World Aquaculture 2023

May 29 - June 1, 2023

Darwin, Northern Territory, Australia


Kate S. Hutson*, Allan J. Mooney, Ingo Ernst, Alex K. Brazenor, Max Scheel, Javier Atalah


The Cawthron Institute, 98 Halifax St East, Nelson, New Zealand


Global aquaculture of fish is impacted by numerous pathogens and parasites. While alternatives are being explored (e.g., vaccines, biological controls, exclusion), the industry relies to a large extent on medicinal baths to treat ectoparasite infestations. Medicinal baths are more effective if they are applied when they are timed to interrupt parasite life cycles (i.e., treatment intervals or therapeutic windows). Repeated use of chemotherapeutants drives the development of resistance in ectoparasites given their high fecundity and short life cycles, thus strategically timed treatments are important because they alleviate treatment frequency and reduce chemical use.

We developed the BeNeZe app – a free online, mobile phone compatible, interactive decision support tool that provides treatment intervals to interrupt the life cycle of ectoparasitic marine flatworms. BeNeZe targets management of ‘skin flukes’ (Benedenia seriolae, Neobenedenia girellae), and ‘gill fluke’ (Zeuxapta seriolae) infections in kingfish and amberjacks (Seriola species) but can be applied to other finfish farming enterprises (e.g., Asian seabass/barramundi, cobia, grouper, and the marine ornamental fish trade). The tool enables rapid determination of treatment intervals for two consecutive medicinal immersion or ‘bathing’ treatments — the first to kill adult worms attached to fish and the second to prevent maturity of new parasite recruits. The tool consolidates complex scientific information into a user-friendly format, helping farmers schedule the best time to treat parasites based on water temperature.

The BeNeZe tool, combined with a disease surveillance plan, can aid the prevention and treatment of parasite outbreaks. The tool could also be adapted for other pathogen/host combinations (e.g., management of sea-lice in salmonid farming). It can also be readily adapted to alternative on-farm decision tools related to degree-days such as net-cleaning and biofouling management.

BeNeZe provides an innovative solution to parasite management that is informed through science and provides clear guidelines for when to treat stock. The tool can be used for multi-species/concurrent infections. Ultimately, BeNeZe reduces treatment number and frequency, reduces infection burdens and improves fish welfare and production.