Reproductive fitness consequences of filial cannibalism in the flagfish, Jordanella floridae

We investigated the effects of filial cannibalism, which is prevalent in teleosts that display parental care, on components of fitness in the flagfish. Currently, filial cannibalism in care-giving teleosts is thought to reflect an adaptive trade-off between current and future reproduction, in which energy or nutrients gained from consuming eggs is invested into future reproduction. Thus, we expected filial cannibalism to increase future reproductive success. We quantified the reproductive fitness consequences of filial cannibalism in the flagfish by comparing two cannibalism treatments (male access to eggs versus no male access to eggs) crossed with two feeding treatments (high and low food). Males were followed over 90 days, approximately one breeding season (i.e. the expected reproductive lifetime of flagfish), and we considered three fitness components: (1) the total number of eggs received (2) the number of spawnings and (3) the frequency of spawning. Contrary to predictions, filial cannibalism reduced male reproductive success. While there was an effect of food on components of fitness (i.e. number of eggs received, number of spawnings, frequency of spawning), there was no effect of filial cannibalism. An enhanced diet was also related to increased male weight, but filial cannibalism was not. Thus, in the flagfish, we have no evidence that energy or nutrients gained from filial cannibalism is directly translated into increased future reproductive success. We discuss our findings in relation to current and alternative theories of filial cannibalism.