title: Using gamma distribution to determine half-life of rotenone, applied in freshwater.
abstract: Following the use of rotenone to eradicate invasive pest fish, a dynamic first-order kinetic model is usually used to determine the half-life and rate at which rotenone dissipated from the treated waterbody. In this study, we investigate the use of a stochastic gamma model for determining the half-life and rate at which rotenone dissipates from waterbodies. The first-order kinetic and gamma models produced similar values for the half-life (4.45 days and 5.33 days respectively) and days to complete dissipation (51.2 days and 52.48 days respectively). However, the gamma model fitted the data better and was more flexible than the first-order kinetic model, allowing us to use covariates and to predict a possible range for the half-life of rotenone. These benefits are particularly important when examining the influence that different environmental factors have on rotenone dissipation and when trying to predict the rate at which rotenone will dissipate during future operations. We therefore recommend that in future the gamma distribution model is used when calculating the half-life of rotenone in preference to the dynamic first-order kinetics model.
authors.affiliation: Department of Biostatistics and Epidemiology, Auckland University of Technology, Auckland, New Zealand. Electronic address: mrohan@aut.ac.nz.
authors.forename: Maheswaran
authors.initials: M
authors.lastname: Rohan
authors.affiliation: Science and Capability, Department of Conservation, Hamilton, New Zealand.
authors.forename: Alastair
authors.initials: A
authors.lastname: Fairweather
authors.affiliation: Science and Capability, Department of Conservation, Hamilton, New Zealand.
authors.forename: Natasha
authors.initials: N
authors.lastname: Grainger
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water; D006207:Half-Life; D007306:Insecticides / Q000032:analysis*; D010573:Pesticide Residues / Q000032:analysis; D012402:Rotenone / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data*
chemical_list: D007306:Insecticides; D010573:Pesticide Residues; D014874:Water Pollutants, Chemical; D012402:Rotenone
keywords: Gamma distribution; Half-life; Rotenone; Rotenone dissipation