Two forms of filial cannibalism, in which an individual consumes its o
wn offspring, have been observed among male damselfishes: whole-clutch
and partial-clutch filial cannibalism. Observations of this behavior
among damselfishes are reviewed here and the results suggest that fili
al cannibalism may be quite widespread. This has implications for the
costs and benefits of male parental care, because guarding males have
unimpeded access to embryos as a source of energy. Thus, a graphical m
odel is explored to evaluate the interaction between the costs and ben
efits of male filial cannibalism and male parental care. The results o
f this analysis suggest that the dichotomy between whole-clutch and pa
rtial-clutch filial cannibalism can be explained by the occurrence of
depreciable parental care in fishes.