Shasta crayfish are documented to live between 10 to 15 years.

Shasta crayfish reach reproductive maturity at 5 years of age. Females can produce one brood of offspring per year containing 10 to 70 eggs.

Mating occurs in late September and October, with fertilized eggs appearing in October to November. Females carry their fertilized eggs on the underside of their abdomen or tail, and the eggs incubate for one to two months. Hatchlings appear in May and the young crayfish remain attached to the females until they are 0.2 to 0.3 inches long and then become free-living.

The Shasta crayfish was first described in 1914 from the Fall River at Fall River Mills and Hat Creek at Cassel. The historical range of the Shasta crayfish is assumed to have been restricted to cold, clear spring water with rocky substrate found in the Pit River drainage in northeastern Shasta County, California, with its distribution throughout the Fall River, Tule River, Hat Creek, Rising River and the segment of the Pit River that joins these drainages which is upstream of Fall River Mills.

The current range of the Shasta crayfish remains limited to Shasta County, California, and has further constricted to only being found in the Pit River drainage and two tributary systems—the Fall River and Hat Creek subdrainages. In the Hat Creek subdrainage, populations have been found in Lost Creek and in Crystal, Baum and Rising River Lakes. In the Fall River subdrainage, populations occur in the following bodies of water: Fall River; Big Lake, also known as Horr Pond; Bit Tule River; Spring, Mallard, Squaw and Lava creeks and Crystal, Thousand and Rainbow springs.

Shasta crayfish are opportunistic eaters and feed mainly at night. The main food source for the Shasta crayfish is unknown. However, it likely feeds on dead fish, algae and aquatic invertebrates, like snails. They compete with signal crayfish and virile crayfish for food and habitat.

Shasta crayfish are small to medium-sized crayfish that grow to be 2 to 4 inches in length and grow 0.04 to 0.12 inches (1 to 3 millimeters) with every molt. Male Shasta crayfish adults have narrower abdomens and larger pincer-like claws than the females. The first two pairs of swimmerets, tiny swimming legs, of the males are hard and modified for sperm transfer to the female during mating.

Measurements
Length: 2 to 4 in (50 to 102 mm)

Most Shasta crayfish are a dark brownish-green on the topside and a bright orange underside, but some can be blue-green with pink undersides. These colors provide camouflage for the crayfish among the volcanic rubble found in the cold water streams where it lives.