Now showing items 1-4 of 4

    • Conference paper

      Induction of molting in hatchery-reared mud crab Scylla serrata juveniles through temperature manipulation or autotomy 

      JJDC Huervana - In ET Quinitio, FD Parado-Estepa & RM Coloso (Eds.), Philippines : In the forefront of the mud crab industry development : proceedings of the 1st National Mud Crab Congress, 16-18 November 2015, Iloilo City, Philippines, 2017 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The effects of water temperature and autotomy of chelipeds on growth, survival and molting of mud crab, Scylla serrata, juveniles were investigated under laboratory conditions in separate experiments. Hatchery-produced crabs at the intermolt stage with 2.0-2.3 cm carapace width and 1.7-2.2 g body weight were either exposed to temperature levels of 29, 32 and 35°C and ambient temperature of 24-31°C or subjected to autotomy (voluntary removal of one or two chelipeds). The crabs were allowed to molt twice prior to termination.

      All crabs held at 35°C had 100% mortality due to incomplete molting during the first molt. The mean survival of crabs upon termination was 58, 64 and 50% for ambient temperature, 29 and 32°C, respectively. Specific growth rate (SGR) of crabs in the ambient (2.83 ± 0.12%) and 29°C (3.02 ± 0.15%) were comparable but significantly lower than (P<0.01) those at 32°C (3.85 ± 0.28%). The molt interval of crabs was significantly shorter in treatments with constant water temperature (29°C: 32 ± 0.80 days, 32°C: 28 ± 1.11 days) compared to ambient temperature (39 ± 0.93 days).

      The survival of crabs with intact chelipeds (51.17 ± 3.56%) was comparable to those with one (50.55 ± 2.36%) or two (43.41 ± 1.59%) autotomized chelipeds. Juveniles with intact (5.80 ± 0.47%) or one autotomized cheliped (5.45 ± 0.30%) had a significantly higher SGR than crabs with both chelipeds autotomized (4.20 ± 0.52%) in the first molt. On the second molt, however, high SGR was observed in crabs with two chelipeds autotomized. The molt interval was significantly shorter in the autotomized crabs (one cheliped: 28 ± 1.66 days; two chelipeds: 23 ± 0.63 days) compared to those with intact chelipeds (36 ± 1.52 days). The results suggest that optimum water temperature for rearing S. serrata juveniles ranges from 29 to 32°C. Likewise, autotomy of one cheliped can promote molting without adversely affecting the growth and survival of the juveniles.
    • Conference paper

      Morphological deformities in mud crab Scylla serrata juveniles exposed to antibiotics during the larval stage 

      GS Pates Jr., ET Quinitio, GF Quinitio & FD Parado-Estepa - In ET Quinitio, FD Parado-Estepa & RM Coloso (Eds.), Philippines : In the forefront of the mud crab industry development : proceedings of the 1st National Mud Crab Congress, 16-18 November 2015, Iloilo City, Philippines, 2017 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The effects of antibiotics on the survival, growth and external deformities of mud crab Scylla serrata larvae and juveniles were determined. Zoeae were exposed to 0, 3, 6, 9, 12 mgL-1 oxytetracycline (OTC) and 0, 0.5, 1, 1.5, 2 mgL-1 furazolidone (furan) until the late megalopa in the first and second experiments. The treatments that gave the best results in the first and second experiments were conducted simultaneously in the third experiment. The surviving crab instar from each replicate were grown in nursery tanks for one month.

      Significantly higher survival and faster growth rate of Z5 were attained when 3 and 6 mgL-1 OTC or 0.5 and 1 mgL-1 furan were used. Morphological deformities observed in zoea 5 were bent dorsal, rostral and furcal spines. Percentage occurrence of morphological deformities was similar in all treatments. Significantly (P<0.05) higher survival and faster growth were attained among Z5 in the treatments using 3 mgL-1 OTC and 0.5 mL-1 furan in the third experiment. Morphological deformities observed in juveniles were fused frontal and lateral spines, asymmetrical and depressed tip of abdominal flap and gap between sternites. High percentage of deformities was observed in juveniles that were previously exposed to 6 mgL-1 OTC or 1.0 mgL-1 furan. There was no significant difference (P>0.05) observed in the survival of juveniles in both treatments of OTC and furan. However, growth was significantly (P<0.05) faster in lower concentrations of the two antibiotics.

      The study shows the apparent negative effects of antibiotics and highlights the need to eliminate or find alternatives, thereby preventing possible harm to the organisms and the environment.
    • Conference paper

      Mud crab fattening project of KAMAMANA in Del Carmen, Siargao Island 

      AE Sulima - In ET Quinitio, FD Parado-Estepa & RM Coloso (Eds.), Philippines : In the forefront of the mud crab industry development : proceedings of the 1st National Mud Crab Congress, 16-18 November 2015, Iloilo City, Philippines, 2017 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The Kaanib ng mga Mangingisda at Magsasaka ng Numancia Aqua-Agrikultura (KAMAMANA), established in Del Carmen, Siargao Island in 2011 is a People's Organization active in promoting the advocacy in 1) protecting the environment and natural resources, 2) providing services for the family welfare, and 3) managing sustainable livelihood programs and community development. One of the major livelihood programs presently being implemented by KAMAMANA is the fattening of mud crab (mangrove crab), Scylla serrata, in plastic containers set up in a mangrove area. Tenurial rights to manage a 2-hectare mangrove area for 25 years was granted to KAMAMANA by the Department of Environmental and Natural Resources.

      Crabs obtained from the mangrove areas of Del Carmen and nearby municipalities are purchased and stocked in plastic containers. The crabs are fed trash fish and mollusks once every afternoon to satiation until they are fattened, usually for 1-2 weeks. The major problem encountered is mortality after molting. Four KAMAMANA members are involved in the crab fattening. When mortalities occur, the dead crabs are usually charged to members assigned in the operation. The fattened crabs are sold to local restaurants, hotels, resorts and walk-in buyers or brought to traders in Surigao City. The net income is divided into the following: members involved in the culture (50%), treasurer (10%), business manager (15%), organizational share (5%), savings (5%) and trust fund (15%).
    • Conference paper

      Strategies to reduce disease incidence in mud crab culture 

      EC Amar, MD Somera, SB Madero, EA Tendencia & JP Faisan Jr. - In ET Quinitio, FD Parado-Estepa & RM Coloso (Eds.), Philippines : In the forefront of the mud crab industry development : proceedings of the 1st National Mud Crab Congress, 16-18 November 2015, Iloilo City, Philippines, 2017 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Mud crab hatchery suffers from low survival due to susceptibility to bacterial infection in the early larval stages among many causes. Despite food safety issues, antibiotics continue to be used in the absence of effective alternatives. In this study, screening of plant extracts was conducted to determine their suitability as antimicrobial agents against pathogens causing low survival in the hatchery. In addition, potential probionts were isolated from the gastrointestinal tract of mud crab, and water and sediments of mud crab grow-out ponds.

      Crude ethanolic extracts from various terrestrial and mangrove trees were tested for in vitro antimicrobial activity and toxicity to mud crab zoea and megalopa. In addition, the in vivo antimicrobial efficacies of the selected extracts were tested by oral administration followed by experimental challenge with Vibrio harveryi. On the other hand, the putative probionts, were tested for pathogenicity against mud crab zoea and megalopa and quorum sensing inhibition activity against V. harveyi. Finally the extracts and probionts were tested for their efficacy in simulated hatchery and grow-out trials.

      Results showed that extracts of Terminalia cattapa and the potential probiont Bacillus subtilis G100R11 showed antimicrobial and probiotic activity in in vitro and in vivo tests. In simulated hatchery trials, T. cattapa administration successfully produced crab instar with a survival of 1.3-1.8% in trials 1 and 2 comparable to antibiotic control. B. subtilis produced crab instar with survival of 0.8-1.0% in trials 1 and 2, better than the commercial probiotic with 0-0.13% survival. Using T. cattapa and B. subtilis, survival was above 30% until zoea 5 but suddenly dropped below 5% during metamorphosis to megalopa where high incidence of incomplete molting was observed. If difficulty affecting the molting process is addressed, high survival from zoea to megalopa and crab instar will be achievable.