Fish rickets, based on their causative agents, can be categorized into bacterial gill disease, fungal gill disease (also known as mold infection), and parasitic gill disease. These conditions significantly impact fish health and aquaculture productivity.
Bacterial gill disease is a prevalent infectious illness among fish, often occurring alongside bacterial enteritis and red skin disease. It causes severe damage to grass carp and adult fish, with mortality rates in grass carp reaching up to 60% during outbreaks. The disease also threatens species such as herring, salmon, and squid. In recent years, with the rise of high-density and intensive aquaculture practices, other species like catfish, tilapia, and clams have also been affected, with mortality rates commonly exceeding 40%. This condition poses a major challenge to sustainable aquaculture, prompting extensive research and the development of effective prevention and control measures.
**I. Pathogens**
1. **Bacterial Gill Disease**: Caused by *Myxococcus*, this bacterium is slender, flexible, and typically appears curved or bent, forming shapes like U, V, or Y. Cells range from 2 to 37 microns in length and reproduce through transverse division. It thrives best at pH 6.5–7.5 and 25°C, with reduced virulence at higher temperatures. It is sensitive to salt concentrations above 0.7% and can grow under both aerobic and anaerobic conditions, though growth is slower under anaerobic conditions.
2. **Fungal Gill Disease (Mycosis)**: Caused by *Plasmodium*, this fungus infects fish gills, producing straight hyphae that rarely branch. In some cases, such as in herring and squid, the hyphae form net-like structures that invade blood vessels and cartilage. Spores are approximately 8 microns in diameter, while hyphae vary in thickness depending on the host species.
3. **Parasitic Gill Disease**: Caused by parasites like *Chinese sturgeon*, these organisms attach to fish gills using hooks. Female *Chinese sturgeon* are cylindrical, milky-white, and measure 2.2–3.0 mm in length. Males are smaller and free-living. These parasites feed on fish tissue, causing inflammation, swelling, and respiratory issues, often leading to secondary bacterial infections.
**II. Symptoms and Epidemic Trends**
1. **Bacterial Gill Disease**: Affected fish exhibit sluggish behavior, floating on the surface, and difficulty breathing. Fins may fade, and gills show excessive mucus, discoloration, and necrosis. The disease is most active between 28–35°C and has become more widespread due to intensified farming practices, affecting various species including tilapia and clams.
2. **Fungal Mycosis**: Primarily affects young fish, with spores attaching to gills and developing into hyphae that destroy tissue and block blood flow. Outbreaks often occur in warm, nutrient-rich waters, particularly in the Yangtze River Basin, where sudden fish deaths are common.
3. **Chinese Sturgeon Infection**: Parasites attach to gills and body surfaces, causing swelling, reduced appetite, and poor growth. Severe infestations can lead to death, especially in older fish. The parasite is prevalent from April to November, with peak activity between June and July.
**III. Prevention and Control Measures**
**A. Bacterial Gill Disease**
1. **Prevention**:
- Administer tissue vaccines to improve survival rates.
- Apply lime to ponds to neutralize acidity and kill pathogens.
- Maintain water quality by regularly adding fresh water and using lime treatments.
- Use aquatic products like Quanchipang Baoshui II to control bacterial growth.
2. **Treatment**:
- Apply bactericidal agents like Bao Shengtang series at specified concentrations.
- Adjust water pH to around 8.5 after treatment.
- Administer medicated baits containing chlorothalonil.
**B. Fungal Infections**
- Keep pond water clean and well-oxygenated.
- Use products like Fei Shuibao to improve water quality.
- Reduce water fertility by replacing part of the water when an outbreak occurs.
**C. Parasitic Infections**
- Regularly apply insecticides like Fish Insect Enemy to control parasites.
- Follow strict guidelines for drug use to avoid toxicity and ensure safety.
**Note**: When using aquatic products like Bao Shengtang series, avoid mixing with alkaline substances and ensure even distribution. Protect against direct contact with skin and eyes, and seek medical attention if poisoning occurs.
Nutrient supplements
What is Nutrient supplements?
Nutritional supplements are preparations used to supplement nutrients that may be lacking in the body's daily diet. These formulations may be single or a combination of multiple nutrients, including but not limited to the following ingredients:
- Protein (e.g. protein powder)
- Fish oil (contains omega-3 fatty acids such as DHA)
- Various vitamins (such as vitamin A, B vitamins, vitamin C, vitamin D, vitamin E, etc.)
- Minerals (e.g. calcium, iron, zinc, selenium, etc.)
- Dietary fiber
- Other specific nutrients, such as Amino Acids, enzymes, probiotics, plant extracts, etc
The purpose of nutritional supplements is to meet the nutritional deficiencies that individuals may have due to special needs, dietary habits, digestive and absorption problems, health conditions (such as disease, pregnancy, aging, etc.) or other reasons. They are usually available in the form of tablets, capsules, oral liquids, powders, etc.
When choosing a nutritional supplement, one should consider an individual's physical condition, diet, and possible side effects. Although nutritional supplements can provide additional nutrients, it does not mean that they are a substitute for a balanced diet. The best strategy is usually to get most of your nutrients through a varied diet and use nutritional supplements when necessary under the guidance of a medical or professional. In addition, excessive consumption of certain nutritional supplements may also pose health risks, so it is recommended to consult a professional before use.
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