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Manage Stress to Improve Fish Health

Fish Health Management

AQUI-S® is used to mitigate unavoidable stressors that negatively impact on fish health. The type, intensity, and duration of the stressor plays a major role in the immune condition of an animal. Elevated, and especially prolonged, plasma cortisol levels act as an immunosuppressant, reducing the number of leukocytes and lymphocytes in the circulating blood, making the fish more vulnerable to parasites, bacteria and fungi. 

health block

While it is impossible to eliminate all stress from a production environment, stressors associated with crowding, handling and treatments can and should be effectively managed. This page provides more details on health-related stressors and the role AQUI-S® has in mitigating them.

is as relevant to the aquaculture industry as it is to human health.

health diagram

Fish Health Management

Fish health management is a term used to describe management practices that are designed to prevent fish disease. Successful fish health management begins with prevention of disease rather than treatment. Sub-optimal water quality, poor nutrition or immune system suppression, generally associated with stressful conditions, allow potential pathogens to cause disease. Sedating fish with AQUI-S® during health management procedures such as vaccinations, bath treatment and health checks will maximise the ability of fish to withstand re-infection by ensuring the immune system is not compromised. Sedation will also prevent mechanical injuries from the handling process and will help fish recover faster.

Health Checks

AQUI S Health Check

Routine monitoring of your animals for bacterial, viral and parasitic diseases is critical to maintain good fish health. During a health check, a sample of the population is thoroughly examined and assessed against various welfare indicators to provide an indication of the health of the whole population. Unfortunately health checks can have detrimental consequences for the health of the animals if the process is not managed correctly. When crowding and removing fish from the water, the fish’s welfare must be prioritised.  AQUI‑S® sedation during crowding and  handling will ensure fish survivability and growth post-handling and will reduce the likelihood of those individuals being carriers or hosts for disease when they are returned to the main population. Using AQUI-S® also shows a commitment to good animal welfare. Refer to the FISHWELL handbook on welfare indicators for Atlantic Salmon for information on welfare indicators.


AQUI S Health Vaccination NC

Although vaccination is no substitute for good animal husbandry, it is a very effective way of protecting fish from viral and bacterial diseases. It is common practice for most aquaculture species to be vaccinated at least once in their production cycle. Vaccination can be done by three main routes; injection, immersion, and oral. Each delivery route has its own advantages and disadvantages. Whilst both immersion and oral vaccination are easier to manage and are generally less stressful for the fish, neither provide as strong and long-lasting immunity as injection vaccination.  Injection vaccination is performed by inserting a needle into the intraperitoneal cavity or the intramuscular tissue. This technique requires the fish to be immobilised. Sedating fish with AQUI‑S® before and during vaccinations will improve survival and the effectiveness of the vaccine. Fish will also return to feeding faster and will perform better post-handling.

Bath Treatments

AQUI S Health Treatment NC

Bath treatments require fish to first be crowded into a smaller volume before they are enclosed and dosed with an insecticide, vaccine, antifungal, fresh water or other chemicals. Existing bath treatments for pathogens and parasites are known to have welfare problems and have been linked to the development of pesticide resistance and a subsequent reduction in treatment efficacy. In these situations, the treatment concentrations and durations are increased to maintain some degree of effectiveness.

Bath treatments can be carried out in an enclosed pen or well boat, and vary in duration from seconds to hours with short treatments often causing as much or more stress as longer treatments. AQUI-S® can be used to sedate animals to a level which ensures they maintain swimming action and equilibrium. Using AQUI‑S® in this manner both prior to and during bath treatments substantially reduces stress and improves treatment success and fish survival. It also ensures a strong immune system, reduced re-infection rates and limited to no loss in growth post-treatment.

welfare regs Link to the cage treatment protocol.          welfare regs Link to the well boat treatment protocol.

Mechanical Treatments

Mechanical delousing treatments require fish to be crowded and then pumped into a treatment system, dewatered and the lice mechanically removed. Three types of mechanical treatment technologies have been developed – the Thermolicer, Optilicer and Hydrolicer. These use warm water and/or high-pressure water to remove lice from the fish. The lice are then collected and destroyed, and the fish returned to the sea pen. Recent studies and new welfare regulations are questioning the ethics of mechanical treatments as they have shown high mortalities and physical damage to the animals – see the Welfare Treatments page for more information.  AQUI-S® can be used to lower stress and activity in the animals prior to mechanical treatment, limiting physical damage and improving post-treatment performance and welfare.

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