty crayfish as bait, and never move them from one body of water to another. Even if you think you're helping them, you could be causing big problems for the native animals in their new home. It's super important to keep animals in their natural habitats.
• Clean Your Gear': If you've been in a lake or river, make sure to clean your boats, fishing gear, and even your shoes to avoid accidentally carrying tiny crayfish or their eggs to a new place.