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

Larval rearing of Penaeus monodon: Feeds and feeding techniques

Larval rearing of P.monodon requires mass culture of selected phytoplankton and zooplankton species. In the protozocal stage, Skelatonoma; Chaetoceros or Tetraselmis is given singly or in combination. The rotifer Brachionus and/or the brine shrimp ArTEMI are added to the diet as larvae metamorphose to the mysis stage. Attempts to replace these organisms with other organisms or with artificial diets are discussed. The use of microparticulate diets as supplement to algal food or Artema increases larval survival to 30-70%. The advantages of using this type of diet are enumerated

Biology and hatchery of mud crabs Scylla spp.

This manual includes the biology of mud crab, and describes principles and procedures for spawning the mature crabs (Scylla serrata, S. tranquebarica, and S. olivacea) and rearing the zoea to fly size crabs. It focuses on the hatchery rearing of S. serrata as this species is more economically viable than the two other species. The techniques may be modified depending on the conditions or problems encountered in a specific site.We thank the Crustacean Hatchery staff Joana Joy dela Cruz, Gaudioso Pates, Joebert Fernando and Ronelio Torrigue for their technical assistance in the refinement of the hatchery techniques, and to Eduard Rodriguez for sharing his expertise on net cage nursery rearing. We are also grateful to Nerissa Salayo, Milagros de la Peña and Ruby Bombeo for sharing their expertise in improving this manual; Jurgenne Primavera, Celia Lavilla-Torres and Evelyn Grace de Jesus-Ayson for comments; Milagros Castaños and Rex Delsar Dianala for the lay-out and preparation of this manual. Three photos on embryonic development were taken at Rajiv Gandhi Centre for Aquaculture (c/o K. Ganesh) in Tamil Nadu, India. Most of the larval rearing results are based on the projects 9217 (Development of Improved Mud Crab Culture Systems in the Philippines and Australia) funded by the Australian Centre for International Agricultural Research and ICA4-CT-2001-10022 (Culture and Management of Scylla spp.) supported by the European Commission (INCO-DC).2nd Ed

Survival and growth of mud crab, Scylla serrata, juveniles subjected to removal or trimming of chelipeds

The effects of removing or trimming the chelipeds at various molt stages on regeneration, molt interval (MI) and specific growth rate (SGR) were determined in mud crab Scylla serrata. These strategies in combination with provision of shelters and food were tested in relation to survival and growth. Hatchery-reared S. serrata juveniles (1.3–2.2 g body weight) in the postmolt, intermolt, and premolt stages were subjected to autotomy of two chelipeds, and trimming of dactylus and pollex. Intact crabs served as the control group. Interval from stocking to first molt was significantly longer in crabs autotomized at intermolt or premolt than in trimmed or intact crabs, but was similar to intact crabs when autotomy was done at postmolt. However, MI from first to second molts was longer compared to intact crabs when chelipeds were removed or trimmed at premolt. After the first molt, autotomy and not trimming caused significant decrease in SGR. The SGRs at the end of the test were similar to intact crabs (postmolt: 7.90 ± 0.39, intermolt: 5.64 ± 0.50) when trimming of chelipeds was done at postmolt (8.01 ± 0.75) or intermolt (4.38 ± 0.40). However, SGR was lower when premolt crabs were subjected to autotomy (4.11 ± 0.67) and trimming (5.29 ± 1.40) than when chelipeds were intact (9.45 ± 0.47). A two-factor experiment was conducted in the second phase where intermolt crabs with autotomized or trimmed chelipeds (factor A) were either fed or starved but provided with shelters or fed but without shelters (factor B). After 10 days, higher survival was obtained in crabs with autotomized (95.55 ± 2.94%) or trimmed chelipeds (93.33 ± 3.33%) than in intact crabs (73.33 ± 6.67%). Survival was not affected by factor B, but higher final mean body weights were attained in fed crabs with (0.78 ± 0.04 g) or without shelters (0.74 ± 0.04 g) than unfed ones (0.48 ± 0.04 g). A third experiment was conducted to verify these results. Crabs with trimmed or intact chelipeds were either fed or unfed. No shelters were provided. Crabs with trimmed chelipeds (88.57 ± 0%) had higher survival than intact crabs (59.76 ± 7.56%) regardless of whether they were fed or starved; and fed crabs (0.82 ± 0.04 g) had higher mean body weight than unfed crabs (0.61 ± 0.07 g) regardless of whether chelipeds were intact or trimmed. These results indicate that trimming or total removal of chelipeds are effective strategies in reducing cannibalism.The authors thank Ms. Jennette de Pedro-Tillo for the technical assistance during the conduct of this study and to Joana Joy dela Cruz-Huervana for the preparation of figures. The study was funded by SEAFDEC/AQD

Seed production of mud crab Scylla spp.

Mud crab farming is an important source of income for fish farmers in the Philippines. The expanding export market for mud crab as an alternative for shrimp has led to intensified collection of wild seed for grow-out and has threatened the wild stocks. To ensure the sustainability of crab farming and reduce the fishing pressure on wild stocks, the SEAFDEC Aquaculture Department developed a technology for large-scale production of juvenile mud crabs, Scylla serrata (giant mud crab), S. olivacea (orange mud crab) and S. tranquebarica (purple mud crab)

Osmotic, total protein and chloride regulation in Penaeus monodon

Abstract only.The osmotic, total protein and chloride ion regulation in two size groups (10 and 30 g) of Penaeus monodon Fabricius was investigated. Preliminary experiments showed that osmolality, total protein and chloride concentrations tend to become stable 24 to 36 hours after molting.Thus,hemolymph values 36 to 240 hours after sampling were not significantly different from each other. Based on these results, only 36 hours (or more) postmolt animals were sampled after transfer from control (32 ppt) to five test salinities (8, 16, 24, 32 and 40 ppt). Hemolymph samples were then taken 1, 2, 3, 5, 7 and 10 days after transfer. Results showed that in general, osmolality, total protein and chloride concentrations in the hemolymph did not vary with time within the same salinity.Both sizes exhibited hyperosmotic and hyperionic regulation in lower salinities and hypoosmotic and hypoionic regulation in higher salinities. The isosmotic values obtained were approximately 676 to 720 mOsm (24 to 28.8 ppt) for the 10 g, and 724 to 792 mOsm (26 to 28.5 ppt) for the 30 g size group. For chloride, the isoionic values ranged from 324 to 339 mM in 10 g prawns. Slopes of the regression lines of hemolymph osmolality versus salinity in 10 g prawns were not significantly different from slopes of similar regression lines in 30 g prawns. These results suggest that the ability to regulate osmotic and total protein concentration in the hemolymph is similar in the two size groups

Ovarian maturation stages of the mud crab Scylla serrata

Ovarian maturation in adult wild-sourced and pond-grown Scylla serrata (Forsskål) was determined based on gross morphology and histological appearance. There were no significant differences noted in the histological features of both wild and pond-reared S. serrata females. Ovarian maturation was classified into five stages: immature, early maturing, late maturing, fully mature and spent. The immature ovaries are thin and translucent to off white and contain oogonia, primary oocytes with large nuclei. The follicle cells were found around the periphery of the lobes and an area among groups of oogonia and oocytes. The follicle cells gradually enclosed the oocytes. The early-maturing ovaries were yellow and small yolk globules started to appear in larger oocytes. In late-maturing ovaries, the colour became light orange and lobules were apparent. Yolk globules occurred in the cytoplasm with larger globular inclusions towards the periphery, while follicle cells were hardly recognizable. Fully mature ovaries were orange to deep orange and had swollen lobules. Large yolk globules were apparent in the entire cytoplasm. Follicle cells were hardly seen. Spent ovaries were similar to the early-maturing and late-maturing stage in partially spawned females. The ovarian development was correlated closely to the gonadosomatic index, oocyte diameter, and ovarian histology. The classification of ovarian maturation provides baseline information for further studies on reproductive biology. Likewise, the information provides a guide for broodstock management in the hatchery.This study was supported by the European Union through the European Commission — Culture and Management of Scylla spp. Project (ICA4-CT-2001-10022). The authors thank Quirico Ganon of Crustacean Hatchery Unit for obtaining the crabs, Jeobert Fernando and Ronelo Torrigue for broodstock maintenance and the staff of the Microtechnique Unit of SEAFDEC/AQD for processing histological samples

Biology and hatchery of mangrove crabs Scylla spp.

This manual includes the biology of crab (Scylla serrata, S. tranquebarica, and S. olivacea), and describes principles and procedures for spawning the mature crabs and rearing the zoea to ‘fly’ size crabs. It focuses on the hatchery rearing of S. serrata as the farming of this species is more economically viable than the two other species. The techniques may be modified depending on the conditions or problems encountered in a specific site.Most of the larval rearing results were based on the projects 9217 (Development of Improved Mud Crab Culture Systems in the Philippines and Australia) funded by the Australian Centre for International Agricultural Research, ICA4-CT-2001-10022 (Culture and Management of Scylla spp.) supported by the European Commission (INCO-DC) and National Mud Crab R&D Program funded by the Philippine Council for Agriculture, Aquatic, and Natural Resources Research and Development of the Department of Science and Technology.ForewordIntroductionBiology of Scylla spp.Crab anatomyTaxonomy and identificationLife history and habitatFood and feedingMolting and regenerationSexual maturityMatingSpawningEmbryonic development and hatchingLarval developmentHatchery OperationsSetting up the hatcheryPreparation of tanks and seawaterProduction of natural foodManagement of broodstockLarval rearingCulture of megalopaHarvesting, packing, and transport of crabletsCommon problems and possible solutionsEconomics of mangrove crab hatcheryReferencesAcknowledgementAppendixGlossary3rd Ed