catches of anadromous fish in the Bay and the adjacent 
coastal zone, and threaten the sport landing of fish 
and shellfish in the Bay as a whole. 
7. Correlations of records of commercial catches of 
salmon, striped bass, and shad with spring runoff to 
the San Francisco Bay (2-4 year means) for pre-project 
years (1915-1940) indicate that there were significant 
landings only when spring Delta outflows were 3.7-6.2 
km 3 (3-5 MAF) for the preceeding 2-4 years. High 
correlations between mean annual Delta outflow and 
landings of striped bass, salmon, and shad strongly 
support the hypothesis that at least 23.4 km 3 (19.0 
MAF) or 70 percent of the long-term average must reach 
the Bay during the 3-5 years prior to the year of catch 
to ensure successful commercial landings. The use of 
lag times or averages of water flow over several years 
to predict fishery abundance has been documented in 
other estuarine systems (Therriault and Levasseur 1986; 
Sutcliffe et al., 1977). It is important to use 
averages which correspond to the reproductive maturity 
of the fish. Figure 7 A-D shows some of these 
correlations. In contrast, the current range of mean 
annual and spring water supply to the Bay for the same 
time lag is 1.5-2.5 and 2-5 times less than the long¬ 
term average, respectively. The relative value of 
negative deviations of 5-year running mean freshwater 
supply to the Bay has dropped 60-85 percent below 
"normal" spring, and 45-60 percent below "normal" 
annual Delta outflow for the period 1921-1980. 
In recent years, commercial fishing has been prohibited 
in San Francisco Bay and Delta waters (since the late 
1950s for salmon and shad, and since 1935 for striped 
bass). Nevertheless, sport catches of these species 
have declined to as little as 3 0 percent of levels of 
20 years ago despite a great increase in sportfishing 
effort, improved treatment of sewage discharges, and 
massive hatchery releases. 
8. Figure 8A illustrates the steady decline of 3-year 
running means of regulated spring Delta outflow since 
1954. The deviations (negative) of water supply to the 
Bay from mean natural Delta outflow were nearly 80 
percent for most of the springs of the 1970s (Figure 
8B). This demonstrates that the estuarine system was 
deprived of significant amounts of freshwater and 
implies that the high levels of diversion are responsi¬ 
ble for the drastic decline in striped bass catches 
(Figure 8C) and the Striped Bass Index (Figure 8D). 
Note the relationship between flow (Figure 8A), and 
catch (Figure 8C) with 3-year lag, e.g., 1954-56 
50 
