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WILLIAM STREIFER
2. Death rates
The existing experimental data are not complete. According to Frank
et al. (1957)’ death rates are dependent on crowding and are a minimum
for eight animalslml. Frank’s data are not expressed as a function of age
and mass, only as a function of age and crowding. We associate mass
dependence with crowding by referring to Richman’s growth-curve
experiment with animals fed 25 000 algal cells/ml/day. Let s(a) be the
average mass of an animal in Richman’s experiment. We assume that all
animals of age a and mass m>s(a) experience a death rate equal to
0.0i
0.04
60
40
20
0
AGE (doys)
FIU. 9a and b. Illustrating two views of the death function 9 (a, m ) vs. a, m.
The death rates of animals with both large and small masses continue to increase
with age and are not constant (tlat) aa shown in the figure.