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03. Science and Technology (Natural Sciences) Committee

Permanent URI for this communityhttps://repository.unesco.gov.ph/handle/123456789/3

In creating a culture of peace and addressing sustainable development challenges, UNESCO aims to cultivate the generation and application of scientific knowledge among its Member States. At UNACOM, we facilitate access to UNESCO’s international programmes in the sciences, such as the Intergovernmental Oceanographic Commission (IOC), Man and the Biosphere (MAB) Programme, and International Geoscience and Geoparks Programme (IGGP), among others.

Through this sector, the Commission aims to contribute to the following SDGs: 11 - Sustainable Cities and Communities, 13 - Climate Action, 14 - Life Below Water, and 15 - Life On Land. With the overarching vision of the 2023-2028 Philippine Development Plan (PDP), UNACOM targets grassroots-inspired cultural heritage and biodiversity protection and conservation, as well as multi-stakeholder partnerships for SDGs promotion.

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    Size-dependent predation on juvenile sandfish, Holothuria scabra by seagrass-associated crabs
    Caasi, Olivier Josh C.; Gosselin, Louis A.; Juinio–Meñez, Marie Antonette (Cambridge University Press, 2023-10-23)
    High mortality of juvenile Holothuria scabra in seagrass nursery areas has been attributed to predation. In this study, laboratory and field experiments were conducted to determine the effect of the size of two seagrass–associated crabs, Thalamita crenata and Dardanus megistos, on the survival of juvenile sandfish at different sizes (1–10 g). Small juvenile sandfish (1–2 g) offered in field trials were more preferred by small Thalamita and large Dardanus. Non-lethal damage caused by both crabs were also evident, indicating differences in the mode of attack and consumption. The incidence of non-lethal wounds in medium and large juveniles in the laboratory indicate higher incidences of unsuccessful attacks by the crabs. Differences in consumption rate may be related to cheliped morphology and handling techniques, and activity patterns affecting encounter rates. Mortality rates of juvenile sandfish due to T. crenata (CW: 4.30–7.05 cm) ranged from 10–43%, while those by D. megistos (SL: 0.90–2.3 cm) was even higher at 34–53% after 24 h trials. This is the first report that a hermit crab D. megistos is a significant predator of juvenile sandfish. Results provide new insights on crab–soft-bodied prey interactions in tropical seagrass areas. These are also important considerations in stock restoration and ocean-based culture. Given that juveniles (≤10 g) are very vulnerable to predation by these common crab species, growing sandfish to larger sizes is essential prior to release in the field.
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    Impacts of aquaculture nutrient sources: ammonium uptake of commercially important eucheumatoids depends on phosphate levels
    Narvarte, Bienson Ceasar V.; Hinaloc, Lourie Ann R.; Gonzaga, Shienna Mae C.; Roleda, Michael Y. (Springer, 2023-09-14)
    In an integrated multitrophic aquaculture (IMTA) system, seaweeds serve as extractive species that utilize excess nutrients, thereby reducing the risk of eutrophication and promoting sustainable aquaculture. However, the use of excessive fish feeds and the resultant faecal waste as nutrient streams can contribute to variations in nitrogen and phosphorus levels (e.g., primarily NH4+ and PO4−3) in the surrounding area and this may impact the physiology of the integrated seaweeds, particularly on how these species take up inorganic nutrients. In this study, the effect of different PO4−3 levels on NH4+ uptake of the three commercially important eucheumatoids Kappaphycus alvarezii, Kappaphycus striatus and Eucheuma denticulatum was examined under laboratory conditions. Seaweed thalli (n = 4) were incubated in seawater media containing 30 µM NH4+, and 0, 0.5, 1.0, 1.5, 3.0 or 5.0 µM PO4−3 for 1 h under a saturating light level of 116 ± 7.13 µmol photons m−2 s−1 inside a temperature-controlled laboratory. Species-specific responses to PO4−3 levels were observed. For K. alvarezii, maximum NH4+ uptake (17.8 ± 1.6 µmol gDW−1 h−1) was observed at 0.5 µM PO4−3 and the uptake rate declined at higher PO4−3 levels. For K. striatus, NH4+ uptake increased with increasing PO4−3 levels, with maximum N uptake (6.35 ± 0.9 µmol gDW−1 h−1) observed at 5.0 µM PO4−3. For E. denticulatum, maximum NH4+ uptake (14.6 ± 1.4 µmol gDW−1 h−1) was observed at 1.0 µM PO4−3. Our results suggest that among the three eucheumatoid species, the NH4+ uptake of K. striatus persists even at high levels of PO4−3. However, our results also showed that K. striatus had the lowest range of NH4+ uptake rates. These results should be taken into consideration when incorporating eucheumatoids in the IMTA system, where PO4−3levels significantly vary in space and time.
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    Ensuring aquatic food security in the Philippines
    Cabral, Reniel; Geronimo, Rollan; Mamauag, Antonio Samuel; Silva, Juan; Mancao, Roquelito; Atrigenio, Michael (National Fisheries Research and Development Institute, 2023-12)
    The human population of the Philippines is expected to reach 158 million by the year 2050, or an increase of 37% relative to 2022. This implies increased demand for aquatic food (or “fish” hereafter). This begs the question of whether the Philippines can meet the expected increase in fish demand. We estimate that even if the Philippines can maintain its current fish production, the Philippines will still require 1.67 million metric tons more fish per year by 2050 to at least maintain its current per capita fish consumption of 34.27 kg per year. Continued mismanagement of inland and marine fisheries will further widen the gap in fish supply. However, we argue that simultaneously rebuilding overfished fisheries, restoring degraded habitats crucial to supporting productive fisheries, addressing current threats to fisheries sustainability, and expanding sustainable marine aquaculture (or mariculture) have the potential to meet future fish demand in the Philippines. Sustainably expanding mariculture requires careful siting and management of mariculture development areas so that mariculture can improve food security without disenfranchising and marginalizing local coastal communities.
  • Electrophoretic evidence for extensive hybrid gene introgression into commercial Oreochromis niloticus (L.) stocks in the Philippines
    Macaranas, J. M.; Taniguchi, N.; Pante, M. J. R.; Capili, J. B.; Pullin, R. S. V. (Hindawi Limited, 1986-10)
    The usefulness of isozyme and protein markers in identifying tilapia species and their hybrids is demonstrated. Genetic characterization of Oreochromis niloticus populations from commercial farms, experimental stations, and government hatcheries in Luzon, Visayas and Mindanao in the Philippines indicates well-established introgression with O. mossambicus. Genetic differentiation of the O. niloticus stocks, measured by Nei's genetic distance, was highly correlated with O. mossambicus gene content. The implications of these results for tilapia genetic improvement are discussed.
  • Spontaneous maturation and spawning of milkfish in floating net cages
    Marte, Clarissa L.; Lacanilao, Flor (Elsevier, 1986-04)
    Milkfish (Chanos chanos Forsskal) reared from wild-caught fry and from hatchery-bred fry matured at 3.5–5.5 years (2.3–4.9 kg). Maturation and spawning of the hatcherybred fish marks the first time the milkfish life-cycle has been completed in captivity. Milkfish at various stages of gonadal development were obtained in July–October 1980 and March–June 1981 derived from wild-caught fry, and in February–June 1983 from the hatchery-bred fish. The fish were held in floating net cages 9 m and 10 m diameter by 3 m deep, located in 7 m deep water off Igang, Guimaras Island, Philippines. Annual ranges of temperature and salinity were 25–33°C and 25–38 ppt, respectively. The fish were fed commercial feed pellet (42% protein) at 1.5–2% of body weight twice daily. Sexual maturation occurred during the natural breeding season of wild milkfish in the nearby waters. Gonadosomatic index (GSI) of mature males was 0.32–3.95 (wild-caught, 0.32–3.95; hatchery-bred, 1.71–3.85). For mature females it was 1.24–8.12 (wildcaught, 1.56–7.62; hatchery-bred, 1.24–8.12). Two spawnings were recorded in August 1980 and eight in May–July 1981 from the broodstock derived from wild-caught fry, with 342–6293 eggs collected from each spawning, while 14 spawnings were observed in May–June 1983 from the hatchery-bred fish, with 770–114 000 eggs collected. The time of spawning was between 23.00 and 02.00 h. Fertilization rate was 55–99% for the broodstock from wild-caught fry and 47–100% for the hatchery-bred fish. Hatch rate varied from 9 to 80%. Factors affecting spontaneous maturation, spawning and rematuration are discussed. Although slight improvements in egg collection were obtained, further innovations in egg collecting techniques will have to be developed. The results indicate the potential for hatchery production of milkfish fry from captive broodstock and for restocking of waters deprived of naturally occurring fry.