Male cortez damselfish, Stegastes rectifraenum, in a central Gulf of California population, ate a large percentage (28.3%) of the clutches they received. This high rate of filial cannibalism permitted the testing of several predictions concerning the types of clutches that should be preferentially eaten and the mating tactics females should employ to reduce cannibalism rates. Males ate clutches that were smaller than average and that were at early stages of development. Experimentally reduced clutches were consumed at higher rates than controls. When multiple clutches were present, males preferentially ate the younger, smaller clutches. Females were more likely to deposit eggs with males who were caring for other early-stage eggs and to avoid males with late-stage eggs. This pattern was accentuated in females that deposited smaller clutches. These results provide evidence that filial cannibalism represents an adaptive response to clutches that do not provide adequate benefits to warrant the costs of parental care.