Effect of tank color on the survival of mud crab Scylla serrata larvae
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Abstract
The survival rate of mud crab or mangrove crab Scylla serrata larvae was evaluated using black and yellow-painted tanks. About 400,000 zoea 1 were stocked in 6 tons of treated seawater. The larvae were initially fed with rotifers and subsequently with newly hatched Artemia until the megalopa stage. The larval rearing water was enriched with a combination of Spirulina powder and frozen micro-algal products that include Nannochloropsis sp., Tetraselmis sp. and Thallasiosira weissfolgii. After 15 to 17 days of rearing, the larvae successfully molted to megalopa stage. A total of 377,062 megalopae were harvested. Although the survival rate of megalopae was higher in yellow tanks (23.63± 0.03%), it was not significantly different when compared to those in black tanks (15.66±0.02%) (P=0.05).
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de los Santos, M. A., Taro, T., Uehara, D., Dwight, I., & Masami, L. (2015). Effect of tank color on the survival of mud crab Scylla serrata larvae. In E. T. Quinitio, F. D. Parado-Estepa, Y. C. Thampi Sam Raj, & A. Mandal (Eds.), Proceedings of the International Seminar-Workshop on Mud Crab Aquaculture and Fisheries Management, 10-12 April 2013, Tamil Nadu, India (pp. 85-88). Tamil Nadu, India: Rajiv Gandhi Centre for Aquaculture (MPEDA).
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Conference paperISBN
9788192989815Related items
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Morphological deformities in mud crab Scylla serrata juveniles exposed to antibiotics during the larval stage
; Quinitio, Emilia T.
; (Wiley, 2017)
The effects of antibiotics on the external deformities, growth and survival of mud crab Scylla serrata larvae and juveniles were determined. Zoeae were exposed to oxytetracycline (OTC) (0, 3.0, 6.0, 9.0, 12 mg L-1) and furazolidone (FZD) (0, 0.5, 1.0, 1.5, 2.0 mg L-1) in the first and second experiments, respectively, until the late megalopa. The crab instars were grown in nursery tanks for 1 month. Larvae survived until megalopa only at 3.0 and 6.0 mg L-1 OTC or 0.5 and 1.0 mg L-1 FZD. These four concentrations were run simultaneously in another experiment. Morphological deformities in zoea 5 were bent dorsal, rostral and furcal spines. There was no significant difference (P > 0.05) on the deformities of zoea 5 in 3.0 and 6.0 mg L-1 OTC and 0.5 and 1.0 mg L-1 FZD. Significantly (P < 0.05) higher survival and faster growth were attained in 3.0 mg L-1 OTC and 0.5 mg L-1 FZD. Deformities observed in juveniles were fused frontal and lateral spines, asymmetrical and depressed tip of abdominal flap and gap between sternites. High percentage occurrence of deformities was observed in the 6.0 mg L-1 OTC and 1.0 mg L-1 FZD in the first and third experiments, respectively. There was no significant difference (P > 0.05) observed in the survival of juveniles in OTC and FZD treatments. However, growth was significantly (P < 0.05) faster in lower concentrations of the two antibiotics. The study shows the effects of OTC and FZD in the morphology of mud crab. Therefore, there is a need to eliminate the use of antibiotics and find alternatives. -
Culture of Scylla serrata megalops in brackishwater ponds
(Asian Fisheries Society, 2001)Three- to five-day old hatchery-reared megalops (4.0 to 6.4 mg body weight) of the mud crab, Scylla serrata, were cultured to the juvenile stage in 20 m2 net cages installed in brackishwater nursery ponds. To establish a suitable stocking density, megalops were stocked at 10, 20, and 30 ind·m-2 in net cages. Treatments were replicated three times over time. After 30 days of culture, mean survival of juveniles ranged from 48.3 to 53.3% and did not vary significantly (P > 0.05) among the three stocking densities. Similarly, the mean final body weights of juveniles ranging from 2.91 to 3.40 g and mass weights 458.9 to 1066 g did not significantly differ among stocking densities. These results show that stocking of crab megalops directly in net cages in a brackishwater pond is feasible at any of the stocking densities tested. -
Updates on the larviculture of mud crab at SEAFDEC/AQD
Quinitio, Emilia T.; ; ; (Aquaculture Department, Southeast Asian Fisheries Development Center, 2017)
Although the mud crab (Scylla serrata) hatchery technology has been developed, issues such as high cost of production due to the need for additional facilities and labor for natural food culture, inconsistent survival rate at megalopa stage due to Molt Death Syndrome (MDS), and disease due to luminescent bacteria (Vibrio spp.), remain to be addressed. Refinements on the existing mud crab larviculture technology were done to address these problems. Poor nutrition, low water temperature and application of prophylaxis during the zoea l stage have been identified as possible causes of MDS. Six shrimp formulated diets (FD) were tested, and 3 of these proved to be suitable for mud crab larvicuture. Larval performance was compared using the 3 diets + natural food (NF, rotifers and Artemia) and NF alone as control. No significant difference was noted in the survival among the 4 treatments, although BP Nippai fed larvae had higher values. Lesser occurrence of MDS was observed in all the larvae fed FD+NF. Three mud crab larval diets with various attractants (squid, annelids, and squid + annelids) were also formulated and fed to the larvae. Results showed no significant difference among the 3 diets. The results of another experiment investigating the effects of the reduction of natural food showed that larvae fed 50% NF + 50% FD and 75%NF + 25% FD had higher survival compared to those fed 75% AD +25% NF and no NF at all. The results indicate that the larvae cannot survive with formulated diet alone. It has been observed that frequency of antibiotic application can be reduced to every 5 days if good quality mud crab larvae are used. Formalin stress test proved to be a reliable method to determine the quality of a batch of newly hatched zoeae. All prophylactic treatments are stopped when megalopae reach the benthic stage. To accelerate the dissemination of science-based mud crab hatchery technology to industry stakeholders, SEAFDEC/AQD entered into an agreement with private hatchery operators, State Universities and Colleges, and Local Government Units on giving assistance during initial hatchery operations. Technicians were given free training, followed by in-situ hatchery operations with assistance from SEAFDEC/AQD with the funding from PCAARRD-DOST. Crablets are now being produced by the collaborators. Increase in the production of hatchery-reared crablets will eventually reduce the dependence on wild-sourced mud crab seed stock for farming.
