Pacifastacus fortis (known as the Shasta crayfish or placid crayfish) is an endangered crayfish species endemic to Shasta County, California, where it is found and first described in 1914, only in isolated spots along the Pit River and Fall River Mills. It is estimated that there are a total of roughly 4000 of the species still alive today. The exact subpopulations for the Shasta crayfish were discovered in 2004 through a genetic study that determined three different genetic clusters: Crystal Lake, the Big Lake group (which includes Big Lake Springs, JeShe, Lava, and Spring Creeks), and Thousand Springs.
Description and ecology
P. fortis is thick and stocky, with relatively heavy chelae. It is usually dark brown dorsally with bright orange areas on its underside. These colors aid in camouflage in its habitat. It grows about 2-4 inches long. It lives in cold, clear, rocky areas of the mountain rivers, and feeds on microbes, algae, and small animals like snails. In October, females typically produce anywhere from 10 to 70 eggs per year, with the older more mature females producing the most eggs and the younger females producing at the lower end.
Causes of endangerment
Pacifastacus fortis is listed as a critically endangered species on the IUCN Red List, However, human intervention affects the species at a much greater proportion. Urbanization, pollution, and other forms of intervention often affect the surroundings of P. fortis, ultimately resulting in significant habitat loss and consequently, a significant decrease in population.
It has always had a very small native range, and that range has been significantly fragmented by such human activities as damming, mining, and agriculture. The Pit River Fish Hatchery was closed to protect this species.
Other nonnative invasive crayfish species such as, Pacifastacus leniusculus, Orconectes virilis, and the Signal Crayfish, as well as water impoundment and diversion have contributed to the continuing decline of P. fortis. Chemicals from agriculture have also washed into streams, and groundwater has been pumped to the point of lowering the water table, further decreasing the numbers of P. fortis over the last three decades. Hydroelectric operations in the area have also contributed to habitat loss, destroying almost all of the preferred substrate of Pacifastacus fortis.
Conservation efforts
The Shasta crayfish was designated as a rare species by California law in 1980 and an endangered species in 1988 both by the State of California and by the Federal Government. Throughout numerous 5-year species reviews from 1988 to 2013, this endangered classification has not changed. The goal of this conservation effort was to create an isolated population of Shasta crayfish that was inaccessible to the invasive signal crayfish which currently outcompetes the native species for food while also contributing to the decline of fertility in the Shasta due to interbreeding between the species.