Foothill Stream Research Articles

Ectoparasites of the western roach from two foothill streams.

Sixty-eight western roach, Hesperoleucus symmetricus symmetricus, from two foothill streams east of Fresno, California were examined for ectoparasites. Results of the limited survey showed nine new records for ectoparasite species for roach. Four species of protozoa, Trichodina sp., Glossatella sp., Ichthyophthirius multifiliis, Myxobolus sp., one species of monogenetic trematode, Urocleidus sp., three species of copepods, Lernaea bagri, L. piscinae and Lernaea sp. and the Hirudinean, Piscicola punctatus, represent the new records. Morphological characteristics and mensural data for Trichodina sp. and Glossatella sp. indicate these protozoa may be new species. Each roach was host to at least one species of ectoparasite. One fish harbored five species of parasites, while the average number of parasite species per fish was 2.5.

Effects of Introduced Bullfrogs, Rana catesbeiana, on the Native Frogs of the San Joaquin Valley, California

Rana catesbeiana was introduced into California between 1914 and 1920 and has since spread throughout the state. In the San Joaquin Valley it has become the dominant frog on the valley floor and has spread into the Sierra Nevada foothills. It is most abundant in the warm low elevation pools of the foothill streams, in areas heavily altered by man, although at least two populations are established above 1600 m elevation. Of the two frog species native to this region, R. aurora is either absent or very rare at the present time, while R. boylii is found mostly in small permanent foothill streams higher than 200 m elevation, in areas not occupied by R. catesbeiana. The disappearance of R. aurora from the region, and the continuing reduction in range of R. boylii, is attributed to habitat alteration coupled with predation and competition from R. catesbeiana. HE bullfrog (Rana catesbeiana Shaw), native to the United States east of the Great Plains, was introduced into California several times between 1914 and 1920 (Storer, 1922). After the initial introduction, it was spread rapidly throughout the state by wellmeaning naturalists and farmers (Storer, 1925). Unfortunately, in the San Joaquin Valley and the Sierra Nevada foothills, one of the main by-products of the introduction of the bullfrog seems to have been the elimination of the red-legged frog (Rana aurora Baird and Girard) from the valley floor and foothill ponds and the reduction of populations of the foothill yellow-legged frog (R. boylii Baird) in the foothill streams. This paper shows how the distributions of R. catesbeiana and R. boylii have become nearly mutually exclusive in the Sierra Nevada foothills and attempts to document the disappearance of R. aurora from the San Joaquin Valley, concomitant with the spread of the R. catesbeiana. METHODS Between 27 July and 4 September 1970, the distribution and ecology of the fishes occurring in the streams of the Sierra Nevada foothills below elevations of 1100 m were studied (Moyle and Nichols, in preparation). At each locality where fish were collected, a rough estimate was also made of abundance of each frog species present, on a 0-3 scale. On this scale, '0' indicated no frogs present, 1, only one or two individuals observed in sample area, 2, frogs present in low numbers, (usually, less than 12 observed), and 3, frogs abundant. The frog abundance was thus rated for most of the streams accessible by road in Tulare, Fresno, Madera, Mariposa, and Tuolumne counties, California. Frogs were found at 95 of the 130 stream localities. During the study period the streams were at their minimum flow. Over half of them were not flowing at all, and water was present only in isolated pools. At each sampling site estimates and measurements were made of environmental factors that were likely to affect the distribution of the fishes, as discussed in detail in Moyle and Nichols (in preparation). The following were measured: 1) Elevation, in meters. 2) Air and water temperature. Since

Observations on Mosquito Populations of an Intermittent Foothill Stream in California

Mosquitoes are well known from the west-slope foothills of the southern Sierra Nevada in California (Freeborn and Bohart 1951) but, as populations, are most notable for their unobtrusiveness. The small to moderate-sized streams which provide virtually all of the natural breeding sites in this zone are dry during the hot, rainless summer and so can be used effectively by mosquitoes only during the brief transition periods between that season and the cool-wet winter. The alternatives are for breeding to be carried on in winter waters which are flushed frequently by storms and in which temperatures average 100 C or less for months at a time or in the restricted and faunistically crowded bits of water that remain scattered along these watercourses through the summer. A general study (Abell 1956) of the seasonal development of the macrofauna in and around one such stream through 1953-1955 has yielded information on larval mosquito occurrence during the calendar year of 1954 that appears to be worth reporting separately at this time. This work was conducted while the author was on a National Science Foundation Fellowship at the University of California, Berkeley. Special thanks are due to the California Department of Public Health, Bureau of Vector Control, for their generous loan of equipment and working space at their Fresno Field Station and to E. C. Loomis and H. F. Bormann, who critically read the manuscript.