Table 6. — Estimates of M t , M r , and p used to evaluate time and magnitude of mortality of 1958 brood-year eggs 



1 These estimates of M were obtained with log-transformed data. 



occasion only (mid-November), and comparisons 

 between the two areas will be limited to the 

 mid-November samples. 



The expected number of eggs based on potential 

 deposition was 201 per m. 2 in both intertidal 

 Harris River and Indian Creek. In mid-Xovem- 

 ber the difference between mean estimates of 



A. 



M T (M r =0.16 in intertidal Harris River, and 



A 



M r =0.13 in intertidal Indian Creek) was not 

 statistically significant. Furthermore, a com- 

 parison of values of p in November gave a chi- 

 square value of 0.46 (1 d.f.), indicating no sig- 

 nificant difference in the frequency of occurrence of 

 dead eggs in intertidal Harris River and Indian 

 Creek. Hence, for the 1958 brood year, there was 

 no conclusive evidence of higher egg mortality 

 in intertidal Harris River than in intertidal 

 Indian Creek. It is noteworthy, perhaps, that in 



A. 



intertidal Harris River M, increased significantly 

 between mid-November and mid-December. It 

 wjiot known if a similar increase occurred in 

 intertidal Indian Creek. 



1959 Brood Year 



Density of spawners was highly variable among 

 and within the study streams in 1959. Estimated 

 densities of females spawning were: 



Intertidal Harris River 25 females per 100 in. 2 



Upstream Harris River 6 females per 100 m. 2 



Intertidal Indian Creek 46 females per 100 m. 2 



Intertidal Twelvemile Creek.. 15 females per 100 m. 2 

 Upstream Twelvemile Creek.. 1 female per 100 m.-' 



Because of the very low density of spawning 

 adults, mortality was not studied in upstream 

 Twelvemile Creek, but observations on mortality 

 were made in upstream Harris River. High 

 stream discharge occurred during spawning, pro- 

 viding more favorable conditions for egg survival 

 during spawning than in 1957. Results of studies 

 on mortality of the 1959 brood year are sum- 

 marized in table 7. 



As observed in 1958, mortality in intertidal 

 Twelvemile Creek was very high initially and 

 apparently was associated again with the direct 

 removal of eggs from the spawning bed. Since 

 estimates from upstream Harris River indicated 



Table 7. — Estimates of Mt, M r , and po used to evaluate time and magnitude of mortality of 1959 brood year eggs 



e traction of points containing fewer than 35 dead eggs per square meter. 

 •' This estimate of M, was obtained from log-transformed data. 



512 



U.S. FISH AND WILDLIFE SERVICE 



