Better Harvest Management Practices

Maintaining the freshness and edible quality of harvested shrimp is very important for the export market. Simple planning and preparation for a harvest can make the work much easier and prevent costly mistakes that may result in wastage or deterioration of the product that you have worked hard to produce. Make sure you have all the equipment on hand and make sure you have coordinated the harvest with the contract processor.

Essential items that must be read fo r a drain harvest include:

  • Drag nets or bag nets
  • Bins for storing chilled prawns pond-side-more than enough to hold the estimated quantity of shrimp
  • Bins for storing ice pond-side-more than enough required to chill the estimated quantity of shrimp
  • Ice delivered or made on the site in an ice-making machine
  • Scoops, hoist or lifting arrangement.

Key Instructions for Harvest Management:

  1. Exchange 20% of the water one week before the planned harvest date. Immediate after water exchange apply agricultural lime (100-200kg/ha) to the pond and pond bottom where it is more black, specially in the corners.
  2. Avoid harvest during the molting period (Full moon or new moon). Two days before harvest check if there are any newly molted shrimp, if newly molted shrimp are ?10%, delay the harvest by a day or two. Do not exchange water or reduce water level 2 to 3 days before harvest.
  3. Do not feed the shrimp 6 hours prior to harvesting to keep the gut empty and improve the shelf life.
  4. Complete the harvesting process (draining and harvesting) within 6-8hrs, between 6PM to 6AM. Avoid harvesting and packing shrimp during hot time of the day. Use the Drag net to harvest. Avoid using cast nets.
  5. If normal of the pond water is difficult, use artificial gates (made up of bamboo sticks or fish nets) in a corner at deeper side of pond for fixing the bag net. Use more pumps if necessary to complete the harvesting in time and to catch most of the shrimp with the bag net.
  6. Thoroughly wash the handpicked shrimps in clean water and pack them separately from net harvested shrimp.
  7. Do not use any chemicals while washing the shrimp or chill killing without the knowledge of the processor.
  8. Make sure good quality ice is used (preferably from the processor) During harvesting and packing.
  9. Workers with wounds, open sores or skin infections should not handle harvested shrimps. Do not smoke or spit at packing area.
  10. Pack the shrimp in transports tubs (insulated boxes) with crushed ice: shrimp @ 2:1 ratio for better preservation. Load the packed crates quickly to the truck and send to the processing plant immediately without any delay.
  11. The quality of a shrimp starts to deteriorate immediately after it dies. The digestive organ, or hepatopanceas, contains a range of enzymes that cause changes to the shrimp’s appearance and texture because they remain active after death. While not feeding the prawns for 24 hours before harvest may reduce the amount of digestive enzymes (mainly proteases) present in the stomach, the hepatopancreas still retains plenty of activity. Any longer than 24hours may make them hungry enough to eat the bottom detritus and spoil the quality of the cooked product. These enzymes digest through the surrounding tissue and attack the ligaments that connect the head (cephalothorax) to the tail meat (abdomen). These weakened tissues will then result in a significant amount of weight loss and head loss during storage and cooking. Initially the only visible defect will be a discoloration of the organ, but this will spread through the head and into the tail meat. As all enzymes operate faster in warmer conditions it is imperative that shrimp be chilled immediately after capture. This can be in ice slurry, in refrigerated sea water (RSW) or under ice. Another enzyme, polyphenol oxidase, will cause the dark pigment known as black spot to develop on the gills, shell of the head and shell of the tail. Unfortunately, unless the shrimp are frozen immediately, a chemical treatment will be required t prevent black spot.

Source : NaCSA

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