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Amphibian Information in KRIS Ten Mile

KRIS Web Background Pages: Sensitive Amphibians

Ten Mile River Basin amphibian data come from annual electrofishing of twenty four aquatic vertebrate monitoring stations since 1993 that are currently maintained by Hawthorne Timber Company. The electrofishing surveys were conducted at the same time each year, and would offer high quality data for interpretation of local population trends over the last nine years except that the focus of the surveys was salmonid fishes and, according to HTC staff, the consistency of effort toward capturing amphibians varied. Consequently, these data are used in KRIS Ten Mile only to note various amphibian species present and distributed among the 24 Ten Mile River Basin stations, and to show possible trends based on repeating patterns in the data among several sites. No study has yet examined the relationships between riparian habitat change in the Ten Mile River Basin and these sensitive amphibian data, but such relationships may be explored in KRIS Ten Mile by comparing USFS vegetation data to amphibian data at particular sites. 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.

KRIS Ten Mile River charts derived from data provided by Hawthorne Timber Company

This chart shows the number of amphibians captured at site SFT9 which is located near the headwaters of the South Fork Ten Mile River. Twelve tailed frog were captured at this site in 1998, the largest capture of this rare amphibian in the entire Ten Mile River Basin electrofishing data set. Three other sites detected presence of tailed frog, including the most upstream sites of the Middle Fork: CFT1 and CFT8. One tailed frog at NFT7 (Buckhorn Creek) in 1994 was the only detection in the North Fork Subbasin. Tailed frog were not found at any site in more than two years. The sites where tailed frog were found had some of the coolest water temperatures in the basin.

Yellow-legged frog were the second most abundant amphibian species in the electrofishing capture record. The data for site NFT9 on the North Fork Ten Mile River, represents one of several sites exhibiting a pattern of increasing Yellow-legged frogs abundance. See also data from NFT4, SFT5, and SFT7.

The following charts represent amphibian data in three tributaries of the South Fork, where a pattern of decline for Pacific Giant Salamander is repeated. A similar pattern is evident for Bald Hill Creek in the North Fork, and Lower Bear Haven Creek in the Middle Fork.


Number of amphibians captured in Lower Smith Creek	Number of amphibians captured in Lower Campbell Creek, .	Number of amphibians captured in Churchman Creek.

In addition to the number of animals captured, amphibian data is presented in KRIS Ten Mile as density and biomass for each site. Biomass may be a particularly good companion metric for monitoring Pacific giant salamander and other species where individual size varies greatly. Biomass and density values for amphibian data in the Ten Mile River Basin should not be used for comparison among sites because they under-represent true values in some cases. This bias is particularly large where high fish abundance saturated netters with their primary task of monitoring fish.

This scatter plot illustrates what correlation may exist between the number of steelhead present at a site and the number of Pacific giant salamanders captured at that site. The chart shows 251 points representing each site from 1993 to 2000. One could hypothesize a positive correlation based on the similar habitat requirements of these two species, or a deviation from positive based on interspecies competition. The chart does show how, according to Hawthorne Timber Company field staff, when steelhead were very abundant (>120), Pacific giant salamanders were less likely to be captured due to the saturation of netters and the priority placed on capturing salmonids.

This chart shows mean Pacific giant salamander and steelhead trout density from 24 electrofishing stations throughout the Ten Mile River Basin. Assuming that the relationship between capture bias for Pacific giant salamanders and steelhead numbers (as shown in above chart) is similar among years, the pattern of Pacific giant salamander density in this chart is indicative of a population decline.

References

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.