Currently, the salmon industry is waging an ongoing war against two parasitic plagues – sea lice and amoebic gill disease (AGD). Traditionally, chemical and medicinal treatments have been used to control outbreaks of these destructive diseases. A growing resistance to available chemotherapeutants for lice control has resulted in the industry adopting non-medicinal alternatives to control this parasite.

This page describes welfare during disease treatments. You can learn about health management and vaccination in the Health section.

Concerns during Disease Treatment

Both chemical / medicinal and mechanical treatments involve similar pre-treatment activity: The fish are crowded and then either treated within the cage or pumped into a well boat or treatment system. This activity is extremely stressful for the animals, as shown by increased avoidance behavior, oxygen consumption and the production of stress hormones including cortisol and catecholamine.
Handling and treatment can also cause physical damage, reducing the fish’s external immune defenses and leaving them vulnerable to infection. The long-term effects of stress include fasting and reduced growth, increased mortalities, and greater susceptibility to disease and reinfection.

Mechanical Treatments

Three types of mechanical delousing technologies now exist: Thermolicer, Optilicer and Hydrolicer. All three technologies require the fish to be crowded and then pumped up into a treatment system prior to the lice being mechanically removed. While these systems have been used extensively by the Norwegian industry since 2015, until now, little published data has been available on the welfare and post-treatment outcomes for fish following exposure.

Recent studies have questioned the ethics of these treatments with high mortality, gill haemorrhage, scale and skin loss, haemorrhaging and vacuolation of thymic tissue, degeneration of nasal epithelium and brain haemorrhage being noted as just some of the adverse side effects. This has resulted in increased scrutiny of mechanical treatments, specifically in relation to animal welfare.

To combat this, farmers are increasingly turning to AQUI-S^® to sedate fish prior to and during mechanical treatments. Lab studies have demonstrated that using AQUI-S^® lowers the stress response and activity of the animal prior to and during mechanical treatments. This limits physical damage to the animals including scale loss and abrasions. Faster return to feeding was also observed in lab studies, which would lead to improved growth post-treatment. The use of AQUI-S^® sedation is also likely to reduce mortality and gill/brain haemorrhaging.

Please contact AQUI-S New Zealand or your distributor directly for more information on this application.

Bath Treatments

Bath treatments for pathogens and parasites involve bathing the animals in a medicinal, chemical or freshwater treatment solution. Existing bath treatments are known to have welfare problems as the chemicals used are often toxic to the fish, and the development of pesticide resistance has led to increasing concentrations of chemicals being used. Bath treatments vary in duration from seconds to hours with short treatments often causing as much or even more stress as longer treatments. AQUI-S^® can be used to sedate animals prior to and during bath treatments. This substantially reduces stress and improves treatment success and fish survival, as well as ensuring a strong immune system and better performance post-treatment.

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Learn more about the Application of AQUI-S^® during bath treatments in cages and well boats on our Health page.