N. lewisi Habitats and Behavior 95 



constant between the control site and any microhabitats used by N. 

 lewisi, and had no apparent bearing on movement. 



Winter Movements and Microhabitat.— During winter, adult N 

 lewisi were found either under large granite rocks or in burrows in the 

 bank 85 percent of the time. Mean water temperature was 6.7° C. Of all 

 movements made during this period, 29 percent were to microhabitats 

 that were 1 C° or more higher than the standard site temperature (Table 

 6), and 28 percent were to microhabitats with higher levels of dissolved 

 oxygen (7-9 ppm) and higher flow rate (x= 14.79 cm/ sec). A decline in 

 overall number of movements was noted for all animals by 67 percent. 

 When the stream temperature dropped below 4°C, movement was to 

 areas where groundwater entered that was 2 to 4 C° higher than the 

 standard site temperature. No sexual difference in frequency of move- 

 ment was observed during the winter period. 



Spring Movements and Microhabitat. — Between March and May 

 the number of movements was 48 percent greater than in all other sea- 

 sons. Generally, as temperature increased to 8°C, females showed 

 increased (27%) movement. At 14° C, female movement declined but 

 overall male movement increased. This period of increased male move- 

 ment coincided with expected breeding and nesting periods. Thirty-six 

 percent of movements made during this period were to microhabitats 

 with higher 2 levels (x=7.9 ppm) and 34 percent were to areas of 

 greater flow (x=7.8 cm/ sec). The primary microhabitats used during 

 period this were considered suitable nesting sites (Ashton and Braswell 

 1980). The microhabitats used 98 percent of the time by both sexes were 

 large bedrock outcrops or large boulders with sand and gravel beneath 

 them. 



Summer Movements and Microhabitat . — Generally, summer move- 

 ments by both sexes, with an overall decline of 40 percent in frequency, 

 were to microhabitats that had lower temperatures (34%) and higher 

 oxygen levels (37%) (Table 6). The use of granite boulders and outcrops 

 in the main flow of the stream increased during this period. 



Fall Movements and Microhabitat. — The overall river environ- 

 ment, including the microhabitats used by N. lewisi, was relatively uni- 

 form in temperature, oxygen levels, and other physical factors. General 

 movements were from the main flow to the winter retreat areas. 



Movements and Microhabitats of Larvae and Post-hatchlings 



Since five post-hatchlings were captured and released in the same 

 area, movements by specific individuals could not be determined. All, 

 however, remained within a 134 m 2 area. At no time were two tagged 

 individuals found under the same cover, but it was not uncommon to 

 find three or more individuals within one square meter of one another. 



