Recently in China, retail giant Dingdong Maicai announced an investment of 260 million RMB to establish the ‘Truly Safe Fish’ system, planning to construct nearly 3,000 sets of smart land-based recirculating aquaculture tanks. By embedding its pledge to ‘sell only safe seafood’ directly within RAS recirculating aquaculture facilities—a move where a consumer-facing giant is penetrating back into the source of aquaculture—this marks a shift where ‘safe seafood’ is evolving from a marketing selling point into a supply chain barrier. For crustacean products such as white-leg prawns, Chinese blue crabs, hairy crabs and lobsters, what does this trustworthy ‘farm-to-table’ chain signify? How does RAS recirculating aquaculture establish a ‘system-level pathogen barrier’ for disease prevention and control, and how does it help aquaculture operators achieve staggered market releases and secure favourable prices? Wolize explains.

Figure 1:System-Level Pathogen Barrier in RAS

I. Changing Consumer Preferences: ‘Safe Seafood’ Has Shifted from a Selling Point to a Prerequisite

Consumer focus regarding seafood is rapidly shifting: from ‘freshness’ to ‘the absence of drug residues, traceable origins and clean aquaculture water’. The procurement standards of supermarkets, e-commerce platforms and restaurant chains have also evolved accordingly—green certification, export registration and end-to-end traceability are becoming the ‘entry tickets’ for high-value-added seafood. The fact that retail giants are stepping in to build their own RAS (Recirculating Aquaculture System) facilities essentially answers the same question: seafood of consistent quality and verifiable origin must be managed right from the aquaculture water body.

In contrast, traditional earthen-pond aquaculture relies on the whims of the weather, introduces pathogens via external water sources, struggles to maintain a closed-loop record of medication use, and sees a concentrated flood of produce hitting the market—each of these aspects directly conflicts with the new standards. Crustaceans are particularly ‘vulnerable’ to the issue of drug residues—in the export trade of prawns and crabs, drug residues and disease history have historically been major sources of trade barriers. For crustacean products, which have rapid cultivation cycles and high shipment frequencies, a single quality issue could result in the loss of an entire year’s orders—the value of RAS recirculating aquaculture is evolving from merely ‘keeping them alive’ to ‘ensuring they can be sold with confidence’.

II. Controllable Diseases: Three Insights for Crustacean Farming from the ‘System-Level Pathogen Barrier’

The concept of a ‘system-level pathogen barrier’, proposed by industry experts, emphasises that disease prevention and control should not rely on ‘treating problems after they arise’, but rather on building multiple layers of defence through systematic design. For crustacean aquaculture, this offers three key insights:

1. Closed-loop water systems: Cutting off pathways for external pathogens

The greatest fear in shrimp and crab farming is the introduction of pathogens via external water sources: once viruses such as White Spot Syndrome Virus (WSSV) or Infectious Hypodermal and Haematopoietic Necrosis Virus (IHHNV) enter the pond via the water, they often wipe out the entire stock. RAS (Recirculating Aquaculture System) utilises a closed-loop water system, requiring only minimal top-ups of external water. This naturally isolates the pond from pathogens, parasites and harmful algae found in wild water sources, thereby reducing the likelihood of disease introduction at source.

2. Multi-stage Interception: Physical Filtration + Dual Protection via UV/Ozone Disinfection

Crustaceans produce large amounts of uneaten feed, and their excrement settles rapidly, creating a natural breeding ground for opportunistic pathogens such as Vibrio bacteria. Rotary microfiltration units promptly remove organic matter—such as uneaten feed and faeces—thereby reducing the conditions for pathogen proliferation; UV and ozone disinfection units continuously inactivate bacteria and viruses in the recirculating water. Disease prevention relies on ‘barriers’ rather than ‘medicines’, so the product is naturally free from drug residues.

3. Substrate Management: The Key Battleground for Crustacean Disease Prevention

Shrimps and crabs both live close to the substrate and are particularly vulnerable and sensitive during moulting periods: substrate decomposition and fluctuations in ammonia, nitrogen and nitrite levels can easily trigger problems such as sudden death, white faeces and moulting disorders. A combined design featuring bottom sediment collection, timely effluent discharge and microfiltration interception keeps the ‘bottom’ under control, which in turn manages the greatest disease risk in crustacean farming — this is also the aspect most commonly overlooked in standard recirculating aquaculture systems.

Figure 2:Year-Round Supply Calendar

III. Off-peak Marketing: Keeping Shrimps and Crabs ‘Available All Year Round’

Crustaceans exhibit extremely pronounced seasonality: during the peak marketing periods for Chinese crayfish and hairy crabs, the market is flooded with supply, driving down prices; once the season ends, however, these crabs become scarce. Although white-leg prawns can be farmed in multiple cycles, open-air ponds are significantly constrained by water temperature. RAS recirculating aquaculture systems, through heat pump temperature control and intelligent environmental management, stabilise the water at the optimal temperature range for each species — allowing them to moult and grow even in winter. Farmers can determine their own harvest schedule, enabling flexible planning of multiple cultivation cycles throughout the year.

This delivers two key benefits: firstly, it maximises the supply period, enabling balanced shipments throughout the year and securing long-term orders from B2B clients such as supermarkets, catering businesses and e-commerce platforms; secondly, it generates off-season price premiums by bringing products to market during periods when traditional supplies—such as crayfish and hairy crabs—are in short supply, leading to increases in both price and sales volume, whilst significantly improving farming turnover efficiency.

IV. Implementation Pathway: A Three-Step Upgrade to a ‘Trusted Aquaculture’ Supply Base

Step 1: Addressing shortcomings in water treatment. Begin by installing standardised water treatment units combining microfiltration, biochemical treatment and disinfection to stabilise water quality at levels of dissolved oxygen ≥6 mg/L and ammonia-nitrogen <0.5 mg/L; this forms the foundation of a ‘system-level pathogen barrier’;

Step 2: Establishing the ‘barrier’. Operate in a closed-water system, implement multi-stage coordinated disinfection, and strengthen bottom sediment management through sediment collection at the pond bottom. Additionally, establish standardised records for inputs to provide a basis for ‘reduced or no use of medication’;

Step 3: Let the data speak for itself. Deploy online monitoring and aquaculture record-keeping systems, integrate these with purchasers’ traceability platforms, and turn ‘traceability’ into a tangible competitive advantage. Where necessary, this should be complemented by Green Food certification and export registration.

V. How is ‘reliability’ verified? — A comparison of key indicators

Table 1: Comparison and validation of different farming systems

Note: The above is a general comparison of the two systems; actual results may vary depending on species, stocking density and management practices.

VI. Frequently Asked Questions (FAQ)

Q1: Can RAS recirculating aquaculture really achieve ‘zero drug residues’?

A: A closed water system combined with multi-stage disinfection significantly reduces the need for medication; under normal management conditions, it is possible to avoid the use of antibiotics; Combined with standardised records of inputs and aquaculture logs, ‘zero drug residues’ is verifiable and auditable—not merely a slogan.

Q2: What are the most common disease issues affecting crustaceans (prawns/crabs)?

A: Viral diseases (such as white spot syndrome) and vibriosis are the two most prevalent issues; mysterious deaths, white faeces and molting disorders triggered by deteriorating bottom sediment are also common. The Wolize solution comprehensively manages bottom sediment quality — from sediment collection at the pond bottom and microfiltration of effluent to biological purification — eliminating the causes of disease before they arise.

Q3: How exactly is staggered market release implemented?

A: By controlling temperature to regulate growth and moulting cycles, harvest times are ‘scheduled’ to coincide with periods when traditional supplies are scarce and prices are higher — for example, bringing crayfish and hairy crabs to market during the off-season; Combined with stable water quality and survival rates throughout the year, B2B clients are confident in signing long-term supply agreements.

Q4: What does the farming sector need to do to meet consumer demands for ‘traceability’?

A: The key lies in data. Online water quality monitoring combined with routine production records automatically generates farming records. Once integrated with the purchaser’s traceability platform, consumers can scan a QR code to view the farming water body and management records — this is precisely the inherent advantage of RAS intelligent environmental control.

VII. Partnership Enquiries

Are you ready to tap into the most lucrative sector of the aquaculture industry and establish a live crustacean farming facility for off-season supply? WoLize’s Facility Aquaculture Engineering Team offers a full-cycle, turnkey solution—from commercial ROI calculations and multi-storey facility design drawings to the supply of core equipment and on-site artificial seawater commissioning.