Filial cannibalism in sticklebacks: a reproductive management strategy?

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Abstract
We studied filial cannibalism (cannibalism of kin) in male threespine (Gasterosteus aculeatus) and black-spotted sticklebacks (G. wheatlandi). G. aculeatus were studied in the laboratory by establishing a population of males defending eggs of different ages. Males of both species were also collected in the field throughout the breeding seasons of 1988 and 1989. To distinguish filial cannibalism from heterocannibalism, we compared territorial males tending eggs to those without eggs. Parental males should be more cannibalistic than non-parental males if filial cannibalism is important. Filial cannibalism was relatively common in laboratory breeding G. aculeatus and in field-breeding G. aculeatus and G. wheatlandi. We also examined the possible adaptive significance of filial cannibalism by testing ROHWER'S (1978) hypothesis that males consume some of their eggs to remain in good physical condition for subsequent breeding cycles. Surprisingly, filial cannibalism by male G. aculeatus was unrelated to food ration. Furthermore, contrary to ROHWER'S prediction, filial cannibalism in male G. aculeatus was more common late in the breeding season both in the laboratory and the field and did not changed seasonally in field-breeding G. wheatlandi.