Predator biocontrol
We simulated varying rates of snail host mortality representing predators as biocontrol agents feeding on hosts based on their body size under different predator densities. We used 22 predator densities of 0–50 N m–2, extending beyond realistic densities used in aquaculture of congeneric species and field experiments of prawn predation on schistosome host snails (Sokolow, Lafferty, and Kuris 2014).
We simulated two scenarios of host mortality by predators,discrete host mortality and continuous host mortality . The discrete risk scenario represents predation exclusively on individuals falling within a given size range in which a lower bound of this size range at zero represents gape-limited predation. In contrast, the continuous risk scenario represents predation risk as a decreasing function of host size, consistent with laboratory studies on size-selective feeding of snail hosts by prawn predators (Sokolow, Lafferty, and Kuris 2014). Hosts not consumed by predators died naturally at baseline mortality rates (hazard rate,hb = 0.001 d­–1).