Southeast Asian Fisheries Development Center
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Low ph water impairs the tactile sense of the postlarvae of the giant freshwater prawn Macrobrachium rosenbergii
No full textThe effect of low pH on the tactile sense of Macrobrachium rosenbergii postlarvae was determined in the laboratory by means of two behavioural assays: shelter (netting) occupancy and jumping response to touch stimuli (taps) by a glass micropipette. The postlarvae were acclimated to pH 4, pH 5, pH 6 and pH 7.5 (control) in 45 L aquaria 5−7 d before the experiments. Shelter occupancy decreased with pH and was significantly lower at pH 4 and pH 5 than at pH 6 and in the control. The jumping response instantly followed a tap 93−98% of the time in the control, pH 6 and pH 5 treatments. However, the postlarvae showed significantly lower jumping response (65%) at pH 4, indicating an impaired tactile sense. Low pH 4−5 probably degrades the chitin of the sensory setae and inhibits the surface mechanoreceptors of the prawn postlarvae
SEAFDEC/AQD highlights 2017
Get PDFSEAFDEC/AQD highlights 2017 is SEAFDEC/AQD’s annual report updating on its accomplishments and progress for the year 2017
Status of sea cucumber fishery and populations across sites with different levels of management in Palawan, Philippines
No full textThis study was conducted to investigate the sea cucumber fishery and compare populations between exploited and unexploited sites. Three islands were selected, the Arrecife Island as the unexploited site and the Johnson and Green Islands representing the exploited sites. In each site, sea cucumber species richness, diversity and densities were assessed by laying as much as 15 transects (50 m × 5 m) per habitat in each island. Differences in species richness, diversity and relative densities across sites and habitats were tested using a Two-way Analysis of Variance (ANOVA) and Tukey test for post hoc comparisons. An interview with gatherers, key informants and focus group discussions were also conducted to gather information on the sea cucumber fishery and its management. Results showed that the unexploited site had a higher species richness (14 vs. 7 and 7). Relative density of species was also higher in the unexploited site at 1245 ind ha-1 while it was only 78 and 39 ind ha-1 in exploited sites (p < 0.05). Interviews and a focus group discussion revealed that national regulations on permit system and size limits were not enforced at the local level and that gatherers had low levels of awareness regarding regulations on sea cucumber harvest. Current management measures appear to be ineffective and insufficient, leaving the sea cucumbers in areas open to exploitation at risk of depletion. Given that sea cucumbers provide substantial income to local communities, the depletion of this resource could compromise the livelihood of people in island communities that rely heavily on marine resources for living. Thus, this study highlights the need to review national policies on sea cucumber fishery and place the management at the local level.This study was jointly funded by the Department of Science and Technology- Science Education Institute (DOST-SEI), the University of the Philippines Visayas and the Western Philippines University. The support and cooperation of the Municipality of Roxas, Palawan, the management of Arrecife Island especially Ms. Glesselle T. Batin, and the sea cucumber gatherers in Green and Johnson Islands are greatly appreciated
Evolution of genome size within the genus Haliotis (Vetigastropoda: Haliotidae)
No full textGenome size (C-value) and the percentage of adenine and thymine nucleotides in the genome (AT content) are fundamental characteristics of every species, and very important parameters in molecular cytogenetic and phylogenic studies, and for the progress of whole-genome sequencing. In this study, the C-value and AT content of nine abalone species inhabiting the Northwest Pacific (around Japan), Southeast Asia, South Africa, and Oceania were determined using flow cytometry. C-value ranged from 1.32 pg for Haliotis varia (Southeast Asia) to 2.01 pg for Haliotis laevigata (Oceania), and AT content ranged from 58.0% for Haliotis planata (Southeast Asia) to 66.3% for Haliotis diversicolor aquatilis (Southeast Asia). Reported chromosome numbers ranged from 2n = 32 to 36, and were higher in Oceanian, South African, and Northwest Pacific species (2n = 36) compared with the Southeast Asian group (2n = 32). This increase of chromosome number in the Oceanian species seems to be related to an increase in the DNA amount, unlike that of Haliotis midae (South African species). An increase of the C-value associated with an increase in DNA amount was also shown in the North Pacific group. These results suggest that increases in the DNA amount occurred independently in the ancestor of each of the different lineages
Quality assessment of newly hatched mud crab, Scylla serrata, larvae
No full textStarvation and exposure to formalin were investigated as possible stress tests for evaluating the quality of mud crab, Scylla serrata, larvae. For the starvation stress test, newly hatched zoeae stocked in 150-ml containers were either starved or fed rotifers. Similarly, newly hatched zoeae were stocked in containers with seawater of 0 (control), 20, 30 and 40 mg/L formalin for the formalin stress test. The zoeae from the same batches were used for seed production to monitor their performance and validate the results of stress tests. Starvation was found to be unsuitable for larval quality evaluation. However, the impact of initial food deprivation on the newly hatched larvae indicates that feeding immediately after hatching is necessary for mud crab larvae. Exposure of larvae to 40 mg/L formalin for 3 hr appeared to be a reliable and practical method for larval quality assessment as the survival of larvae in the mass production tanks validated the classification of good and poor quality batches in the stress tests. On this basis, a hatchery operator can decide which batch should be cultured further. Finally, there appears to be a link between the quality of larvae and the performance at the megalopa and early juvenile crabs.This study (Br-01 C2007 and Br-03 C-2010) was supported by the SEAFDEC/AQD and Trust Fund of the Government of Japan and PCAARRD-Department of Science and Technology. The authors express their gratitude to the Crustacean Hatchery staff for the technical assistance
Phylogeographic patterns in the Philippine archipelago influence symbiont diversity in the bobtail squid-Vibrio mutualism
No full textMarine microbes encounter a myriad of biotic and abiotic factors that can impact fitness by limiting their range and capacity to move between habitats. This is especially true for environmentally transmitted bacteria that cycle between their hosts and the surrounding habitat. As geologic history, biogeography, and other factors such as water temperature, salinity, and physical barriers can inhibit bacterial movement to novel environments, we chose to examine the genetic architecture of Euprymna albatrossae (Mollusca: Cephalopoda) and their Vibrio fischeri symbionts in the Philippine archipelago using a combined phylogeographic approach. Eleven separate sites in the Philippine islands were examined using haplotype estimates that were examined via nested clade analysis to determine the relationship between E. albatrossae and V. fischeri populations and their geographic location. Identical analyses of molecular variance (AMOVA) were used to estimate variation within and between populations for host and symbiont genetic data. Host animals demonstrated a significant amount of variation within island groups, while symbiont variation was found within individual populations. Nested clade phylogenetic analysis revealed that hosts and symbionts may have colonized this area at different times, with a sudden change in habitat. Additionally, host data indicate restricted gene flow, whereas symbionts show range expansion, followed by periodic restriction to genetic flow. These differences between host and symbiont networks indicate that factors “outside the squid” influence distribution of Philippine V. fischeri. Our results shed light on how geography and changing environmental factors can impact marine symbiotic associations at both local and global scales
Overview of the mud crab industry in the Philippines
No full textMud crab farming has long been established in the Philippines and the country is the second top producer in the world. Except for Scylla paramamosain, the three other species, S. serrata, S. tranquebarica and S. olivacea are commonly found in the country, but S. serrata is the preferred species for farming. Crab seeds for farming are mainly from the wild and in recent years, a small percentage from the hatchery. Due to the apparent decline of the wild crab stocks, provincial and municipal ordinances have been issued by a number of Local Government Units (LGUs) along with the Bureau of Fisheries and Aquatic Resources (BFAR) to conserve and manage the remaining resources. From the hatchery, megalopa or crab instars are grown in net cages installed in the nursery pond. Mud crab farming engages mostly in long-term grow-out culture of juvenile crabs to market size for 3-5 months, short-term fattening of lean crabs for 15-45 days, and recently, soft-shell crab production. Polyculture of juvenile crabs to market size with one to three other commodities in earthen brackishwater ponds is usually practiced. Mud crabs for soft-shell crab production are mainly from the wild, while SEAFDEC/AQD demonstrates the use of hatchery-produced juvenile mud crabs as seedstock.
Refinement is continuously being done to improve the economic viability of producing crabs, although basic technologies have been developed for all phases of culture (hatchery, nursery, grow-out, fattening and soft shell crab production). The major issues facing the industry are the lack of seedstock, difficulty of zoea 5 to molt to megalopa stage, cannibalism particularly at the nursery phase, species identification at the juvenile stage, use of fish as aquafeed, diseases, effects of climate change and quality of crabs at postharvest. In 2012, the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD) of the Department of Science and Technology (DOST) started funding projects under the National Mud Crab Science and Technology Program (NMCSTP) to address these issues. The major aim of the Program was to improve the production, profitability and sustainability of crab farming. SEAFDEC/AQD leads in capacity building with focus on the sustainability of the mud crab industry. Various collaborations and research studies on mud crab culture enabled SEAFDEC/AQD to package mud crab technologies, conduct local and international training courses and on-site technology demonstrations, and publish extension manuals and scientific publications since the mid1990s. Research and Development activities have been translated into improved production. With the recent developments and refinements of technologies, it is expected that the Philippines will increase its production by 25-50% in the next 5 years