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

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

Research on crustaceans

Crustacean research at the SEAFDEC Aquaculture Department during the last three years focused mostly on the tiger shrimp Penaeus monodon. Studies were done along six problem areas: (1) developing spawning techniques for captive broodstock, (2) defining physico-chemical levels tolerable by larvae or postlarvae, (3) finding alternative feeds or fertilizers for extensive culture, (4) reducing the cost and evaluating the quality of formulated feeds for semiintensive culture, (5) preventing and controlling disease, and (6) documenting the chemicals used in shrimp culture and their effects on the environment. To reduce feed costs, substitutes for expensive feed components were screened and the specific nutrient requirements of tiger shrimp during culture were determined. A few studies were made on other crustaceans. The vitellogenin levels during maturation of the white shrimp P. indicus were measured. The digestibility of feedstuffs was also tested in the white shrimp. Culture techniques are being developed for the mudcrab Scylla serrata in ponds, pens, and cages

Shrimps

During 1988-1991, research at the Aquaculture Department of SEAFDEC on the shrimp Penaeus monodon has been directed towards a) the development of captive broodstock, b) the refinement of hatchery and grow-out techniques, c) the development of diets for the various stages of culture, and d) the prevention and control of diseases. Biochemical, morphological, and histological characterization of the male and female reproductive systems were conducted to provide basic information for the development of techniques for pond-reared broodstock. Studies on the refinement of hatchery techniques included determination of the environmental and feeding requirements of larvae and postlarvae to serve as basis for the improvement of management practices. Refinement of grow-out techniques included studies on the physiological response of this species to vital environmental factors and studies on the role of natural food organisms during culture. Nutrition studies have resulted in the formulation, testing, and improvement of diets for broodstock, larvae and postlarvae, juveniles, and subadult shrimps. Methods of prevention and control of the luminous bacterial disease, chronic soft shell syndrome, aflatoxicosis, monodon baculovirus (MBV) infection, and other relevant diseases have been investigated through the identification of causative agents and bioassay of possible chemo-therapeutants. Studies to improve larval rearing of alternative shrimp species such as P. indicus, P. merguiensis, and P. japonicus have likewise been pursued. Nutritional requirements of the white shrimp species were evaluated to develop suitable formulated feeds for the different culture stages

Broodstock management and seed production of Penaeus monodon (Fabricius)

Research on the maturation of Penaeus monodon at AQD has focused on three broad areas, namely, reproductive biology and ecology, induced maturation and broodstock management. Studies on reproductive biology provided information on the life cycle, ovarian maturation stages, courtship and mating behavior, minimum size at sexual maturation (sperm occurrence, first spawning), and morphological egg types. Induced maturation has mainly been done through the eyestalk ablation method. Nutritional and environmental parameters were studied to enhance reproductive performance or as an alternative to ablation. Pond-reared and wild broodstock sources and marine pen and land-based tanks as maturation systems were also tested and compared. Size, shape, color, substrate material and other aspects of tank design and construction, sex ratio, stocking density, water management, and other parameters of the management system were also studied and refined. Early techniques in larval and postlarval rearing of P. monodon at AQD were based on the community culture method of growing natural food in larval tanks. However, low and inconsistent survival led to a shift in rearing methods toward pure phytoplankton culture grown in separate tanks as food for the larvae. Henceforth, refinement of rearing methods have been conducted to improve larval survival through effective water management, nutrition, and disease control. Efforts are continuously being geared toward making the technology affordable to Filipino farmers

A brief account of the experience of Sabah Fisheries Department in fish larval rearing

Venturing into the aquaculture sector especially in pond and cage culture is a step that has been taken up by entrepreneurs and traditional fishermen of Sabah. However, shortage in the supply of fish fry is a stumbling block to the progress of the industry. The Sabah Fisheries Department has taken steps to overcome this problem by setting up a hatchery with the objectives to transfer know-how on hatchery technologies to the private sector besides producing fry for distribution. The Tanjong Badak multi-species hatchery is a newly established hatchery, completed in mid-1990. The species reared for production purposes are tiger shrimp and finfish which include red snapper, grouper, sea bass and polkadot grouper. The Department has not close to producing sea bass fry. Shrimp fry at juvenile stages (PL 40) are distributed as subsidies to local fish farmers while some are reared at the Department's various cage and pond culture projects. Limited success in producing grouper and red snapper fry have been achieved to date. The incidence of very low fertilization rates of eggs coupled with low survival rates are major problems facing the hatchery. In conclusion, the Sabah Fisheries Department's experience in fish larval rearing is still limited. Greater scientific research and studies need to be carried out to improve further the performance of the hatchery to achieve the target of fry sufficiency for the aquaculture industry

Shrimp seed production at SEAFDEC/AQD

Broodstock management and seed production techniques have evolved from laboratory and verification tests that are conducted to increase survival and growth rates of cultured fish species. The present methods of induced maturation and hatchery rearing of shrimp (Penaeus monodon) used at the SEAFDEC Aquaculture Department are examples

Survival of newly-hatched larvae of Epinephelus malabaricus at different salinity levels.

The development of an appropriate hatchery culture-technique for grouper Epinephelus malabaricus requires knowledge on the biology of this species. The environmental requirements, a critical aspect of biology, have, however, not yet been investigated. This study specifically deals with the influence of salinity on the survival of newly-hatched larvae