The dispersal of Lepeophtheirus salmonis within and among New Brunswick Atlantic salmon farms

The objective of this study was to estimate the infestation pressure (a measure of the dose of exposure of parasitic sea lice which could result in the infestation of a new fish host) applied by Lepeophtheirus salmonis for the Bay of Fundy, New Brunswick, in the Atlantic salmon aquaculture industry, using the Fish-iTrends database for 2009-2018. Infestation pressures were calculated as temporally weighed average abundances of sea lice with a time lag within a site (IIP) and among sites (EIP). The EIP was also spatially weighted with a Gaussian kernel density estimate for bandwidths ranging from 1 to 60 km. A multivariable linear mixed model for the abundance of adult female (AF) was utilized. The EIP with a bandwidth of 10 km had the best fit as determined with the Akaike's Information Criterion. AF within and among sites, and pre-adult and adult male abundances resulted in an increase in the abundance of AF (all p <0.001). Sea surface water temperature and topical treatments were significant predictors in the abundance of AF in our final model (p < 0.001). This study concludes that sea lice burdens within salmon farms in the Bay of Fundy, are affected by within-site management and could be improved by synchronizing treatments among sites.