262 



Fishery Bulletin 88(2). 1990 



ar^ment that the decrease in recruitment is a direct 

 consequence of the dam rather than the result of grad- 

 ual habitat degradation or increasing fishing pressure 

 (Hallock et al. 1982, Hallock 1983). A similar effect had 

 been observed by Reisenbichier (1986) but he found 

 that the spawning runs resulting from the 1964, 1965, 

 and 1966 brood years were intermediate between the 

 stock-recruit curves associated with the time periods 

 before and after these years. With our deconvolved 

 recruitment estimates, the 1964 brood year appears to 

 have been abnormally low, but 1965 and 1966 appear 

 comparable with earlier years. Data for the Feather 

 River and the American River do not fit stock-recruit- 

 ment curves as well as the Sacramento River data. Our 

 data include few years before the damming of the 

 Feather River and none for the American River before 

 the construction of Nimbus Dam. On both of these 

 rivers, the hatchery contribution to the spawning 

 escapement is large, hence lack of a clear stock-recruit- 

 ment relationship is not surprising. 



To assess the influence of the freshwater environ- 

 ment on Sacramento Valley stocks, we computed cor- 



relations between population variables and environ- 

 mental variables on three rivers— the Sacramento, the 

 Feather, and the American— as well as the total of 

 these three, and relevant environmental variables. 

 Population variables were total spawners, adult spawn- 

 ers, jacks, and recruitment estimated by deconvolution 

 of adult spawners. We thus tested for environmental 

 effects on all spawners, as well as differential effects 

 on jacks and adults, and recruitment to the adult 

 spawner population. Environmental variables were the 

 flow of each river, total diversions of flow in the 

 Sacramento-San Joaquin Delta, diversions as a percent- 

 age of flow, delta inflow, and delta outflow. We pre- 

 sent all correlations that were significant at the 0.1 

 level using the standard uncorrelated series test, and 

 annotate with asterisks the significance of each of these 

 according to the more conservative test that allows for 

 intraseries correlation. 



The results (Table 1) provide no evidence for an in- 

 fluence of the freshwater environment on numbers of 

 total spawners, jacks, adults, or adult recniits to these 

 stocks. In fact, the number of correlations significant 



