Breeding Techniques of Early Breeding of Carp in Cold Region
In the Ningxia region, naturally bred fry larvae typically become available in mid to late May, which results in smaller fish size and lower survival rates during winter. To address this issue, local squid farmers have increasingly turned to air-fry transportation from southern Wuzi, although this method is costly and can introduce pathogens. In 2004, an artificial breeding experiment was conducted in March and April to achieve earlier fry release, aiming to boost production and income.
**Materials and Methods**
1. **Broodstock Breeding and Selection**
- **Breeding Ponds**: The cultivation ponds covered 8 acres, all rectangular plastic greenhouses oriented east-west. The bottom sludge was 10–15 cm deep, with a water depth of 1.2 meters. Before stocking, dry lime (100–150 kg/mu) was used for disinfection.
- **Broodstock Source**: A total of 875 sturgeon were used, including 575 females and 300 males, aged between 2 to 8 years, weighing 1.0–4.0 kg.
- **Feeding and Management**: Stocked on February 20th at a density of 50–80 tails/mu, fed 1–2 times daily with concentrate feed (malt, grain buds, cakes), at 5–10% of body weight. After 30 days of intensive care, gonads developed well.
- **Selection Criteria**: Broodstock were selected from individuals weighing 1–3 kg, with no injuries, smooth bodies, and normal activity. Female bellies were large and soft, with visible ovaries when viewed from above, while males had significantly smaller bellies.
2. **Artificial Oxytocin and Incubation**
- **Oxytocin Production**: A standard cement pool (3.8 m × 3.1 m × 1.2 m) with 50–60 cm water depth was used. Water came from the Yellow River, aerated and heated to maintain 22–26°C.
- **Hormone Injection**: A single dose of DOM+LRH-A2 (3 mg DOM + 10 μg LRH-A2/kg) was injected into the body cavity. The injection angle was 45–60°, avoiding internal organs.
- **Artificial Insemination**: Dry insemination was used. Eggs were collected by gently squeezing the female’s abdomen, then mixed with male sperm. This process continued until all eggs were collected.
- **Incubation**: Fertilized eggs were placed in muddy water to stick, then washed and treated with methylene blue. Hatching was carried out in running water with a gentle rotation, yielding about 800,000 eggs per cubic meter.
3. **Artificial Seedling Cultivation**
- **Pre-cultivation**: Ponds were prepared with quicklime (115 kg/mu), and water was filled to 50–70 cm before stocking. Fermented manure (305 kg/mu) was added one week prior to release. Stocking density was 120,000–150,000/mu.
- **Incubation Period**: After hatching, fry were fed cooked egg yolk and later transitioned to soy milk and fertilizer. Regular checks ensured disease control and optimal growth.
**Test Results**
- **Broodstock Breeding**: 875 broodstock were used, with 114 semi-produced and 575 fully productive. Egg production rate was 80.18%, with effective fertility of 49/g body weight.
- **Hatching Rate**: Three batches were produced, totaling 509.10 million larvae. The second batch showed a 15.38% drop in hatching rate due to residual enzymes.
- **Survival Rate**: Fry reached 19.87 mm in length, with over 3 million exceeding 24 mm. Survival rate was 95.7% for flower fry and 35% for wuzi.
**Discussion**
- Early propagation using plastic greenhouses allowed fry to be released 20 days earlier than natural conditions, improving economic returns.
- Proper timing of spawning based on weather changes was crucial. Water temperature and flow were key factors in successful spawning.
- Disease prevention, especially against aquatic mold, was vital. Methylene blue treatment improved hatching success.
- Early fry faced challenges due to cold temperatures, highlighting the need for controlled environments.
- Spawning volume was low in some batches, likely due to young broodstock or aging. Optimal broodstock age was 2–6 years, with sufficient protein feeding ensuring high fertility.
This study demonstrated that early artificial breeding can significantly enhance productivity and sustainability in trout farming in Ningxia.
Author: Gansu Agricultural University
Dosidicus Gigas Giant Squid, Frozen Dosidicus Gigas Squid,Frozen Giant Squid Tube,IQF Giant Squid Tube
Zhejiang Industrial Group Co., Ltd. , https://www.xingyeseafood.com