Freshwater Fish, Pacific Northwest
The Crayfish is typical of most shrimp like crustaceans and is characterized by a joined head and thorax, or midsection, and a segmented body, which is sandy yellow, green, white, pink or dark brown in color.
Crayfish have two pairs of sensory antennae and a pair of eyes on movable stalks. The appendages of the thorax include four pairs of walking legs which, as well as walking, are used to probe cracks and crevices between rocks looking for food. Crayfish also own one pair of claw bearing legs, which it extends in front of its body while moving. The claws are specialized for cutting, capturing food, attack, and defense. A pinch can hurt! The crayfish also has several pairs of specialized food handling legs.
They have a hard outside skeleton. This jointed exoskeleton provides protection and allows movement, but limits growth. As a result, they regularly get too big for their skeletons and shed them to grow a new larger one. This is called molting. and occurs six to ten times during the first year of rapid growth, but less often during the second year. For a few days following each molt, they have soft exoskeletons and are more vulnerable.
Crayfish are common in streams and lakes and often conceal themselves under rocks or logs. They are most active at night, when they feed largely on snails, algae, insect larvae, worms, and tadpoles; some eat vegetation. Studies show that mature adults become most active at dusk and continue heavy feeding activity until daybreak while young crayfish are more likely to be the ones out during the day.
Most live short lives, usually less than two years. They are very tasty and easily harvested in our rivers and lakes.