A model of oxygen-mediated filial cannibalism in fishes

Parental male fishes may consume some of the egg clutches they guard in order to improve the survival of developing embryos under low oxygen conditions. However, the mechanism by which males determine the proportion of a clutch to consume is poorly understood. We conducted a modelling study for the beaugregory damselfish, Stegastes leucostictus, a marine teleost that does not ventilate its eggs, to investigate fitness benefits of different filial cannibalism strategies. We used three models of filial cannibalism. In the first model, males were able to track environmental conditions and cannibalise a clutch in relation to the available oxygen. In the second model, males cannibalised a fixed proportion of each clutch to varying degrees. In the final model, males did not engage in filial cannibalism. Our model for males that were able to track environmental conditions showed a good fit to empirical data, and this model proved the most successful male strategy in response to variability in spawning rate, water temperature and clutch size. Males that cannibalised a fixed but high proportion of their clutches had higher reproductive success than males cannibalising a low proportion or that did not cannibalise their clutches. We discuss our findings in the context of male cannibalism strategies and the evolution of male filial cannibalism.