| Yocum, McCollum | C.F., M.T. | Status of the fisher in northern California, Oregon and Washington. | 1973 | California Fish and Game 59(4):305-309 |
"Apparently fisher became very scarce during the 1920’s and 1930’s and remained at a low population level until the noticeable increase that occurred in the 1960’s and 1970’s in Humboldt, Trinity, and Del Norte counties. Possibly the increase in porcupines throughout these counties furnished a food supply that allowed fisher populations to increase." P. 305
This 1973 paper goes on to give accounts of fisher observations and records in California, Washington and Oregon.