  The degree to which population fluctuations arise from variable adult
survival relative to variable recruitment has been debated widely for marine
organisms. Disentangling these effects remains challenging because data
generally are not sufficient to evaluate if and how adult survival rates are
regulated by stochasticity and/or population density. Using unique time-series
for a largely unexploited reef fish, we found both population density and
stochastic food supply impacted adult survival. The estimated effect of
variable survival on adult abundance (both mean and variability) rivaled that
of variable recruitment. Moreover, we show density dependent adult survival can
dampen impacts of stochastic recruitment. Thus, food variability may alter
population fluctuations by simultaneously regulating recruitment and
compensatory adult survival. These results provide an additional mechanism for
why intensified density independent mortality (via harvest or other means)
amplifies population fluctuations and emphasizes need for research evaluating
the causes and consequences of variability in adult survival.
