Stress in fishing

  • . Stocking density

    The amount of fish you can safely and legally keep in your system (fish welfare) depends on many factors. There would be, among other things:

    • Feed rate / quantity / feed type
    • Pump performance and reservoir size/circulation speed
    • Amount of water or nutrient solution
    • Water temperature
    • water flow
    • Oxygen content
    • Nitrite and nitrate content
    • Number of plants in the bed or in the hydroponic system
    • Volume of the plant bed or amount of nutrient solution
    • Fish species or species
    • Aquarium size

    Not all the decisive factors are mentioned here!

    In smaller systems but beyond your own needs , you can expect around 10-12 fish in a 1000 liter aquarium = 1m 3  = 1 IBC container (open at the top).

     

    Be sure to consult with an official veterinarian about the legal regulations before building the fish farm. These change regularly!

    Here are the regulations, some of which come from breeding in ponds because the legislature has not yet derived all the regulations for aquaponics:

     

    Stocking densities according to EU organic aquaculture regulations:

    15 kg/m³ brook trout (Salvelinus fontinalis)
    15 kg/m³ Coregonen (Whitefish Coregonus)
    15 kg/m³ trout (Oncorhynchus, Trutta)
    20 kg/m³ Arctic char (Salvelinus alpinus)
    25 kg/m³ brown and rainbow trout
    20 kg/m³ salmon: brown trout (Salmo trutta fario), lake trout (Salmo trutta lacustris), sea trout (Salmo trutta trutta), rainbow trout (Oncorhynchus mykiss)
    10 kg/m³ milkfish (Chanos chanos)
    10 kg/m³ tilapia (Oreochromis sp.)
    10 kg/m³ Mekong catfish (Pangasius sp.)
     
    Quote : The prerequisites are compliance with the ban on deterioration in water quality (2) (in accordance with Directive 2000/60/EC European Water Framework Directives), as well as an oxygen saturation of at least 7 mg/L and a minimum inflow rate of 3 seconds liters per ton of fish. Under no circumstances should the animals show injuries (e.g. to the fins) that indicate that the stocking density is too high. Tropical freshwater fish (e.g. milkfish Chanos chanos, tilapia Oreochromis sp., Mekong catfish Pangasius sp.): the stocking density in ponds and net enclosures (pens, enclosures) must not exceed 10 kg/m3 as an upper limit. 
     
    COMMISSION REGULATION (EC) No 710/2009 of 5 August 2009
    https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:204:0015:0034:DE:PDF
     

    Salmonids in freshwater:
    Trout (Salmo trutta) - Rainbow trout (Oncorhynchus mykiss) - Brown trout (Salvelinus fontinalis) - Salmon (Salmo salar)
    - Arctic char (Salvelinus alpinus) - Grayling (Thymallus thymallus) - American arctic char (Salvelinus namaycush) -
    Huchen (Hucho hoo)

     

    Production system: Production must take place in open systems. The water change rate must ensure an oxygen saturation of at least 60%, be tailored to the needs of the animals and ensure sufficient drainage of the water in the holding area.

    Maximum stocking density

    Salmonids other than those listed below: less than 15 kg/m 3
    Salmon: 20 kg/m 3
    Brown trout and rainbow trout: 25 kg/m 3
    Arctic char: 20 kg/m 3

    Sturgeon (Acipenseridae) in freshwater
    production system: The water flow in each housing unit must meet the physiological needs of the animals.
    The outgoing water must be of equivalent quality to the incoming water.

    Maximum stocking density 30 kg/ m3

    Carp fish (Cyprinidae) and other associated species in polyculture, including perch, pike, catfish, pike, sturgeon.

    In fish ponds, which are completely drained at regular intervals, and in lakes. Lakes must be used exclusively for organic production, including agriculture in their dry areas. The fishing area must have an inflow of fresh water and be large enough so that the animals' well-being is not impaired. After harvesting, the fish are kept in fresh water. 

    Flag shrimp (Penaeidae) and freshwater shrimp (Macrobrachium spp) 

    Establishment of production units: Settlement in areas with infertile clay soils to minimize the environmental impact of pond construction. Pond construction with the existing clay. The destruction of mangrove stands is not permitted.

    Transition time Six months per pond, corresponding to the usual lifespan of shrimp in aquaculture
    Origin of the parents: At least half of the parents must come from offspring after three years of operation of the facility. The remaining parent stock must come from pathogen-free wild stocks from sustainable fishing. The first and second generations must be screened before being introduced into the systems.
    Removal of eyestalks is prohibited
    Maximum stocking densities and production quantities


    Cultivation: maximum 22 postlarvae/m 2
    Maximum density: 240 g/m 2

    Milkfish (Chanos chanos), cichlids (Oreochromis sp.), shark catfish (Pangasius sp.)
    Production systems Ponds and net cages
    Maximum stocking density

    Shark catfish: 10 kg/m 3
    Cichlids: 20 kg/m 3

    Sources include: https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:204:0015:0034:DE:PDF

    Context: 

  • . Typicall fish diseases

    In aquaponics systems, fish can be susceptible to various diseases, just like in traditional aquaculture setups.
    Some common fish diseases that may occur in aquaponics include:

     

    • Columnaris Disease (Flexibacteriosis):

      • Caused by the bacterium Flavobacterium columnare.
      • Symptoms include white or grayish patches on the skin, frayed fins, and lethargy.
     

    • Aeromonas Infections:

      • Caused by bacteria of the genus Aeromonas.
      • Symptoms may include ulcers, fin rot, hemorrhages, and abdominal swelling.
     

    • Dropsy:

      • A symptom rather than a specific disease, dropsy is characterized by fluid retention and swelling of the abdomen or body cavity.
      • Can be caused by various bacterial, viral, or parasitic infections.
     

    • Ichthyophthirius (Ich):

      • A protozoan parasite commonly known as "white spot disease."
      • Symptoms include white spots on the skin, rapid breathing, and rubbing against objects.
     

    • Dactylogyrus (Gill Flukes) and Gyrodactylus (Skin Flukes):

      • Parasitic flatworms that infect fish gills or skin.
      • Symptoms include increased mucus production, respiratory distress, and skin irritation.
     

    • Koi Herpesvirus (KHV):

      • A highly contagious virus affecting common carp and koi.
      • Symptoms include lethargy, loss of appetite, skin lesions, and respiratory distress.
     

    • Viral Hemorrhagic Septicemia (VHS):

      • Caused by a rhabdovirus, VHS primarily affects salmonids but can also impact other fish species.
      • Symptoms include hemorrhages, abdominal distension, and lethargy.
     

    • Cyprinid Herpesvirus 3 (CyHV-3):

      • Also known as koi herpesvirus (KHV), this virus primarily affects koi and common carp.
      • Symptoms include skin lesions, lethargy, and respiratory distress.
     

    • Fin Rot:

      • Often caused by bacterial infections, fin rot leads to the deterioration of fins.
      • Symptoms include frayed or eroded fin edges and reddening or inflammation of the fin base.
     

    • Bacterial Septicemia:

      • General term for bacterial infections that spread throughout the bloodstream.
      • Symptoms may include lethargy, loss of appetite, skin discoloration, and hemorrhages.
     

    Preventive measures such as maintaining optimal water quality, practicing good hygiene, quarantining new fish, and providing balanced nutrition can help minimize the risk of disease outbreaks in aquaponics systems. Additionally, early detection and prompt treatment of sick fish are crucial for preventing the spread of diseases and minimizing losses.

    How to avoid them

    Preventing fish diseases in aquaponics systems involves implementing various management practices to maintain optimal water quality, minimize stress on fish, and prevent the introduction and spread of pathogens. Here are some key preventive measures:

     

    • Maintain Optimal Water Quality:

      • Regularly monitor and maintain water parameters such as temperature, pH, ammonia, nitrite, nitrate, and dissolved oxygen levels within recommended ranges.
      • Ensure proper filtration and aeration to remove waste products, maintain oxygen levels, and promote a healthy aquatic environment.
      • Perform routine water changes to dilute accumulated toxins and replenish essential nutrients.
     

    • Practice Good Hygiene:

      • Keep the aquaponics system and equipment clean and free of debris, algae, and biofilm buildup.
      • Regularly clean and disinfect equipment, such as pumps, filters, and grow beds, to prevent the buildup of pathogens.
      • Practice proper hand hygiene and use separate tools and equipment for different aquaponic components to prevent cross-contamination.
     

    • Quarantine New Fish:

      • Quarantine newly acquired fish in a separate tank or system for a period of time (usually 2-4 weeks) to monitor for signs of illness before introducing them to the main aquaponics system.
      • Observe quarantined fish for symptoms of disease such as abnormal behavior, appetite loss, lesions, or fin damage.
     

    • Provide Proper Nutrition:

      • Offer a balanced diet appropriate for the species of fish being cultured, ensuring they receive essential nutrients and vitamins to support immune function and overall health.
      • Avoid overfeeding, as excess uneaten food can decompose and degrade water quality, leading to increased disease risk.
     

    • Monitor Fish Health:

      • Regularly observe fish behavior, appetite, and appearance for signs of illness or distress.
      • Conduct routine health checks and screenings, including visual inspections, netting and handling fish for closer examination, and observing water quality parameters.
     

    • Avoid Stress:

      • Minimize stress on fish by providing adequate space, shelter, and hiding places within the aquaponics system.
      • Avoid sudden changes in environmental conditions, such as rapid temperature fluctuations or water chemistry swings, which can stress fish and weaken their immune systems.
     

    • Practice Biosecurity:

      • Limit the introduction of potential pathogens by purchasing fish from reputable sources with known health histories.
      • Restrict access to the aquaponics system to authorized personnel only, and implement biosecurity protocols to prevent contamination from outside sources.
     

    By implementing these preventive measures and maintaining a proactive approach to fish health management, aquaponics practitioners can minimize the risk of disease outbreaks and maintain a healthy and productive system for both fish and plants. Regular observation, monitoring, and timely intervention are key to identifying and addressing potential issues before they escalate.

     

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