The majority of crayfish species live east of the Rocky Mountains and in the Southeastern states. Many live in streams, rivers, and lakes, while others are restricted to springs, swamps, and even un- derground waters (cave crayfish). Native crayfish come in a variety of colors (white, blue, red, brown, gray, yellow), shapes, and sizes (1 to 6 inches in length).
Crayfish serve as important links in the food chain, feeding on living and dead plants, other invertebrates, and fish. They are a primary food for fish (bass), water birds (herons), mammals (raccoons), and others. In fact, over 240 species of wild animals in North America eat crayfish.
Like its saltwater cousin, the lobster, the crayfish is sold as gourmet food. Nearly 80,000 tons of crayfish, with a value of more than $200 million, are farmed in ponds or trapped in wetlands each year. Crayfish also are important indicators of water quality and environmental health, flourishing in clean waters and perishing in polluted waters. Most crayfish live from 2 to 4 years, although some cave crayfish may live over 10 years.
Crayfish are threatened by habitat destruction caused by dams, water pollution, erosion, siltation, in-stream gravel dredging and, particularly, the introduction of nonnative crayfishes and other exotics. About 65 species of crayfish are endangered, threatened, or listed as species of special concern by the states in which they live, and 48 percent of our native crayfish species are in need of protection. These numbers are best estimates only. The exact status of crayfish endangerment or extinction rates in the United States is largely unknown because very few distribution and population surveys have been completed.
Most Americans believe that we should protect our native aquatic animals as a legacy to our children. Citizens can help safeguard life in our waterways. To protect our aquatic biodiversity, they can join conservation groups, adopt a local stream or river, and report all suspected water pollution problems to state natural resource agencies.
What Is a Crayfish?
Crayfish are small lobster-like animals that live in freshwater streams, ponds, lakes, swamps, and marshes throughout the world. They are invertebrates (animals without a backbone) that belong to a group called the Arthropoda (joint-footed) animals related to the insects, spiders, scorpions, millipedes, and mites. They belong to the group Crustacea (shell) and the order Decapoda (ten legs).
Some say the name comes from the word “cray” which refers to a hole or burrow. Carapace Others believe it is from a French word meaning “crevice.” Some crayfish dig and live their entire lives in burrows. Native American crayfish are a diverse and interesting group of aquatic animals; they come in a variety of sizes, shapes, colors, and forms.
What do they look like?
Crayfish, as other Crustacea (crabs, lobsters, and shrimp), are heavily armored with a hard exoskeleton or “shell,” that must be shed periodically so that the animal can grow. This exoskeleton serves to protect the crayfish from predators and provides a framework for the body. Despite its hard armored shell, the crayfish is agile and fast, thanks to flexible, jointed segments.
The body of the crayfish consists of two sections:
- the front of the body called the cephalothorax (head and chest) and,
- the abdomen or rear half of the body.
The cephalothorax of the body is entirely covered by the shell (carapace), whereas the back part of the body or abdomen consists of seven jointed segments and a large, fan-like tail.
They have two large, compound eyes consisting of thousands of eyelets (providing a mosaic view like that of insects) supported on stalks.
They use their two kinds of antennae (short, jointed inner antennules and long outer antennae) to taste the water and find food. The inner antennules are used for chemoreception (tasting the water and food). The outer ones are used for the sense of touch. The over-lapping mouth parts and heavy tooth-like mandibles are used to crush and shred food before it is eaten.
Crayfish have ten legs (one pair of large claws and four pairs of slender walking legs). The first pair of legs has the claws (pincers), which are used for defense, mating, burrow building, egg laying in females, and feeding. These strong claws are specialized for capturing, cutting, and crushing food. Their pinch can hurt. When threatened, the crayfish assumes a defensive position with the body lifted and the claws elevated and spread. At this time the crayfish may retreat slowly by walking backwards.
The first two pairs of small walking legs are tipped with small pincers that are used to probe in cracks and holes for food, and are used for eating, walking, and grooming. The last two pair of legs are used for walking and mating. Crayfish can regenerate their limbs if they are broken off, but regenerated legs and claws often are smaller or misshapen when compared to the originals.
The large, fan-shaped tail, flattened from top to bottom, is used for quickly swimming backwards. Large muscles in the abdomen curl the tail fan forward beneath the body propelling the crayfish rapidly backwards. Typically crayfish walk slowly forward on their legs, but if they are startled, crayfish use rapid flips of their tails to quickly swim backwards in a series of jerking movements to escape danger.
Crayfish breathe by internal gills like fish, but many (especially burrowing crayfish) can remain out of water for considerable amounts of time under humid conditions. The plume-like gills are located in gill chambers on each side of the body. Gill flaps attached to the mouthparts help circulate oxygenated water for breathing.
Scientists use the size, shape, color, shell markings, and reproductive organs to identify the many species. Crayfish can vary in color from white to blue to red to green to black or brown. Most crayfish are brown-green in color in order to blend into the stream bottom and hide from predators.