flow/1959 catch). Regressions between sportfishing 
catches of striped bass for this period and Delta 
outflow for the 3 years preceeding the year of catch 
with a 0-2 year time lag are similar to those between 
striped bass commercial catch and flow shown in Figure 
8 . 
9. In the literature on the status of Chinook salmon 
spawning populations in the Sacramento-San Joaquin 
watershed, four factors have been proposed to explain 
their precipitous population decline: dams, water 
diversions, pollutants, and the loss of habitat 
(California Department of Fish and Game, 1983). The 
early winter run is considered a major source of 
recruitment for this stock (Hallock and Fisher, 1985). 
Between 1967-1982, when reliable counts were made of 
winter salmon runs, the 5-year running means of regu¬ 
lated spring water supply to the estuary was about 
35-80 percent of spring perennial mean runoff (1921- 
1978). The average annual volume of water diversion 
was approximately 12.2 km 3 (11.0 MAF; Figure 9) and 
cumulative withdrawals from the Sacramento-San Joaquin 
river water supply to the estuarine system reached 
about 190 km 3 (158 MAF; Figure 9A) between 1967 and 
1982. During the same period the number of winter-run 
Chinnok salmon returning to spawn in the upper part of 
the Sacramento River was reduced as much as 60 times 
(Figure 9D, Hallock and Fisher, 1985) despite attempts 
to mitigate this decline with release of millions of 
hatchery-reared juveniles (Figure 9C, California 
Department of Fish and Game, 1983). 
While all of the factors mentioned above may contribute to 
reduction of the salmon population in this watershed, our data 
strongly suggest that overall reduction of runoff and cumulative 
losses of water and biochemical constituents resulting from 
diversions will continue to be the principal factors governing 
migration, spawning success, and recruitment in this stock. 
Kjelson et al. (1982) also attribute decreases in salmon 
populations to increases in water diversions. They found that 
the March-June runoff of up to a total of 8.6 km 3 (7 MAF), 
lagged 2.5 years, may provide optimal conditions for Chinook 
salmon spawners during nursery migration. Similar deterioration 
of ecological conditions and biological productivity following 
excessive freshwater withdrawals has occurred in estuaries in 
Africa, Asia, Australia, Europe, and the United States. 
(Hedgpeth, 1970; Aleem, 1972; Baydin, 1980; Cross and Williams, 
1981; L'vovich, 1974; Meleshkin et al., 1973; Mancy, 1979; 
Rozengurt, 1971, 1974, 1983a, b; Rozengurt and Herz, 1981; Mann, 
1982; Tolmazin, 1985; and White, 1977). 
54 
