La bioseguridad en la acuicultura

Biosecurity in aquaculture

Biosecurity in aquaculture aims to minimise the risk of introducing an infectious disease and spreading it to animals in a facility, as well as the risk of sick animals or infectious agents leaving a facility and spreading to other sites and other species susceptible to contamination. These practices also reduce stress on the animals, making them less susceptible to disease and thereby increasing the quality of individual animals.

Main objectives of biosecurity

There are three areas where aquaculture needs to pay particular attention to ensure that farms produce quality fish.

– Proper biomass management, with the aim of obtaining healthy stocks and optimising their health and immunity through good husbandry.

– Pathogen control: The purpose of which is the prevention, reduction or elimination of pathogens.

– Management of people and employees to be educated in the correct implementation of the biosecurity policies of the farm.

A key component of biosecurity is understanding the risks present in a given environment. Factors to consider include the types of animals being raised, the water source, the type of feed used and other practices that could introduce disease-causing agents or stressful situations to the animals. Other important considerations are the proper methods of handling and shipping live fish and seafood products, as well as how waste from an aquaculture facility is handled. 

Many aquaculture facilities use chemicals and antibiotics to treat their fish when they become sick; these chemicals can be harmful to humans if ingested. For this reason, it is also important to implement practices that control potential run-off into nearby areas where people may come into contact with the water.

There are several measures that can be taken to improve biosecurity in aquaculture. These include proper zoning of facilities to prevent movement from one area to another, limiting access to certain areas to authorised persons only, regular monitoring and testing of animals for diseases, and implementing a quarantine system for newly introduced animals. Other important practices include ensuring that fish are housed in appropriate conditions (e.g. appropriate water temperature and salinity), that feed is stored in clean conditions so as not to introduce pathogens or contaminants, and that waste products are disposed of correctly.

In addition, it is important to maintain good hygiene practices among workers in aquaculture facilities. This means washing hands thoroughly before and after handling or feeding fish, wearing protective clothing such as gloves and aprons, and disinfecting equipment that comes into contact with the animals.

Effective management of the fish stock on the farm.

Getting healthy animals into the farm is essential to get off to a good start. Eggs, fry and broodstock should be purchased from reputable suppliers. Most suppliers offer verified information that guarantees that the animals are free of pathogens. This is undoubtedly the best way to acquire new fish for the farm.

Before acquiring new fish the farm should learn as much as possible about their health, their origin, their medical history including previous treatments, diseases or any other circumstances that may have influenced their health status. Without access to clear and concise information on these parameters, it is best not to purchase the fish or to subject them to a specific and thorough medical examination soon after purchase.

Moreover, strains of some aquaculture species are known to be more resistant to specific diseases. Monitoring the lineage and genetics of your broodstock helps to avoid inbreeding and ensures the production of healthy gametes and offspring, thus guaranteeing the quality of the final product.

Good practice in quarantine processes

An optimal quarantine model brings together elements such as isolation, observation, diet adjustment, sampling and, of course, treatment.

Typically, to prevent exposure to other pathogens, fish are kept in closed groups throughout the quarantine period. This prevents the population from being affected by the addition of new fish to the group, allowing a much more effective analysis of the risks faced by the group.

A quarantined group of fish should be physically isolated from other quarantined stocks and, of course, from resident stocks. Isolation methods should be integrated into the design of the facility and system. If logistics preclude complete isolation, populations should be separated by tanks. Regardless of the level of isolation, appropriate sanitation and disinfection measures should be used to reduce cross-contamination between established and separated quarantined populations.

Observation is another essential element to be applied during quarantine. The normal and abnormal behaviour of the animals should be studied so that diseases or abnormalities can be detected at an early stage allowing for a much more effective dietary adjustment and care of the whole group.

During the sampling and treatment stage, fish are sampled to identify specific diseases. The ideal process is based on a full necropsy assessment of several specimens.

However, for the most valuable specimens, a technique that avoids culling can be carried out to examine small sections of skin, fins and gills for parasites and blood culture for systemic bacterial infections.

The results of this whole process are used to improve quarantine methods and the use of medication.

Pathogen management

Not all pathogens present the same risks and dangers. Some are of greater concern than others. They are usually classified according to their ability to survive, the ease with which they can infect and cause disease, and even by their diagnosis and control. Although some pathogens cause disease more readily than others, environmental and host factors, especially the species and its immune status, will ultimately determine whether and to what degree fish become ill.

High animal density in a production unit, or even sediment can help to concentrate micro-organisms. Food not consumed by the fish and other organic matter present in the enclosure will support the survival and spread of pathogens. The most common species are perhaps Aeromonas and Vibrio. These are bacteria that prefer these highly organic environments, which can sometimes infect and live inside a fish without showing symptoms of disease.

Another group of bacteria, Streptococcus species, are not as common as Aeromonas and Vibrio but are difficult to remove once established within a system. Mycobacteria also live within biofilms that line tanks, filters and pipes. Some parasites, including trichodynids, sessile ciliates, Tetrahymena and Uronema, thrive in organic debris and dead or dying fish.

Procesos de saneamiento y desinfección

Saneamiento y Desinfección en ocasiones pueden llevar a confusión ya que no son lo mismo. Ambos procesos son absolutamente necesarios en cualquier piscifactoría para llevar un buen control de las enfermedades.

La limpieza es el primer paso hacia la consecución de un modelo óptimo de gestión de procesos de saneamiento y desinfección. Consiste en eliminar todo el material extraño (tierra, material orgánico, biopelícula), de los objetos de la unidad de producción. La desinfección es el segundo paso y elimina la gran mayoría o incluso todos los microorganismos patógenos presentes en el tanque o cercado. La desinfección es efectiva solo si los organismos en todas las superficies se exponen a un desinfectante apropiado en la concentración recomendada durante el tiempo recomendado.

Llevar una gestión adecuada de los procesos de desinfección permite disponer de un conocimiento adecuado del estado de la explotación y de los riesgos que pueden detectarse gracias al registro de las operaciones de esta naturaleza.

Learning from other sectors

Biosecurity is a relatively new concept in aquaculture. For this reason, it is worth taking note of how other types of farms face the challenges of their daily activity in order to try to extrapolate as far as possible good practices to a model that has yet to develop a large part of its production system.

For example, in the poultry industry, isolation techniques, sanitation, order of entry, fattening stations are implemented to control that external elements can have a substantial impact on the farm. These types of measures can be used to design processes that ensure that fish develop in environments that are conducive to their growth and condition.