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Amphibian Information in KRIS Big River

KRIS Web Background Pages: Sensitive Amphibians Main Page

Distribution of Sensitive Amphibians in the KRIS Mendocino Project Area


Amphibian data in KRIS Big River come from electrofishing surveys by Mendocino Redwood Company (MRC), and Hawthorne Timber Company. MRC collected data at approximately 20 sites in the Big River in the years 1994-1996, and 2000. As discussed on the Fish Population page, MRC did not use highly quantitative methods and did not revisit more than a few sites in all years. Surveys note only the presence and number of "frogs" and "salamanders" and only in database note fields are species such as yellow-legged and red-legged frogs mentioned. MRC data can be found in the four source tables (one for each year) behind MRC fish topics in KRIS Big River.

An aquatic vertebrate monitoring site in Two Log Creek, and another in the Little North Fork Big River, were established by Georgia Pacific in 1993 and are currently maintained by Hawthorne Timber Company.  Quantitative electrofishing surveys at these sites (and 24 in the Ten Mile basin) were conducted at the same time each year during the period 1993-2000.  The surveys follow protocols described in Ambrose and Hines (1998), and offer high quality species-level data for interpretation of local population trends at two sites in the Big River basin (see charts below).  

Although the two large timber companies managing land within the Big River basin have made an effort to include information on amphibians when reporting electrofishing results, information on sensitive amphibians in the Big River is sorely lacking.  Aside from the two sites currently maintained by Hawthorne Timber Company, no monitoring program exists to generate data on amphibian population trends. Nevertheless, studies could be conducted to explore relationships between riparian habitat change in the Big River Basin and the presence or abundance of sensitive amphibians. USFS vegetation data and water temperature data is readily available in KRIS Big River for analyzing riparian and water quality conditions. Studies in the Mattole Basin have examined  linkages between riparian conditions and amphibian populations, and these represent the best information available on the topic in northwestern California. Samples from HTC show Pacific giant salamanders and yellow-legged frogs as the only amphibian species present, and MRC field notes make no mention of tailed frogs and southern torrent salamanders. The latter two species are known to have occurred in the area (see notes on distribution) and their absence in most of the Big River is consistent with the early seral canopy conditions and elevated water temperatures in much of the basin.

KRIS Big River charts derived from data provided by Hawthorne Timber Company

amph_twolog.gif (16591 bytes)

This chart shows the number of amphibians captured at site BIG4 in Two Log Creek from 1993 to 2000.  Pacific giant salamander and yellow-legged frog were the only amphibian species captured. Both these species can more readily adapt to changes in canopy conditions and water temperature than tailed frogs or torrent salamanders. Data provided by the Hawthorne Timber Company.


amphi_lnf.gif (15031 bytes) The Little North Fork Big River was sampled by HTC from 1993 to 2000 and a chart of results is at left. Like in Two Log Creek, Pacific giant salamanders and yellow-legged frogs were the only amphibian species captured. Data provided by the Hawthorne Timber Company.


Ambrose, J., and D. Hines. 1998. Ten Mile River Watershed 1997 Instream Monitoring Results. Georgia-Pacific West Inc. dba The Timber Company. Fort Bragg, CA. 51 pp.

Welsh, H.H. Redwood Sciences Laboratory, Arcata, CA.