Predatory decapods for biological control of pest snails: Ecological, behavioural and mechanical aspects

Integrated pest management (IPM) is invaluable in fighting parasitic diseases carried by freshwater snails as disease-transmitting vectors. Here, we studied the effectiveness of two non-GMO monosex decapods, the giant freshwater prawn Macrobrachium rosenbergii and the Australian redclaw crayfish Cherax quadricarinatus, as biocontrol agents against such disease-transmitting snails, namely, Melanoides tuberculata, Thiara scabra, Tarebia granifera and Haita acuta, found in fishponds. In food-choice experiments, the two decapods preferred snails which had thinner, weaker shells, with this feeding selectivity being stronger for the prawns than for the crayfish, which demonstrated more opportunistic feeding behavior. Notably, the crayfish were more efficient in snail predation than the prawns, displaying both shorter handling times and lower encounter rates. Subsequent physical–mechanical tests on the snails revealed that the snail species least preferred by the prawns had significantly 2.5 times thicker shells, which required 8 N more force to initially break. Practical implication: our findings suggest that the two monosex decapods could provide sustainable biocontrol solutions, potentially enhancing IPM strategies in aquaculture and offering win-win-win sustainable polyculture for fish farmers, with the biocontrol agent, which could be tailored to farmers' preferences, doubling as a valuable polyculture-produced protein.