water withdrawals. In such a case, the estuarine ecosystem 
would survive regulated water supply fluctuations because they 
are within range of natural conditions. If diversions exceed 
these natural limits for prolonged periods, there will be little 
prospect of recovery because the natural resilience of the 
system will be reduced and deteriorating conditions will produce 
serious damage to its resources (Aleem, 1972; Rozengurt and 
Haydock, 1981; and Rozengurt and Herz, 1981). In many parts of 
the world, massive water diversions from estuaries have greatly 
reduced or eliminated major fisheries, with annual losses 
amounting to hundreds of millions of dollars, as a result of 
destruction of habitats and degradation of conditions necessary 
for reproduction and maturation (Aleem, 1972; White, 1977; Cross 
and Williams, 1981). 
In 1980, these problems were examined by the National 
Symposium on Freshwater Inflow to Estuaries in San Antonio, 
Texas. The Summary and Recommendations of this Symposium 
included the following: 
Published results regarding water development in rivers 
entering the Azov, Caspian, Black and Mediterranean Seas in 
Europe and Asia all point to the conclusion that no more 
than 2 5-3 0 percent of the historical river flow can be 
diverted without disasterous ecological consequences to the 
receiving estuary. Comparable studies on six estuaries by 
the Texas Water Resources Department showed that a 32 per¬ 
cent depletion of natural freshwater inflow to estuaries 
was the average maximum percentage that could be permitted 
if subsistence levels of nutrient transport, habitat main¬ 
tenance, and salinity control were to be maintained. 
(Clark and Benson, 1981, page 524). 
In the San Francisco Delta-Bay system where annual fresh¬ 
water flows have been reduced by as much as 62 percent (Nichols 
et al. 1986), fish populations have declined radically. The 
striped bass population is down to 2 0 percent and egg production 
is at 10 percent of levels of the 1960s (Striped Bass Working 
Group, 1982) and Chinook salmon population has declined to 30 
percent of 1960 levels (Kjelson et al., 1982). Many other 
investigators have attempted to quantify the relationship 
between river flow and fish abundance with varying degrees of 
success (Chadwick, 1971; Stevens, 1977; Smith and Kato, 1979). 
Materials and Methods 
In order to establish ecological criteria and make recommen¬ 
dations for management and protection of the San Francisco Bay 
estuarine system, two crucial questions must be answered: 
37 
