The Miracle of "Sweetening" Brackish Water

TừFor a long time, the land of Lap Le (now Nam Trieu ward, Hai Phong city) has been famous for sea fishing and aquaculture. However, the shift from traditional farming practices to the application of science and technology, combined with building geographical indications for brackish-water black carp, is opening up a new direction. This is not just a story about farming techniques, but also an information and knowledge problem—bringing scientific expertise to the alluvial flats to elevate aquaculture value.

Along the right dike of the Bach Dang River in the final days of the year, harvesting at aquaculture ponds in Nam Trieu Ward is in full swing. Unlike the common belief that black carp is strictly a freshwater species, local farmers have domesticated it to thrive in brackish water, creating a product of superior quality.

Promoting information transparency and standardizing technical procedures not only reduces disease risks but also serves as the foundation for achieving food safety and VietGAP certifications, paving the way into supermarkets and high-end kitchens," shared Mr. Nguyen Duc Van, Director of Mat Rong Cooperative.

Mr. Pham Van Khai, Head of the Economic Department of Nam Trieu Ward, noted that the locality currently has over 100 aquaculture households outside the dike, spanning hundreds of hectares. The unique advantage lies in the estuarine alluvial flats, where the brackish-water environment continuously circulates with the tides, rich in minerals and plankton.

Practical data shows a clear gap in productivity. While freshwater black carp yields in Northern provinces average around 20 tons/ha, Nam Trieu reaches up to 50 tons/ha. For polyculture or intensive high-yield species like sea bass, productivity can reach 60–70 tons/ha, or even 90 tons/ha.

Mr. Dinh Van Han, a pioneer with 21 years of experience in bringing black carp to brackish waters, shared: "Brackish-water black carp meat is firmer, more elastic, and significantly more flavorful than freshwater carp. That's why traders from famous braised fish regions like Vu Dai village (Ninh Binh) regularly come here to place orders."

With farm-gate prices ranging from 75,000 to 80,000 VND/kg, each hectare of black carp can yield approximately 1 billion VND in profit per crop after costs. This is an enviable figure for many aquaculture regions nationwide.

However, high profits always come with significant risks if scientific information is lacking. Previously, local farmers practiced extensive farming based purely on experience. After each crop, the pond environment accumulated excess feed and waste, generating toxic gases that led to ulcer diseases and parasites, reducing survival rates.

Recognizing this issue, the Hai Phong agricultural sector and the Department of Science and Technology intervened with in-depth research and discussions. City-level scientific research projects were implemented to provide information and establish semi-intensive commercial farming procedures for brackish-water black carp.

The new procedure demands strict compliance right from the pond preparation stage. Under the updated practices, the farming cycle typically lasts 1.5 to 2 years, with some ponds extending up to 3 years for fish to reach a weight of 8–10 kg. After harvest, dredging, bottom drying, and disinfection are thoroughly performed to break disease cycles. Stocking density, nutritional regimes, and water quality management are monitored using environmental sensors rather than visual judgment.

The Challenge of Information, Deep Processing, and Branding

A food-for-thought reality facing Vietnamese agriculture today is the cycle of "good harvest, falling prices" due to selling mostly raw products. To tackle this challenge in Nam Trieu Ward, the role of new-generation, youth-led cooperatives is being strongly promoted.

Established in May 2024, the Lap Le Aquaculture Development Cooperative is a prime example of innovative thinking—connecting, updating, and disseminating scientific and technical information, policies, regulations, and effective models to its members. Instead of relying solely on selling live fish, the cooperative has invested in modern machinery, including industrial slicers, vacuum packaging machines, and blast freezers, to enable deep processing.

Mr. Vu Van Da, Director of the Cooperative, shared: "We want to eliminate the mindset of bulk raw selling. Our one-night-dried brackish-water black carp is our first 3-star OCOP product, which also won third prize in the 2024 National Farmer Innovation Competition. Deep processing elevates the product's value, extends shelf life, and allows it to reach distant markets as a luxury gift item."

Alongside enterprise efforts, state regulatory guidance is essential for establishing trademark sovereignty, providing scientific insight, and delivering tailored aquaculture solutions. The Hai Phong Department of Science and Technology has repeatedly hosted advisory panels to promote scientific awareness while launching the project "Support for Managing, Exploiting, and Developing the Collective Trademark 'Lap Le Aquaculture'."

This represents a fundamental step in addressing market information deficits for local farmers. With an established brand, product information becomes transparent, ensuring that the commercial value of Nam Trieu black carp extends far beyond raw material prices. As information flows freely, scientific practices take root, and the brand gains recognition, the black carp will truly serve as a brand ambassador for Hai Phong agriculture, driving long-term prosperity for aquaculturists in this estuarine region.