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UPV Theses and Dissertations

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Discipline: search.filters.discipline.FisheriesSDG: search.filters.sdg.SDG 13 - Climate action

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    Does a coral reef enhance the productivity of its surrounding waters?
    Peñafiel, Christen P. (University of the Philippines Visayas, 2019-06)
    Coral reefs have long been assumed and continually claimed to be origins of very high productivity, but how they attract organisms from and export nutrients to their neighboring waters remains largely unknown. Specifically, this study aimed at determining the space-time dynamics of nutrients and biomass redistribution around Hibotkan Rock Sanctuary (HRS), Banate, Iloilo, a sanctuary reef established by Municipal Fisheries Ordinance No. 12 covering an area of 25 ha. Twelve (12) sampling stations were established for space-time nutrient profiling, phytoplankton count, and supplementary measurements of water parameters, and four (4) stations for fish (biomass) visual survey. Results were analyzed using spatio-temporal plots and the Pearson correlation matrix (5% significant level). Nitrite was observed to be limiting, while nitrate was the most abundant in the waters of HRS. The predominant temporal variations of nutrients followed the flood tide (FT) and ebb tide (ET) cycles. In general, the tidal current direction appeared to control the redistribution of the nutrients (NO3-, NO2-, PO43-, and SiO44-). This study further revealed that stations of high nutrient concentration usually coincided with low levels of dissolved oxygen (DO). Species of fish observed were all indigenous and well-known inhabitants of the coral reefs. Furthermore, no other families of fishes (such as those of commercial value) were caught on record. Overall, there was no clear indication of import or export of living biomass in the HRS area. It can be inferred from the results that the fabled high productivity of coral reefs has no clear scientific basis; consequently, the Marine Protected Areas (MPAs) concept also appears to have no solid foundation.
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    Effects of dietary pH on growth performance and feed utilization of Nile tilapia (Oreochromis niloticus)
    Fabay, Ryan V. (University of the Philippines Visayas, 2020-06)
    Two feeding trials were conducted to investigate the effects of dietary pH (pH 2.5, 3.7, 4.6, 5.7-control, pH 7.0, and pH 8.0) and dietary acid source (acetic acid, citric acid, hydrochloric acid and control-no acid) on growth rate and feed utilization efficiency of the Nile tilapia fry. In addition, attractability indices of the diets at different pH and dietary acid sources were determined. Results of the first feeding trial showed that the feed with pH adjusted to 4.6 resulted in increased growth rate and improved feed utilization efficiency in the Nile tilapia. In the second feeding trial, the use of either hydrochloric, citric or acetic acid in adjusting the pH to the optimal 4.6 did not affect the growth performance of the fish. This study demonstrated that pH and not actually the kind of acid diet promoted growth and efficiency in the Nile tilapia fry. Furthermore, this study provides new information on the use of acid in aquaculture as feed additive for tilapia fry, which can be added to fish feed literature.
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    Some aspects of ecology, biology, and fishery of the horse mussel Modiolus metcalfei (Hanley, 1843) in Dumangas, Iloilo
    Uba, Kaent Immanuel N. (University of the Philippines Visayas, 2019-06)
    The exploitation of Modiolus metcalfei in Dumangas, Iloilo has been going on since the 1970s. It has undergone the cycle of resource depletion to recovery but its management remains hindered by the poor understanding of its ecology, biology, and fishery. The present study characterized the habitat, investigated the aspects of morphology, allometry, asymmetry, feeding biology, and analyzed the value chain of M. metcalfei fishery in the area. Monitoring of physicochemical parameters, sediment grain size and organic matter content, estimation of population density were conducted for six months. Morphology, allometry, and asymmetry were investigated using combined linear and geometric morphometric methods while pre-ingested food and plankton composition in the water were determined qualitatively. Moreover, interviews and observations were conducted to analyze the value chain of the horse mussel fishery. Although the physicochemical parameters were at optimal levels, results in the analysis of asymmetry indicated developmental instability and ecological stress. The primary factors influencing the variation in morphology were sex and environmental fluctuations. The horse mussel mainly relied on phytoplankton, primarily diatoms, for food. The lack of support from enablers, lack of adequate enforcement, and lack of post-harvest infrastructure hindered the full development of the fishery. Moreover, poverty dimensions were revealed in the analysis of the value chain. To craft better management policies, studies on the population dynamics and reproductive biology are recommended.