Metadata: Lethal_Experiment_BehaviourData All behaviour data from three mesocosm experiment runs. -snailnumber: number of snails (Potamopyrgus antipodarum) in each mesocosm at the beginning of each experiment round -NumberDel: number of Deleatidium spp. In each tank at the beginning of each experiment round -fyes_no: whether fish were present (f) or not (c) -Time: whether the measurement was taken during dark or light periods -InitialCount: number of Deleatidium observed immediately when checking each mesocosm -Snailontile: number of P. antipodarum on tiles in each mesocosm -ProportionDel: number of Deleatidim observed relative to the initial number added -tanknumber: number of each mesocosm -runnumber: what experiment round each observation is attributed to -measurement number: whether this is the first or second measurement for dark and light periods. Snails_EatenData Data from experiment round 1 showing the number of P. antipodarum consumed. Negative numbers means extra snails were found in the tag (error from counting in) -numsnails: number of snails (Potamopyrgus antipodarum) in each mesocosm at the beginning of the round -numsnailseaten: number of snails removed from the mesocosm at the end of the experiment Lethal_Experiment_PredationData All predation data from all three experiment rounds -snailnumber: number of snails (Potamopyrgus antipodarum) in each mesocosm at the beginning of each experiment round -NumberDel: number of Deleatidium spp. In each tank at the beginning of each experiment reound -Del Out: number of Deleatidium in each mesocosm at the end of the experiment -Number eaten: Number of Deleatidium removed from each tank -Proportion eaten: proportion of total Deleatidium population eaten Non-lethal experiment data Temperature control room behaviour data with no fish present. -tanknumber: number of each mesocosm -Treatment: presence (snail, ~30,000/m2) of P. antipodarum or absence (control) -LightLevel: whether the measurement was taken in dark (Dark) or light (Light) periods -Time: time when each measurement was taken -InitialCount: number of Deleatidium observed immediately when checking each mesocosm -NumDelSubstrate: number of Deleatidium on tiles in each tank -NumDelTank: number of Deleatidium on tank surface but not on tiles -NumDelDrift: number of Deleatidium drifting -Snailontiles#: number of snails on tiles.