1,721,052 research outputs found
Updates on the seed production of mud crab
Get PDFWidespread 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
Selection, transport and acclimation of prawn fry
No full textThe most important criterion among many used by operators for choosing poostlarvae to stock in ponvds, is the stage of development. THe stages considered suitable for stocking (about PL20) can be identified by examination of anatomical features including the rostal spine number, the length of carapace and sixth abdominal segment. Pigmentation in uropods, size uniformity and activity of post larvae are useful considerations. During Transport,decreasing water temperature to lwer metabolic rate helps ensure the adequacy of oxygen in bags. Upon stocking, acclimation to the temperature and salinity of pond water is very importan. If changes are sudden, regulatory mechanisms may fail, resulting in moralities
Survival of Penaeus monodon postlarvae and juveniles at different salinity and temperature levels.
No full textPenaeus monodon postlarvae (PL1, PL5, PL10, and PL15) and juveniles (0.2 and 2 g mean weights) were acclimated gradually within 6 h to test temperatures of 22°, 28°, and 33°C. After 24 h, the postlarvae were abruptly transferred to salinity levels of 8, 16, 24, 32, 40, or 50 ppt, and juveniles to 0, 4, 8, 16, 20, 24, 28, 32, 40, 50, or 60 ppt. All test animals were previously reared in 32 ppt sea water at a temperature of 27-29°C. Survival rates were compared after four days for PL1, PL5, and PL 10, and 10 days for PL 15. Tests for juveniles lasted seven days. Length and total (TPI) or mean (MSI) population stage indices were compared for postlarvae.
Survival rates of postlarvae and juveniles were generally lower at 33°C. Length and MSI of postlarvae were higher at 33°C than at 22°C. TPI at PL10 and PL15 were not significantly affected by salinity. Optimal salinity ranges for postlarvae and juveniles were identified based on the different parameters measured
Shrimp seed production at SEAFDEC/AQD
Get PDFBroodstock 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
Research on crustaceans
Get PDFCrustacean 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
Get PDFDuring 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
Development of a sustainable mangrove crab industry through science-based research
No full textFarming of mangrove crab (or mud crab) species, e.g. Scylla serrata, S. tranquebarica and S. olivacea has long been established in the Philippines although the preferred species for growing is S. serrata. The Philippines’ total production of mangrove crab from aquaculture in 2013 was estimated at 16,160 metric tons valued at PhP 5.2 billion, making the country the second top producer of mangrove crab in the world (FAO, 2015). The sources of crab seeds for farming are from the wild and in recent years, a small percentage from hatcheries. Degradation of the natural habitat and uncontrolled collection of all sizes of crabs have resulted in the depletion of the natural population of mangrove crab. As a stopgap measure, the Bureau of Fisheries and Aquatic Resources (BFAR) together with the provincial and municipal government issued ordinances that prohibit the gathering and selling of crablets (≤3 cm) outside the municipality of origin to reduce not only the volume of harvest from the natural habitat but also the collection and trading of ovigerous (berried) females. This has resulted to increased acceptability of hatchery-reared crab juveniles by crab growers. Through the R&D efforts of the Philippine-based SEAFDEC Aquaculture Department, dissemination of sustainable management of mangrove crab culture to the region has been intensified for a sustainable mangrove crab industry in Southeast Asia
Larval survival and megalopa production of Scylla sp. at different salinities
No full textSalinity tolerance was determined for each zoeal stage of Scylla sp. Larvae from ablated pond-grown females were abruptly transferred to salinities of 12, 16, 20, 24, 28 and 32 ppt. Spawning salinity or previous rearing salinity was 32 ppt, except for Z5 which were previously reared at 26 ppt. The mean median lethal time or LT50 values were compared between salinities. For Z1 and Z2, highest values were obtained at 20–32 ppt. Z3 had highest LT50 values at 20–24 ppt and Z4 at 24–32 ppt. For Z5, highest LT50 values were obtained at 20–32 ppt. Another batch of Z3 and Z4 were subjected to the same abrupt salinity transfers and reared to the megalopa stage. Significantly higher percentages of larvae metamorphosed to the megalopa stage at salinities of 20–28 ppt when transfer to test salinities was at Z3. When transfer was at Z4 or Z5, the highest percentage of larvae moulted to the megalopa stage at 24–28 ppt or at 28 ppt, respectively
Influence of salinity on survival and molting in early stages of three species of Scylla crabs
No full textEarly instars of three mud crab Scylla species were reared in different salinities and survival and growth were compared. Scylla olivacea were reared in salinities of 12, 16, 20, 24, and 32 g/l (control). Scylla serrata and S. tranquebarica were reared in salinities of 8, 16, 20, 24, and 32 g/l (control) After 75 days, survival of S. olivacea and S. serrata was not affected by salinity but survival in S. tranquebarica was significantly higher in 8-20 g/l than in 24 and 32 g/l. The molt interval was shorter in S. olivacea, and more animals attained the fifth molt, than in the other species. The molt interval was shorter in 12-20 g/l than in 24 and 32 g/l for S. olivacea, did not vary among test salinities for S. serrata, and was shortest in 20 and 24 g/l in S. tranquebarica where fewer animals attained a fourth molt in 32 g/l than in 8-20 g/l. The molt increment was influenced by salinity only in S. olivacea. At the end of the test, all three species exhibited lower internal carapace width and mean body weights in 32 g/l. Among the three species, S. serrata was most versatile in tolerating a wide range of salinities during nursery culture.This study was supported by the European Commission (INCO-DC) under project grant no. ICA4-CT-2001-10022 entitled ‘Culture and Management of Scylla Species’ and SEAFDEC/AQD with contribution no. 2011-04. The authors wish to thank Mr. Tonymer Castillo and Mr. Federico Ledesma for invaluable assistance in collecting samples and in the conduct of the experiments, the Crustacean Hatchery staff especially Jennette de Pedro and Quirico Ganon for helping with the larval rearing, and Dr. Jurgenne Primavera for the encouragement to work in the project
Broodstock management and seed production of Penaeus monodon (Fabricius)
Get PDFResearch 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
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