Mud Crab Aquaculture

[GaryWhite]

Greetings All !


What follows is a series of research articles which discuss some variables (system design, stocking density, disease control, temperature, and diet) which will undoubtably be important to those who are experimenting with the captive culture of crabs ...


Truong Trong Nghia, Mathieu Wille, Tran Cong Binh, Hoang Phuoc Thanh, Nguyen Van Danh, Patrick Sorgeloos (2007)
Improved techniques for rearing mud crab Scylla paramamosain (Estampador 1949) larvae
Aquaculture Research 38 (14), 1539–1553.



Abstract

A series of rearing trials in small 1 L cones and large tanks of 30–100 L were carried out to develop optimal rearing techniques for mud crab (Scylla paramamosain) larvae. Using water exchange (discontinuous partial water renewal or continuous treatment through biofiltration) and micro-algae (Chlorella or Chaetoceros) supplementation (daily supplementation at 0.1–0.2 million cells mL−1 or maintenance at 1–2 millions cells mL−1), six different types of rearing systems were tried. The combination of a green-water batch system for early stages and a recirculating system with micro-algae supplementation for later stages resulted in the best overall performance of the crab larvae. No clear effects of crab stocking density (50–200 larvae L−1) and rotifer (30–60 rotifers mL−1) and Artemia density (10–20 L−1) were observed. A stocking density of 100–150 zoea 1 (Z1) L−1, combined with rotifer of 30–45 mL−1 for early stages and Artemia feeding at 10–15 nauplii mL−1 for Z3–Z5 seemed to produce the best performance of S. paramamosain larvae. Optimal rations for crab larvae should, however, be adjusted depending on the species, larval stage, larval status, prey size, rearing system and techniques. A practical feeding schedule could be to increase live food density from 30 to 45 rotifers mL−1 from Z1 to Z2 and increase the number of Artemia nauplii mL−1 from 10 to 15 from Z3 to Z5. Bacterial disease remains one of the key factors underlying the high mortality in the zoea stages. Further research to develop safe prophylactic treatments is therefore warranted. Combined with proper live food enrichment techniques, application of these findings has sustained a survival rate from Z1 to crab 1–2 stages in large rearing tanks of 10–15% (maximum 30%).

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2109.2007.01814.x



Here's what a mud crab looks like:
http://www.mbi.nsysu.edu.tw/~fiddler/figure/fig_crab/Scylla_paramamosain.jpg


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[GaryWhite]

Greetings All !


Vu Ngoc Ut, Lewis Le Vay, Truong Trong Nghia, Tran Thi Hong Hanh (2007)
Development of nursery culture techniques for the mud crab Scylla paramamosain (Estampador)
Aquaculture Research 38 (14), 1563–1568.
doi:10.1111/j.1365-2109.2006.01608.x



Abstract

Cannibalism is one of the main causes of mortality in the culture of the mud crab Scylla paramamosain, particularly in the early post-larval and juvenile stages when the densities of hatchery-reared crabs may be very high before stocking into ponds or release into the wild for stock enhancement. In a series of experiments investigating cannibalism mitigation, the influence of stocking density, the effectiveness of sand substrate, brick and shell shelters and feed type were compared in culture of crabs from instar 1 for short nursery periods of 15–30 days. Inclusion of brick and shell shelters significantly increased survival over sand substrate alone. However, inclusion of shelters did not affect growth rates. In scaled-up nursery production in lined-ponds, with shelters, live Artemia biomass and fresh chopped shrimp or tilapia were found to be equally effective feeds for juvenile crabs stocked at a density of 70 m−2 from instar 1 and grown for 30 days [52–66% survival, 21.6–24.6 mm carapace width (CW)]. In an extended nursery period for a further 30 days, crabs of 22 mm CW, stocked at 30 m−2 in the same ponds, attained a final size of 34.5–36.2 mm CW with a survival of 64.3–67.0% using the same feeds.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2109.2006.01608.x



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[GaryWhite]

Greetings All !


David L Mann, Tom Asakawa, Beverley Kelly, Trent Lindsay, Brian Paterson (2007)
Stocking density and artificial habitat influence stock structure and yield from intensive nursery systems for mud crabs Scylla serrata (Forsskål 1775)
Aquaculture Research 38 (14), 1580–1587.
doi:10.1111/j.1365-2109.2006.01626.x



Abstract

Intensive nursery systems are designed to culture mud crab postlarvae through a critical phase in preparation for stocking into growout systems. This study investigated the influence of stocking density and provision of artificial habitat on the yield of a cage culture system. For each of three batches of postlarvae, survival, growth and claw loss were assessed after each of three nursery phases ending at crab instars C1/C2, C4/C5 and C7/C8. Survival through the first phase was highly variable among batches with a maximum survival of 80% from megalops to a mean crab instar of 1.5. Stocking density between 625 and 2300 m−2 did not influence survival or growth in this first phase. Stocking densities tested in phases 2 and 3 were 62.5, 125 and 250 m−2. At the end of phases 2 and 3, there were five instar stages present, representing a more than 20-fold size disparity within the populations. Survival became increasingly density-sensitive following the first phase, with higher densities resulting in significantly lower survival (phase 2: 63% vs. 79%; phase 3: 57% vs. 64%). The addition of artificial habitat in the form of pleated netting significantly improved survival at all densities. The mean instar attained by the end of phase 2 was significantly larger at a lower stocking density and without artificial habitat. No significant effect of density or habitat on harvest size was detected in phase 3. The highest incidence of claw loss was 36% but was reduced by lowering stocking densities and addition of habitat. For intensive commercial production, yield can be significantly increased by addition of a simple net structure but rapidly decreases the longer crablets remain in the nursery.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2109.2006.01626.x



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[GaryWhite]

Greetings All !


Veronica R Alava, Emilia T Quinitio, Jennete B de Pedro, Flora Mae P Priolo, Zenith Gaye A Orozco, Mathieu Wille (2007)
Lipids and fatty acids in wild and pond-reared mud crab Scylla serrata (Forsskål) during ovarian maturation and spawning
Aquaculture Research 38 (14), 1468–1477.
doi:10.1111/j.1365-2109.2007.01793.x




Abstract

Wild-caught and pond-reared female mud crab Scylla serrata at different stages of ovarian maturation were collected from Samar and Capiz, Philippines. Crabs were categorized into five stages according to the external morphological and microscopic appearance of the most advanced oocytes. The ovaries, hepatopancreas, muscle and newly spawned eggs (NSE) were analysed for lipid class components and fatty acids. Total lipid was higher in pond-reared than in wild-caught crabs but increased with ovarian maturation in both groups. Ovarian lipid peaked at the fully mature stage, coinciding with a decline in hepatopancreatic and muscle lipids. Lipid levels declined significantly in spent females. The tissues contained elevated highly unsaturated fatty acids such as arachidonic (20:4n-6), eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids, but at higher levels in late maturing and fully mature ovaries and in NSE. The type of lipid class and fatty acid components in mature ovaries as well as in NSE are generally considered to be indicative of their importance in reproductive physiology and embryonic and larval development.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2109.2007.01793.x



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[GaryWhite]

Greetings All !



Chaoshu Zeng (2007)
Induced out-of-season spawning of the mud crab, Scylla paramamosain (Estampador) and effects of temperature on embryo development
Aquaculture Research 38 (14), 1478–1485.
doi:10.1111/j.1365-2109.2007.01826.x




Abstract

Treated with combined bilateral eyestalk ablation and maintenance of water temperature at 22.5±1.5 °C, mud crab Scylla paramamosain females with mature ovaries were induced to produce eggs outside the natural spawning season in subtropical southern China. Newly extruded eggs from a crab were incubated in vitro at 10, 15, 20, 25, 27, 30, 35 °C, respectively, and the embryonic development was closely monitored. Abnormal cell division was observed at temperatures 10 and 35 °C. At 15 °C, development remained at the gastrula stage by day 32 post-spawn, at which time the experiment was terminated. Hatching of in vitro incubated eggs occurred between 20 and 30 °C. An increase in incubation temperature from 20 to 25 °C reduced the incubation duration by 14 days, 2.6 times of that measured for a similar 5 °C increase from 25 to 30 °C. Embryonic development of S. paramamosain was divided into stage 0–10, and the duration of each stage was recorded for each incubation temperature. The information obtained allows accurate prediction of hatching time of female crabs incubated under variable temperatures. Larvae hatched from in vitro incubated eggs were reared to reach first juvenile crab stage and their dry weights were similar to those of larvae hatched naturally.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2109.2007.01826.x



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[GaryWhite]

Greetings All !


Truong Trong Nghia, Mathieu Wille, Stijn Vandendriessche, Quach The Vinh, Patrick Sorgeloos (2007)
Influence of highly unsaturated fatty acids in live food on larviculture of mud crab Scylla paramamosain (Estampador 1949)
Aquaculture Research 38 (14), 1512–1528.
doi:10.1111/j.1365-2109.2007.01815.x




Abstract

Two experiments were carried out to investigate the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels in rotifers (Brachionus plicatilis) and Artemia on the survival, development and metamorphosis of mud crab Scylla paramamosain larvae. Five different lipid emulsions, varying in the level of total n-3 and n-6 highly unsaturated fatty acids (HUFA), DHA, EPA and ARA were used to manipulate the fatty acid profile of the live food. Fatty acid profiles of the live food and crab larvae at zoea one, three and five stages were analysed to study the HUFA uptake by the larvae. The fatty acid content of the live food affected the fatty acid profiles of the crab larvae. In both experiments, the survival rate in the zoeal stages was not statistically different among treatments. However, larval development rate and metamorphosis success were affected by the dietary treatments. In this respect, the DHA/EPA ratio in the live food seems to be a key factor. Enrichment emulsions with a very high (50%) total HUFA content but a low DHA/EPA ratio (0.6), or zero total HUFA content caused developmental retardation and/or metamorphosis failure. An emulsion with a moderate total HUFA (30%) and a high DHA/EPA ratio (4) was the best in terms of larval development during the zoeal stages and resulted in improved metamorphosis. Dietary ARA seemed to improve first metamorphosis, but its exact role needs further clarification. For the larval rearing of S. paramamosain, an enrichment medium containing about 30% total n-3 HUFA with a minimum DHA/EPA ratio of 1 is recommended. Further investigation is needed on the total HUFA and optimum DHA/EPA ratio requirements for each crab larval stage.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2109.2007.01815.x



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