Modelling of cleaning waste distribution to map gill health risks

Biofouling organisms growing on net pens cause multiple problems and are therefore removed regularly using in-situ net cleaning. In the process, the cleaning waste consisting of fouling organisms and their fragments is released into the pen. Contact with such cleaning waste containing hydroids, one of the most common biofouling organisms, can cause gill damage in the cultured salmon. In addition, biofouling organisms can harbour pathogens. In the presented study, we analysed and characterised the cleaning waste released into the pen. After conducting sinking speed analyses of the major particle groups, the particle distribution in and around the net pen was modelled. By calculating residence times inside the cage and creating distribution maps showing dispersion around the farm site, the risk of exposure to this potentially hazardous material could be estimated. In addition, this study provides input for the mapping of disease transmission.