Zinc was correlated with decreased levels of serum 
proteins hypothesized to be immunoglobulins. 
o Fish exposed to benzene or zinc had higher levels of 
protozoan gill parasites than controls. 
o The effects of benzene and zinc together resulted in 
greater effects on the fish than either pollutant 
alone, including the following: 
Inflammatory response to parasitic worms was 
accelerated. 
Blood cells and serum proteins were more 
deleteriously affected. 
Liver tissue was more deleteriously affected. 
6. Population Effects . Although influences other than 
toxic chemicals (e.g, Delta outflow, larval food supply 
and entrainment; Stevens et. al. 1985) also are involved 
in the decline of the striped bass fishery, the fol¬ 
lowing hypotheses were also supported by the study 
findings. 
o There has been a reduction in numbers of larvae to 
young-of-the-year juveniles. Laboratory studies 
showed that larvae accumulate high levels of toxic 
pollutants (e.g., benzene) with deleterious effects 
(Eldridge et. al . 1981). These studies should be 
corroborated in the field. We suggest that toxic 
pollutants and parasitic cestode lesions may also 
increase mortality of juveniles and subadults. 
o There has been a reduction in the number of 
spawning adults. The poorer condition of older 
adults is at least partially due to the combined 
effects of parasitism and pollutants. It is also 
likely that increased mortality of adults has 
occurred, leading to fewer older fish that normally 
have the highest fecundity. Ultimately, this will 
lead to decreased egg production by the population 
and decreased abundance of juveniles. According to 
Stevens et. al . (1985), this is probably an impor¬ 
tant cause of the decline in the striped bass popu¬ 
lation. 
o The reduction in the number of eggs (fecundity) per 
spawner, due to the combined effects of pollutants 
and parasitism, was at least 36-50 percent in 1978. 
This reduction was assessed from measurements of: 
- delayed rate of maturation (vitellogenesis) 
100 
