Soft-shell mud crab farming

Farming of soft-shell mud crab (Scylla serrata) has been practiced for some time now in a number of Asian countries. Because of its profitability, there is an increasing interest to engage in this aquaculture business venture. Crabs collected from the wild are the major source of stocks for farming. However, the use of hatchery reared crabs is encouraged so as not to deplete the wild population. Although communal rearing of crabs for soft-shell crab production in cages or in tanks is also practiced, this manual describes the individual rearing of crabs in boxes based on experience in Ranong, Thailand. The techniques can be modified depending on the site. This manual provides a section on the biology of mud crab that includes species identification, molting, and autotomy and regeneration which discloses important information related to the management of soft-shell crab farming. This is followed by a detailed discussion on the setting up and management of the farm for soft-shell crabs. The basis for the computation of cost and return analysis is included under the section on profitability. Cost of materials and labor varies in each country hence only the materials needed and other technical assumptions are listed as basis for computation

Biology and hatchery of mud crabs Scylla spp.

This manual describes the principles and procedures for spawning the mature crabs (Scylla serrata, S. tranquebarica, and S. olivacea) and rearing the zoeae to juveniles. Hatchery conditions should satisfy the ecological requirements of each specific stage, thus the manual starts with a section on biology of mud crabs.We thank the Crustacean Hatchery staff Emeterio Borlongan, Quirico Ganon, Eliseo Tisuela and Rudy Bravo for their competent technical assistance in the larval rearing runs, to Eduard Rodriguez for net cage nursery rearing, and to Jennette de Pedro for providing invaluable computer assistance. We are also grateful to Jurgenne Primavera, Milagros de la Peña, Nerissa Salayo, and Marietta Duray for sharing their expertise in improving this manual; Celia Lavilla-Torres for her contribution on diseases; AQD’s Publications Review Committee Relicardo Coloso, Teodora Bagarinao, Luis Maria Garcia, Gilda Po, and Wilfredo Yap for invaluable comments; Edgardo Ledesma for the line drawings; and to Rey Tenedero for the hatchery layout and other engineering aspects. Some of the results are based on the project 9217 funded by the Australian Centre for International Agricultural Research.1st Ed

Updates on the seed production of mud crab

Widespread interest in mud crab species is increasing because these are highly prized both in domestic and export markets. Among the three mud crab species commonly found in the Philippines, Scylla serrata, S. olivacea, and S. tranquebarica, S. serrata is preferred by farmers because it is larger and less aggressive than the other species. Likewise, S. serrata is the most widely distributed species in the Indo-west Pacific region. Hatchery-produced seedstock are presently used by some crab farmers in their grow-out operations. In the hatchery phase, feeding mud crab larvae with shrimp formulated diets and natural food was found to reduce the occurrence of molt death syndrome, one of the major problems in seed production. Larvae given 25% formulated diet (FD) + 75% natural food (NF; rotifers and Artemia) and 50% FD + 50% NF showed better performance than those larvae fed 100% FD, 100% NF and 75% FD + 25% NF indicating that usage of natural food, especially the expensive Artemia, can be reduced. Since the early crab instar (C) produced in the hatchery need to be grown further before stocking in grow-out ponds, two phases of nursery culture have been developed. C1-2 are grown to 1.5-2.0 cm carapace width (CW) size in the first phase and further grown to 3.0-4.0 cm CW in the second phase. Nursery rearing is done in net cages installed in ponds for easy retrieval. A combination of mussel or trash fish and formulated diet is used as feed. Domestication of the mud crab S. serrata as a prerequisite to selective breeding has been done at SEAFDEC/AQD. Likewise, defining criteria for the determination of quality of newly hatched zoeae for stocking in the hatchery was initiated. Newly hatched zoeae were subjected to starvation and stress test using formalin. Starvation failed to elicit responses that were significantly different between the good and poor quality larvae hence it is not suitable for larval quality evaluation. Based on three-year data, the formalin stress test gave mean cumulative mortalities of 2.38±0.32, 8.24±0.88, 20±1.58 in good quality larvae, and 43.74±2.39 while 22.93±4.19, 63.68±7.17, 84.29±3.88 and 97.65±1.06 for poor quality larvae at 0 (control), 20, 30 and 40 ppm formalin, respectively. As formalin level increased, cumulative larval mortality also increased regardless of the quality of the larvae. Formalin stress test proved to be a reliable method to determine whether a batch of newly hatched zoeae was of good or poor quality

Proceedings of the Regional Technical Consultation on Stock Enhancement for Threatened Species of International Concern, Iloilo City, Philippines, 13-15 July 2005

This 150-page book documents the proceedings of an experts' consultation held at AQD in July 2005. It contains nine review papers and seven country papers

Prawn hatchery operations

The manual, an updated version of the 1984 SEAFDEC/AQD manual, presents the underlying principles and step-by-step instructions of prawn larval and post-larval rearing. The techniques described are not only applicable to Penaeus monodon, but may also be modified and applied to other penaeid and metapenaeid species. The following aspects are covered: Site selection; Life cycle; Hatchery design and planning; Hatchery operations; Diseases; and Economics.1st Ed

The SEAFDEC/AQD experience in stock enhancement

The Aquaculture Department (AQD) of the Southeast Asian Fisheries Development Center (SEAFDEC) started stock enhancement activities in 2000 as part of the Coastal Fishery Management Project in Malalison Is., Culasi, Antique, Philippines (SEAFDEC/AQD 1998). This was the same year as the Bangkok Declaration and Strategy for Aquaculture Development (NACA/FAO, 2000), which affirmed the potential of stock enhancement to increase fish supply. Since then, research on seed production, and release and monitoring strategies has been initiated on the abalone (Haliotis asinina), seahorses (Hippocampus barbouri, and H. kuda), mud crabs (Scylla serrata, S. olivacea and S. tranquebarica), top shell (Trochus niloticus), and window-pane oyster (Placuna placenta). Closing the life cycle and mass production of juveniles have been attained for most of these species, but actual releases have been conducted only for abalone and mud crabs. In this review article, we describe the present situation of stock enhancement of abalone, mud crab and seahorse at AQD

Mud crab hatchery and nursery operations

A brief account is given of mud crab (Scylla spp) farming activities in the Philippines. The expanding market for mud crab is the cause of intensified collection of wild juveniles. To counter the threat to wild population and ensure the sustainability of mud crab farming, there is a need to produce juveniles in hatcheries. Hatchery and nursery operations, and investment costs/returns are outlined

Hepatopancreas cells as monitor cells for the nutritional value of prawn diets in aquaculture

Abstract only.The hepatopancreas is considered to be the central organ of metabolism in decapod Crustacea. It is a system of blind tubules consisting of four cell types. The E-cells at the summits of the tubules develop into R-cells (for resorption of nutrients), F-cells (for production of digestive enzymes) and B-cells (function unknown). The ultrastructure of Penaeus monodon R-cells changes largely after starvation and feeding different diets. B-cells show slight reactions, while F- and E-cells are rather constant. Thirteen day-starvation results in a large decrease of the cell size and in a significant reduction of all cell organelles. After seven days starvation and four days refeeding with various extreme diets, the R-cells develop completely different food-specific ultrastructures. A distinct proliferation of the endoplasmic reticulum is characteristic of protein diets. Large fat drops are the main feature after refeeding with cod liver oil. Sucrose feeding results in "empty" cells with only few organelles. The most diversified ultrastructure with fat droplets and a high amount of all cell organelles is obtained by feeding a mixed diet. The study indicates that R-cells are very sensitive to the application of different diets. They could be used as monitor cells for the nutritional value and the availability of a diet for prawns. Particularly poor or badly formulated feed could be detected early by electron microscopy. This method may be very helpful for the development of artificial prawn diets in aquaculture, especially if natural sources will be used as food components

Life cycle of mud crab

Researched and conceptualized by Emilia T. Quinitio

Status of mud crab industry in the Philippines

Mud crab farming has long been established in the Philippines. Scylla serrata, S. tranquebarica and S. olivacea are the common species found in the Philippines. S. serrata is the preferred species for farming by crab growers. The total production of mud crab from aquaculture was estimated at 13,720 valued at US$77,025,000 and 14,437 tons valued at US$86,511,000 in 2009 and 2010, respectively. The sources of crab seeds for farming are from the wild and in recent years, from the hatchery although in small percentage. The overexploitation of mud crabs and habitat losses have resulted in both reduced landings and mean capture size. To stem the wild harvest, the provincial and municipal government along with the Bureau of Fisheries and Aquatic Resources have introduced ordinances that prohibit the gathering and selling of crablets (≤ 3 cm) outside the municipality of origin. This resulted to increased acceptability of hatchery-reared crabs by crab growers. Basic technologies in all phases of culture (hatchery, nursery and grow-out) have been developed. However, there are still several issues that need to be addressed. In the hatchery phase, one of the major causes of low survival are the Molt Death Syndrome in which zoea 5 has difficulty molting to megalopa and diseases due to bacterial and fungal infection in eggs and larvae. The use of antibiotics as treatment for Vibrio spp. has proven to improve larval survival. However, the use of antibiotics can lead to the development of resistant strains of bacteria and abnormalities that become apparent at the juvenile stage. In the nursery phase, economic losses have been attributed to cannibalism. Providing sufficient food and shelters, reducing stocking density, size grading and removal or trimming of claws are the common strategies used to mitigate the high level of cannibalism. Recent findings showed that incorporating tryptophan in the diet can reduce the aggressive behavior of crabs. In the grow-out phase, culture of juvenile crabs to market size with one or two more commodities in earthen brackishwater ponds is the most prevalent practice. Due to the cannibalistic nature of mud crab, polyculture (usually with milkfish and shrimp) pond is carried out. Stocking density of each commodity varies with the size and the number of seed stock available and the abundance of natural food growth in the pond. Culture period ranges from 4-5 months. Monoculture of crabs is usually done for short term culture as in fattening in various systems. Mud crab culture is also integrated with the existing mangroves. Formulated diets have been verified in commercial grow-out ponds and showed promising results. Mud crabs are commonly fed with low value fish, molluscs and other unprocessed natural foods. Mortality in mud crabs in grow-out phase is oftentimes due to the white spot syndrome virus. The domestication of S. serrata has been done at SEAFDEC/AQD. The duration from spawning of the base population to F1 broodstock size was 10-14 months and from F1 to F2 was 11-12 months. Selective breeding of S. serrata is currently being done. The results serve as guide to understand and eliminate the obstacles to broodstock management and seed production. Recently, The Department of Science and Technology has funded the National Mud Crab Science and Technology Program being implemented by SEAFDEC/AQD and University of the Philippines Visayas to refine the existing technologies in all phases of culture and to aggressively promote the establishment of several mud crab hatcheries and nurseries in the Philippines. The Bureau of Fisheries and Aquatic Resources is also implementing the Philippine National Aquasilviculture Program, which includes the rehabilitation of mangrove forests and culture of commercially important aquatic animals including mud crab in established mangrove areas. On-site training on all phases of culture of mud crab has also been done by SEAFDEC/AQD not only in the Philippines but also in other countries like Brunei, Myanmar, India and Timor Leste. With the establishment of several hatcheries and nurseries, there will be sufficient seed stock supply for farming, thereby decreasing the dependence on wild stock