A Detailed Walkthrough of Diseases and Treatments in Fish Farming

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Aquaculture, the cultivation of aquatic organisms like fish, is a fascinating and economically significant industry that plays a pivotal role in meeting the world’s growing demand for seafood. However, just like any other form of agriculture, fish farming faces its fair share of challenges, and one of the most critical aspects is the health of the fish population. Fish are susceptible to a variety of diseases, infections, and parasites that can severely impact their growth and overall well-being. In this context, understanding different treatment methods, such as dip treatments and bath treatments, becomes paramount for fish farmers and aquaculture enthusiasts alike. In this guide, we will explore these treatment techniques, their applications, and the importance of precise execution in maintaining the health and vitality of your aquatic companions.

Bacterial Infections

• Condition: Fin and Tail Erosion
• Causative Agents: Aeromonas, Pseudomonas, and Vibrio
• Indications: Appearance of a white border on fin margins; fragility and breakage of fin rays.
• Remedies: Submerge the affected fish in a solution containing 500ppm copper sulfate for a brief 1-minute duration.

 

• Condition: Ulcerative Lesions
• Causative Agents: Aeromonas hydrophilla and Pseudomonas
• Indications: Presence of open sores or ulcers on the body.
• Remedies: Conduct a 1-minute immersion treatment using a 1:2000 copper sulfate solution for 3-4 days.

 

• Condition: Dropsy
• Causative Agent: Pseudomonas punctata
• Indications: Accumulation of fluid within the body cavity; protruding scales; exophthalmic condition.
• Remedies: Administer a 2-minute dip treatment in a 5ppm potassium permanganate solution.

 

• Condition: Eye Ailment
• Causative Agent: Aeromonas liquifaciens
• Indications: Vascularization of the cornea followed by opacity and decay of the eyeball.
• Remedies: Apply Chloromycetin (8-10 mg/liter) bath for 1 hour over 2-3 days.

Fungal Infections

• Condition: Water Mold Infection (Saprolegniasis)
• Causative Agent: Saprolegnia parasitica
• Indications: Fish succumbs after skin ulceration or exfoliation, leading to hemorrhaging, blindness, and the emergence of white hair-like growths in affected areas.
• Remedies: Submerge the fish for 3 seconds in a 1:10,000 malachite green solution or for 5-10 minutes in a 3% common salt solution or potassium permanganate solution.

Protozoan Diseases

• Condition: Ichthyophthiriasis (White-Spot Disease)
• Causative Agent: Ichthyophthirius multifilis
• Indications: Small whitish cysts approximately 1mm in diameter on the skin, gills, and fins.
• Remedies: Conduct a 5-day bath treatment in a 2ppm methylene blue solution, or use an hourly dip treatment in a 1:5,000 formalin solution for 7-10 days.

 

• Condition: Boil Disease
• Causative Agent: Myxobolus pfeifferi
• Indications: Development of large boils ranging from the size of a nut to that of a hen’s egg on various parts of the body.
• Remedies: Bathe the fish in a 3% common salt solution or a 1:2,500 formalin solution for 10 minutes.

 

• Condition: Whirling Disease
• Causative Agent: Myxobolus cerebralis
• Indications: Caudal bending, deformities in the oral region, and darkening of the tail region.
• Remedies: Eradicate all infected fish by applying quicklime (pond disinfectant) at a rate of 2 tons per hectare.

 

• Condition: Costiasis
• Causative Agent: Costia necatrix
• Indications: Bluish coating on the skin, irregular patches of lesions.
• Remedies: Perform a bath treatment in a 3% common salt solution or a 1:2,500 formalin solution for 10 minutes.

Trematode Infections

• Condition: Gyrodactylosis
• Causative Agent: Gyrodactylus sp.
• Indications: Fading colors, drooping scales, and skin peeling.
• Remedies: Conduct a dip treatment in a 5% common salt solution or a 1:5,000 formalin solution for 5 minutes.

 

• Condition: Dactylogyrosis
• Causative Agent: Dactylogyrus sp.
• Indications: Fading colors, drooping scales, and skin peeling.
• Remedies: Perform a dip treatment in a 5% common salt solution or a 1:5,000 formalin solution for 5 minutes.

 

• Condition: Diplostomiasis (Black Spot Disease)
• Causative Agent: Diplostomulum sp.
• Indications: Small black nodules approximately 1-5mm in diameter in affected areas.
• Remedies: Administer a dip treatment in a 3:1,00,000 picric acid solution for 1 hour or Di-n-butyl tin oxide at a rate of 250mg/kg fish.

Cestode Infections

• Condition: Ligulosis
• Causative Agent: Ligula sp.
• Indications: Fish appears dull and sickly, with parts of the alimentary canal swollen or completely obstructed by cestode cysts or worms.
• Remedies: Conduct a dip treatment in a 3:1,00,000 picric acid solution for 1 hour or Di-n-butyl tin oxide at a rate of 250mg/kg fish.

Nematode Infections

• Causative Agents: Philometra sp., Camallanus sp.
• Indications: Fish looks dull and sickly, with parts of the alimentary canal swollen or entirely obstructed by roundworms.
• Remedies: Administer a dip treatment in a 3:1,00,000 picric acid solution for 1 hour or Di-n-butyl tin oxide at a rate of 250mg/kg fish.

Acanthocephala Infections

• Causative Agent: Acanthogyrus sp.
• Indications: Presence of yellowish-white fibro epithelioma on the lips, skin, and fins of the fish.
• Remedies: Treatment with quicklime.

Hirudinea Infections

• Causative Agent: Hemiclepsis sp.
• Indications: Abnormal fish movements due to irritation as the parasites feed on the host’s blood.
• Remedies: Conduct a dip treatment using a 1:100,000 solution of glacial acetic acid.

Copepod Infestations

• Causative Agents: Argulus sp., Ergasilus sp., Lernea sp., Caligus sp., Pseudocycnus sp., Clavellisa sp.
• Indications: Loss of scales, the presence of red spots, and damage to the gills.
• Remedies: Treatment involving a half-hour immersion in a 500ppm formalin solution, mechanical removal using forceps followed by a bath in a weak potassium permanganate solution for 2-3 minutes, a bath in a 1:1,000 glacial acetic acid solution for 5 minutes, and subsequently, a bath in a 1% common salt solution for 1 hour. Pond disinfection can be achieved by applying lindane at a rate of 8ml per 1,000 liters.

Viral Infections

• Disease: Lymphocystis
• Causative Agent: Lymphocystis spp. (A DNA Iridovirus)
• Indications: Lethargy and potential effects on balance and swimming control, especially along the lateral line.
• Remedies: Promote frequent water changes and reduce ammonia and nitrite levels to alleviate stress, allowing the fish to combat the infection and shrink tumors naturally.

 

• Disease: Infectious Pancreatic Necrosis (IPN)
• Causative Agent: IPN virus
• Indications: Darkening of color, tail-chasing, and spiral swimming behavior.
• Remedies: Ensure a clean water supply and provide optimal nutrition.

Other Diseases

Gas Bubble Disease

Gas bubble disease may occur due to nitrogen saturation in water, often resulting from rapid temperature changes. Fish fry, in particular, can experience high mortality rates. Affected fish may exhibit an angled swimming posture with their heads pointing downward. Symptoms may also include the presence of bubbles beneath the skin, on fins, around the eyes, in the stomach and intestine, or in blood capillaries. Remedies include agitating the water to reduce nitrogen saturation or transferring affected fish to other ponds. Supersaturated levels of oxygen have also been linked to gas bubble disease in fish.

Vitamin Deficiencies

Symptoms of vitamin deficiencies in fish can include scoliosis (curved spine), reduced growth, and anorexia (lack or loss of appetite). Signs of these deficiencies may manifest as low fish weight and lethargy.

Varieties of Treatment:

Immersion Treatment:

In the immersion treatment, fish are exposed to a relatively concentrated chemical solution for a brief duration, typically less than one minute. Here’s the procedure:

1. Prepare the chemical solution in a suitable container like a bucket, half-drum, or trough.
2. Place the fish or a group of fish in a specialized dip net.
3. Submerge the fish into the solution for the specified time frame
4. Immediately after treatment, return the fish to well-oxygenated water.

Bathing Treatment:

During bath treatment, fish are immersed in a diluted solution of the chemical for an extended period, which can range from a few minutes to up to one hour for short baths or even 24 to 48 hours for longer baths, especially in cases of very low chemical concentrations. Follow these steps:

(a) Short Bath:

For a short bath, mix the required amount of chemical with water in a plastic watering can. Lower the water level in the tank or circular enclosure by one-third to one-half. Gradually reintroduce water while evenly distributing the previously mixed chemical over the entire water surface. If necessary, stir the water with a clean broom, an agitator, or an aerator to ensure thorough dispersion of the chemical throughout the water column. Once the water returns to its usual level, treat for the recommended duration. Afterward, drain two-thirds of the water while resuming water inflow.

(b) Long Bath:

In the case of a long bath, halt the water inflow into the tank or pond. Reduce the water volume by draining some water, ensuring it’s at an appropriate level for the stock density and water temperature conditions. Calculate the water volume and determine the necessary chemical quantity. Dilute this chemical amount considerably, often at least 100 times, by mixing it in several plastic containers before application. Add this diluted solution to the tank or pond, making an effort to evenly disperse it over the entire water surface and thoroughly incorporate it with the pond water. Treat for the recommended duration. Subsequently, reopen the water inflow and elevate the water level to its normal state. If required, repeat the draining and refilling process.

In conclusion, proper diagnosis and timely application of the appropriate treatments are crucial for maintaining the health and well-being of your fish. Whether it’s through dip treatments or bath treatments, the care you provide to address various infections and diseases can make a significant difference in the vitality of your aquatic companions. Always remember to follow recommended procedures and guidelines to ensure the best outcomes for your fish population.