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05 October, 2007

Shrimp Sampling 04 - Sampling Using Nets

This sampling activity is usually done for relatively large-sized shrimp (2.5 grams) was thus caught in a used mesh. Besides being used for the regular sampling, the nets also used for incidental sampling.

Materials / Equipment
  1. Nets with 6 m diameter, length 3 to 4 m with mesh sizes vary depending on location and the author (mesh size adjusted to the size of the targeted shrimp). Reviewed based on sampling equipment, hence the nets serves as a tool for shrimp sampling.

  2. Container (plastic bucket) that has been filled with water as a place for the targetted shrimp.

  3. Scales sat with a capacity of 6 kg or hanging weights, as a tool to measure the average weight of shrimps.

  4. Calculator is required to calculate the average shrimp weight.

  5. Stationery used to document the results of counting the number of shrimp and calculating average weight of shrimp and other observations.

Stage Activities of Sampling Using Nets
  1. Specify a point location as a place to let down the nets (in one of the sampling using nets usually have several locations to get the expected results can represent the population of shrimp in a ponds.

  2. Sprinkle the nets with relatively perfect , ie nets can be developed with a maximum at the time were scattered and wait some time to let the nets can reach the pond bottom.

  3. Lift the nets and enter the nets body along with their catch into a container (plastic bucket) that has been filled with water. At the time of lift the nets things that need to be observed is the profile of sewage, which carried on as an indicator of the condition of pond bottom.

  4. Remove the shrimp from the mesh on the also container carefully to avoid physical damage to the targetted shrimp which can affect the quality of shrimp indirectly.

  5. Separate with other aquatic biota that are carried on in the nets. Aquatic biota can be an indicator of the level density and type of competitors / predators of shrimp in the ponds.

  6. After the release of shrimp from the mesh is completed then place a small container which already contains samples of shrimp on the scales sitting / hanging scales (make sure the scales are in normal / good condition).

  7. Measure and record the total weight of shrimp samples in the container based on the pointer is in the scales sitting / hanging.

  8. Measure the weight of the container in a state where the shrimp samples contains water to determine the total weight of shrimp samples with the actual results of how heavy the item 8) above less the weight of the item 9). Example if the item 8) weight = 3.5 kgs, and the item 9) weight = 1.5 kgs, the actual total weight of shrimp samples = 3.5 kgs - 1.5 kgs = 2.0 kgs.

  9. Calculate the total number of shrimps in the container such as observed conditions / quality of shrimp. If found the shrimp which is indication of a problem then the note issue as a material technical decisions related to farming or other aspects. The shrimp that have been measured and observed to be immediately returned to the pond to prevent water quality degradation of shrimp samples..

  10. Calculate the average weight of shrimps (average body weight / ABW) on the sampling results with the formula: total weights divided by the total number of shrimps. For example if the total weight of shrimps = 2000 grams (2.0 kgs), a total of 200 shrimps s then the ABW = 2000 grams: 200 shrimps = 10 grams / shrimp.

  11. Repeat the above process for multiple point locations within the pond.

  12. Record the results of calculations and observations as a reference in the decision making process.
Notes :
  • The process of spreading the nets into the waters of ponds should be done by people who are already skilled / proficient in doing so the sampling activities can be run effectively and efficiently

  • The process of sampling using nets activities should be performed around 2.5 - 3 hours after feeding so that shrimp samples would be more effective because the shrimp is still spreading in the vicinity of the feed so it is still within range of the sampling nets.

  • Sampling activities should be conducted not in the condition of the water circulation and operation of the waterwheel is recommended as minimum as possible, thus opening the nets are not disturbed by water currents caused.

  • Sampling activities should be performed quickly enough to avoid a decline in the quality of the shrimp samples.

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Related Post :

  1. The Concept of Size and Quality of Shrimp for Price
  2. Shrimp Sampling 03 - Sampling of Ancho
  3. Shrimp Sampling 02 - Equipments/Tools and Shrimp Sampling Stages
  4. Shrimp Sampling 01 - Background, Objectives and Kind of Samplings

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