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

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)

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

Domestication of the mud crab Scylla serrata

The significant decrease in wild mud crab population highlights the need to manage the resources and domesticate crabs. This paper presents the initial results of the domestication of mud crab Scylla serrata aimed at producing good-quality captive broodstock. The analysis of the genetic structure of the base population was done as a prerequisite for domestication. Adult S. serrata from the northern to southern parts of the Philippines (Cagayan, Camarines, Samar, and Surigao) were obtained for genetic diversity analysis and domestication. Analysis of molecular variance showed that differences in the genetic variability between the four populations were not significant. Moreover, no significant deviation from Hardy–Weinberg Equilibrium was observed in each sample population and even in pooled populations. Body weight was positively correlated with the carapace width. Second spawning occurred 41–46 days after the first spawning and 34 days from second to third spawning. However, there was a decrease in the number of zoea in repeat spawnings. Twenty-four first-generation (F1) families were produced from the four sites. The duration from spawning of the base population (P0) to attainment of broodstock size F1 was 10–14 months. Four second-generation (F2) families were produced after 11–12 months. Up to the F2, crabs tested negative for six viruses: white spot syndrome virus, infectious hypodermal and hematopoietic necrosis virus, gill-associated virus, yellow head virus, Taura syndrome virus, and infectious myonecrosis virus. The reproductive performance of P0 was comparable to the succeeding generations. Several families were obtained from one population in a year. However, due to the cannibalistic behavior of crabs, more space is required for the nursery and grow-out phase. The domestication of S. serrata is the first study done on any mud crab species in the Indo-west Pacific region. The initial results would serve as guide to understand and eliminate the barriers to mud crab domestication. The breeding technology developed from this study will support the production of good-quality seedstock for farming.This study was partly supported by the Japanese Trust Fund—Government of Japan under the ASEAN-SEAFDEC FCG Mechanism Program. The technical support of the crustacean hatchery (TMS) and grow-out (DBS) staff is acknowledged