Vietnam’s Vannamei Shrimp : Black Spot or Defect
Natural Phenomena Affecting Vannamei Shrimp Harvest
Vannamei shrimp farming is sensitive to several natural phenomena that can significantly affect yields:
Salinity Fluctuations: Changes in water salinity levels, particularly during the dry and rainy seasons, are one of the most important factors influencing vannamei shrimp growth. Vannamei shrimp prefer moderate salinity levels, and sharp fluctuations in salinity can lead to poor growth rates and higher mortality.
Water Temperature: Water temperature directly affects the metabolic rate of vannamei shrimp. Optimal temperatures for vannamei shrimp range from 26°C to 32°C. Extreme temperatures, either too high or too low, can lead to disease outbreaks and poor feed conversion efficiency.
Disease Outbreaks: Bac Lieu, like other provinces in the Mekong Delta, faces periodic outbreaks of diseases such as white spot syndrome virus (WSSV), early mortality syndrome (EMS), and bacterial infections like Vibrio parahaemolyticus, all of which can severely affect shrimp health and harvests.
Lifecycle of Vannamei Shrimp
Broodstock: Adult shrimp (broodstock) are maintained in hatcheries, where they spawn larvae.
Larvae: The larvae develop in hatcheries and are then transferred to farms for further growth.
Juvenile Stage: Once they reach the juvenile stage, they are stocked in ponds. Under optimal conditions, they grow rapidly, reaching market size in 3–4 months.
Harvest: Harvesting typically takes place when the shrimp reach the target weight, often 20–25 grams each. This can vary depending on market demand.
Black Spot in Vannamei Shrimp: Issues and Solutions
One of the common quality issues with raw material vannamei shrimp is the occurrence of black heads or melanosis, a condition that leads to black discoloration in the shrimp's head. Black head in shrimp is typically caused by:
Poor Handling: Inefficient handling during harvest and transportation can lead to bruising and stress, which contributes to melanosis.
Delayed Processing: Shrimp that are not processed quickly after harvesting are more prone to developing black heads.
Enzyme Reaction: Black head is a result of an enzymatic reaction (polyphenol oxidase) in the shrimp tissue.
Improvements and Suggestions:
Immediate Icing or Cold Chain Management: Ensuring that shrimp are immediately placed on ice after harvest can help minimize the occurrence of black heads. A strong cold chain management system from farm to processing plant is crucial.
Use of Anti-Melanosis Treatments: The use of food-grade anti-melanosis treatments, such as sodium metabisulfite or natural extracts, can prevent or reduce the occurrence of black heads in shrimp during storage and processing.
Farmer Training: Training shrimp farmers in best practices for harvesting and handling can improve the quality of raw materials, reducing defects such as black heads.
Recommendations to Strengthen Raw Material Collection
To improve the quality and consistency of raw material vannamei shrimp, several measures can be implemented such as Enhanced Cold Chain Logistics and Disease Management Systems
How to execute them in details?
Farmer Cooperation: Establishing cooperatives or clusters where small-scale farmers work together can improve coordination, reduce costs, and improve the overall quality of shrimp harvested.
Disease Management Systems: Investments in early disease detection systems, biosecurity protocols, and improved water management techniques can help mitigate disease outbreaks, which are one of the biggest threats to shrimp yields.
Enhanced Cold Chain Logistics: Strengthening cold chain logistics, from farm to processing facility, can ensure that shrimp remain fresh and free from defects like black heads and spoilage.
Sustainability Certification: Encouraging more farms to pursue ASC (Aquaculture Stewardship Council) or GlobalGAP certification for sustainable shrimp farming can improve farm management and product quality.
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