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Monitoring of the Mud crab stocks is the Key to Successful Production (Prepared by Edmundo Enderez) Mud crab (Scylla serrata) culture in pond, pen, and cages require close monitoring of the stocks in order to know what appropriate measure will be adopted to enhance technical feasibility and financial viability of the project. This paper is written based on several experiences of the author in providing assistance to different mud crab culture projects in Surigao, Samar, Bohol, and Cabusao. In monitoring, the data periodically gathered are: carapace width and corresponding weight on a weekly basis of each mud crab caught using crab lift net or “bintol”, actual feed consumed (based on what remains in the feeding tray or specific feeding spot of the pond) against required amount on a daily basis. The data can be used in determining the following: 1) condition of stock (thin/empty or full/good/robust), 2) growth rate (average, slow, fast), 3) nutrition from feeds (adequate or not) given, and 4) estimated number of stocks. 1. Condition of the stocks a. The Graph below shows the plotted data on carapace width and weight of mud crab being cultured for fattening. Plots above the yellow/red line indicate that the male/female mud crab is in good condition while those below the yellow/red line indicate that the male/female mud crab is in thin condition. This is the so-called graphical approach in determining mud crab condition. Condition of Stocks (thin or meaty or robust)
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Page 1: Monitoring of Cultured Mud Crab Stocks is the Key to Success

Monitoring of the Mud crab stocks is the Key to Successful Production(Prepared by Edmundo Enderez)

Mud crab (Scylla serrata) culture in pond, pen, and cages require close monitoring of the stocks in order to know what appropriate measure will be adopted to enhance technical feasibility and financial viability of the project. This paper is written based on several experiences of the author in providing assistance to different mud crab culture projects in Surigao, Samar, Bohol, and Cabusao.

In monitoring, the data periodically gathered are: carapace width and corresponding weight on a weekly basis of each mud crab caught using crab lift net or “bintol”, actual feed consumed (based on what remains in the feeding tray or specific feeding spot of the pond) against required amount on a daily basis. The data can be used in determining the following: 1) condition of stock (thin/empty or full/good/robust), 2) growth rate (average, slow, fast), 3) nutrition from feeds (adequate or not) given, and 4) estimated number of stocks.

1. Condition of the stocks

a. The Graph below shows the plotted data on carapace width and weight of mud crab being cultured for fattening. Plots above the yellow/red line indicate that the male/female mud crab is in good condition while those below the yellow/red line indicate that the male/female mud crab is in thin condition. This is the so-called graphical approach in determining mud crab condition.

Condition of Stocks (thin or meaty or robust)

Page 2: Monitoring of Cultured Mud Crab Stocks is the Key to Success

b. There is practical approach in determining the condition of the stocks: whether thin/empty and good/full. The pictures below show mud crab that are empty and full based mon the appearance of claws and then what to do to with the mud crab to confirm such condition

c. In marketing the harvested mud crab, the buyers would classify the produce as either thin (empty) or good (full) through the practical approach. The practical approach in the classification of mud crab condition can be checked through the graphical approach. It must be noted that some buyers who would like to earn more may classify mud crab as empty/thin or near good/full when in fact based on the graphical approach it is already good/full, thus they would bargain for lower price of the produce.

2. Growth by Change in Carapace Width and Frequency of Molting

a. The Graphs below show the change in average carapace width of mud crab cultured in pond. After 1 month of culture, the average carapace width or its weight increased from 77.5 grams to 150 grams. About 1 to 2 moltings had occurred during the 1 month culture period.

Page 3: Monitoring of Cultured Mud Crab Stocks is the Key to Success

b. The above Graphs indicate that the change in actual average carapace width follows the projected growth with corresponding frequency of molting.

3. Growth by Weight and Feeding Rate

a. The Graph below shows that growth during 1 month culture period follows the standard

Page 4: Monitoring of Cultured Mud Crab Stocks is the Key to Success

growth rate for Scylla serrata cultured in pond. By August 15 or after 2.5 months of culture the ABW will reach 275 to 350 grams.

b. The change in growth in terms of weight from 77.5 grams (ABW) to 150 grams (ABW) necessitates adjustment in feeding rate from 8% to 6%. The Illustration below shows the amount of feeds to be given to 290 pcs of stocks with ABW of 150 grams at 6% feeding rate should be 2.6 kgs. If the adjusted amount of feed given is 4 kgs which is based on the “rule of thumb” by the technician who is more inclined to the practical approach. The presence of competitors such crab locally-called “talangka” is not in large quantity to allow for the provisoin of 4 kgs. Then the need to reduce the amount of feeds to the right amount to account for the competition, possible at 3 kgs per day.

Page 5: Monitoring of Cultured Mud Crab Stocks is the Key to Success

c. If the amount of feed consumed is only 2 kgs instead of 3kgs per day, then there could be reduction in the number of stocks. The estimated number of stocks based on the amount of feed consumed is determined based on the formula below. If the reduction of stock is confirmed, then appropriate actions can be done like finding out what causes it and how it will be prevented; then possibly replacing the number of stocks that were lost with same number of current size.

4. Nutrition

a. The feeds given to mud crab cultured in pond, pen, and cages consist of trash fish, shells or snails, and crustaceans. The main food given is trash fish. Although for 1 week, meat of mangrove snail (Telescopium telescopium) was provided.

b. Several studies indicate that feeding the mud crab with pure golden apple snail (kohol) resulted to better growth that using a combination of kohol and trash fish and much better than pure trash fish. Findings in other studies show that a combination of snails/shells and trash fish resulted to better growth.

c. The following Table shows the different types of food and their corresponding contents. It would be better to try a combination snails and fish and find out which is the best in a given condition, time, and place of culture.

NutritionContents Food

Golden apple snail

Mangrove snail (Telescopium)

Tilapia Mullet(banak)

Anchovy(dilis)

Energy 347 KJ 330 KJ 400 KJ 627KJ 547 KJCarbohydrates 6.6 g 0 0 0 0Fat 0.4g 1.7g 1.7g 4g 4gProtein 12.2g 16.8g 20g 24g 20Sodium 40mg 851mg 52mg 71mg 104mgSource: browsed from the internet