In the scorching summer heat, it's also the peak season for catching fish and shrimp. While farmers and fishmongers enjoy the harvest, the sudden occurrence of dead fish during fishing and transport has become a major concern. In polyculture ponds where fish, pigs, and ducks coexist, or in ponds affected by disease, the problem is especially severe. After netting, it's common to see dozens to even thousands of catties of dead fish. By the time the fish reach the market, they often show signs of redness, scale loss, mucus shedding, and even mass mortality, leading to poor sales, price drops, and significant financial losses.
In 2009, a massive fish die-off occurred during netting, affecting all sizes and breeds, causing huge economic damage. To prevent such losses, an effective pre- and post-netting treatment method has been introduced, offering a practical solution for the industry.
**Traditional Netting Challenges**
Traditionally, fishermen have relied on high doses of copper sulfate to shrink fish scales before netting, which can irritate the fish and increase mucus production. During transport, salt and antibiotics are used to protect the fish, while disinfectants like chlorine dioxide and quicklime are applied to the ponds afterward. However, these methods are not only environmentally harmful but also ineffective and sometimes lead to more fish deaths.
The main causes of fish and shrimp mortality after netting include:
1. **Poor Water Quality**: After months of breeding, excess feed and waste accumulate at the pond bottom, releasing harmful substances like ammonia, nitrites, and hydrogen sulfide. When the net is pulled, these toxins are stirred up, causing acute poisoning.
2. **Liver Overload**: Fish and shrimp often suffer from heavy liver burdens, making them more vulnerable to stress and illness.
3. **Stress Response**: The process of netting and transport causes extreme stress, leading to physical damage and death.
4. **Overuse of Medicines**: Excessive use of antibiotics and disinfectants can impair the fish’s natural mucus production, making them more susceptible to disease.
Farmers often rush to sell sick fish and shrimp to avoid losses, but this only worsens their condition, especially during hot weather when stress and mortality rates are high.
**"Five Steps to Pull Nets" – A Better Approach**
Based on three years of field experience in Guangdong, the Fangcao Hang Seng Fisheries Technical Service Center developed a five-step method to reduce fish and shrimp mortality during netting. This approach focuses on improving the environment and reducing stress, and it has been widely adopted in areas like Shunde and South China Sea with excellent results.
1. **Reduce Feeding 2 Days Before Netting**: Stop feeding two days before to lower metabolism, reduce oxygen demand, and minimize fecal contamination during transport.
2. **Improve Water Quality Before Netting**: Use probiotics like Bacillus and EM bacteria 3–5 days prior to enhance water quality and reduce toxic substances at the pond bottom.
3. **Use Anti-Stress Products**: Apply herbal-based anti-stress solutions like "Ginger Kushen Liquid" and "Compound Kushen Kosuisan Powder" 5–12 hours before netting to reduce stress and protect the fish from injury.
4. **Apply High-Concentration Solutions in the Cage**: After netting, apply a concentrated version of "Ginger Sophora flavescens" to help restore mucus and strengthen the fish’s resilience.
5. **Purify the Water Immediately After Netting**: Use agents like alumina or zeolite powder to clean the water and prevent disease outbreaks caused by disturbed pond conditions.
This five-step method is safe, cost-effective, and free from chemical residues, meeting the standards for aquatic product safety. It can be used across various species, including fish, shrimp, crabs, and shellfish. Given the investment already made in seedlings, feed, and management, reducing post-harvest losses is a smart and profitable move worth trying.
Guangzhou Fuerle Health Technology Co., Ltd , https://www.fuerlegroup.com