Economic modelling of mouth rot in British Columbia Atlantic salmon farming

Abstract

Bacterial stomatitis, or mouth rot (MR), caused by Tenacibaculum maritimum, is a persistent health issue for farmed Atlantic salmon (Salmo salar) in seawater, leading to elevated mortality and reduced growth during the early months of production. Despite its impact, economic estimates of MR have been lacking. We developed a model to estimate selected direct costs associated with MR at the farm and industry levels in British Columbia (BC), Canada. This model incorporated parameters directly affected by MR, including revenue loss from mortality, and antibiotic treatment costs, while accounting for the feed-cost offset associated with mortality. To address variability across farms, MR-associated mortality, non-MR mortality, smolt weight, the number of treatments for MR, fish sale price, feed price, price of drug, and the proportion of farms affected by MR were simulated (Monte Carlo simulation with 10,000 iterations) using ModelRisk. Results indicated that MR imposed an average farm-level economic burden of USD 0.74 million (SD: USD 0.45 million) per production cycle and an industry-level burden of USD 10.58 million (SD: USD 6.54 million) annually. This study provides model-based estimates of selected direct economic costs associated with MR, based on BC specifications, and highlights the need for improved mitigation strategies and policy prioritization for this disease.