Farm size as a factor in hydrodynamic transmission of pathogens in aquaculture fish production

Global aquaculture production has rapidly increased over recent decades, primarily through the increase in production per farm unit. However, size (biomass) may be a factor in the transmission of infectious diseases between hydrodynamically linked fish farms. A combined epidemiological-simplified hydrodynamic model is used to demonstrate that as farm units increase they experience higher numbers of infections caused by a range of pathogen characteristics. The model demonstrates that as farm size increases in areas where faster currents prevail, there is a need to increase the separation distance between farms to prevent pathogen transmission. A comparison of production regimes demonstrates, however, that fewer, highly separated, larger farms reduce overall losses compared to numerous smaller farms in close proximity to each other.