title: Group-level factors associated with chemotherapeutic treatment regimens in land-based trout farms in Ontario, Canada.
abstract: The lowest level at which fish farmers ordinarily make management decisions is the individual holding unit. To identify factors associated with chemotherapeutic treatment initiation at the holding-unit level, we created a unit of measurement called the "farm-tank-lot" (FTL), which allowed the movements and mixing of groups of fish to be followed during an entire production cycle. Each FTL was comprised of fish with a common history housed in a specific holding unit. Our 21-month prospective observational study (conducted on 14 land-based trout farms in Ontario, Canada) showed that the FTL was a biologically meaningful unit of concern and a feasible unit of measurement on land-based trout farms.Multivariable logistic and Poisson regressions revealed that fish size and growth rate both were associated negatively with the probability and frequency of treatment. FTLs that existed for longer periods of time were more likely to be treated and treated more often. There was a significant farm effect. Future field studies of disease in cultured fish should incorporate these factors into their design and analysis.
authors.affiliation: Department of Population Medicine, Ontario Veterinary College, University of Guelph, Ont., N1G 2W1, Guelph, Canada. mthorbur@uoguelph.ca
authors.forename: M A
authors.initials: MA
authors.lastname: Thorburn
authors.forename: G F
authors.initials: GF
authors.lastname: Teare
authors.forename: S
authors.initials: S
authors.lastname: Wayne Martin
authors.forename: R D
authors.initials: RD
authors.lastname: Moccia
mesh_terms: D000818:Animals; D003625:Data Collection; D003661:Decision Support Techniques; D005393:Fish Diseases / Q000188:drug therapy*; D016015:Logistic Models; D008137:Longitudinal Studies; D009864:Ontario; D016012:Poisson Distribution; D014337:Trout