The Calaveras River is an unusual tributary to the San Joaquin River in California’s Central Valley, being fed mostly by rain rather than melting snow. This creates a flashy system similar to a coastal stream. Historically, the Calaveras would flood in the winter and dry up in the summer, with some sections going completely dry and creating disconnected pools. The construction of reservoirs has changed the patterns of the river by maintaining a more consistent flow of water year-round, which has allowed fish like rainbow trout/steelhead (Oncorhynchus mykiss) to persist where historically they would have occurred only sporadically.
Since 2001, FISHBIO has conducted a long-term monitoring program for O. mykiss on the Calaveras River. Program activities include rotary screw traps, snorkel surveys, benthic macroinvertebrate sampling, redd surveys, temperature monitoring, and fyke netting. FISHBIO staff regularly tag captured O. mykiss with surgically implanted 23-mm PIT tags to study life-history variation in this species. FISHBIO is also working to develop a Habitat Conservation Plan for the Calaveras River that provides measures to address potential effects of Stockton East Water District and Calaveras County Water District operations on salmonids, and lists conservation measures to minimize and mitigate for any identified impacts.